Fight Aging!

The research and medical communities are slow to undertake work on combination therapies. Regulation makes it exceedingly expensive to assess multiple combinations, and there are numerous other perverse incentives to challenge any effort to build combination therapies with components developed and manufactured by different groups. Short of working around the existing system of regulation, and methods of doing this at scale are lacking at the present time, this is a challenging problem to solve. People follow incentives. Given this, it it is entirely plausible that there are many largely unexplored instances in which existing classes of medication for age-related disease might synergize to be more effective together.

In this context, clinicians and researchers have been discussing polypills for quite some time. The term polypill usually means a combination of existing treatments for cardiovascular disease such as statins to reduce blood cholesterol, ACE inhibitors to lower blood pressure, diuretics to reduce fluid retention, and so forth. The data to date strongly suggests that many reasonable polypill combinations will improve upon single medication use, and possibly do so at lower overall doses, and thus with lower side-effects.

Here, researchers report on a recent large clinical trial of a polypill, carried out in a comparatively poor population who are largely without access to the panoply of medications available in wealthier regions. The effect size is about what one would expect: in the world of the immediate past in which no-one was trying to tackle the causes of aging, and thus comparatively little can be achieved, reductions in blood cholesterol and blood pressure have been outstanding successes. Reducing cardiovascular mortality by a third without in any way addressing the underlying causes of cardiovascular mortality is quite the feat. In the immediate future, when senolytic drugs and other therapies that do address the causes of aging start to become widely used, we should expect to see much larger beneficial changes in population health.

Four-in-one pill prevents third of heart problems

A daily pill containing four medicines can cut the number of heart attacks and strokes by a third, a study shows. The polypill contains blood-thinning aspirin, a cholesterol-lowering statin, and two drugs to lower blood pressure. The researchers said the pill had a huge impact but cost just pennies a day. They suggest giving it to everyone over a certain age in poorer countries, where doctors have fewer options and are less able to assess individuals.

The study was based in more than 100 villages in Iran and about 6,800 people took part. Half the people were given the polypill and advice on how to improve their lifestyle, with the other half just getting the advice. After five years there were 202 major cardiovascular events in the 3,421 people getting the polypill and 301 in the 3,417 not getting the pill. The polypill led to large reductions in bad cholesterol but had only a slight effect on blood pressure, the study showed. The drug was given to people over the age of 50 whether they had had a previous heart problem or not.

In the UK and other wealthier countries doctors have the time to assess the needs of individual patients and a wide choice of different drugs, such as statins, to chose from. "In the UK, the advantages would be more marginal and you would probably want a clinical trial to see any benefits over what is offered at the moment."

Effectiveness of polypill for primary and secondary prevention of cardiovascular diseases (PolyIran): a pragmatic, cluster-randomised trial

The PolyIran study was a two-group, pragmatic, cluster-randomised trial nested within the Golestan Cohort Study (GCS), a cohort study with 50,045 participants aged 40-75 years from the Golestan province in Iran. Clusters (villages) were randomly allocated (1:1) to either a package of non-pharmacological preventive interventions alone (minimal care group) or together with a once-daily polypill tablet (polypill group). Randomisation was stratified by three districts (Gonbad, Aq-Qala, and Kalaleh), with the village as the unit of randomisation.

The non-pharmacological preventive interventions (including educational training about healthy lifestyle - eg, healthy diet with low salt, sugar, and fat content, exercise, weight control, and abstinence from smoking and opium) were delivered by the PolyIran field visit team at months 3 and 6, and then every 6 months thereafter. Two formulations of polypill tablet were used in this study. Participants were first prescribed polypill one (hydrochlorothiazide 12.5 mg, aspirin 81 mg, atorvastatin 20 mg, and enalapril 5 mg). Participants who developed cough during follow-up were switched by a trained study physician to polypill two, which included valsartan 40 mg instead of enalapril 5 mg. Participants were followed up for 60 months. The primary outcome - occurrence of major cardiovascular events (including hospitalisation for acute coronary syndrome, fatal myocardial infarction, sudden death, heart failure, coronary artery revascularisation procedures, and non-fatal and fatal stroke) - was centrally assessed by the GCS follow-up team.

We enrolled 6838 individuals into the study - 3417 (in 116 clusters) in the minimal care group and 3421 (in 120 clusters) in the polypill group. During follow-up, 301 (8.8%) of 3417 participants in the minimal care group had major cardiovascular events compared with 202 (5.9%) of 3421 participants in the polypill group (adjusted hazard ratio [HR] 0.66). When restricted to participants in the polypill group with high adherence, the reduction in the risk of major cardiovascular events was even greater compared with the minimal care group (adjusted HR 0.43). The frequency of adverse events was similar between the two study groups.

The maintenance processes of autophagy recycle damaged structures and protein machinery in the cell. Autophagy is influential on the course of aging, as illustrated by the fact that many of the interventions capable of slowing aging in animal models involve increased autophagic activity. Some, like calorie restriction, have been demonstrated to require autophagy in order to extend healthy life span. Further, autophagy declines with age, and this is associated with the progression of a range of age-related diseases. Better maintenance of cells means better function of tissue and a slower onset of age-related dysfunction. The research community spends a great deal of time and effort in the investigation of autophagy and how to adjust its operation, but for all that, comparatively little concrete progress has been made towards clinical therapies that upregulate autophagy in humans.

Changes of the skin belong to the most recognizable signs of aging. Accordingly, skin aging is a major area of interest for cosmetic and skin care industries. From the medical viewpoint, aging of the skin is associated with health problems including increased skin fragility, delayed wound healing, and the increased occurrence of skin cancers, the most abundant types of malignancies in humans. For a long time it has been recognized that the rate of skin aging is determined by intrinsic and extrinsic drivers, but only recent advances in skin gerontology have helped to dissect the molecular and cellular processes that underlie the aging of the skin.

Several of the aging processes are triggered or enhanced by the presence of damaged molecules and organelles within cells, and their turnover is controlled partly by autophagy. Besides proteostasis and organelle maintenance, other factors that are accepted hallmarks of aging, such as nutrient sensing and genomic instability are under the control of or elicit the activation of autophagy, making autophagy a major counter-regulatory process that supports skin homeostasis and healthy aging.

The skin provides several examples to illustrate the two main interactions between autophagy and aging: (1) Autophagy decreases the rate of aging and (2) the activity of autophagy declines during aging. Autophagy suppresses aging in a cell-autonomous manner by maintaining intracellular homeostasis and in a non-autonomous manner by contributing to various cell features that protect other cells. For instance, autophagy supports the differentiation of epithelial cells which allows them to protect other cells against the external environment. Since autophagy achieves the removal and recycling of intracellular material only to a certain extent, potential toxic cell components and dysfunctional lysosomes tend to accumulate during the life-time of cells. Some of the compromised cells succumb to cell death whereas others remain alive but lose their capacity to execute intracellular processes, including autophagy, with full efficiency. Loss and dysfunction of cells manifest in aging.

Long-lived and mostly quiescent stem cells require autophagy for intracellular homeostasis and for continuous ability to supply functional progeny cells. Inherent decline or exogenous suppression of autophagy leads to stem cell loss by competition, differentiation, or cell death. In short-lived differentiating cells, autophagy also contributes to intracellular homeostasis, however, autophagic activity needs to be maintained only over a short time for these cells to be functional. Nevertheless, autophagy defects can be inherited from the long-lived precursor cells (stem cells) and potentially compromise processes such as the defense against microbes, the release of cytokines, and most importantly, the protection against stress factors from the environment. In long-lived differentiated cells, autophagy contributes to the maintenance of cell survival and function. A decrease of autophagy leads to the accumulation of damaged or even toxic components and/or energy crisis. These disturbances of intracellular homeostasis impair the processes essential for cell functions and eventually lead to a loss of these cells.

Link: https://doi.org/10.3389/fcell.2019.00143

One of the Juvenescence founders is here enthusiastic about the potential for treating aging as a medical condition. While one should always filter the remarks of people who run companies via a cynical view of their incentives, as talking up the company, the industry, and the prospects is very much expected, it is in fact the case that the longevity industry as a whole has tremendous potential. It will up-end the whole of healthcare, all expectations of what it means to be older, and will most likely become the largest industry on the planet. It will alleviate more suffering, pain, and death than any other human endeavor to date, by a very large margin.

Exactly which of the specific projects and companies will turn out to produce the lion's share of the benefits is hard to predict in advance. That said, I am of course willing to argue that following the SENS methodology of repairing underlying damage is going to be far more effective, on balance, than interventions that target downstream metabolic states or processes. Thus of the present set of approaches, senolytic therapies to clear senescent cells seem far more likely to change the world significantly than is the case for, say, mTOR inhibitors that mimic some of the effects of calorie restriction.

Earlier this year, an executive from Juvenescence-backed AgeX predicted the field of longevity will eventually "dwarf the dotcom boom." Greg Bailey, the UK-based anti-aging biotech's CEO, certainly hopes so. The business of anti-aging is gaining steam - Bank of America has forecast the market will balloon to $610 billion by 2025, from an estimated $110 billion currently - but investors are cautious.

"I think there's a huge amount of skepticism. There's an enormous number of charlatans ... I understand why they would be thinking you know, is this real? Walk into your local drugstore, you're going to see about 50 products that claim to be anti-aging, and I can assure you that none of them are." Bailey suggested that investors are not quite as enthusiastic about placing bets on anti-aging, as they are in the tech world. "Institutions tend to move in lockstep when they're investing. VCs are astonishing, you know, if one of them buys the yellow halter top, all of them have to buy a yellow halter top. We're dramatically underserved. It's not getting the exposure that tech gets, considering the size of the market. There is a disconnect on what investors - sophisticated investors - institutions, how they're viewing this, I don't think they quite grasp how fast this is going to happen, and how big it's going to be."

Juvenescence has now raised $165 million in the last 18 months - in January it unveiled the first $46 million tranche of the Series B - and the money is being used to fund longevity projects with the lofty goal of extending human lifespans to 150 years. It is a popular vision. Inspired by Juvenescence, venture capitalist Sergey Young - who is in charge of all things longevity at the non-profit XPRIZE and VC fund BOLD Capital Partners - unveiled a $100 million fund with the same goal in February. Google-owned stealthy biotech Calico is after the same prize - and has partnered with AbbVie.

Juvenescence has been busy, collaborating with different groups and setting up joint ventures, such as Alex Zhavoronkov's AI shop at Insilico Medicine - and has invested in firms including AgeX and LyGenesis. In February, Juvenescence debuted an anti-aging joint venture with the Buck Institute dedicated to inducing ketosis. In recent months, it spawned a new biotech called Souvien Therapeutics, which is developing medicines to address the epigenetic underpinnings of neurodegenerative diseases, and injected $6.5 million in equity financing into a preclinical metabolic disease biotech dubbed BYOMass. Juvenescence will maintain a focus on regeneration. "I'm mindful that if you live to 150, you know, people don't want to be all wrinkled, and in a wheelchair. So what we want to be able to do is regenerate tissues."

Link: https://endpts.com/healthier-longer-lifespans-will-be-a-reality-sooner-than-you-think-juvenescence-promises-as-it-closes-100m-round/

Numerous research and development initiatives have emerged from the heterochronic parabiosis studies of the past decade or more, in which an old and a young mouse have their circulatory systems linked. Researchers have moved on from the initial experiments to the search for circulating factors in blood that change in ways that are harmful in aged individuals, and which might be adjusted to improve cell and tissue function. This area of research is one of many to explore the question of how much of degenerative aging is the result of (a) direct consequences of molecular damage versus (b) the result of inappropriate cellular reactions to the existence of damage, the latter mediated to some unknown degree by signaling carried in the bloodstream.

Is it possible to ignore the damage and extend healthy life just by suppressing the reactions to damage? It would be very strange if the answer were that this works comprehensively and damage never has to be repaired. Further, the consequences of any given form of underlying damage can be thought of as a network of diverse chains of cause and effect spreading from a single root: it will require far more work to identify and address all of these reactions to damage than to focus down on a means of repairing the damage. Still, and unfortunately, the concept of damage repair, striking at the root of aging, remains a comparatively unpopular strategy in the research community for some reason. Near all work on the treatment of aging is focused on tinkering with the downstream consequences of damage, and therefore probably a highly inefficient use of funds and time, even given the successes that arise.

One of the more noted scientific teams involved in parabiosis research here report on their recent work, opening this open access paper with a bold statement on the degree to which they believe aging to result from signaling changes, reactions to damage. They are focusing down on just a few signaling factors in the bloodstream, TGF-β and oxytocin, and finding ways to alter amounts in circulation in comparative isolation, without adjusting other factors as well. Given that earlier work on GDF-11 as circulating signal involved in cellular responses to aging has resulted in a great deal of ongoing research and at least one biotech startup, the results here seem interesting enough to drawn in funding for further, similar projects.

Rejuvenation of brain, liver and muscle by simultaneous pharmacological modulation of two signaling determinants, that change in opposite directions with age

We hypothesize that altered intensities of a few morphogenic pathways account for most or all the phenotypes of aging. In heterochronic parabiosis, a young and old animal are surgically connected to share a common blood circulation. Experiments in mice showed this shared circulatory milieu restored tissue health and regeneration of the old partner; and at the same time, the young partner experienced a regenerative decline in a number of tissues. However, parabiosis is not clinically translatable and infusion of young blood or plasma into old mammals is controversial and fraught with multiple side-effects. Blood fractionation is typically cumbersome, and it is inherently complicated by the fact that the rejuvenative activities are likely to be contained in multiple molecularly different fractions. Plus, the assays for determining such activity are themselves complex, thus adding to the hurdles of a screen for active blood molecules. With these observations to consider, what would be the key set of molecular parameters that were changed by the blood heterochronicity and what would be the best translational way forward?

The changes that manifest with aging include altered cell metabolism, increased Reactive Oxygen Species (ROS), inflammation, senescence, and decline in immune function. However, from the viewpoint of tissue maintenance and regeneration, we postulated that these arise from changes in tissue growth and homeostasis and specifically in key signaling networks regulating stem cells and their differentiated niches. In support of this idea, pathway modifier-based approaches for the enhancement of aged tissue repair and maintenance have been reported, for example, by systemic delivery of OT which induces MAPK/pERK signaling, by forced activation of Notch-1, by antagonism of TGF-beta/pSmad signaling, or by antagonism of the Jak/Stat pathway.

The highest risk from modulating key cell-fate regulatory signaling pathways come from changing levels too far above or too far below normal healthy levels. Such drastic alterations result in severe multi-tissue side-effects. But high levels of a single modifier might be required to overcome the many age-specific molecular changes. For example, ectopic oxytocin (OT) might be needed at a considerably high dose to overcome age-elevated TGF-beta 1. And, the Alk5 inhibitor (Alk5i) of the TGF-beta receptor might be needed at high dose to overcome the lack of OT and other hormones with age.

Using a two-prong approach of simultaneously diminishing TGF-beta signaling and adding OT (which activates pERK via the oxytocin receptor (OTR)), we were able to reduce the required dose of Alk5i, shorten the duration of treatment and to achieve a more broad rejuvenation of the three germ-layer derivative tissues: brain, liver and muscle. And, we found that Alk5i+OT downregulated the number of cells that show an age-associated increase of the cyclin dependent kinase (CDK) inhibitor and marker of senescence, p16, thereby representing a pharmacological combination of two FDA approved drugs to normalize this checkpoint protein, which when chronically elevated negatively impacts tissue health.

Translationally, this study points toward a pharmacological approach to rapidly enhance the health and maintenance of multiple old tissues. Here we focused on a few key age-related parameters of the three germ layer tissues: neurogenesis and neuroinflammation of the brain, regeneration and fibrosis of the skeletal muscle and adiposity and fibrosis of the liver. In future work if would be interesting to study how these seemingly unrelated aging features become rapidly rejuvenated by A5i+OT, and if additional phenotypes, such as muscle innervation, neural plasticity, metabolism, etc. also become improved in old animals. The observed rejuvenating effects are at least as robust as, and act faster than, heterochronic parabiosis.

One of the major challenges in aging research is determining whether or not models of cellular or organismal damage and its consequences are in any way relevant to the natural processes of aging. One can hit a brick with a hammer, but that says very little about how bricks weather over the years. One can hit the brick very carefully with the hammer in ways that produce results that look weathering-like, but can that be used to tell us anything about weathering? In cells the line between artificial and natural damage can be hard to pin down, but the fine details of the processes involved always matter. It is easy to break cells and see them become dysfunctional as a result, but hard to determine the relevance of that breakage to natural aging. Even in the example here, in which researchers are trying to achieve something very similar to the consequences of excessive oxidative damage in mitochondria that is observed in aging, it is possible to argue that the methodology used has little relevance to the actual damage of aging in its details, and therefore may not be a useful model.

Researchers have carried out a causal experiment to kick off a mitochondrial chain reaction that wreaks havoc on the cell, all the way down to the genetic level. "I like to call it 'the Chernobyl effect' - you've turned the reactor on and now you can't turn it off. You have this clean-burning machine that's now polluting like mad, and that pollution feeds back and hurts electron transport function. It's a vicious cycle." The researchers used a new technology that produces damaging reactive oxygen species - in this case, singlet oxygen - inside the mitochondria when exposed to light. "That's the Chernobyl incident. Once you turn the light off, there's no more singlet oxygen anymore, but you've disrupted the electron transport chain, so after 48 hours, the mitochondria are still leaking out reactive oxygen - but the cells aren't dying, they're just sitting there erupting."

At this point, the nucleus of the cell is being pummeled by free radicals. It shrinks and contorts. The cell stops dividing. Yet, the DNA seems oddly intact. That is, until the researchers start looking specifically at the telomeres - the protective caps on the end of each chromosome that allow them to continue replicating and replenishing. Telomeres are extremely small, so DNA damage restricted to telomeres alone may not show up in a whole-genome test, like the one the researchers had been using up to this point. So, to see the genetic effects of the mitochondrial meltdown, the researchers had to light up those tiny endcaps with fluorescent tags, and lo and behold, they found clear signs of telomere fragility and breakage. Then, in a critical step, the researchers repeated the whole experiment on cells with inactivated mitochondria. Without the mitochondria to perpetuate the reaction, there was no buildup of free radicals inside the cell and no telomere damage.

Link: https://www.upmc.com/media/news/082619-pnas-van-houten

Excess visceral fat tissue leads to chronic inflammation via a range of mechanisms that include the creation of more senescent cells than would otherwise exist. Senescent cells secrete a potent mix of inflammatory and other signals that degrade tissue function in many ways. Since the accumulation of lingering senescent cells is a cause of aging, being overweight doesn't just increase risk and severity of age-related disease, and shorten life expectancy, but also literally accelerates aging. The more fat tissue, the worse the outcome over the long term. As this paper points out, however, this is only the case for excess visceral fat tissue. When lean, the normal, smaller amounts of this tissue are actually anti-inflammatory and beneficial.

Adipose tissue is host to various immune cells and it is well established that during obesity, the amount of inflammatory macrophages increase in adipose tissue. Visceral adipose tissue (VAT), surrounding the inner organs, has been shown to be more inflammatory active than subcutaneous adipose tissue (SAT), as increased amounts of visceral/abdominal fat associates with high levels of circulating inflammatory markers and a high number of pro-inflammatory cells in their adipose tissue.

Interestingly, in human and rodent studies, ageing is associated with an increase in the amount of visceral adipose tissue and/or level of inflammation. It is, however, unclear to what extent these age-related changes are a result of ageing per se or rather the result of changes in life-style with e.g. reduced levels of physical activity without a corresponding reduction in caloric intake. A human cross sectional study reported that whereas ageing is associated with increased inflammation, life-long endurance training resulted in lower circulating levels of inflammatory markers in both young and elderly individuals.

In the current study, we wanted to investigate the inflammatory status and tissue integrity of VAT in an exercise-training model of lean adult and old mice. We randomized adult (11 months; n = 21) and old (23 months; n = 27) mice to resistance training or endurance training, or to a sedentary control group. Strikingly, we observed an anti-inflammatory phenotype in the old mice, consisting of higher accumulation of anti-inflammatory M2 macrophages and IL-10 expression, compared to the adult mice. In concordance, old mice also had less VAT mass and smaller adipocytes compared to adult mice. In both age groups, exercise training enhanced the anti-inflammatory phenotype. In conclusion, in the absence of obesity, visceral adipose tissue possesses a pronounced anti-inflammatory phenotype during aging which is further enhanced by exercise.

Link: https://doi.org/10.1038/s41598-019-48587-2

Today's research is a comparison of alternate day fasting and calorie restriction in human subjects. Or rather, I think, one might look on it as an examination of alternate day fasting as an alternative approach to achieving calorie restriction. The type of alternate day fasting here is the better form, in which 36 hours are spent fasting, only eating in a 12 hour window every other day. In practice that means eat normally one day, then fast until the morning two days later. This tends to reduce average calorie intake down to something very similar to a straight calorie restricted diet. That calorie restricted diet might be 1500 kcal/day for an averagely sized human being, and I can assure you that it is very, very hard to eat more than 3000 kal in a 12 hour period, at least not without resorting to heavy duty junk food.

So is alternate day fasting just calorie restriction? In animal studies there are significant differences in gene expression profiles between these two approaches, which is enough to suspect that perhaps fasting and feeding versus a consistent low calorie intake are two different beasts. The effects on metabolism are sweeping in either case, which makes analysis challenging, but the important mechanisms, the upregulation of cellular stress response systems such as autophagy, appear the same. More recent research into fasting mimicking diets has attempted to find the point at which low calorie intake triggers benefits, and quantify how long the low calorie diet must be sustained. The results there suggest that additional benefits emerge after three to four days, in terms of a culling of immune cells. That work also suggests that the process of refeeding after a fast is necessary in order to obtain the full benefits.

So it is possible that neither alternate day nor straight calorie restriction are strictly optimal, and something more intermittent would be better. Still, either alternate day or calorie restriction are such a huge improvement over the dietary choices adopted by most people that it seems almost foolish to spend much time on further optimization. This is particularly true when that time and energy could be put towards advancing the development of rejuvenation therapies capable of turning back aging in ways that no amount of fasting can achieve.

Not Eating for 36 Hours Is Shown to Be a Surprisingly Sustainable Diet, Study Shows

New research outlines a novel way to intermittently restrict calorie intake, a method that achieves the same health benefits while possibly being more manageable than constantly restricting calories. An international team of researchers presented the results of a clinical trial in which "alternate day fasting" resulted in reduced calorie intake, reduced body mass index, and improved torso fat composition. Known as "ADF," it is a diet regimen in which adherents avoid all food and caloric beverages for 36 hours, then eating whatever they want for 12 hours - donuts, cookies, dumpster pizza, whatever.

In this randomized controlled trial, 30 non-obese volunteers who had done ADF for at least six months were compared over a 4-week period to 60 healthy control subjects. While the results of this clinical trial show that ADF had similar health benefits to caloric restriction, even though the "feast days" could include a lot of unhealthy calories. The researchers also write that ADF has some distinct advantages over CR. Mainly, they say it may be easier to maintain the habit.

Previous work on intermittent fasting has shown that restricting an animal's calories - without depriving them of adequate nutrition, of course - can increase their lifespan, though much of the work has been limited to monkeys and other non-human animals. This latest study builds on that existing research by following a mid-sized human cohort for enough time to show not just significant benefits but also no negative side effects.

Alternate Day Fasting Improves Physiological and Molecular Markers of Aging in Healthy, Non-obese Humans

Caloric restriction and intermittent fasting are known to prolong life- and healthspan in model organisms, while their effects on humans are less well studied. In a randomized controlled trial study, we show that 4 weeks of strict alternate day fasting (ADF) improved markers of general health in healthy, middle-aged humans while causing a 37% calorie reduction on average. No adverse effects occurred even after more than 6 months.

ADF improved cardiovascular markers, reduced fat mass (particularly the trunk fat), improving the fat-to-lean ratio, and increased β-hydroxybutyrate, even on non-fasting days. On fasting days, the pro-aging amino-acid methionine, among others, was periodically depleted, while polyunsaturated fatty acids were elevated. We found reduced levels sICAM-1 (an age-associated inflammatory marker), low-density lipoprotein, and the metabolic regulator triiodothyronine after long-term ADF. These results shed light on the physiological impact of ADF and supports its safety. ADF could eventually become a clinically relevant intervention.

Mitochondria in cells throughout the body become dysfunctional with age, with the proximate cause of this issue being a decline in the quality control mechanisms responsible for clearing out damaged and worn mitochondria. Researchers here show that the increased levels of reactive oxygen species produced by mitochondria in aged smooth muscle cells is important in the stiffening of blood vessels that occurs with advancing age. This loss of the ability of blood vessels to appropriately constrict and relax in response to circumstances leads to hypertension, a chronic state of raised blood pressure that is very damaging over the long term. In this context, it is worth noting that a clinical trial of a mitochondrially targeted antioxidant showed improvement in smooth muscle function and consequent reduction in blood vessel stiffness.

Aging is characterized by increased aortic stiffness, an early, independent predictor and cause of cardiovascular disease. Oxidative stress from excess reactive oxygen species (ROS) production increases with age. Mitochondria and NADPH oxidases (NOXs) are two major sources of ROS in cardiovascular system. We showed previously that increased mitochondrial ROS levels over a lifetime induce aortic stiffening in a mouse oxidative stress model. Also, NADPH oxidase 4 (NOX4) expression and ROS levels increase with age in aortas, aortic vascular smooth muscle cells (VSMCs), and mitochondria, and are correlated with age-associated aortic stiffness in hypercholesterolemic mice.

The present study investigated whether young mice (4 months-old) with increased mitochondrial NOX4 levels recapitulate vascular aging and age-associated aortic stiffness. We generated transgenic mice with low (Nox4TG605; 2.1-fold higher) and high (Nox4TG618; 4.9-fold higher) mitochondrial NOX4 expression. Young Nox4TG618 mice showed significant increase in aortic stiffness and decrease in phenylephrine-induced aortic contraction, but not Nox4TG605 mice. Increased mitochondrial oxidative stress increased intrinsic VSMC stiffness, induced aortic extracellular matrix remodeling and fibrosis, a leftward shift in stress-strain curves, decreased volume compliance and focal adhesion turnover in Nox4TG618 mice.

Nox4TG618 VSMCs phenocopied other features of vascular aging such as increased DNA damage, increased premature senescence and replicative senescence and apoptosis, increased proinflammatory protein expression and decreased respiration. Aortic stiffening in young Nox4TG618 mice was significantly blunted with mitochondrial-targeted catalase overexpression. This demonstration of the role of mitochondrial oxidative stress in aortic stiffness will galvanize search for new mitochondrial-targeted therapeutics for treatment of age-associated vascular dysfunction.

Link: https://doi.org/10.1016/j.redox.2019.101288

It is becoming clear that dysfunction in the supporting immune cells of the brain, the microglia, is important in the progression of neurodegenerative conditions such as Alzheimer's disease. This certainly involves microglia becoming senescent, as demonstrated by the ability of senolytic treatments to reverse pathology in animal models of Alzheimer's disease. But it most likely also involves a more subtle shift in the behavior of microglia, from a more regenerative M2 polarization to a more inflammatory and aggressive M1 polarization.

Both classes of microglial behavior are necessary in the grand scheme of things, but aging appears to be accompanied by an excess of M1 and too few M2 microglia (and macrophages as well, which have a similar set of behaviors) in most circumstances and tissues examined to date. The causes of this shift in cell behavior are barely explored at this point; it is unclear how it relates to the underlying molecular damage that drives aging. Nonetheless, it is certainly harmful.

Alzheimer's disease (AD) is a progressive, age-related neurodegenerative disorder thought to be triggered by the appearance and build-up of amyloid-β (Aβ) plaques in the cortex. Genome-wide association studies have identified numerous genes that confer increased risk for developing the disease; however, the mechanisms underlying plaque formation remain unclear. Within the central nervous system (CNS), microglia perform homeostatic maintenance, immune-related, and phagocytic functions. Their reported capacity for Aβ phagocytosis and clearance led to the suggestion that age-related changes in microglial function reduce clearance of neuronally derived Aβ from the brain, thus allowing plaque formation.

We and other groups report that following the initial period of plaque formation, microglia surround the plaques and subsequently mount a harmful and non-resolving inflammatory response. Despite this response, however, Aβ clearance and plaque modulation/dynamics is unaffected, yet the removal of the microglia at advanced stages of pathology protects against synaptic and neuronal loss.

Here, we set out to explore the contributions of microglia to plaque formation in the initial stages of the disease, which requires prolonged depletion of microglia throughout the plaque-forming period. To that end, we designed, synthesized, and optimized a potent, specific, orally bioavailable, and brain-penetrant CSF1R inhibitor, PLX5622, to deplete microglia for more than 6 months in 5xFAD mice. With the elimination of microglia, we uncovered critical roles of these cells in plaque formation, compaction, and growth, mitigating neuritic dystrophy, and modulating hippocampal neuronal gene expression in response to Aβ pathology.

Ultimately, these data demonstrate that microglial elimination is associated with the prevention of plaque formation and the downregulation of hippocampal neuronal genes that occur in a preclinical model of AD progression. These results indicate that microglia appear to contribute to multiple facets of AD etiology - microglia appear crucial to the initial appearance and structure of plaques, and following plaque formation, promote a chronic inflammatory state modulating neuronal gene expression changes in response to Aβ/AD pathology.

Link: https://doi.org/10.1038/s41467-019-11674-z

Apolipoprotein E (APOE) is a well studied gene, given that variants are associated with a greater risk of developing Alzheimer's disease. That said, high blood pressure and high blood cholesterol levels are just as important as risk factors for Alzheimer's disease when compared against all but the worst APOE variant, APOE4. Looking beyond Alzheimer's, in most cases lifestyle choices and their consequences on the operation of metabolism, particularly becoming overweight, have larger effects on risk of age-related disease than genetic variants. The common wisdom of a 75%/25% split between environment and genetics respectively in the matter of age-related disease and mortality may be overestimating the contribution of genetics, per more recent data.

The point of investigating the activities of specific protein variants in which risk or scope of age-related is shifted is this: that the work may lead towards points of effective intervention. Not the gene or protein itself, usually, but something in the mechanisms with which it interacts. The late stages of all age-related conditions are enormously complex, and having the example of differences that affect the progression of the condition can help to pin down which of the many, many possible metabolic processes are most important. That is somewhat in evidence in the research materials here, but of course says nothing about how to effectively target those important mechanisms.

Rare Luck: Two Copies of ApoE2 Shield Against Alzheimer's

Mention ApoE and Alzheimer's, and the conversation turns to the E4 allele, the strongest susceptibility gene for the disease. But ApoE has another side, in ApoE2. Though this isoform protects against AD, scientists have barely studied it. Now ApoE2 is attracting scrutiny as scientists are asking exactly how some people maintain their mental acuity into old age. A study of ApoE genotypes in 5,000 autopsy-confirmed cases of AD revealed that people with two copies of E2 see their risk of dementia plummet by a stunning 90 percent compared with those with the common E3/E3 genotype. Other work suggested that this could be because ApoE2 reduces amyloid and tau pathology, and boosts gray-matter volume in critical brain regions. E2's benefits seem specific to Alzheimer's, not generic to neurodegeneration.

ApoE is the major cholesterol-carrying protein in the brain. It has been studied since its discovery as an AD risk gene in the early 1990s, but is newly emerging as a hub for glial responses to amyloid and tau aggregate deposition. The gene exists as three polymorphic alleles - E2, E3, and E4 - with a worldwide frequency of 8 percent, 78 percent, and 14 percent, respectively. Several mutated forms are also known. ApoE4 receives by far the most attention from AD researchers, because it boosts the risk of AD up to 15-fold depending on the study population, and occurs in 40 percent of people with AD. E2, the protective allele, has received scant attention, because it is the least common of the three and largely absent from AD samples.

ApoE4 Glia Bungle Lipid Processing, Mess with the Matrisome

It is suggested that ApoE4 predisposes people to Alzheimer's disease by modulating astrocytes and microglia. Researchers describe transcriptional differences between iPSC-derived human astrocytes and microglia that express ApoE4/4 or ApoE3/3. The ApoE4/4 glia generated more cholesterol than their E3/3 counterparts. They exported and degraded it poorly, causing lipid to build up inside them. The E4/4 glia also pumped out greater amounts of proinflammatory cytokines and extracellular matrix proteins than E3/3s.

Does this have anything to do with Alzheimer's? Lo and behold, in Alzheimer's disease brains, astrocytes and microglia behaved quite similarly to these ApoE4/4 glia. They accumulated lipid and ratcheted up inflammation. Importantly, they did so regardless of their ApoE genotype. The data imply that ApoE4 may nudge microglia and astrocytes toward an Alzheimer's-like state. Perhaps faulty lipid metabolism is one of the earliest changes on the path to Alzheimer's. If so, restoring glial lipid regulation could be a therapeutic approach.

The accumulation of lingering senescent cells is a cause of aging, via the inflammatory and other signals secreted by these cells. This is now widely accepted in the research community, and the first senolytic drugs that can selectively clear some of the burden of senescent cells already exist. Unfortunately it is not yet widely appreciated that these first low cost rejuvenation therapies do in fact exist, and are easily obtained and used. Hundreds of millions of people suffer from inflammatory conditions of aging that can likely be effectively treated via even just a single dose of senolytic drugs. Producing more human data for these existing treatments and bringing them to the vast patient population who would benefit should be much more of a priority than it is today.

Given that any new understanding of the biochemistry of senescent cells might lead to a novel basis for therapies that can greatly improve health in old age, there is a great deal of funding these days for efforts to map the biochemistry of the senescent state. These efforts are giving rise to new startup biotech companies, a few every year, and new candidate small molecule senolytics at an accelerated rate. Here, researchers announce a new database of genes associated with cellular senesence, one of a number of scientific initiatives likely to accelerate progress towards a full understanding of the biochemistry of senescent cells.

Cellular senescence, a permanent state of replicative arrest in otherwise proliferating cells, is a hallmark of ageing and has been linked to ageing-related diseases like cancer. Senescent cells have been shown to accumulate in tissues of aged organisms which in turn can lead to chronic inflammation. Many genes have been associated with cell senescence, yet a comprehensive understanding of cell senescence pathways is still lacking. To this end, we created CellAge, a manually curated database of 279 human genes associated with cellular senescence, and performed various integrative and functional analyses.

We observed that genes promoting cell senescence tend to be overexpressed with age in human tissues and are also significantly overrepresented in anti-longevity and tumour-suppressor gene databases. By contrast, genes inhibiting cell senescence overlapped with pro-longevity genes and oncogenes. Furthermore, an evolutionary analysis revealed a strong conservation of senescence-associated genes in mammals, but not in invertebrates.

Using the CellAge genes as seed nodes, we also built protein-protein interaction and co-expression networks. Clusters in the networks were enriched for cell cycle and immunological processes. Network topological parameters also revealed novel potential senescence-associated regulators. We then used siRNAs and observed that of 26 candidates tested, 19 induced markers of senescence. Overall, our work provides a new resource for researchers to study cell senescence and our systems biology analyses provide new insights and novel genes regarding cell senescence.

Link: https://doi.org/10.1101/743781

Presbyopia in the aging eye manifests as a difficulty in focusing on close objects. It is caused by hardening of the lens, which is in part the result of cross-linking in the extracellular matrix of that tissue, though other mechanisms are involved as well. Cross-links are hardy metabolic byproducts resulting from the normal operation of metabolism, capable of degrading the structural properties of tissue, particularly elasticity, by linking proteins together and restricting their motion. Cross-linking is likely of great importance in skin aging and cardiovascular aging. The primary age-related cross-links of the lens are not the same as those of other soft tissues in the body, however: disulphide bonds rather than glucosepane. So this research is interesting for all of us heading towards older age and dysfunctional vision, but only in the context of dysfunctional vision. As a first attempt, there is clearly some room for improvement in the degree to which the approach taken breaks cross-links, but, given this proof of principle, that further improvement should follow in the years ahead.

A new topical agent is coming closer than ever to improving the accommodative range for presbyopes. The agent, lipoic acid choline ester (UNR844, Novartis, formerly EV06), is a reducing agent that is purported to reduce the disulfide bonds that form between lens proteins, thus increasing the deformability of the crystalline lens. "This chemical was designed to improve the internal rheology of the cytosol within the lens fibers inside the lens capsule. It is safe, well-tolerated, and showed statistically significant near visual acuity improvement in clinical trials compared to placebo. The widespread use of this drug stands to radically alter the visual performance of humans within our lifetimes."

Presbyopia is not just a matter of lens compliance. It is caused by a few different events, each of which constitutes a potential treatment target: the crystalline lens enlarges over time (ectoderm), the ciliary body undergoes atrophic changes, the vitreous becomes less viscous, and the lens loses its flexibility. The hypothesis that drove the development of UNR844 addressed lens flexibility or the lack thereof in presbyopia. When lens proteins become oxidized over time, disulfide bonds form, rendering them less able to move relative to one another during the act of accommodation.

"The theory was that if we had a way to chemically reduce these disulfide bonds, the proteins would regain increased degrees of freedom and allow a greater range of deformation of the lens, translating into a greater dynamic range of accommodation." Lipoic acid is a naturally occurring antioxidant and reducing agent. To allow the reducing agent to achieve sufficient concentration within the eye, researchers developed a prodrug to improve the compound's penetration, allowing it to metabolize and convert to its active form (dihydrolipoic acid [DHLA]) once within the lens. DHLA reduces disulfide bonds between lens proteins and restores lens microfluidics. Proof of concept was confirmed in vitro with human cadaver lenses and in vivo in rabbit eyes, where in both trials the drug produced lens softening and an increase in lens deformability.

The Phase 1/2 clinical study evaluated safety and efficacy of EV06 ophthalmic solution 1.5% in improving distance corrected near visual acuity (DCNVA) in subjects with presbyopia. The prospective, randomized, double-masked, placebo-controlled study included 75 patients (45-55 years) with hyperopia, myopia, or emmetropia, and a diagnosis of presbyopia. At baseline, the study patients had DCNVA below 20/40 in each eye. The study drug was given for 91 days and patients were monitored during a 7-month follow-up period. Visual acuity improvements were most pronounced when subjects employed bilateral vision, with 84% achieving 20/40 bilateral vision or better versus 52% in the placebo group.

Link: https://www.eyeworld.org/has-presbyopia-found-encore

The authors of today's open access review paper focus on recent research into autophagy and aging, specifically work using flies as the model organism. Autophagy is the name given to a collection of cellular maintenance processes responsible for recycling damaged cell components, molecular machinery, and metabolic waste. In chaperone-mediated autophagy, selective chaperone proteins pick up other molecules and carry them to lysosomes for disassembly. In macroautophagy, unwanted cellular components are engulfed by an autophagosome, which then travels to a lysosome and fuses with it. In microautophagy, a lysosome engulfs the material to be recycled directly. A lysosome is always the end of the journey, where a mix of enzymes reduces structures and molecules into component parts suitable for reuse.

A sizable majority of the interventions proven to slow aging in short-lived laboratory species (such as flies) involve increased autophagy. Many, such as calorie restriction, do not produce benefits at all in the absence of functional autophagy. When cells are better maintained over time, with less outstanding molecular damage that can cause further downstream consequences, the outcome is a slower pace of decline into age-related dysfunction and disease. This has led to a wide range of research projects, and at least one startup biotech company, focused on trying to produce therapies capable of boosting the operation of autophagy to improve human health.

The plausible size of benefits resulting from an autophagy-based therapy can be seen by looking at the effects of regular exercise and calorie restriction in humans. Improved health is the outcome, but not a significant increase in life span. For evolutionary reasons, stress response mechanisms have a much greater relative impact on the life span of short-lived species. Mice live 40% longer when calorie restricted, while benefiting from boosted autophagy, while humans most certainly do not. This is most likely because seasonal famines last for a much larger proportion of a mouse life span, and the calorie restriction response evolved to increase fitness in this scenario.

On the Fly: Recent Progress on Autophagy and Aging in Drosophila

Besides the description of the characteristics of the aging process, the most significant finding of aging research is that aging now is considered to be a malleable process. The lifespan of organisms can be extended by both environmental and genetic traits and more importantly, their healthspan can simultaneously be improved during aging, which shows that it is possible to reach the ultimate goal of aging research. Recently, a growing body of evidence shows that alterations of autophagy, the main self-degradative process of eukaryotic cells, likely plays a central role in the aging process.

Observations in various organisms indicate that aging and autophagy have a bidirectional connection with each other. On one hand, autophagic degradation shows an age-dependent decline and impairment of autophagy contributes to the development of age-associated diseases. On the other hand, lifespan-extending interventions largely depend on the autophagy machinery for their beneficial effects on longevity. Strikingly, multiple longevity pathways seem to converge on autophagy, and genetic or environmental factors that affect lifespan through these pathways at least partly exert their effects via the modulation of autophagy. These observations point to the key role of autophagy in aging, and suggest that increased autophagy may compensate for at least some of the cellular hallmarks of aging. Thus, the housekeeping functions of autophagy can counteract the accumulation of cellular damage, which is considered to be a primary mechanism driving aging.

Studies in animal models including Drosophila revealed that autophagy defects lead to the rapid decline of neuromuscular function, neurodegeneration, sensitivity to stress (such as starvation or oxidative damage), and stem cell loss. Of note, recently identified human Atg gene mutations cause similar symptoms including ataxia and mental retardation. Physiologically, autophagic activity is known to decrease during aging, and this defect likely contributes to the development of such age-associated diseases. Many manipulations that extend lifespan (including dietary restriction, reduced TOR kinase signaling, exercise, or treatment with various anti-aging substances) require autophagy for their beneficial effect on longevity, pointing to the key role of this housekeeping process. Importantly, genetic (e.g., Atg8a overexpression in either neurons or muscle) or pharmacological (e.g., feeding rapamycin or spermidine to animals) promotion of autophagy has been successfully used to extend lifespan in Drosophila, suggesting that this intracellular degradation pathway can rejuvenate cells and organisms.

The liver is the most regenerative organ in mammals, capable of regrowing lost sections, albeit imperfectly in comparison to the capabilities of highly regenerative species such as salamanders. Researchers here demonstrate that the sex hormone estradiol is involved in the regulation of liver regeneration, and that regeneration can be accelerated via artificially increased levels of estradiol. This is particularly interesting in the context of recent work showing that loss of estradiol with aging is involved in loss of muscle mass, due to effects on stem cell activity. One might wonder if this sort of mechanism will show up in other tissues as well.

The endogenous hormone estradiol is widely recognized as a stress signaling molecule. It is mainly produced by the ovary, and its production can be induced under certain contexts and stimuli such as during the estrus cycle and in late pregnancy. Estradiol exerts its multiple functions by binding to GPR30, estrogen receptor (ER) α, or ERβ, which are members of the nuclear receptor super family.

Estradiol production is also induced after liver resection/injury, suggesting this hormone plays a role in liver regeneration. Several genes that participate in liver regeneration have been identified, including those encoding the inflammatory cytokines tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6). In particular, we have previously focused on the molecules essential for triggering liver regeneration after partial hepatectomy (PH) using mouse models. In addition to these cytokines, the production of the chemical hormone estradiol is also induced in the acute phase of liver injury after PH, via the ovary and testes.

We have further demonstrated that estrogen induces hepatocyte proliferation after PH, which was delayed by ovariectomy. This estradiol induction after PH was in turn found to induce ERα expression in the mainly periportal hepatocytes. Moreover, the WT mice showed transient steatosis during liver regeneration after PH. Therefore, we hypothesized that PH initially triggers estradiol production, leading to elevated ERα expression, to consequently initiate the processes of β-oxidation enzyme expression for anti-steatosis.

In the present study, we tested this hypothesis by analyzing the liver regeneration process in ERα knockout (KO) mice compared with that in their wild-type (WT) littermates. Estradiol administration accelerated liver regeneration through ERα, indicating the feasibility of the estrogen-ERα axis as a target. These findings establish the foundation for the therapeutic application of estradiol to accelerate liver regeneration after resection in clinical settings.

Link: https://doi.org/10.2147/CEG.S214196

Researchers have found that microglia in the aging brain have a tendency to accumulate lipids, and that those that do are harmful. This is a fascinating discovery, given that microglia are essentially the central nervous system version of macrophages elsewhere in the body, and lipid accumulation in macrophages leading to senescence and inflammatory behavior is an important mechanism in atherosclerosis. Further, it is well established that microglia in the brain become inflammatory, senescent, and dysfunctional in later life, and this behavior contributes to the progression of neurodegenerative conditions. It has been demonstrated that removing senescent microglia can turn back Alzheimer's pathology in mouse models of the condition, for example. This lipid accumulation might be an important aspect of dysfunction in microglia, though it is anyone's guess at this point as to where it sits in the web of cause and effect.

Microglia in the brain assume a dizzying array of states. Now researchers describe a new one: lipid droplet-accumulating microglia (LAM). These lipid-stuffed cells resemble the foamy macrophages seen in atherosclerotic lesions. They accumulate in the hippocampus of the aging brain and appear to be bad news, hiking inflammation and reactive oxygen species while having little ability to phagocytose debris. Notably, inflammatory stimuli induce LAM, as do some genetic variants associated with neurodegenerative disease.

Previous studies have identified a smorgasbord of distinct transcriptional profiles delineating subtypes of microglial states. A handful of these have been correlated with neurodegenerative disease. These include disease-associated microglia (DAM), which cluster around plaques in mouse models of amyloidosis, and the similar microglial neurodegenerative phenotype (MGnD) found in multiple mouse disease models. A recent study characterized human Alzheimer's microglia (HAM), which were isolated from the Alzheimer's brain. It is still unclear how all these types relate to each other and what they do.

While examining hippocampal sections from aged wild-type mice by electron microscopy, researchers were struck by the accumulation of lipid droplets inside microglia. These microglia resembled cells first described by Alois Alzheimer, who reported lipid-stuffed glia clustering around amyloid plaques in the Alzheimer's brain more than 100 years ago. Researchers quantified the phenomenon in mice, finding that more than half the hippocampal microglia in 20-month-old wild-type animals contained from one to three lipid droplets. Droplets were rare in other brain regions, and nearly absent in 3-month-old mice.

To characterize these LAM, the authors isolated microglia from aged mouse hippocampi and sorted out those with high lipid content. Transcriptional profiling revealed 692 genes that were differently expressed between cells with low and high lipid content. In particular, genes involved in the production of reactive oxygen species, lipids, and pro-inflammatory cytokines were up in LAM, while genes responsible for phagocytosis were down. Notably, this transcriptional profile was in many respects the opposite of DAM, which turn up phagocytotic genes.

Functional studies of LAM reinforced these transcriptional findings. When the authors injected myelin debris into aged mouse hippocampus, microglia without lipid droplets engulfed it, but few LAM did. LAM isolated from brain produced more reactive oxygen species (ROS) than did low-lipid microglia, and they secreted higher levels of several pro-inflammatory cytokines such as CCL3, CXCL10, and IL-6. How do these cells arise? Because many of the LAM genes are regulated by inflammation, researchers speculate that they are products of an inflammatory response.

Link: https://www.alzforum.org/news/research-news/newly-identified-microglia-contain-lipid-droplets-harm-brain

Calorie restriction is the best studied of all interventions shown to slow aging and extend life in short-lived laboratory species. In humans it produces significant health gains, somewhat greater than any established medical technology can provide to essentially healthy individuals, at least until the broader advent of senolytic drugs. Unfortunately, it does not extend life by any great degree in long-lived species such as our own. The response to calorie restriction serves to increase evolutionary fitness during periods of famine, increasing the odds of individuals surviving to reproduce once food is plentiful again. Seasonal famines are of a given length, long relative to a mouse life span, short relative to a human life span, so only the mouse evolves to live 40% longer in calorie restricted conditions.

The mechanisms by which calorie restriction produces benefits broadly overlap with those of fasting, and in recent years some research groups have made inroads in finding the 80/20 point of calorie intake in humans at which a low calorie intake produces most of the benefits of a zero calorie intake. Calorie restriction upregulates the operation of cellular maintenance processes such as autophagy and the unfolded protein response, which leads to better cell and tissue function over the long term. It also produces sweeping changes in the operation of cellular metabolism, but autophagy appears to be the critical mechanism that mediates effects on long term health and longevity.

Some of the effects of calorie restriction on metabolism are similar enough to aspects of diabetes for the state to be called pseudo-diabetes, or beneficial diabetes. Relatedly, mTOR inhibitors are used to mimic some of the effects of calorie restriction, and the first generation of such inhibitors have undesirable side-effects that are somewhat diabetes-like. In today's open access paper, the author argues that the research community too readily categorized the side-effects of mTOR inhibitor rapamycin as entirely harmful, those mediated by inhibition of the mTORC2 protein complex, and in fact much of it may be pseudo-diabetes and thus of benefit. I'm not sure that I entirely agree, but this is an interesting position, given that a strong focus in the present clinical development of mTOR inhibitor drugs is to find a way to avoid these specific effects by focusing on inhibition of only the mTORC1 protein complex rather than all activities of mTOR.

Fasting and rapamycin: diabetes versus benevolent glucose intolerance

In 2012, a paper entitled "Rapamycin-induced insulin resistance is mediated by mTORC2 loss and uncoupled from longevity" turned everything upside down. Data were misinterpreted to indicate rapamycin causes diabetes. Because the paper was published in a high profile journal, basic researchers believe that rapamycin is harmful and causes diabetes, which prompted calls for development of rapamycin-like drugs without rapamycin effects. In fact, however, this paper does not show that rapamycin causes type 2 diabetes; it shows that prolonged treatment with rapamycin causes glucose intolerance and insulin resistance in mice, which is in agreement with earlier studies. Furthermore, the study showed that these metabolic alterations were associated with increased longevity, indicating better health.

In humans, diagnosis of diabetes depends on the arbitrary choice of a threshold for fasting blood glucose: it was 140 mg/dl before 1997 and 126 mg/dl after 1997. But what is the arbitrary diagnostic threshold in mice? It is not defined. Is the slight increase in fasting glucose sufficient for a "diagnosis" of diabetes in mice? Does such hyperglycemia decrease life span or cause nephropathy? It does not. As we will discuss next, similar glucose intolerance and insulin resistance can also be caused by prolonged fasting and extreme very low calorie diet (VLCD). Prolonged fasting and starvation cause a condition well known in the past but unknown to modern researchers: starvation pseudo-diabetes.

During starvation or prolonged fasting, glucose utilization by nonbrain tissues is inhibited in order to feed the brain. Prolonged fasting is characterized by low insulin levels, gluconeogenesis, lipolysis, ketogenesis, and ketosis (ketone bodies in the blood), glucose intolerance, and hepatic resistance to insulin. When a starved animal is fed with glucose, it cannot utilize the glucose (glucose intolerance), leading to transient glycosuria (glucose in the urine) and polyuria (high urine volume).

Given that rapamycin is a starvation- or CR-mimetic, its metabolic effects can be viewed as "starvation-mimicking side effects." I advance the hypothesis that in animals (and humans) rapamycin can cause a reversible and benevolent condition, identical to starvation pseudo-diabetes. If so, this condition may, in theory, prevent development of genuine type 2 diabetes and its complications. For example, rapamycin prevents diabetic nephropathy. The results of recent studies are consistent with the idea that rapamycin-induced metabolic alterations are reversible and beneficial in nature. Hyperglycemia may be a marker of beneficial processes, given that rapamycin ameliorates nephropathy, despite elevating blood glucose levels in a mouse model of type 2 diabetes.

The notion of benevolent insulin resistance also resolves the insulin resistance paradox; that is, insulin resistance is associated with both decreased or increased life span. Insulin resistance due to activation of mTOR shortens life span, whereas insulin resistance due to inhibition of mTOR increases life span. Simply stated, insulin resistance associated with TOR overactivation is bad, but insulin resistance associated with inactive TOR is good. This is the mTOR-centric view on glucose metabolism. Detrimental metabolic alterations should have detrimental consequences, such as diabetic complications, but there is no evidence that rapamycin-induced glucose intolerance is detrimental. On the contrary, rapamycin improves nephropathy in diabetic mice, despite increasing blood glucose levels.

The endoplasmic reticulum is a cellular component involved in protein synthesis in cells, finalizing these molecules for use by folding them correctly. When the endoplasmic reticulum becomes cluttered with work in progress, or otherwise slowed down, this state is called endoplasmic reticulum stress. This triggers the unfolded protein response (UPR) to clear out any problem molecules and restore function. Researchers here show that mild endoplasmic reticulum stress and consequent UPR activation is one of the mechanisms by which calorie restriction improves health and tissue function, thereby extending life in short-lived species. We might compare this with what is known of the ability of calorie restriction to upregulate the cellular maintenance processes of autophagy, which serve an analogous purpose in clearing out damaged proteins and structures elsewhere in the cell, thereby maintaining a better cell state and function.

The endoplasmic reticulum (ER) deteriorates with age and fails to mount an effective stress response against misfolded proteins (UPRER), leading to protein folding disorders. Proteostasis collapse has long been associated with incidences of various diseases of protein aggregation. The catastrophic collapse of cellular proteostasis marks the commencement of the aging process. Thus, interventions that can delay the onset of the collapse has positive effects on health and longevity. Here, we show that dietary restriction (DR) effectively delays proteostasis collapse by maintaining robust UPRER and ER-associated degradation (ERAD) during adulthood, leading to increased life span. This is partially mediated by a sublethal dose of ER stress early during development that primes the ER for better function later in life. We also show that the mechanism maybe conserved in a mammalian cell culture model of protein aggregation. Since a sublethal ER stress generated by DR is able to confer health and life span benefits at adulthood, this mechanism may be categorized as hormesis.

DR has long been argued as a case of hormesis. While DR confers health and life span benefits, extended periods of DR or starvation may be detrimental. Even in C. elegans, DR produces a typical bell-shaped curve with ad libitum and least fed worms showing no life span benefits. Incidentally, the mechanisms of hormesis in case of DR mostly point toward mitochondrial metabolism. Glucose restriction, another mode of DR that also increases life span, works through a process of mitohormesis involving ROS-mediated up-regulation of cellular detoxification machinery. Additionally, lowering insulin-IGF1 signaling that is akin to reduced glucose metabolism requires mitohormesis to increase life span. Although, IRE-1 was found to be involved in life span regulation during DR, the mechanism was not linked to ER hormesis. Our study now elucidates how ER hormesis functions during DR, adding to the list of known mechanisms by which the conserved life span-extending intervention of diet restriction works.

We show that exposing worms to an early transient ER stress is able to increase life span and improve proteostasis in adulthood by the process of ER hormesis. It appears that a cellular memory is created by the sublethal ER stress during development that helps maintain a prolongevity transcriptional status. In support of this, we observe that the expression of the ERAD genes are increased early in eat-2 mutant worms and maintained into adulthood, even when the basal ER stress is low during DR. In future, the nature of the memory needs to be deciphered. We have shown here that DR as well ER hormesis prevents decline of UPRER efficiency that occurs with age. We observe that the basal ER stress levels are lower and that the organism can mount a robust UPRER when challenged.

The FOXA transcription factor PHA-4 plays a central role in DR-mediated longevity in C. elegans. It appears that the PHA-4 controls many prolongevity aspects of DR. It transcriptionally regulates the expression of genes coding for chromatin modifiers required for modulation of gene expression, xenobiotic detoxification pathway components, the superoxide dismutase system, as well as those involved in the splicing and nonsense-mediated decay pathway. In this study, we show that PHA-4 regulates the expression of the ERAD component genes, the transient UPRER, as well as modulates UPRER at adulthood. These finding show that the transcription factor controls diverse aspects of the regulatory network that provides prolongevity benefits of DR, qualifying as the central regulator of this process.

Link: https://doi.org/10.1073/pnas.1900055116

This review paper looks over the technology of induced pluripotency in the context of its ability to advance the state of regenerative medicine. A little over a decade ago, it was discovered that expression just a few genes in any adult cell reprogrammed it to become an induced pluripotent stem cell, near identical to an embryonic stem cell. Such pluripotent cells are capable of forming any type of cell in the body, given the research and development needed to establish the right recipe of stimuli and signals. This technology is not just interesting as a way to potentially produce supplies of any cell and tissue type needed for regenerative therapies, but also for the fact that reprogrammed cells restore lost mitochondrial function and reverse their epigenetic markers of age - though still retaining many other forms of age-related molecular damage. That second discovery has given rise to companies such as Turn.bio, working on ways to reprogram cells in situ in the body to restore tissue function.

In 2006, researchers reported for the first time the reprogramming of induced pluripotent stem cells (iPSC) from mouse somatic cells by forced expression of the transcription factors Oct4, Sox2, Klf4, and c-Myc, now termed Yamanaka factors. Subsequently, the Yamanaka factors, or other combinations of factors were successfully used to reprogram a wide range of mouse or human somatic cells into iPSC. iPSC achieve a high degree of dedifferentiation and acquire properties similar to those of embryonic stem cells (ESC). Indeed, iPSC and ESC are morphologically indistinguishable, and in vitro these cells have the potential to differentiate into cells of the three germ layers (ectoderm, endoderm, and mesoderm) and to originate virtually all cells of adult organisms.

Work by many researchers worldwide has led to the understanding of the molecular bases and to the improvement of the cell reprogramming process, bringing iPSC closer to safe clinical applications. However, the full translational potential of iPSC is still hampered by flaws, such as the inefficiency and the frequent incomplete reprogramming of the cells, and de novo mutations occurring during the reprogramming process and during the cultivation of generated iPSC. The efficiency to reprogram somatic cells into iPSC remains low (often much less than 1%), and likely further decline in aged cells or in cells with a high number of divisions.

An interesting concept of cell-aging reversion in vivo, which has prolonged the lifespan of a mouse model of premature aging, has also emerged with the reprogramming technology. Indeed, the short-term exposure to Yamanaka factors has contributed to a partial reprogramming of cells, and amended the physiological and cellular hallmarks of aging, due to a probable remodelling of the epigenetic marks which are acquired during aging. Further understanding of the partial reprogramming timings and markers may harness balanced conditions to obtain rejuvenated cells with a full potential to perform their functions and with a minimal dedifferentiation state to avoid oncogenic risks. Partial reprogramming approaches and the consequent epigenetic rejuvenation may serve to develop future interventions for the treatment of age-related diseases, improvement of health and longevity.

The ability to generate pluripotent stem cells, iPSC, from human somatic cells using a simple experimental approach easy to implement, has undeniably opened new possibilities for modelling diseases and to undertake developmental studies that could never have been performed before. The bulk of the molecular mechanisms involved in the reprogramming process has been largely unveiled, which has already allowed great improvements in the iPSC generation process. Consequently, iPSC have achieved a quality sufficient to be used in novel clinical approaches. The use of patient-derived iPSC offers the possibility to develop and test patient-specific pharmacotherapies and derive stem cells which may be corrected for genetic defects before their use for autologous purposes. In the field of cancer, the study of iPSC biology and their reprogramming mechanism has not only provided new insights in epigenetic changes contributing to cancer, but has positioned iPSC as a cell source to originate immune cells with great potential for the development of immunotherapies against cancer.

Although many technical hurdles remain to be surpassed for iPSC technology to fully reach its potential. In just over ten years after its first development this technology has remarkedly led to several clinical applications, and provide new ways of obtaining disease models in vitro to better study the mechanism of human pathologies and to improve patients' treatment in a more adequate and personalized manner. Thus, iPSC technology has already been "a giant leap" in terms of obtaining human cells with incredible versatility and potential for therapeutic applications.

Link: https://doi.org/10.4252/wjsc.v11.i7.421

Very few of the presently available interventions for aging are forms of rejuvenation, and of these most are debatable or have small, unreliable effects. Beyond senolytic drugs to clear some fraction of senescent cells from aging tissues, an approach that is producing sizable, reliable effects in animal studies and that will soon enough become a major part of healthcare for the old, other present treatments can only be argued to be forms of rejuvenation. Either they are not addressing root cause damage, or their effect sizes are so marginal as to make it unclear as to whether anything interesting is taking place. Consider photobiomodulation for example, or other forms of laser treatment that might possibly produce benefits via slightly reducing the burden of senescent cells in skin. These are weak indeed in comparison to the effects that should arise from senolytic drugs, assuming the similar levels of clearance of senescent cells are obtained in humans as have been observed in mice.

But where does one find the information that might aid in deciding which treatments are useful versus marginal? The Forever Healthy Foundation is performing a public service by picking some of the more credible of presently available potential interventions in the aging process, a list that does include treatments capable of only small benefits, and conducting a deep review on each. The outcome in each case is a comprehensive risk and benefit assessment that will be of great use to anyone minded to try these interventions in advance of widespread use and the necessary decade or so it takes for anything to work its way through the system of trials.

The Forever Healthy Foundation staff published their first analysis today, covering the presently popular approach of upregulating NAD+ levels in mitochondria in order to turn back some fraction of the age-related decline in mitochondrial function, an important aspect of aging. To the degree that this works, it is not repairing underlying damage; I would say it is more akin to pressing the accelerator harder in a failing engine. Nonetheless, a range of supplements and other approaches exist to accomplish this goal, and a recent small clinical trial suggests that this approach can produce benefits to cardiovascular function in old individuals. The strategy is not free from concerns, however, and the review suggests that younger people should avoid these supplements.

Rejuvenation Now

Senolytics, NAD+ restoration, lipid replacement, decalcification, mTOR modulation, geroprotectors ... - the first generation of human rejuvenation therapies is available today. However, the field is still very young and the information often spotty. New therapies are emerging, and existing ones are updated or replaced. Many of us can not or do not want to wait for decades until we have all the knowledge, perfect therapies and a lifetime of experience on how to implement such therapies. To take advantage of this exciting development right now, we need to navigate this time of transition and make very personal decisions about which treatments to apply and when. Arming ourselves with the best knowledge about therapeutic options is vital.

To rise to this challenge, we have created our Rejuvenation Now initiative to: (a) continuously identify potential new rejuvenation therapies; (b) systematically evaluate new and existing therapies on their benefits, risks, procedures and potential application; (c) evaluate providers for specialized therapies (such as stem cell treatments); (d) freely share our evaluations, protocols, and learnings. The initiative is set up as an international collaboration of scientists and doctors in combination with the team we are building at our foundation's headquarters.

NAD+ Restoration Therapy Risk-Benefit Analysis

This analysis of NAD+ restoration therapy is part of Forever Healthy's Rejuvenation Now initiative that seeks to continuously identify new therapies and systematically evaluate them on their risks, benefits, procedures and potential application. NAD+ is a pyridine nucleotide found in all living cells. It plays an important role in energy metabolism and is a substrate for several enzymes (including those involved in DNA repair). NAD+ levels may decline markedly with age and restoring those levels to a youthful state is believed to have beneficial effects on health and longevity.

Restoration of NAD+ levels has been shown to have beneficial effects on several organ systems and diseases with an excellent acute toxicity profile. The main benefits are in diseases or conditions that threaten the energetic status of the cell such as ischemic stroke, heart failure/infarction, and mitochondrial diseases. The highest level of evidence for NAD+ restoration therapy in humans is for skin diseases. There is a multitude of potential benefits for which the evidence level is still quite low because of the lack of clinical trials.

The major risks are related to tumorigenesis, the buildup of metabolites with undesirable effects, and an increase in the proinflammatory senescence-associated secretory phenotype of senescent cells. These have not appeared in clinical trials to date but have been identified during mammalian preclinical trials. More clinical trials are necessary to adequately assess the risk of long term NAD+ supplementation. Short and medium-term supplementation (up to twelve weeks) with NR elevates NAD+ levels safely and effectively but there is a lack of studies examining the potential adverse health effects of chronic, year-long NAD+ supplementation.

It is well known that hypertension, raised blood pressure, results in greater risk of a range of age-related conditions, particularly cognitive decline and dementia. The mechanisms of interest include damage to the blood-brain barrier, allowing unwanted molecules and cells into the brain, where they can spur chronic inflammation, and rupture of small blood vessels in the brain, resulting in microbleeds that are effectively tiny strokes, destroying small regions of tissue. Over time, this all adds up, and is why even methods that force a lowering of blood pressure without addressing the underlying causes of hypertension can produce a sizable reduction in risk of age-related disease and mortality. As noted in the data presented here, this is a matter of accumulated damage over time, so maintaining a lower blood pressure is a life-long concern.

In a study that spanned two and a half decades and looked at data from more than 4,700 participants, researchers have added to evidence that abnormal blood pressure in midlife persisting into late life increases the likelihood of developing dementia. Although not designed to show cause and effect, the study suggests that maintaining a healthy blood pressure throughout life may be one way to help decrease one's risk of losing brain function. In their study, they found that those people with the high blood pressure condition hypertension during middle age and during late life were 49% more likely to develop dementia than those with normal blood pressure at both times. But, putting one at even greater risk was having hypertension in middle age and then having low blood pressure in late life, which increased one's dementia risk by 62%.

High blood pressure was considered any measurement more than 140/90 millimeters of mercury, whereas low blood pressure was defined as less than 90/60 millimeters of mercury. A cognitive exam, caregiver reports, hospitalization discharge codes, and death certificates were used to classify participant brain function and determine cognitive impairment. High blood pressure can be genetic, but can also be the result of not enough exercise and poor diet. As people age, the top blood pressure number (systolic) oftentimes increases while the bottom number (diastolic) can decrease due to structural changes in the blood vessels. Dementia itself may lead to a lowering of blood pressure, as it may disrupt the brain's autonomic nervous system. Further, stiffening of the arteries from disease and physical frailty can also lead to low blood pressure in late life.

Link: https://www.hopkinsmedicine.org/news/newsroom/news-releases/abnormal-blood-pressure-in-middle-and-late-life-influences-dementia-risk

Adult neurons retain the developmental infrastructure to be able to regrow damaged axons, in principle, but this capability is repressed after early development ends. Researchers here explore the details of the controlling mechanism. The goal at the end of the day is to produce the means to unlock regrowth in adult nerve tissue, particularly the spinal column. A great deal of research and development in regenerative medicine is of this nature, a search for ways to reenable the processes of regulated growth that took place during early development.

It is commonly accepted that neurons of the central nervous system shut down their ability to grow when they no longer need it; this occurs normally after they have found their target cells and established synapses. However, recent findings show that old nerve cells have the potential to regrow and to repair damage similar to young neurons. "Actually, this is quite surprising. It is by no means a matter of course that young and adult nerve cells share the same mechanisms. Neurons show vigorous growth during embryonic development. Mature nerve cells, on the other hand, usually do not grow and fail to regenerate. Our study now reveals that although the ability to grow is inhibited in adult cells, the neurons keep the disposition for growth and regeneration."

Neurons only show their growth talent during embryonic development. At this stage, they form long projections called axons in order to connect and thus transmit signals. However, the ability to grow and thus regrow after injury dwindles when the nervous system reaches the adult stage. Only neurons of the periphery, e. g. those in the arms and legs, retain a pronounced potential for mending damaged connections. However, if axons in the spinal cord are severed, they do not regrow. Consequently, the pathway for nerve impulses remains disturbed.

In recent years scientists identified various factors that influence the growth of neurons. Certain proteins - those of the cofilin/ADF family - proved to play a pivotal role. During embryonic development, these molecules control the formation of cell protuberances that ultimately evolve into axons. The scientists found that the growth and regrowth of neurons is fueled by the turnover of actin filaments. These string shaped molecules belong to the molecular scaffold that gives the cell its form and stability. The proteins of the cofilin/ADF family partially dissolve this corset. It is only through this breakup that the structure of the cell can change - and thus the neuron can grow and regenerate. "In our recent study, we found that it is precisely these proteins that drive growth and regeneration, also in adult neurons. An approach for future regenerative interventions could be to target actin."

Link: https://www.dzne.de/en/news/public-relations/press-releases/press/bonn-researchers-identify-key-proteins-for-the-repair-of-nerve-fibers/

The World Health Organization (WHO) is not a group to be looking towards for leadership in the matter of treating aging as a medical condition. This is unfortunate, as the WHO propagates the International Classification of Diseases (ICD) that medical regulators use as a list of conditions for which treatments are permitted, and further has a fair degree of influence over government policy. If there is to be a summary of the WHO position on aging, it is that people should be wealthier, exercise more, and smoke less. Also more should be spent on compensating for the harms done by aging. There is no mention of treating aging as a medical condition, or even of research and development in medical science.

Thus enormously expensive government-funded advocacy for lifestyle change is about the sum of the ambition on display at the WHO, despite the fair number of groups attempting to improve WHO programs through open comment and feedback processes. And this in an era of radical progress in biotechnology, and the advent of the first working rejuvenation therapies that clear senescent cells from old tissues! That efforts such as those of the International Longevity Alliance and others to influence the WHO, with the aim of getting the organization to pay more attention to medical research, inevitably produce very little movement is one of the reasons why I think it pointless to attempt to steer bureaucracies.

To my mind it is far better to build the first rejuvenation therapies, achieve success, and let the lumbering giants of human society then catch up to the reality on the ground. If you want the best possible chance to create meaningful change in the world, then work on building new technologies. If you want to waste most of your life, then try to change institutions from the inside.

Decade of Healthy Ageing 2020-2030

The Decade of Healthy Ageing (2020-2030) is an opportunity to bring together governments, civil society, international agencies, professionals, academia, the media, and the private sector for ten years of concerted, catalytic and collaborative action to improve the lives of older people, their families, and the communities in which they live. Healthy ageing is the process of developing and maintaining the functional ability that enables wellbeing in older age. Functional ability is about having the capabilities that enable all people to be and do what they have reason to value.

Populations around the world are ageing at a faster pace than in the past and this demographic transition will have an impact on almost all aspects of society. The world has united around the 2030 Agenda for Sustainable Development: all countries and all stakeholders pledged that no one will be left behind and determined to ensure that every human being can fulfill their potential in dignity and equality and in a healthy environment. A decade of concerted global action on healthy ageing is urgently needed. Already, there are more than 1 billion people aged 60 years or older, with most living in low- and middle-income countries. Many do not have access to even the basic resources necessary for a life of meaning and of dignity. Many others confront multiple barriers that prevent their full participation in society.

Decade of Healthy Aging Zero Draft (PDF)

The extent of the beneficial opportunities that arise from increasing longevity will depend heavily on one key factor: health. If people are experiencing these extra years of life in good health, their ability to do the things they value will be little different from that of a younger person. If these added years are dominated by poor health, the implications for older people and for society are much more negative.

Poor health does not need to dominate older age. Most health problems confronting older people are associated with chronic conditions, particularly noncommunicable diseases. Many can be prevented or delayed by engaging in healthy behaviours such as not smoking and drinking, eating well and undertaking regular physical activity. Even for people with declines in capacity, supportive environments can ensure that they live lives of dignity and continued personal growth. Healthy ageing can be a reality for all.

Proposal of the International Longevity Alliance for the WHO's Decade of Healthy Ageing (2020-2030)

We certainly welcome WHO's vision of the world in which all people can live longer and healthier lives. However, the Zero draft does not address sufficiently "Strategic objective 5: Improving measurement, monitoring and research on Healthy Ageing" of the WHO's Global strategy and action plan on ageing and health. Regarding the Zero draft of the proposal for the Decade of Healthy Ageing from June 12, 2019, its section 4.4 "Fostering research and innovation" should be significantly strengthened with biomedical and clinical research agenda. In fact, a separate section should be developed on biomedical research and innovation on ageing.

Research and development in the areas of biological ageing and ageing-related disease is the major long-term strategy to improve health and the quality of life in older ages. Therefore, the work and cooperation in the area of biomedical and clinical research in ageing and ageing-related diseases by the WHO, the WHO parties, and non-governmental stakeholders' should be explicitly stated as an agenda item for the Decade of Healthy Ageing. There is a growing body of consensus about the need to include research and development for healthy longevity as a part of the global WHO agenda. Aging health and R&D for healthy longevity must be included into the WHO Work Program.

It is always pleasant to see portions of the mainstream research community come around to working seriously on parts of the SENS agenda for rejuvenation research, even if they are the better part of 20 years too late to the party. Here, the link is made between lysosomal dysfunction and aspects of Alzheimer's disease. Lysosomes are the recycling units of the cell, organelles packed with enzymes capable of digesting near everything that needs to be dismantled into component parts, be that damaged cell components, metabolic waste, or excess proteins. Unfortunately "near everything" is not the same as "everything", and lysosomes in long-lived cells, such as those of the brain, become cluttered with hardy metabolic byproducts. As a result the whole process of cellular maintenance falters, and cells become damaged and dysfunctional.

The SENS approach to the dealing with this problem is to deliver new enzymes to the lysosome, each capable of breaking down one or more of the problem compounds, tackled in some order of importance. For example, LysoClear is a startup biotech company developing a method of clearing A2E, resulting from earlier research at the Methuselah Foundation and SENS Research Foundation. There are, unfortunately, all too few other programs of this sort at an advanced stage. Perhaps linking lysosomal dysfunction to the big budgets focused on Alzheimer's disease will help to address that problem.

Plaques and tangles have so far been the focus of attention in Alzheimer's disease. Plaques, deposits of a protein fragment called beta-amyloid, look like clumps in the spaces between neurons. Tangles, twisted fibers of tau, another protein, look like bundles of fibers that build up inside cells. "The dominant theory based on beta-amyloid buildup has been around for decades, and dozens of clinical trials based on that theory have been attempted, but all have failed. In addition to plaques, lysosomal storage is observed in brains of people who have Alzheimer's disease. Neurons - fragile cells that do not undergo cell division - are susceptible to lysosomal problems, specifically, lysosomal storage, which we report is a likely cause of Alzheimer's disease."

An organelle within the cell, the lysosome serves as the cell's trashcan. Old proteins and lipids get sent to the lysosome to be broken down to their building blocks, which are then shipped back out to the cell to be built into new proteins and lipids. To maintain functionality, the synthesis of proteins is balanced by the degradation of proteins. The lysosome, however, has a weakness: If what enters does not get broken down into little pieces, then those pieces also can't leave the lysosome. The cell decides the lysosome is not working and "stores" it, meaning the cell pushes the lysosome to the side and proceeds to make a new one. If the new lysosome also fails, the process is repeated, resulting in lysosome storage.

"The brains of people who have lysosomal storage disorder, another well-studied disease, and the brains of people who have Alzheimer's disease are similar in terms of lysosomal storage. But lysosomal storage disorder symptoms show up within a few weeks after birth and are often fatal within a couple of years. Alzheimer's disease occurs much later in life. The time frames are, therefore, very different." Researchers posit that long-lived proteins, including beta-amyloid and tau, can undergo spontaneous modifications that can make them undigestible by the lysosomes. The changes occur in the fundamental structure of the amino acids that make up the proteins and are the equivalent of flipping the handedness of the amino acids, with amino acids spontaneously acquiring the mirror images of their original structures.

"Enzymes that ordinarily break down the protein are then not able to do so because they are unable to latch onto the protein. It's like trying to fit a left-handed glove on your right hand. We show in our paper that this structural modification can happen in beta-amyloid and tau, proteins relevant to Alzheimer's disease. These proteins undergo this chemistry that is almost invisible, which may explain why researchers have not paid attention to it. It's been long known that these modifications happen in long-lived proteins, but no one has ever looked at whether these modifications could prevent the lysosomes from being able to break down the proteins. One way to prevent this would be to recycle the proteins so that they are not sitting around long enough to go through these chemical modifications."

Link: https://news.ucr.edu/articles/2019/08/12/alternate-theory-what-causes-alzheimers-disease

This densely written open access paper breezes through a sizable fraction of the the present consensus on the mechanisms driving aging. When reading through this sort of review, it is worth bearing in mind that different perspectives on the nature of aging may well categorize a given mechanism as either causative or a downstream consequence, or more important or less important in the progression of aging. That debate is more vital than it might at first seem. Making the wrong choice in a target mechanism for the development of therapies to treat aging will likely slow down progress by a couple of decades, as poor strategies are implemented and then found to have only modest beneficial effects, doing little to halt the progression of aging because they are intervening far downstream of the causes.

It is easy enough to say, well, try everything and the best approaches will win out in time. Yes, indeed, that will happen, but it will take quite the long time if, at the start, the wrong approaches are more dominant in the marketplace of ideas. We already have the past four or five decades as an example of just how long such a process can continue before better ideas start to make headway. Many of us don't have the luxury of waiting for the research and development communities to take the long way around.

Throughout history, humankind has been preoccupied with longevity, death, and immortality, as evidenced by the first known epic, describing Gilgamesh's futile quest for immortality. Death due to old age, however, appears to be rather rare in nature, as most species are confronted with various extrinsic sources of mortality, including predation, malnutrition, and life-threatening temperatures, all of which can limit the life span of individuals in their natural habitats. The vastly different life spans among closely related species were selected mainly via pressure exerted by extrinsic mortality risks that had to be balanced with the need for successful offspring generation. Some trees may persist thousands of years, whereas some insect species live for only a few days and other species, such as the small freshwater animal hydra, are thought to live indefinitely.

Over the past three decades, environmental and metabolic factors as well as evolutionarily conserved pathways that influence life span have been identified. Examples include several stress factors that, in excess, can negatively affect life span but that, in moderation, can trigger protective responses that lead to life span extension in a process called hormesis. For example, DNA damage is thought to accumulate in tissues during aging. DNA damage drives the aging process via mechanisms ranging from interference with replication and transcription to the DNA damage response (DDR) that triggers apoptosis and cellular senescence. A similar relationship can be observed regarding the nutritional state of animals, as severe nutrient and energy limitation can lead to death; however, calorie restriction (CR) or intermittent fasting has positive effects on life span in several model organisms, and modulation of metabolic parameters in a 2-year human trial showed potential benefits.

The immune system is an important regulator that not only profoundly influences life span directly by preventing premature death due to infections but also protects organisms via cancer surveillance and removal of senescent cells. While the prowess of the immune system fades during aging through a process called immunosenescence, nuclear DNA damage, accumulating extranuclear DNA, and senescent cells fuel inflammation. Targeting senescent cells has shown positive effects on immune function in mice and therefore appears to be a promising field of research to improve tissue aging in the elderly, including attempts to re-establish a balanced output of aging HSCs to regenerate lymphopoiesis during aging. In contrast, the senescence program might protect cells from transforming into cancer cells and has been implicated in tissue regeneration after skin injury. Together, these observations indicate that senescent cells serve dual roles in influencing life span: pro-longevity tumor suppression and tissue repair versus involvement in pro-aging inflammatory reactions.

Link: https://doi.org/10.12688/f1000research.19610.1

As a rule, the journalistic community struggles to correctly represent any complex situation, community, or state of affairs. It is outsiders writing on a topic they generally know little of, under a deadline, and with few to no consequences attending mistakes and misrepresentations. To a journalist, any field looks like a confusing bristle of self-promoters and high-profile figures, all of them contradicting one another on points that require a good amount of technical knowledge to understand. It is the blind men and the elephant wherein some of the blind men have book deals to promote, or companies to talk up, and most of the others are just hard to find in the phone directory. The reality of it is under there somewhere, but no professional journalist has either the time or the motivation to find it.

This collection of articles from the MIT Technology Review (and those of us who have been around for a while will appreciate the irony of this particular publication grappling with the topic of treating aging as a medical condition) is fairly typical for the popular science media. It is a disconnected tour of some of the high points that will provide little anchoring context or understanding for those who are unfamiliar with the field. There is the sense that something is underway, yes, but the details are floating disconnected and the true shape of the whole is not conveyed.

What is the true shape of the whole? There is major change and progress ahead, the research community is moving towards literal rejuvenation of the old, and the advent of senolytic drugs to selectively remove harmful senescent cells from old tissues has woken up the scientific and development establishments to the potential to effectively treat aging. Yet near all of the higher profile researchers and other folk are largely working on approaches that are really not that exciting, not capable of producing rejuvenation, and will have only small effects in the grand scheme of what is possible. But because of the general sense of potential in the field, those approaches will be funded, promoted, and widely discussed, simply because they are interventions aimed at aging. It will be quite challenging for a time to sort out the wheat from the chaff.

What if aging weren't inevitable, but a curable disease?

A growing number of scientists are questioning our basic conception of aging. What if you could challenge your death - or even prevent it altogether? What if the panoply of diseases that strike us in old age are symptoms, not causes? What would change if we classified aging itself as the disease? David Sinclair, a geneticist at Harvard Medical School, is one of those on the front line of this movement. Medicine, he argues, should view aging not as a natural consequence of growing older, but as a condition in and of itself. Old age, in his view, is simply a pathology - and, like all pathologies, can be successfully treated. If we labeled aging differently, it would give us a far greater ability to tackle it in itself, rather than just treating the diseases that accompany it.

It is a subtle shift, but one with big implications. How disease is classified and viewed by public health groups such as the World Health Organization (WHO) helps set priorities for governments and those who control funds. Regulators, including the US Food and Drug Administration (FDA), have strict rules that guide what conditions a drug can be licensed to act on, and so what conditions it can be prescribed and sold for. Today aging isn't on the list. Sinclair says it should be, because otherwise the massive investment needed to find ways to fend it off won't appear.

Has this scientist finally found the fountain of youth?

Reprogramming is a way to reset the body's so-called epigenetic marks: chemical switches in a cell that determine which of its genes are turned on and which are off. Erase these marks and a cell can forget if it was ever a skin or a bone cell, and revert to a much more primitive, embryonic state. The technique is frequently used by laboratories to manufacture stem cells. But Izpisúa Belmonte is in a vanguard of scientists who want to apply reprogramming to whole animals and, if they can control it precisely, to human bodies. Izpisúa Belmonte believes epigenetic reprogramming may prove to be an "elixir of life" that will extend human life span significantly.

The transhumanists who want to live forever

James Clement, 63, is a spry man with a shaved head and clear eyes, who spends his days gulping vitamins and trying to figure out how to make people live longer, including himself, his parents, and even me. From a home and several outbuildings in Gainesville, Florida, Clement runs BetterHumans, which he calls the world's "first transhumanist research organization." With funds from wealthy elderly men he knows, he is independently exploring drugs known to extend the healthy life span of rodents. Using a calculator, he extrapolates what a suitable human dose might be, and then finds people who will take them.

Who wouldn't want to reach 110, if not 500? Unlike mere armchair futurists, the life extensionists are prepared to experiment on themselves, and others, using vitamins and prescription cancer drugs, as well as compounds available only by finagling them from chemical suppliers. Lately the idea of living longer, maybe a lot longer, seems more realistic. As biologists uncover the fundamental facts of life, even ivory-tower academics now claim they know what the molecular "hallmarks" of aging are. In their lab animals, at least - roundworms and white mice - they can regularly increase life spans by 20% or 30% and sometimes more.

Given these clues, Clement has financed and supervised four small studies, in volunteers, of treatments found to extend the healthy lives of rodents - the immune drug rapamycin, supplements that increase NAD+ levels, a combination of compounds that kill off senescent cells, and injections of plasma concentrated from umbilical cords. His aim is "to do as many small trials as possible" to generate and publish basic information on safety and possible benefits. With that, he says, people interested in life extension "can decide to take the risk."

Dysfunction of the blood-brain barrier, allowing molecules and cells not normally present in the central nervous system to enter, is one of the features of dementia. If nothing else, this causes inflammation in the brain as the immune system is roused to try to clear out the unwanted materials. Chronic inflammation in the immune cells of the central nervous system is an important part of the progression of neurodegenerative conditions, and in Alzheimer's disease shows up after the initial accumulation of amyloid-β. This sequence of events may be due in part to amyloid-β causing blood-brain barrier dysfunction, though there are certainly numerous other mechanisms to consider.

Amyloid-β plaques, the protein aggregates that form in the brains of Alzheimer's patients, disrupt many brain functions and can kill neurons. They can also damage the blood-brain barrier - the normally tight border that prevents harmful molecules in the bloodstream from entering the brain. Researchers have now developed a tissue model that mimics the effects of amyloid-β on the blood-brain barrier, and used it to show that this damage can lead molecules such as thrombin, a clotting factor normally found in the bloodstream, to enter the brain and cause additional damage to Alzheimer's neurons. "We were able to show clearly in this model that the amyloid-β secreted by Alzheimer's disease cells can actually impair barrier function, and once that is impaired, factors are secreted into the brain tissue that can have adverse effects on neuron health."

The blood vessel cells that make up the blood-brain barrier have many specialized proteins that help them to form tight junctions - cellular structures that act as a strong seal between cells. Alzheimer's patients often experience damage to brain blood vessels caused by amyloid-β proteins, an effect known as cerebral amyloid angiopathy (CAA). It is believed that this damage allows harmful molecules to get into the brain more easily.

Researchers decided to study this phenomenon, and its role in Alzheimer's, by modeling brain and blood vessel tissue on a microfluidic chip. They engineered neurons to produce large amounts of amyloid-β proteins, just like the brain cells of Alzheimer's patients. The researchers then devised a way to grow these cells in a microfluidic channel, where they produce and secrete amyloid-β protein. On the same chip, in a parallel channel, the researchers grew brain endothelial cells, which are the cells that form the blood-brain barrier. An empty channel separated the two channels while each tissue type developed.

After 10 days of cell growth, the researchers added collagen to the central channel separating the two tissue types, which allowed molecules to diffuse from one channel to the other. They found that within three to six days, amyloid-β proteins secreted by the neurons began to accumulate in the endothelial tissue, which led the cells to become leakier. These cells also showed a decline in proteins that form tight junctions, and an increase in enzymes that break down the extracellular matrix that normally surrounds and supports blood vessels. As a result of this breakdown in the blood-brain barrier, thrombin was able to pass from blood flowing through the leaky vessels into the Alzheimer's neurons. Excessive levels of thrombin can harm neurons and lead to cell death.

Link: http://news.mit.edu/2019/alzheimers-model-blood-brain-0812

Jim Mellon and his allies are in fine form as they continue their quest to establish an industry focused on extending healthy human life spans by treating aging as a medical condition. They have brought in another $100M to Juvenescence, a company founded to make the formative investments needed to build an industry, backing biotech startups working on approaches to regeneration, rejuvenation, and slowing aging. While largely focused on small molecule drug development, of which senolytic treatments are to my eyes much more interesting than the other approaches taken to date, Juvenescence has funded groups like Lygenesis, working on delivery of organoid tissue as a regenerative therapy. It will be interesting to see what the Juvenescence principals choose to do with the funds from this present round.

Juvenescence, a life sciences company utilising expert drug developers and artificial intelligence experts to create therapeutics and technologies to treat diseases of aging and to increase human longevity, is pleased to announce the successful closure of its $100 million Series B round, including a total of $10 million from its founders and a further $10 million each from four cornerstone investors, including Grok Ventures, the investment company of Mike Cannon-Brookes (Atlassian cofounder), and Michael Spencer's private investment company, IPGL. This brings the total to $165 million that Juvenescence has raised in 18 months and speaks to the extraordinary opportunity as well as interest in developing therapeutics with the capacity to modify aging.

Juvenescence is creating a longevity ecosystem, with world class scientists, seasoned drug developers, machine learning experts and a strong team with financial acumen to navigate this emerging new biotech growth sector and to develop 12 therapeutic candidates within the field of healthy aging. "This has been such an exciting six months for Juvenescence. We have been able to add extraordinary people to the Juvenescence team who will bring our age modifying therapeutics to market. We have also augmented our team working on using machine learning for drug discovery and for drug development: culminating with closing on this $100 million Series B financing which provides us with sufficient working capital to progress many of our programs to their initial inflection points".

Link: https://juvenescence.ltd/juvenescence-closes-100-million-series-b-round-plans-follow-on-and-incremental-investments-in-longevity-drug-development/

"Healthy aging" is a popular concept in the research community. It is the idea that aging is somehow separate from age-related disease, and if we could just effectively treat age-related disease, then people would have a healthier old age, but the shape and length of life would be much the same. This is very wrong-headed. Aging (whatever parts of the decline one is willing to say are not age-related disease) and age-related diseases (the large declines in function that everyone acknowledges are bad) arise from the same underlying mechanisms, the accumulation of cell and tissue damage and the consequences of that damage. The only difference is a matter of degree.

Trying to cure age-related disease without repairing the underlying damage that causes aging is futile. We know it is futile because this is exactly the strategy that the scientific and medical community have been following, at enormous expense and investment of time, in past decades. There is only marginal, incremental progress to show for this effort. Yet as soon as just one method of repairing damage, the clearance of senescent cells, started development in earnest, less than a decade ago, it resulted in easily obtained benefits in animal studies. Now the effects of senolytic drugs to selectively kill senescent cells threaten to be much larger and more reliable in the treatment of age-related disease and dysfunction than anything achieved to date by the rest of the field of medicine.

This open access paper, in which the authors give a summary of the present lack of good biomarkers for aging, is an example of the way in which the concept of healthy aging steers research strategy in the wrong direction. Researchers invested in this concept will try to square the circle, in search of ways to distinguish age-related disease from aging. They will draw lines and declare some of aging, and the suffering and declining function it causes, to be completely acceptable and thus not worthy of treatment. This is all madness, and the concept of healthy aging should be consigned to the pit, never to be seen again.

Hallmarks of senescence and aging

Every living organism lives in a permanent struggle with extrinsic and intrinsic agents that can damage it. Without its own repair mechanisms, life of living creatures would be extremely short, since the accumulation of harmful substances would damage the cellular elements, their function, which would ultimately result in damage to the various tissues and accelerated aging of the entire organism. Most of the aging definition involves a gradual, heterogeneous impair in the structure, function, and maintenance of repair systems of various organs and an increased inclination to various diseases. One could say that the age/aging phases are easy to recognize, but the mechanisms responsible for the aging process are difficult to define and harder to prove. Technological progress has established various methodological approaches to detect some cellular and molecular mechanisms associated with aging. Among others, scientists have focused recently on senescence (cellular aging, biological aging) mechanisms as one of the key factor in a complex aging process.

Aging is an intrinsic feature of all living beings. The complex process of biological aging is the result of genetic and, to a greater extent, environmental factors and time. It occurs heterogeneously across multiple cells and tissues. As the rate of aging is not the same in all humans, the biological age does not have to be in accordance with the chronological age. Many age-associated changes and hallmarks are evident in the human body. In the background of all the changes that occur during aging are three key factors - inflammation, immune aging, and senescence.

In order to examine why and how people become old with different rate, it is necessary to define the primary indicators/biomarkers of the healthy aging process. Only in this way it will be possible to distinguish the phenomenon of aging due to the processes caused by various diseases that are commonly associated with the aging process. In this sense, the scientific community is continually investing great efforts in discovering such biomarkers.

According to the American Federation for Aging Research recommendations, aging biomarkers should meet several criteria. They have to: 1. predict the rate of aging (correlate with aging); 2. monitor a basic process that underlies the aging process (determine "healthy aging", not the effects of disease); 3. be able to be tested repeatedly without harming the person; 4. be applicable to humans and animals. However, currently, there is no biomarker that would meet all of these criteria. Currently, due to the stated fact that many of the hallmarks of aging do not meet biomarker definition criteria, it may be better to use terms a) hallmarks of senescent cells or hallmarks of aging or b) possible biomarkers of senescence.

Thus in summary, there are currently no standardized biomarkers of cellular aging process or the healthy aging of the organism. Biomarkers described in literature do not meet all criteria of an ideal aging biomarker and actually represent various hallmarks of the aging process. Most biomarkers currently being examined as senescence or aging biomarkers are related to age-related illnesses rather than the process of healthy aging. As the effector mechanisms of senescence are neither necessarily specific to senescence nor present in all forms of senescence (the rate of senescence is not the same for all types of cells), the interpretation of existing biomarkers of senescence (for now the hallmarks or possible biomarkers) should be context dependent. Additionally, a combination of multiple biomarkers should be used.

Detection of biomarkers, in particular their quantification and validation, are necessary for understanding the senescence processes (diagnostic biomarkers), monitoring of the rate of senescence (prognostic and predictive biomarkers) and the possible use of appropriate therapy intervention (pharmacodynamic biomarkers). The identification and selection of reliable biomarkers, and the use of reproducible methods could help to better understanding of complex web of senescence and aging processes, but it will also open some new questions. Despite new findings at the cellular and molecular level the understanding the aging process is still limited.

The human genetics of longevity are exceedingly complex, that much is possible to say from the research to date. Nearly every study of associations between gene variants and longevity in a human population identifies some correlations, and, barring just a few genes, none of those associations are found in any other study. So the genetics of longevity involves myriad tiny conditional contributions, each such contribution very dependent on a web of environmental factors and a network of other gene variants. This is one of the reasons why I see efforts to map the genetics of centenarians and long-lived families to be of only scientific interest. Given what we know of the genetics of longevity, research programs of that nature are very unlikely to deliver the basis for therapies that can make any meaningful difference to the pace of aging.

Human average life expectancy in developed countries has increased dramatically in the last century, a phenomenon which is potentially accompanied by a significant rise in multi-morbidity and frailty among older individuals. Nevertheless, some individuals appear someway resistant to causes of death, such as cancer and heart disease, compared with the rest of the population, and are able to reach very old ages in good clinical conditions, while others are not. Thus, during the last two decades we have witnessed an increase in the number of studies on biological and molecular factors associated with the variation in healthy aging and longevity.

Several lines of evidence support the genetic basis of longevity: from the species-specific maximum lifespan to the genetically determined premature aging syndromes. Studies in human twins, that aimed to distinguish the genetic from the environmental component, highlighted a heritability of life span close to 25%. In centenarians' families, the offspring of long-lived individuals not only exhibit a survival advantage compared to their peers, but also have a lower incidence of age-related diseases. On the other hand, population studies found that genetic factors influence longevity in age- and sex-specific ways, with a most pronounced effect at advanced age and possibly in men compared to women. All this evidence indicates that a genetic influence on longevity exists, laying the foundation for the search for the genetic components of extreme long life.

Consequently, over the past three decades, there has been a surge in genetic research, due in part to advances in molecular technologies, starting as studies of single genetic variants in candidate genes and pathways, moving on to array-based genome-wide association studies (GWAS) and subsequently to next generation sequencing (NGS). However, despite a plethora of studies, only few variants (in the APOE, FOXO3A, and 5q33.3 loci) have been successfully replicated in different ethnic groups and the emerging picture is complex.

For instance, it is an understatement to think that long-lived people harbor only favorable variants, completely avoiding risk alleles for major age-related diseases; indeed, there is evidence that many disease alleles are present in long-lived people. It is more probable that the longevity phenotype is the result of a particular combination of pro-longevity variants and risk alleles for pathologies, likely interacting in networks in a sex- and age-specific way. Finally, characteristics of aging are extremely heterogeneous, even among long-lived individuals, due to the complex interaction among genetic factors, environment, lifestyle, culture and resiliency. Population and study specificity, lack of statistical power for such a rather rare phenotype and missing heritability represent further hard obstacles to overcome in genotype-phenotype association studies. Thus, many challenges remain to be addressed in the search for the genetic components of human longevity.

Link: https://doi.org/10.3390/genes10080585

Maintaining fitness through the practice of regular exercise improves health in old age, slowing the pace of damage to the brain and consequent cognitive decline. While there is largely only correlational data in humans to show a link between exercise and a slower pace of neurodegeneration, many animal studies make it clear that exercise causes an improved trajectory for health in later life. It does not extend overall life span in mice, as is the case for calorie restriction, but is otherwise very effective for an intervention that is essentially free.

This beneficial outcome is likely due to a combination of overlapping mechanisms, and it is presently hard to say which of those mechanisms are more important. Exercise upregulates cellular maintenance processes such as autophagy, and it is well demonstrated in animal studies that more autophagy improves long term health. Exercise also reduces chronic inflammation, and, when present, that inflammation drives a more rapid progression of all of the common age-related conditions. Fitter people tend to carry less visceral fat tissue, and excess visceral fat accelerates the pace of aging through a more rapid creation of senescent cells, as well as other processes that increase chronic inflammation. Fitter people also exhibit better cardiovascular function and lesser degrees of age-related hypertension, both of which are important when it comes to avoiding structural damage and functional decline in brain tissue.

Researchers examined 317 participants enrolled in the Wisconsin Registry for Alzheimer's Prevention, an ongoing observational study of more than 1,500 people with a history of parents with probable Alzheimer's dementia. Registrants were cognitively healthy and between the ages of 40 and 65 years at the time of enrollment. Participation in the registry included an initial assessment of biological, health and lifestyle factors associated with the disease and follow-up assessments every two to four years.

All participants completed a questionnaire about their physical activity and underwent neuropsychological testing and brain scans to measure several biomarkers associated with Alzheimer's disease. The researchers compared data from individuals younger than 60 years with older adults and found a decrease in cognitive abilities as well as an increase in biomarkers associated with the disease in the older individuals. However, the effects were significantly weaker in older adults who reported engaging in the equivalent of at least 30 minutes of moderate exercise five days a week.

In another study, researchers studied 95 people, also from the registry, who were given scores called polygenic risk scores, based on whether they possessed certain genetic variants associated with Alzheimer's. Similar to the previous research, the researchers also looked at how biomarkers changed with genetic risk and what role, if any, aerobic fitness might play. Not surprisingly, people with higher risk scores also showed increased biomarkers for the disease. Again, the researchers found that the effect was weaker in people with greater aerobic fitness, a score incorporating age, sex, body mass index, resting heart rate, and self-reported physical activity.

A third study examined MRIs from 107 individuals from the registry who were asked to run on a treadmill to determine their oxygen uptake efficiency slope, a measure of aerobic fitness. In line with previous studies, the researchers again found that an indicator of Alzheimer's disease, known as white matter hyperintensities, significantly increased in the brain with age, but not so much in participants with high levels of aerobic fitness.

Link: https://www.apa.org/news/press/releases/2019/08/exercise-decline-alzheimers

The most common age-related neurodegenerative conditions are associated with the build up of various protein aggregates, chemically altered or misfolded proteins that can form solid deposits in and around cells when in that state. These protein aggregates are characterized by the ability to spread and grow, acting as seeds for more aggregation. They include the well known amyloid-β and tau of Alzheimer's disease, the α-synuclein associated with Parkinson's disease, and so forth. In recent years researchers have been devoting ever more effort to investigations of a less well known protein aggregate, TDP-43, associated with ALS and frontotemporal lobar degeneration. Today's open access paper is representative of work taking place to understand TDP-43 aggregates and how and why they form in the aging brain.

The goal of research into protein aggregates is to either find a way to remove them, or to find a way to prevent them from forming in the first place. Protein aggregation is a feature of old people, not young people, despite the fact that the mechanisms that can give rise to aggregation are present throughout life. Thus the damage and change of aging, the rising dysfunction in near all cellular processes, is in some way involved in allowing the presence of protein aggregates to rise to pathological levels. In the research here, the finger is pointed at age-related impairment of the cellular housekeeping systems of the proteasome and autophagy, both of which will break down excess TDP-43 when functioning correctly, at least up until a point.

Partial Failure of Proteostasis Systems Counteracting TDP-43 Aggregates in Neurodegenerative Diseases

Frontotemporal lobar degeneration with ubiquitin positive inclusions (FTLD-U) and amyotrophic lateral sclerosis (ALS) are devastating neurodegenerative diseases characterized by the mislocalization and cytosolic accumulation of the predominately nuclear TAR DNA-binding protein 43 (TDP-43) in the central nervous system. The presence of TDP-43 neuropathology in ~97% of ALS and ~50% of FTLD cases provides a molecular link, showing both diseases to be on the spectrum of the TDP-43 proteinopathies.

A number of physiological functions are perturbed in FTLD and ALS, including impaired protein homeostasis, RNA dysmetabolism, and reduced nucleocytoplasmic transport of mRNAs and proteins. The cytoplasmic deposition of TDP-43 occurs concomitantly with the depletion of native TDP-43 from the nucleus, causing neurodegeneration in both FTLD-U and ALS by a combination of gain-of-function (GOF) and loss-of-function (LOF) mechanisms. Cytosolic aggregates are known to be intrinsically toxic and able to recruit nuclear TDP-43, exacerbating their deleterious effects by contributing to the nuclear LOF.

In this scenario, it is crucial for neurons to maintain TDP-43 protein homeostasis by the ubiquitin-proteasome system (UPS) and the autophagy-lysosomal pathway (ALP). Indeed, a progressive decrease in the efficiency of both protein degradation systems has been reported as a major factor contributing to FTLD-U and ALS onset in aging patients. This hypothesis is also supported by genetic evidence, as many of the mutations associated with FTLD and ALS affect genes involved in UPS- or ALP-mediated degradation. Recent studies showed that the cytosolic accumulation of TDP-43 is turned-over mainly by the UPS, with ALP contributing to its degradation when TDP-43 accumulates as intractable aggregates.

Here we found an early ROS production and caspase-3 activation in murine neuroblastoma N2A cells, following cytosolic transfection with preformed inclusions of human TDP-43 in the absence of any recruitment of the nuclear TDP-43 reservoir. Moreover, our data identify mitochondria as the main responsible sites for the alteration of calcium homeostasis induced by TDP-43 aggregates, which, in turn, stimulates an increase in reactive oxygen species and, finally, caspase activation. We also showed that the UPS and ALP systems are unable to efficiently degrade at least a fraction of the TDP-43 inclusions in neurodegenerative diseases.

Cells that enter a senescent state have many purposes in the body. They are involved in both wound healing and cancer suppression, for example. Senescence also serves to remove somatic cells that reach the Hayflick limit on replication. Senescent cells secrete a potent mix of signals to rouse the immune system and encourage local tissue regrowth and remodeling. This is all useful in the short term, where senescent cells accomplish the immediate task at hand and then self-destruct or are destroyed by immune cells. Wounds are healed, and potentially cancerous cells destroyed.

Yet cellular senescence is a cause of aging. The problems arise due to the tiny fraction of senescent cells that evade destruction and linger in the body in increasing numbers with advancing age. Signals that are useful in the short term become ever more destructive in the long term, producing chronic inflammation and actually encouraging the growth of cancerous cells. In the paper noted here, researchers dig into which of the many molecules secreted by senescent cells are responsible for their ability to increase the risk of colon cancer, identifying GDF15 as an important factor in this process.

The risk of colorectal cancer (CRC) varies between people, and the cellular mechanisms mediating the differences in risk are largely unknown. Senescence has been implicated as a causative cellular mechanism for many diseases, including cancer, and may affect the risk for CRC. Senescent fibroblasts that accumulate in tissues secondary to aging and oxidative stress have been shown to promote cancer formation via a senescence-associated secretory phenotype (SASP).

Given that CRC is an age- and diet-related disease and that the cellular and molecular mechanisms that underlie adenomatous polyp initiation and transformation are only partly understood, we carried out a series of studies to determine whether senescence-associated mechanisms may play a role in the polyp-to-CRC sequence. In this study, we provide both correlative and functional evidence that senescent fibroblasts and an essential SASP factor, GDF15, induce physiological and molecular changes that promote the adenoma-carcinoma initiation and progression sequence in the colon.

We assessed the role of senescence and the SASP in CRC formation. Using primary human colon tissue, we found an accumulation of senescent fibroblasts in normal tissues from individuals with advanced adenomas or carcinomas in comparison with individuals with no polyps or CRC. In in vitro and ex vivo model systems, we induced senescence using oxidative stress in colon fibroblasts and demonstrated that the senescent fibroblasts secrete GDF15 as an essential SASP factor that promotes cell proliferation, migration, and invasion in colon adenoma and CRC cell lines as well as primary colon organoids via the MAPK and PI3K signaling pathways. In addition, we observed increased mRNA expression of GDF15 in primary normal colon tissue from people at increased risk for CRC in comparison with average risk individuals. These findings implicate the importance of a senescence-associated tissue microenvironment and the secretory factor GDF15 in promoting CRC formation.

Link: https://doi.org/10.1111/acel.13013

Inhibition of mTOR, and specifically of the mTORC1 protein complex these days, while trying to avoid inhibition of the mTORC2 complex, is a strategy for modestly slowing aging. It is what I would consider a good example of a worse strategy, in that it aims to adjust the operation of metabolism to make it more resilient to the damage of aging, rather than attempting to repair the damage of aging. It will thus produce benefits to health and longevity that are small in the grand scheme of what is possible. This is true of near all of the initiatives arising from the study of the metabolic response to calorie restriction and other stresses, in which cell maintenance processes such as autophagy are upregulated to beneficial effect.

Another issue with adjusting metabolism into a new state, rather than repairing damage to try to reset metabolism to a known good state, is that it will likely have detrimental side-effects that are hard to map and categorize, as metabolism is enormously complex. The research here offers an example of the type, a discovery made many years in to the development of mTOR inhibitors as therapeutics. While systemic mTOR inhibition appears beneficial in mice, researchers have now shown that loss of mTORC2 in the hypothalamus is detrimental.

The mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that plays critical roles in the regulation of growth, metabolism, and aging. The mTOR protein kinase is found in two distinct protein complexes; mTOR complex 1 (mTORC1) integrates numerous environmental and hormonal cues, including the availability of amino acids, to regulate key anabolic processes including ribosomal biogenesis, protein translation, and autophagy, while mTOR complex 2 (mTORC2) plays a role in cytoskeletal organization and is a key effector of insulin/PI3K signaling. The pharmaceutical rapamycin, which acutely and robustly inhibits mTORC1, extends the lifespan in organisms including yeast, worms, flies, and mice, even when begun late in life or when treatment is intermittent.

While it has long been presumed that inhibition of mTORC1 by rapamycin mediates its beneficial effects on longevity, we and others have found that prolonged treatment with rapamycin also inhibits mTORC2, both in cell culture and in vivo in mice. However, inhibition of mTORC2 by rapamycin is limited to specific cell lines and tissues, most likely determined by the relative expression of FK506-binding proteins (FKBPs). In the nematode Caenorhabditis elegans, mTORC2 regulates metabolic processes via several distinct signaling pathways and can have positive or negative effects on lifespan depending on the tissue that is targeted, the temperature, and the food source.

Over the last decade, significant progress has been made in understanding the roles of both mTOR complexes in the regulation of key metabolic tissues. Less well understood is the role of mTOR complex signaling in the brain. mTOR Complex 1 is clearly an important regulator of neuronal behavior; hypothalamic mTORC1 is a key sensor of nutrient sufficiency and acute activation of hypothalamic mTORC1 suppresses food intake. In contrast, the role of brain mTORC2 signaling in the regulation of metabolism, health, and longevity has been less studied. mTORC2 signaling in the brain plays important roles in whole body metabolism, but the specific neuronal populations mediating these effects and the long-term implications for health and longevity remain to be elucidated.

Here, we show that loss of hypothalamic mTORC2 signaling in mice decreases activity level, increases the set point for adiposity, and renders the animals susceptible to diet-induced obesity. Hypothalamic mTORC2 signaling normally increases with age, and mice lacking this pathway display higher fat mass and impaired glucose homeostasis throughout life, become more frail with age, and have decreased overall survival. We conclude that hypothalamic mTORC2 is essential for the normal metabolic health, fitness, and lifespan of mice. Our results have implications for the use of mTORC2-inhibiting pharmaceuticals in the treatment of brain cancer and diseases of aging.

Link: https://doi.org/10.1111/acel.13014

Loss of the myelin layer that sheathes nerves is the proximate cause of severe conditions such as multiple sclerosis, but this sort of loss occurs to a lesser degree in the course of normal aging, and contributes to cognitive decline. In today's open access research materials, scientists draw a line of cause and effect between (a) increasing stiffness of the brain tissue that hosts niches where stem cells reside, (b) dysfunction of those stem cells mediated by the specific stiffness-sensing mechanism of Piezo1, a process that may exist in other stem cell populations as well, (c) the loss of myelin-generating cells normally produced by the stem cells, and (d) the consequent degradation of myelin and nervous system function.

Without looking into underlying causes of increasing stiffness of brain tissue in stem cell niches, the researchers here demonstrate restored stem cell function via blocking the mechanism by which the stem cells sense stiffness. This is an interesting demonstration, but I'd tend to regard it as more of a strong hint to further investigate the causes of tissue stiffness in the aging brain rather than as a basis for therapies. There is some work in the literature on stiffness of brain tissue, but not an enormous amount; most of it is correlational in nature, rather than a search for deeper mechanisms. Stiffness of brain tissue shows distinct patterns for different age-related neurodegenerative conditions, for example. The use of brain magnetic resonance elastography allows living brains to be mapped for stiffness, which should allow for greater progress towards understanding in the years ahead.

Why does brain tissue stiffen with age? This may or may not have anything to do with the mechanisms of tissue stiffening that are better studied in skin and blood vessels. These include cross-linking of the extracellular matrix, wherein persistent byproducts of metabolism link together the complex extracellular matrix molecules, restricting their movement and altering the structural properties of the tissue, particularly elasticity. There is also the loss of elastin molecules, accumulation of inflammatory senescent cells, and so forth. Perhaps none of that is all that relevant in the brain, however. Research indicates that the water content of brain tissue is important to tissue stiffness, as is the pH of the tissue. One can speculate on what age-related changes in blood flow to the brain, or loss of capillary networks, might do to these measures of the environment.

Cambridge scientists reverse ageing process in rat brain stem cells

As our bodies age, our muscles and joints can become stiff, making everyday movements more difficult. This study shows the same is true in our brains, and that age-related brain stiffening has a significant impact on the function of brain stem cells. Researchers studied young and old rat brains to understand the impact of age-related brain stiffening on the function of oligodendrocyte progenitor cells (OPCs). These cells are a type of brain stem cell important for maintaining normal brain function, and for the regeneration of myelin - the fatty sheath that surrounds our nerves, which is damaged in multiple sclerosis (MS). The effects of age on these cells contributes to MS, but their function also declines with age in healthy people.

To determine whether the loss of function in aged OPCs was reversible, the researchers transplanted older OPCs from aged rats into the soft, spongy brains of younger animals. Remarkably, the older brain cells were rejuvenated, and began to behave like the younger, more vigorous cells. To fully understand how brain softness and stiffness influences cell behavior, the researchers investigated Piezo1 - a protein found on the cell surface, which informs the cell whether the surrounding environment is soft or stiff. "When we removed Piezo1 from the surface of aged brain stem cells, we were able to trick the cells into perceiving a soft surrounding environment, even when they were growing on the stiff material. What's more, we were able to delete Piezo1 in the OPCs within the aged rat brains, which lead to the cells becoming rejuvenated and once again able to assume their normal regenerative function."

Niche stiffness underlies the ageing of central nervous system progenitor cells

Ageing causes a decline in tissue regeneration owing to a loss of function of adult stem cell and progenitor cell populations. One example is the deterioration of the regenerative capacity of the widespread and abundant population of central nervous system (CNS) multipotent stem cells known as oligodendrocyte progenitor cells (OPCs). A relatively overlooked potential source of this loss of function is the stem cell 'niche' - a set of cell-extrinsic cues that include chemical and mechanical signals. Here we show that the OPC microenvironment stiffens with age, and that this mechanical change is sufficient to cause age-related loss of function of OPCs.

Using biological and synthetic scaffolds to mimic the stiffness of young brains, we find that isolated aged OPCs cultured on these scaffolds are molecularly and functionally rejuvenated. When we disrupt mechanical signalling, the proliferation and differentiation rates of OPCs are increased. We identify the mechanoresponsive ion channel PIEZO1 as a key mediator of OPC mechanical signalling. Inhibiting PIEZO1 overrides mechanical signals in vivo and allows OPCs to maintain activity in the ageing CNS. We also show that PIEZO1 is important in regulating cell number during CNS development. Thus we show that tissue stiffness is a crucial regulator of ageing in OPCs, and provide insights into how the function of adult stem and progenitor cells changes with age. Our findings could be important not only for the development of regenerative therapies, but also for understanding the ageing process itself.

It is good to see that more of the promising technical approaches to aspects of aging, originally put forward by people in the SENS rejuvenation research network some years ago, are now making solid progress towards commercial implementation. The LIFT, or GIFT, approach to cancer therapy involves the transplantation of suitably aggressive leukocyte or granulocyte immune cells from a donor. At the time it was first demonstrated to be highly effective in mice, more than a decade ago, the underlying mechanisms were not well explored, and that always makes it hard to obtain further support from scientific funding institutions. This is despite the point that the approach has the potential to be a near universal cancer therapy, applicable to most or all forms of cancer, even at very late stages.

Thus, unfortunately, the work progressed only very slowly for some years, materially supported by philanthropic funding and non-profit efforts. This is not an unusual story when it comes to development of new medical biotechnologies. Our communities and institutions are not good at identifying the best of work taking place in the lab and organizing to push it forward towards the clinic in a timely manner. Fortunately it is now becoming much easier to raise venture capital for the development of ambitious new biotechnologies, and so the approach is under development by LIfT Biosciences, who just received an influx of funding from Kizoo Technology Ventures, a group well known for their support of SENS style rejuvenation therapies.

Kizoo, part of the Forever Healthy Foundation, has announced today that it will be supporting biotech company LIfT Biosciences, a company that focuses on creating a new generation of cancer therapies that use our own immune systems. LIfT Biosciences is developing a new type of cancer immunotherapy approach that uses neutrophils to seek and destroy all types of solid tumors. Neutrophils are a particular type of white blood cell that protect us from infections and perform other functions. They comprise around 40 to 60 percent of the total number of white blood cells in our bodies and are the first immune cells to arrive during a bacterial infection.

The company is developing the world's first cell bank of neutrophils that are designed to seek and destroy any solid tumor, regardless of its particular strain and unique genetic makeup, providing a more universal approach to cancer. The cell bank would potentially be able to supply a range of cell therapies to deal with different types of solid tumors, and it uses a cell therapy system known as Neutrophil only Leukocyte Infusion Therapy (N-LIfT). The system uses an ex-vivo approach and could be more cost-effective than other approaches using leukocyte therapy.

The company is initially going after a form of pancreatic cancer known as pancreatic ductal adenocarcinoma (PDAC), which has a very low survival rate, with only 3% of patients diagnosed surviving for five years. The company is currently finishing up preclinical research prior to launching a human clinical trial. The goal of the trial will be to demonstrate remission in high unmet need solid tumour cancers by 2021, which will include pancreatic cancers such as PDAC.

Link: https://www.leafscience.org/kizoo-announces-support-for-n-lift-cancer-immunotherapy/

The immune system is deeply involved in the intricate, complex processes of tissue regeneration, and the research community has much left to catalog of the countless interactions that take place between immune cells and other cell populations during regeneration. One interesting discovery is that a subclass of T helper cells can encourage growth of blood vessels. Thus, given a way of attracting and retaining the appropriate T helper cells in a tissue suffering ischemia, it may be possible to encourage sufficient regrowth of blood vessels to treat conditions involving inadequate blood flow, such as critical limb ischemia. Researchers here report on positive results from an implementation of this approach in mice.

Peripheral artery disease (PAD) is a narrowing of the arteries in the legs or arms. A new approach to generating new blood vessels to treat PAD takes advantage of the surprising combination of implantable biomaterial scaffolds and childhood vaccines. In models of mice with hindlimb ischemia (a severe form of PAD), the technique increased the concentration of T cells at the ischemic site and stimulated angiogenesis, blood flow, and muscle fiber regeneration for up to two weeks. "One of the most exciting aspects of this work is that it provides a new method of enhancing blood vessel formation that does not rely on traditional biologics, such as cells, growth factors, and cytokines, that are typically used to promote vascularization. Also, it more broadly suggests that advances in bioengineered T-cell therapies, which have traditionally been used to treat cancers, may be utilized to promote wound healing and regeneration."

The researchers focused on T helper 2 (TH2) cells, a type of immune cell that has been found to secrete molecules that promote blood vessel growth in addition to producing cytokines that initiate immune responses. TH2 cells are also the crucial "memory" element of vaccinations against pathogens. For reasons that are not yet fully understood, delivering a small amount of aluminum in a vaccine greatly enhances TH2 cell formation, and nearly all Americans receive aluminum-containing childhood vaccines that protect them from a variety of diseases. The researchers had a hunch that vaccinated people could potentially mount a stronger TH2 cell response if the right triggering antigen was introduced; and, if that antigen was incorporated into a biomaterial scaffold located near a blocked artery, TH2 cells could be recruited to the scaffold and release their angiogenesis-promoting compounds where they are needed to help treat ischemia.

Researchers injected mice with ovalbumin, the primary protein found in egg whites, to create a mild immune reaction like an infectious antigen, along with aluminum hydroxide. Two weeks later the mice got a "booster" of the same vaccine, and four weeks later they were implanted with an ovalbumin-containing scaffold in their ischemic hindlimbs. These mice displayed higher numbers of ovalbumin-specific TH2 cells and eosinophils (angiogenesis-promoting cells that are activated by TH2 cells) in their ischemic muscles than mice that received the implant without the priming vaccine. Vaccinated mice also displayed a lower level of tissue death, higher blood vessel density, greater blood perfusion, and more regenerating muscle fibers in their ischemic hindlimbs after two weeks than unvaccinated mice that received the implant.

Link: https://wyss.harvard.edu/another-trick-up-the-immune-systems-sleeve-regrowing-blood-vessels/

A harmful accumulation of lingering senescent cells occurs in all tissues over the course of aging. A cell entering a senescent state ceases to replicate and begins to generate an mix of signals known as the senescence-associated secretory phenotype (SASP). These signals drive chronic inflammation, remodel the surrounding tissue structure, and encourage nearby cells to also become senescent. This can be helpful in the short term, such as following injury, where it can aid in regeneration. When sustained over the long term, it is a cause of aging and age-related disease, however.

Cells become senescent constantly, largely somatic cells reaching the Hayflick limit on cellular replication, but also potentially cancerous, damaged cells. Near all senescent cells either self-destruct via the process of apoptosis or are destroyed by the immune system quite soon after they enter this state. Several different components of the immune system readily attack and destroy errant cells, those that are damaged and potentially cancerous, and those that are senescent. So the question arises as to why any senescent cells survive to linger in tissues for the long term.

While it is true that the immune system declines in effectiveness with age, and there is good evidence for this to degrade its ability to destroy cancerous and senescent cells, some fraction of senescent cells nonetheless still manage to linger past their welcome even in a youthful physiology. In today's open access paper, researchers dig into how exactly this unwanted survival happens, and demonstrate the ability to break the mechanism responsible. The data in the paper is all obtained from cell cultures, but it is nonetheless quite compelling. Given a suitable set of targets in the biochemistry of senescence, it may be possible to enable the immune system to target and destroy the persistent senescent cells that would otherwise manage to evade its attentions, thereby building the basis for a new class of senolytic therapies capable of producing rejuvenation in the old.

Targetable mechanisms driving immunoevasion of persistent senescent cells link chemotherapy-resistant cancer to aging

Recent reports in mice show that cellular senescence can also regulate immune processes leading to the elimination of senescent cells (SnCs). In mouse models of hepatocarcinoma and liver fibrosis, restoring p53 function enables senescent cells to be eliminated by natural killer (NK) cells in part via NKG2D detection, while oncogenic RAS-induced senescence of hepatocytes promotes immune responses involving CD4+ T cells, neutrophils, and macrophages that lead to SnC removal. In mouse models of cutaneous wound repair, p53/p21- and p16-proficient SnCs are cleared after healing is complete. Notably, however, p53 and p16 are not required to trigger cellular senescence in human tissues/cells, and many senescence features are p53 or p16 independent, suggesting that additional mechanisms may regulate the interplay between SnCs and the immune system.

Despite evidence of immune surveillance and clearance of SnCs in mice, SnCs accumulate with age in patients and are found in inflamed and damaged tissues, premalignant lesions, and arrested tumors and after chemotherapy or radiotherapy. Persistent SnCs can contribute to age-associated pathologies and tissue dysfunction, including cancer. These effects have been attributed to the senescence-associated secretory phenotype (SASP), which includes inflammatory factors secreted by tissue-resident SnCs.

NKG2D ligands (NKG2D-Ls) are cell surface semaphores that mediate the immune recognition and clearance of cells that are transformed, damaged, stressed, or infected. NKG2D-Ls are mostly absent in healthy tissues. We previously observed an increase in NKG2D-L expression upon senescence induction in vitro in normal human fibroblasts. We measured the expression of NKG2D-L MICA and MICB in tumor samples from 10 patients with prostate cancer before and after mitoxantrone (MIT) treatment, which we previously showed induces cellular senescence based on cell cycle arrest and SASP markers. We found that after senescence-inducing genotoxic chemotherapy, residual tumors expressed significantly higher levels of MICA/B.

These results show that DNA-damaging chemotherapies induce tumors to develop a senescence phenotype associated with elevated levels of NKG2D-Ls. Although this may agree with the notion that SnCs upregulate NKG2D-Ls, it is surprising because NKG2D-Ls should promote the immune detection and clearance of those cells. Thus, other characteristics likely allow these SnCs to elude immune recognition and persist while expressing elevated levels of NKG2D-Ls.

As a first model, we induced cellular senescence by DNA damage or replicative senescence in normal human fibroblasts expressing wild-type p53/p16, or inactivated p53 (p53-), or knocked-down p16 (p16-). Although the p53/p21 and p16/pRb pathways are important effectors of cellular senescence, the upregulation of NKG2D-Ls in fibroblasts occurred regardless of p53 loss before or after senescence-inducing damage, and irrespective of their p16 status. Our other observations in which cells arrested and senesced with high levels of p16 but low levels of NKG2D-Ls, led us to postulate that the induction of NKG2D-L expression by SnCs may depend on the DNA damage response (DDR) but not on cell growth arrest per se.

SnC cycle arrest is carried out by cyclin-dependent kinase inhibitor (CDKI) p16 or p21. To mimic the senescence arrest elicited by these CDKIs, we overexpressed p16 or p21 in fibroblasts. We found that these cells showed limited changes in levels of NKG2D-L. This demonstrates that the expression of NKG2D-Ls is not a consequence of CDKIs' activation or senescence per se, but rather a response to damage that is separable from the growth arrest. Hence, p16 neither establishes nor triggers NKG2D-L expression, and the immunogenic program of cellular senescence can be dissociated from other senescence characteristics, including cell cycle arrest and p16 expression.

To explore how the fate of these different types of SnCs may depend on NKG2D-Ls, we cocultured leukocytes with SnCs or their presenescent counterparts, and measured cytotoxicity. We found that IL-2-preactivated primary natural killer (NK) cells were the main effectors of SnC cytolytic killing. Blocking the NKG2D receptor significantly prevented the killing of SnCs. These results show that NKG2D-Ls are key limiting factors that mediate the immune detection of damaged SnCs and orchestrate the balance between elimination/clearance and survival/persistence of SnCs.

A subset of damaged SnCs actively evades leukocyte recognition and killing. We had initially noticed that the elimination of damaged SnCs in leukocyte cocultures was never complete. So, we treated these persistent SnCs with fresh batches of leukocytes, and scored survival. We found that 70%-80% of the original persistent SnCs remained impervious to killing. Thus, persistent SnCs possessed inherent properties that allowed them to actively evade recognition and cytolysis. To characterize persistent SnCs, we compared NKG2D-L expression in SnCs that had not been exposed (naive) or had been exposed (persistent) to leukocytes. Surprisingly, persistent SnCs expressed equal or greater levels of intracellular NKG2D-L compared with naive cells. However, immunofluorescence showed strikingly diminished levels of NKG2D-Ls on the surface of persistent SnCs relative to naive one.

Since cancer cells can promote their immunoevasion by shedding NKG2D-Ls, SnCs may also shed NKG2D-Ls to elude immune detection and persist. We found that the cell culture media of senescent fibroblasts and epithelial cells contained soluble NKG2D-L MICA and that the media from persistent SnCs contained markedly higher levels of soluble NKG2D-Ls compared with naive counterparts. Thus, SnCs shed NKG2D-Ls regardless of cell type and p53 status, and this was amplified in persistent SnCs that avoided killing.

Because MMP3 was among the most upregulated MMPs across damaged SnCs, we used it as a marker of senescence detectable by immunofluorescence. In contrast to the high but variable MMP3 levels observed among naive SnCs, persistent SnCs consistently displayed intense MMP3 staining. To test the possibility that MMPs inhibition might preserve the cell surface presentation of NKG2D-Ls and thus enhance the killing of persistent SnCs, we used the broad-spectrum MMP inhibitor GM6001. GM6001 effectively blocked MICA shedding in a dose-dependent manner and increased cell surface NKG2D-Ls. Critically, GM6001 treatment of fibroblast and epithelial cancer SnCs prior to coculture with leukocytes markedly decreased SnC survival. Moreover, GM6001 treatment of already-persistent SnCs prior to a second round of leukocytes led to their near complete clearance.

In conclusion, our data show how oncogenic and tumor-suppressive drivers of cellular senescence regulate surveillance processes that can be circumvented to enable SnCs to elude immune recognition but can be reversed by cell surface-targeted interventions to purge the SnCs that persist in vitro and in patients. Since eliminating SnCs can prevent tumor progression, delay the onset of degenerative diseases, and restore fitness; since NKG2D-Ls are not widely expressed in healthy human tissues and NKG2D-L shedding is an evasion mechanism also employed by tumor cells; and since increasing numbers of B cells express NKG2D ligands in NKG2D receptor-deficient mice as they age, we propose that therapeutic interventions designed to increase cell surface presentation of NKG2D-Ls could be effective senolytic strategies to resensitize persistent SnCs to immune detection and rescue their clearance, whether in cancer or aging settings.

This open access review examines what is known of the role of fibroblast growth factors in mechanisms relevant to skin aging, such as loss of collagen and elastin from the extracellular matrix. This type of paper always makes for an interesting read, and fully mapping the cellular metabolism of aging is the right goal from a fundamental science perspective. When it comes to near term intervention in the aging process, this sort of examination is less helpful, however. Yes, growth factor expression levels change in aging skin cells, and that has consequential effects. But this is in and of itself far removed from the underlying causes of degenerative aging. It is itself a consequence and not a cause. The most efficient way forward is to focus on causes, not to try to intervene downstream in the complexities of a disrupted mechanism. If a complicated metal structure is rusting to structural failure, you fix the rust, you don't try to rework the structure. The same principle applies here, alongside the ever important note that effect sizes tend to be small and unreliable in this sort of work.

Growth factors have become an important therapeutic option to avoid aging, because they are responsible for cell differentiation and maturation, being directly correlated with the minimizations of the topical esthetic changes resulting from age advancement. Growth factor proteins are naturally secreted by cells and interact directly or are sequestered by the surrounding extracellular matrix for presentation to cell surface receptors. The introduction of growth factors in certain damaged sites in the body seeking to stimulate regeneration is clinically related to regenerative medicine, where researchers intend to replace or repair damaged cells, tissues, and organs to effectively restore normal function.

Among the existing growth factors, we highlight the fibroblast growth factor (FGF), which induces the synthesis of type 1 collagen and therefore presents a relevant role in the process of skin aging control. Collagen is the protein responsible for the structure, elasticity, and firmness of the skin and it is produced by cells called fibroblasts. During the aging process, the proliferative and metabolic activity of fibroblasts decreases and their functions are impaired, leading to reduction of the synthesis of structural substances such as collagen, elastin, hyaluronic acid, and chondroitin. In addition, decreased levels of growth factors, reduced amount of collagen, abnormal accumulation of elastin, and reduction in the epidermal and dermal thickness were observed during the aging process.

The FGF family members increase the proliferation and activation of fibroblasts by stimulating the accumulation of collagen as well as stimulating endothelial cell division. With the aging process, fibroblasts have their activity diminished and consequently the synthesis and activity of proteins that guarantee elasticity and resistance such as elastin and collagen are also affected. Thus, in aged skin, there is a lower production of collagen by the fibroblasts and a greater action of the enzymes that degrade it. This lack of balance speeds up the aging process. Although the functions of FGFs are well characterized, their mechanisms of action are still not completely clear. It is known that it involves inter- and extracellular signaling pathways that may be related to the RAS-MAP kinases pathways, PI3K-AKT, PLC-γ, or STAT. Therefore, FGF cell signaling involves interactions with multiple cell signaling pathways and complex feedback mechanisms.

Activation of FGF-1 improves skin elasticity and induces the synthesis of collagen and elastin. One study investigated the impact of FGF-1 on skin cells; results showed that recombinant FGF-1 has a strong effect on cellular proliferation of keratinocytes and fibroblasts. FGF-2 reduces and prevents expression lines and wrinkles through the activation of new skin cells and stimulates the proliferation of cells of mesodermal, ectodermal, and endodermal origin, mainly fibroblasts and keratinocytes. Researchers aimed to evaluate an in vivo method for aged skin rejuvenation through direct injection of intradermal FGF-2. The following rejuvenating effects were observed: improvement of skin smoothness, atrophied skin thickness, and improved viscoelasticity. Keratinocyte growth factor (KGF) is a member of the FGF family. While most FGFs influence the proliferation and/or differentiation of various cell types, KGF appears to act specifically on epithelial cells. A study evaluating the ability of KGF to reduce the visible signs of aging. The results showed that eighteen of the twenty subjects experienced significant improvement.

Link: https://doi.org/10.1159/000501145

Cancer cells abuse signals used elsewhere in normal mammalian biochemistry to prevent immune cells from destroying other cells, such as CD47. Interfering in these "don't eat me" signals has produced significant gains in the development of effective cancer therapies that can target multiple types of cancer. Here, researchers describe a newly discovered "don't eat me" signal, CD24, that should allow this class of cancer therapy to be expanded to target cancers that have proved resilient to existing implementations. This and related lines of work that lead to more general anti-cancer platforms are one of the reasons why young people today should have little concern over cancer in their old age yet to come. It will be near entirely a controllable condition, treated efficiently with few side effects, by mid-century.

Normally, immune cells called macrophages will detect cancer cells, then engulf and devour them. In recent years, researchers have discovered that proteins on the cell surface can tell macrophages not to eat and destroy them. This can be useful to help normal cells keep the immune system from attacking them, but cancer cells use these "don't eat me" signals to hide from the immune system. Researchers had previously shown that the proteins PD-L1, CD47, and the beta-2-microglobulin subunit of the major histocompatibility class 1 complex, are all used by cancer cells to protect themselves from immune cells. Antibodies that block CD47 are in clinical trials. Cancer treatments that target PD-L1 or the PDL1 receptor are being used in the clinic.

Researchers now report they have found that a protein called CD24 also acts as a "don't eat me" signal and is used by cancer cells to protect themselves. "Finding that not all patients responded to anti-CD47 antibodies helped fuel our research to test whether non-responder cells and patients might have alternative 'don't eat me' signals. "You know that if cancers are growing in the presence of macrophages, they must be making some signal that keeps those cells from attacking the cancer. You want to find those signals so you can disrupt them and unleash the full potential of the immune system to fight the cancer."

The search showed that many cancers produce an abundance of CD24 compared with normal cells and surrounding tissues. In further studies, the scientists showed that the macrophage cells that infiltrate the tumor can sense the CD24 signal through a receptor called SIGLEC-10. They also showed that if they mixed cancer cells from patients with macrophages in a dish, and then blocked the interaction between CD24 and SIGLEC-10, the macrophages would start gorging on cancer cells. Lastly, they implanted human breast cancer cells in mice. When CD24 signaling was blocked, the mice's scavenger macrophages of the immune system attacked the cancer. Of particular interest was the discovery that ovarian cancer and triple-negative breast cancer, both of which are very hard to treat, were highly affected by blocking the CD24 signaling.

The other interesting discovery was that CD24 signaling often seems to operate in a complementary way to CD47 signaling. Some cancers, like blood cancers, seem to be highly susceptible to CD47-signaling blockage, but not to CD24-signaling blockage, whereas in other cancers, like ovarian cancer, the opposite is true. This raises the hope that most cancers will be susceptible to attack by blocking one of these signals, and that cancers may be even more vulnerable when more than one "don't eat me" signal is blocked.

Link: http://med.stanford.edu/news/all-news/2019/07/new-dont-eat-me-signal-may-provide-basis-for-cancer-therapies.html

Every type of tissue is supported by its own dedicated stem cell population, delivering a supply of daughter somatic cells that replace losses and maintain tissue function. Unfortunately, stem cell function declines with age. This has numerous causes, all of which descend from the underlying accumulation of molecular damage outlined in the SENS research proposals for rejuvenation biotechnologies. Downstream of those causes, stem cells become less active due to some combination of internal damage, damage to their niche of supporting cells, and changes in the signaling environment. The latter two classes of issue appear more influential in the best studied stem cell populations, such as the satellite cells of muscle tissue.

Thus most research and development intended to restore stem cell function is presently focused on trying to override signaling or cell programming in order to force stem cells into greater activity, regardless of the present state of their environment. This may produce benefits to tissue function that are sizable enough to be worth the effort and cost of development, but one cannot just forever ignore the underlying damage of aging with impunity.

For one thing, not every aspect of aging can be fixed by throwing cells at the problem: there are protein aggregates and other forms of molecular waste that are not adequately cleared for reasons that have little to do with stem cells. There is mitochondrial dysfunction throughout cell populations. And so forth. Further, is most likely that stem cells falter in function in response to a damaged environment because this acts to limit cancer risk, though at the cost of a drawn out decline. Thus many of the strategies outlined in this open access paper may turn out to have increased incidence of cancer as a side-effect, even when they achieve meaningful gains in the near term.

However, we can balance that expectation against the animal studies of telomerase gene therapies to lengthen telomeres. In mice that approach both improves stem cell function and reduces cancer risk. In that case, it may be that improved function of the immune system in anti-cancer immunosurveillance offsets the raised risk due to forcing damaged cells into greater activity. That said, a great deal more work is required to understand where the line is drawn on cancer risk in the many approaches to improved stem cell function.

Rejuvenating Strategies of Tissue-specific Stem Cells for Healthy Aging

DNA damage accumulation is critical for age-dependent loss of tissue-specific stem cell function. This type of accumulation is dependent on the attenuation of the DNA repair and response pathway. For example, DNA damage markers, such as histone H2A phosphorylation and comet tails, have been quantified in hematopoietic stem cells (HSCs) and muscle stem cells (MuSCs) from young and old mice and indicated strand breaks significantly accrue in HSCs and MuSCs during aging. It is therefore reasonable to suggest that an increase in the activity of DNA repair pathways may slow down or prevent the accumulation of age-related defects in stem cells and thereby promote the healthy function of aged tissues.

A gradual decline of the telomere length that occurs through the loss of telomerase during aging has been observed in mouse and human tissues. In the mouse model, the loss of telomerase displays telomere shortening, stem cell depletion, and impaired tissue injury responses. However, with telomerase reactivation, telomerase reverse transcriptase (TERT)-deficient mice extend telomeres and reverse degenerative phenotypes. Protection of telomeres 1A (Pot1a), a component of the Shelterin complex that protects telomeres, is highly expressed in young HSCs, whereas it progressively declines with age. In aged mice, treatment with exogenous Pot1a protein could reverse the HSC activity and sustain their self-renewal.

Increased expression of several cell cycle inhibitors, such as p53/p21, p16Ink4α, p19Arf, and p57Kip2 can lead to an essentially irreversible arrest of cell division and promote stem cell senescence. In MuSCs, HSCs, and neural stem cells (NSCs), the expression of p16Ink4α accumulates with age, but p16Ink4α repression through various methods can improve the function of aged stem cells and prevent cellular senescence. For example, silencing of p16Ink4α expression in geriatric satellite cells restores their quiescence and regenerative potential. In a potentially insightful study, researchers showed that autophagy is critical to the prevention of stem cell senescence by repressing the expression of p16Ink4α, and treatment with pharmacological rapamycin to stimulate autophagy could rejuvenate the MuSCs.

Many studies point that altered epigenetic marks of aging stem cells not only alter the transcriptional programs that dictate the function of the stem cells but also alter the potential differentiation towards distinct effector lineages. Recently, aberrant global and site-specific induction of active chromatin marks such as Hoxa9, has been investigated in aged satellite cells, while the inhibition or deletion of Hoxa9 can improve MuSC function and muscle regeneration in aged mice. Another example of successful rejuvenation comes from a study in which aged HSCs express a lower level of the chromatin organizer Satb1 than their young counterparts, while overexpression of Satb1 can improve their ability to generate lymphoid progeny via epigenetic reprogramming.

Signals can directly influence all aspects of stem cell functions including quiescence, proliferation, and differentiation. Signaling pathways involving p38-MAPK, janus kinase (JAK) / signal transducers and activators of transcription (STAT), Notch, and mechanistic target of rapamycin kinase (mTOR) contribute to the modulation of tissue stem cell functions, and their changes with age could affect tissue maintenance and repair systems. Hence, the proper modulation of these pathways is related to the reverse senescence of adult stem cells, which present the enhanced regenerative capacity of the tissues. For example, following overactivation of the p38α/β MAPK pathway, aged satellite cells are over-activated, and then increasingly generate their committed progenitors, while reducing self-renewal. However, pharmacological inhibition of p38α/β MAPK in aged satellite cells is able to restore the engraftment potential and improve their self-renewal ability by restoring asymmetric division.

It is known that tissue-specific stem cells are located in niches. The niche components can be considered somatic and stromal cells, immune cells, extracellular matrix (ECM), innervating neuronal fibers, and the vasculature. Although the niche structure varies among the different adult stem cell types, the stem cell niche provides essential cues to influence cell fate decisions. The aging of niche cells and age-dependent alterations in the components of stem cell niche are able to cause a loss of stem cell function. Fibroblast growth factor-2 (FGF-2), for example, is upregulated in the aged satellite cell microenvironment, whereas inhibition of FGF signaling can rescue the self-renewal capacity of old MuSCs. In addition, the cell surface receptor β1-integrin and the ECM protein fibronectin are dysregulated in aged MuSCs, and reconstitution of these components is able to restore the muscle regenerative capacity.

In addition to stem cell niche, aging also causes changes in circulating signals that directly or indirectly impact functions of tissue stem cells. These signals include soluble molecules secreted by any tissue in the body, which can be hormones, growth factors, and other signaling molecules or immune-derived signals secreted by infiltrating immune cells. Wnt ligand level is higher in old mouse serum and canonical Wnt signaling directly antagonizes Notch signaling in satellite cells. But Wnt inhibitors effectively restored the satellite cell function in aging, and a similar result is obtained in aged mesenchymal stem cells. The level of TGF-β is significantly increased in old human and mouse serum, which causes the damage and senescence of satellite cells. However, blockage of TGF-β signaling can reverse the activity of satellite stem cells, improving the myogenesis of aged mice.

Senescent cells accumulate with aging in several tissues of humans and animals, which is a common feature of age-related pathologies. Not only differentiated cells but also tissue-specific stem cells become senescence during aging. Moreover, the complex senescence-associated secretory phenotype (SASP) is highly expressed with accumulated senescent cells, which can alter the microenvironment and contribute to age-related pathologies. For example, the tissue regenerative capacity is impaired by the limited stem cell function because of their senescent state. And this decreased regenerative capacity is also regulated by the SASP that is secreted by senescent cells. Thus, the selective clearance of senescent cells and SASP suppression will be a promising therapy for age-related diseases. This concept has been successfully tested in physiologically aged mouse models.

As stem cells are the longest-living cells within an organism, stem cell aging is highly relevant as a driver of organismal aging, health, and longevity. In this review, we demonstrate that by targeting aging mechanisms, the aging associated phenotypes and functions of tissue-specific stem cells can be reversed. These restorative interventions hold promise for the possibilities of regenerative medicine and the treatment of many age-related diseases and dysfunctions.

HDAC inhibitors are a comparatively poorly understood category of drugs that act to modestly slow aging in short-lived laboratory species. As such, they most likely function through some form of upregulation of cellular stress responses, thus activating cellular maintenance processes that lead to improved cell and tissue function. That said, the chain of cause and effect leading from the known mechanism of action to that stress response upregulation is not clearly mapped. As for all approaches that slow aging via stress response mechanisms, we should remember that the effects on life span in short-lived species are much larger, relatively speaking, than those in long-lived species such as our own, even when the short term effects on the operation of metabolism are quite similar.

Calorie restriction is the canonical example of an intervention that upregulates maintenance processes, such as autophagy, that are activated under conditions of cellular stress. Calorie restriction can extend life span by up to 40% in mice, but certainly doesn't add more than a few years to human life expectancy, even while producing significant benefits to health. Further, therapies that upregulate the same mechanisms as calorie restriction are typically only recreating a fraction of the effects on metabolism, and thus should not be expect to produce the same degree of benefits. This is all worth bearing in mind.

It has become increasingly clear that epigenetics, including DNA methylation, histone modifications, and chromatin state, play a crucial role in the aging process. For example, by assessing changes in DNA methylation patterns, a person's age can be predicted within 5 years of accuracy. Histone modifications, including methylation and acetylation states, have been intimately linked to lifespan regulation. Together, these modifications dictate chromatin state, affecting both gene transcription and genome stability. Epigenetic changes occurring with age provide a tantalizing therapeutic target. In contrast to DNA mutations, epigenetic alterations represent reversible changes, offering the potential for a true "rejuvenating" therapeutic intervention. Of the various epigenetic alterations occurring with age, the influence of histone acetylation, a process balanced by the activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs), on lifespan regulation has been the most characterized, mainly due to the advent of HDAC inhibitors from the cancer biology field.

The exact means by which HDAC inhibitors extend lifespan has not been fully resolved; however, a number of possible mechanisms can be envisioned. One possible scenario is that HDAC inhibitors reverse the natural age-related changes occurring in the histone acetylation landscape. This is the most simple explanation for their benefits, supported by the observation that many acetylation marks on histones generally decrease with age and in certain age-related diseases. A second possible mechanism of HDAC inhibitors is that they may affect histones and nucleosomes to directly activate transcription of pro-longevity genes. This is supported by observations that an endogenous HDAC inhibitor, β-hydroxybutyrate (BHB), can increase acetylation in the promoter of the pro-longevity transcription factor FOXO3a resulting in its increased expression, and indeed, BHB's lifespan extending effects depend on HDAC genes.

A third possible mechanism through which HDAC inhibitors may increase lifespan is through hormesis. In this scenario, while high doses of HDAC inhibitors may be toxic, low doses would elicit activation of protective genes to regain homeostasis, ultimately improving function. This is supported by observations that flies treated with HDAC inhibitors show upregulation of heat shock protein chaperones, a class of genes that are usually upregulated under stress. A fourth possibility is that HDAC inhibitors may regulate lifespan by modifying the acetylation state of non-histone proteins, activating signaling cascades that promote longevity independent of histone modifications.

Despite the promising outlook of HDAC inhibitors for healthy aging, much work remains to be done to better understand their safety and how to minimize adverse side effects. Owing to their origins in the cancer biology field, many cell-type and dose-dependent negative effects of HDAC inhibitors on cell viability have been documented. Careful optimization of dose and drug pharmacokinetics should be made prior to pursuing any strategy in which HDAC inhibitors would be used as a prophylactic drug for healthy aging. More specifically, less-toxic versions of current drugs may be required. Understanding of the mechanism by which HDAC inhibitors extend lifespan is noticeably limited, and many mechanistic options remain. Deeper study of the specific modes of action of these compounds is necessary prior to their implementation as geroprotective compounds.

Link: https://doi.org/10.15252/emmm.201809854

Researchers here process statistical data to suggest that major surgery in later life accelerates cognitive decline. It would be interesting to compare data on serious injuries rather than surgery, as one of the possible mechanisms underlying this effect is a greater presence of senescent cells than would otherwise be the case. Senescent cells produce systemic chronic inflammation, and that is important in the progression of age-related neurodegeneration. Senescent cells are also generated in the course of wound healing, such as recovery from surgery, and some small fraction will always linger, failing to self-destruct or to be cleared from the body by the immune system. Thus we might expect severe injuries and major surgeries to produce some long term consequences to the pace of aging throughout the body. But this is pure speculation; the mechanism could just as well be something else.

Cognitive decline starts before conventional definitions of old age (often 65 years) and accelerates with aging and accumulation of comorbidities. Certain health events, such as stroke, can lead to profound changes in the cognitive trajectory such that there is a permanent "step change" in cognitive function. For 60 years a major concern has been that surgery might also drive long term changes in cognition. Yet studies investigating associations between surgery and long term cognitive outcomes have produced inconsistent results, with reports of cognitive harm, no effect, and cognitive improvement. Despite inconclusive evidence, considerable concern remains about the potential for surgery to induce cognitive impairment. Longer life expectancy implies an increasing number of surgical operations in older adults, hence a better understanding of the extent of any change in cognition after surgery is urgently required.

We use cognitive data from 7532 adults, investigating whether incident major surgical admissions are related to long term changes in the cognitive trajectory, using five waves of cognitive assessments spanning approximately 20 years, with adjustment for major medical admissions. To facilitate interpretation of results, we translate effect estimates to equivalent years of cognitive aging and relate changes to the effect of stroke, an event with an established impact on cognition. We primarily aimed to establish the mean population effect of major surgery on cognitive decline.

After accounting for the age related cognitive trajectory, major surgery was associated with a small additional cognitive decline, equivalent on average to less than five months of aging. In comparison, admissions for medical conditions and stroke were associated with 1.4 and 13 years of aging, respectively. Substantial cognitive decline occurred in 2.5% of participants with no admissions, 5.5% of surgical admissions, and 12.7% of medical admissions. Compared with participants with no major hospital admissions, those with surgical or medical events were more likely to have substantial decline from their predicted trajectory. In conclusion, major surgery is associated with a small, long term change in the average cognitive trajectory that is less profound than for major medical admissions. During informed consent, this information should be weighed against the potential health benefits of surgery.

Link: https://doi.org/10.1136/bmj.l4466

Adam Ford of Science, Technology, and the Future carried out a number of interviews while at Undoing Aging in Berlin earlier this year. The interview materials are steadily being processed and uploaded, and that just recently included this interview with Jim Mellon, billionaire investor and philanthropist, cofounder of Juvenescence, and a very down to earth fellow who is interested in improving the human condition by targeting aging with new biotechnologies. Accordingly, he has used his resources to put himself into a position to talk up the longevity industry, move research forward, and attract a great deal more funding for the next stage in the process of guiding the first treatments to slow and reverse aspects of aging from the laboratory to the clinic. These are interesting times, as our community expands considerably, and the state of the science and the medicine is progressing ever more rapidly.

My name is Jim Mellon, and I'm the chairman of Juvenescence, which is a company involved in the science of longevity. It is relatively recently formed, it is about a year and a bit old, but we've raised a significant amount of funding - nearly $160 million now - in the last year to advance the cause of longevity science. By the end of this year, we will have made 18 investments. Most of them are subsidiary companies of ours, so we control those companies. We give both development and financial backing to the scientist-entrepreneurs and institutions that we collaborate with.

I am fortunate to have two partners who have broad experience in the biotech and healthcare area, in particular Declan Doogan, who was the head of drug development at Pfizer for a long period, and then he worked at Amarin, which as you know is a very successful biotech company with a nearly $10 billion market valuation today. About four years ago, the three of us started a company called Biohaven, which is now listed on the New York Stock Exchange and has a valuation of about $2.5 billion. The company has approval for a drug for migraine, which will be on the market in the US next year. There is a good team of veteran drug developers who have come together to create this Juvenescence company, and we're very, very excited about it. We're the biggest investors in the company ourselves, on the same terms as other investors. We will take the company public in the first quarter of next year, barring market disasters, and probably on the US stock exchanges.

We're interested in this field of longevity science and able to raise significant funding because we've been in biotech for quite a long period of time, together, and created a number of companies. It seemed to be a natural outgrowth of the great developments that have occurred in the last few years. The unveiling of the human genome identified aging pathways that can now be manipulated. For the first time ever, you and I are in the cohort that is able to be bioengineered to live a healthier and longer life. It is still in a very primitive stage; we're in the internet dial-up era equivalent, but the science is advancing very quickly.

I always say that I wrote my first book on biotech seven years ago, it was called Cracking the Code, and since then we've had CRISPR/Cas9, which didn't exist seven years ago, we've had the cure for Hepatitis C, we've had artificial intelligence for the development of novel compounds. The latter of which is a key part of our strategy, as investors in In Silico Medicine, which I think you are familiar with. Then, of course, you have cancer immunotherapy, which didn't exist seven years ago, and is now a $100 billion / year industry. So what is going to happen in the next seven years? We don't know, but you can bet that it is going to be very, very good. So, if you want to regard it as a casino table, we're covering all the markers that we can with the funds that we've raised. We hope to raise a substantial further amount on the initial public offering of the company in the first quarter of next year, and that will give us enough resources to carry out five phase II trials without partners, so that we can get the maximum leverage on the products that we're developing.

So far we've invested in small molecules, which is the specialization of our team. For instance we have a senolytic drug in development in that area. We've also invested in stem cells; we're the largest investor in Mike West's company AgeX Therapeutics, which is now a public company in the US. We own about 46% of that company. Then via Lygenesis we've also got our first product going into patients in the first quarter of next year, sick patients in a phase II trial, for organ regeneration, regenerating the liver, using hepatocytes to seed lymph nodes to act as organic bioreactors to grow fully functioning liver tissue. The FDA has agreed to the protocol for doing that in sick patients, which is a remarkably fast path to demonstrating successful outcomes in that area. If that is successful, then we will look to regenerate other organs, in particular the thymus, which as you know is related to aging in a big way.

So we're moving very, very quickly. We've got great colleagues; Margaret Jackson from Pfizer is on our team. Howard Federoff, ex-Pfizer, is on our team. Annalisa Jenkins, who was head of drug development and research and development at Merck Serono, a very big company, is on our team. We've put it all together remarkably quickly. But we have experience in doing that, and so we're full of confidence. This is a remarkable time to be alive, and I want to be alive for at least another 20 or 30 years beyond what would be considered to be my allotted life span. The same is the motivating factor for my cofounders, Declan Doogan and Greg Bailey.

Working to extend life is an ethical cause. No-one can argue, successfully at least, that this isn't a good thing to do. There are some people who say "well, it is for the haves and not for the have-nots" but that is rubbish, because ultimately all these drugs will become generally available, and some of them already are. Metformin, which as you aware is a drug that has some anti-aging properties, costs essentially nothing. It is a generic drug. In the same as antibiotics and ulcer drugs and so forth were once expensive and are now very cheap, the same thing will happen to drugs for longevity. Gene therapy and stem cells is another matter, though, and that will probably be an expensive thing for some time to come. But undoubtedly, the cost will come down for those as well.

The other people who argue against work on aging talk about overpopulation; if there are all these old people, will there be enough room on the planet. Well the answer is, we're already alive, so we're not going to be adding to the population. You and I are already here. The big issue on population is how many children does each woman have around the world, and that figure is falling dramatically, to the point where we can see populations actually shrinking. Just as an example, if Japan doesn't all immigration, or doesn't have a baby boom, its population will fall from 126 million today to 50 million by the year 2100. So both those arguments, the haves versus the have-nots, and the overpopulation concern, are nonsensical arguments. In my view there is absolutely no reason why governments, institutions, the general population, the voting population, shouldn't be pushing really hard to make this happen.

Regarding the aging of the existing population and how to cope with it, the main point made by Aubrey de Grey, and other eminent scientists as well, is that if you treat the top of the cascade of damage in aging, then you are going to treat the underlying diseases of aging that pharmaceutical companies are trying to address. But for those pharmaceutical companies, it is a whack-a-mole exercise, so if you get one disease and that is cured, then you'll get another one, and they'll have to cure that one. Ultimately we become destabilized and we die, all of us. So let us try and treat aging as the central disease, and from that as the unitary disease, we'll be treating the cascade that follows from that.

Some people say it is hubris to target aging, but I think that this is because until relatively recently nothing worked. It has been an aspiration of human beings for millennia to find the fountain of youth, and nothing has worked. So people are skeptical about the fact that it might be working now. Why now rather than 20 years ago or 20 years in the future? But the fact is that it is now, and we need to seize the moment and rise to the challenge. We need much more funding to come into this area, and that funding will drive the science. We need many more advocates for this cause to come to the fore and spread the word, that this is going to be monumentally great for humanity.

In my own case, I've set up a charity with Andrew Scott, who wrote The 100 Year Life, and we do a Longevity Week in London. We did the first one last year, and we're doing the next one in November of this year, to spread the word. This will have a big societal impact, on consumption, on the way in which we look at the trajectory of life, but it is also going to have a major impact on us as human beings. In the past you'd have expected to live to about 85 or 90, the same with me, and now we're very likely to live to 110 or 120. So let's do it. Let's make it happen. I think that all of us, yourself, myself, have relatives, dear friends, acquaintances, who are suffering the indignities of aging as it currently exists. We would like to relieve that burden of suffering by extending the healthy span of life. The personal motivation is a very big factor. Here in Berlin, there are 300 or 400 people at this conference, and I imagine that all of them, beyond the business side of things, have an altruistic motivation for this as well. More people need to do it, so get on to it!

The elevator pitch for high net worth people thinking about investing in this space is that, first of all, we're at the front end of a huge upward curve. I said earlier on that this was like the internet dial up phase of longevity biotech. If you'd invested in the internet in the very early days, you'd be more than a billionaire now, you'd be one of the richest people on the planet. We're at that stage now, so the opportunity for investors is huge. But you could do both. You could invest in something like the SENS Research Foundation or the Buck Institute or one of those wonderful organizations that is trying to advance the cause, and at the same time invest in some of the companies that come out of those institutions. We've undertaken two joint ventures with the Buck Institute, we've made a couple of investments as a result of introductions by the SENS Research Foundation, including the organ regeneration program. So if you're a sensible billionaire, you will be putting some of your funds to work in a combination of a charitable enterprise that drives the science and the businesses themselves that come out of those enterprises.

Retrotransposons are genetic sequences that can copy themselves to new locations in the genome. This activity increases with age, for reasons that are still poorly understood, and it is an open question as to the degree to which this is important as a cause of tissue dysfunction with aging. The arguments for and against are much the same as those for stochastic mutation of nuclear DNA to be a meaningful contribution to degenerative aging, with the most compelling model being the one in which mutations in stem or progenitor cells can spread widely in a tissue through their descendant somatic cells.

This open access paper is focused on assessing the growth in retrotransposon activity and the increasing burden of senescent cells with advancing age, the latter of which is of great interest given the development of senolytic therapies capable of selectively destroying senescent cells in old tissues. The two topics are not completely divorced from one another, as senescent cells have been shown to have higher retrotransposon activity, and this is necessary for the harmful signals that they generate, known as the senescence-associated secretory phenotype (SASP).

Tissue aging is the gradual decline of physiological homeostasis accompanied with accumulation of senescent cells, decreased clearance of unwanted biological compounds, and depletion of stem cells. Senescent cells were cell cycle arrested in response to various stimuli and identified using distinct phenotypes and changes in gene expression. Senescent cells that accumulate with aging can compromise normal tissue function and inhibit or stop repair and regeneration. Selective removal of senescent cells can slow the aging process and inhibits age-associated diseases leading to extended lifespans in mice and thus provides a possibility for developing antiaging therapy.

To monitor the appearance of senescent cells in vivo and target them, a clearer understanding of senescent cell expression markers is needed. We investigated the age-associated expression of three molecular hallmarks of aging: SA-β-gal, P16INK4a, and retrotransposable elements (RTEs), in different mouse tissues at three different stages in the aging process (1 month, 12 months, and 24 months). Our data showed that the expression of these markers is variable with aging in the different tissues. P16INK4a showed consistent increases with age in most tissues, while expression of RTEs was variable among different tissues examined.

Increased β-gal staining in cerebellar Purkinje neurons might reflect locomotor incoordination that is often associated with aged individuals. Increased β-gal staining also was observed in the hippocampus and substantia nigra, which are major brain regions associated with neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, respectively. In addition, human aging is associated with reduced amounts of cerebrospinal fluid (CSF) and increased protein concentrations, which might be attributed to an aged choroid plexus. Thus, specific brain regions appear to be highly sensitive to an aging phenotype, which suggested that further investigations are warranted, especially for the choroid plexus and for the unique functions of CSF in healthy people and patients.

Similar to the brain, mouse kidneys demonstrated significant upregulation of the aging markers used in this study, especially in the renal cortex. It was surprising that the kidneys expressed a senescent phenotype earlier than any of the other organs included in this study. These findings might reflect the essential role of the kidney in the aging process. Previous studies have not focused on this relationship. The kidney is important in maintaining homeostasis of the body, suggesting that aging of the kidney is more likely to occur earlier than other organs and possibly the age-related decline of other organs might be a consequence of failure of the kidney to effectively eliminate circulating age-inducing molecules. Since elderly humans have less renal functional reserve and are more susceptible to chronic renal diseases, actions to preserve renal function might help to delay or alleviate aging-related consequences in the whole body.

We demonstrated that aging significantly influenced specific brain regions, the renal cortex, pulmonary bronchioles, and interstitial cells of the testes but had little or no effect on lung parenchyma, the liver, heart, and testicular seminiferous tubules. In conclusion, the gradual functional decline of peripheral organs might be a consequence of the aging brain or kidneys either through aging of neurons that influence these organs or through failure of the kidneys to eliminate age-associated molecules that occur due to environmental and genetic causes. Additionally, the age-dependent changes in RTE expression may be related to changes in function rather than directly associated with the aging process. The upregulation of RTEs in the mouse brain and kidneys might positively enhance the clearance of P16INK4a-positive cells.

Link: https://doi.org/10.1155/2019/2818415

The gut microbiome is influential on the progression of health, perhaps to a similar degree as regular moderate exercise. Age-related changes in these microbial populations can promote chronic inflammation and tissue dysfunction, though the direction of causation is still up for debate when it comes to many of the details of the relationship between tissue and immune issues in the intestine and an altered gut microbiome. Nonetheless, less desirable microbes undertake activities that can raise the risk of cancer resulting from inflammation of the intestines, occurring in conditions such as inflammatory bowel disease. Researchers here demonstrate that suitable adjustment of microbial populations in mice can lower the incidence of cancer in this circumstance. This is one application among what will no doubt be many cases in which the gut microbiome can be shifted in ways that promote better health over the long term.

People living with inflammatory bowel disease (IBD) have a three- to sevenfold higher risk of developing colon cancer. Researchers have now shown that precision editing of the bacterial populations in the gut reduces inflammation-associated colorectal cancer in mice. "The most significant finding in this study is that manipulating the intestinal microbiome is sufficient to affect the development of tumors. One could envision a time in which medications that change the behavior and composition of the bacteria that live in the gut will be part of the treatment for IBD."

In addition to colorectal cancer, long-standing IBD is associated with imbalances in the bacterial species that line the gut. "Our intestinal tract is teeming with microbes, many of which are beneficial and contribute to our overall health. Yet, under certain conditions, the normal function of these microbial communities can be disturbed. An overabundance of certain microbes is associated with increased risk for the development of diseases, including certain cancers." The strategy used in the study targets metabolic pathways that are only active during intestinal inflammation and only in some forms of bacteria, providing an Achilles' heel for reducing their abundance. The current study builds on work that found the approach prevented or reduced inflammation in a mouse model of colitis, while having no obvious effect on healthy control animals with balanced bacterial populations in their guts.

"For example, most E. coli bacteria are harmless and protect the human gut from other intestinal pathogens such as Salmonella, a common cause of food poisoning. However, a subset of E. coli bacteria produce a toxin that induces DNA damage and can cause colon cancer in research animals. We developed a simple approach - giving a water-soluble tungsten salt to mice genetically predisposed to develop inflammation - to change the way potentially harmful E. coli bacteria generate energy for growth. Restricting the growth of these bacteria decreased intestinal inflammation and reduced the incidence of tumors in two models of colorectal cancer. Tungsten is a heavy metal and should not be used by anyone due to its toxicity. This is a proof-of-concept study that will guide us in developing future drugs with similar activity and less toxicity."

Link: https://www.utsouthwestern.edu/newsroom/articles/year-2019/precision-editing-gut-bacteria.html

A fair number of research groups are presently working on ways to force large numbers of cells in the body to adopt more youthful epigenetic profiles. Much of this research is an outgrowth of the discovery of induced pluripotency, the ability to reprogram any cell into a pluripotent stem cell that is largely indistinguishable from an embryonic stem cell, capable of generating any of the cell types in the body. This process also happens to reset many of the epigenetic markers of age that are found in cells in old tissues, alongside restoring mitochondrial function by clearing out damaged mitochondria, and a few other interesting changes. The article here focuses on one representative project, but readers here might be more familiar with the work of Turn.bio in the same space, since it was covered recently.

The important question to be addressed here is this, since it is frequently mentioned: are epigenetic changes a cause of aging? To my eyes the answer is no, a thousand times no. They are - they must be - a downstream consequence of the true cause, which is the molecular damage that accumulates with age as a normal side-effect of the operation of cellular metabolism. However, since these epigenetic changes themselves cause further harm, one can, in principle and in animal studies, produce benefits by forcing cells to adopt a more youthful epigenetic profile for various genes of interest. But this does nothing to address the cause of aging, the underlying damage.

Without repair, the underlying causative damage of aging will continue to cause all of the problems that cannot be ameliorated by forcing a mass change in epigenetic programming and consequent cellular behavior. Consider the presence of molecular waste that the body cannot effectively clear, such as persistent cross links degrading extracellular matrix elasticity, or hardy constituents of lipofuscin making autophagy inefficient in long-lived cells, or potentially cancerous nuclear DNA damage. I predict that epigenetic reprogramming is not going to meaningfully address these line items, because youthful cells and tissues cannot meaningfully address these forms of damage if present. Reprogramming may well turn out to be as useful a tool as stem cell therapies for the purpose of regeneration of functional tissues, though with a very different focus on the type of functional improvement obtained. But be wary of those who claim that epigenetic change is the cause of aging, and that turning it back will fix all issues.

Has this scientist finally found the fountain of youth?

Izpisúa Belmonte, a shrewd and soft-spoken scientist, has access to an inconceivable power. These mice, it seems, have sipped from a fountain of youth. Izpisúa Belmonte can rejuvenate aging, dying animals. He can rewind time. But just as quickly as he blows my mind, he puts a damper on the excitement. So potent was the rejuvenating treatment used on the mice that they either died after three or four days from cell malfunction or developed tumors that killed them later.

The powerful tool that the researchers applied to the mouse is called "reprogramming." It's a way to reset the body's so-called epigenetic marks: chemical switches in a cell that determine which of its genes are turned on and which are off. Erase these marks and a cell can forget if it was ever a skin or a bone cell, and revert to a much more primitive, embryonic state. The technique is frequently used by laboratories to manufacture stem cells. But Izpisúa Belmonte is in a vanguard of scientists who want to apply reprogramming to whole animals and, if they can control it precisely, to human bodies.

Izpisúa Belmonte believes epigenetic reprogramming may prove to be an "elixir of life" that will extend human life span significantly. Life expectancy has increased more than twofold in the developed world over the past two centuries. Thanks to childhood vaccines, seat belts, and so on, more people than ever reach natural old age. But there is a limit to how long anyone lives, which Izpisúa Belmonte says is because our bodies wear down through inevitable decay and deterioration. "Aging is nothing other than molecular aberrations that occur at the cellular level." It is, he says, a war with entropy that no individual has ever won.

The treatment Izpisúa Belmonte gave his mice is based on a Nobel-winning discovery by the Japanese stem-cell scientist Shinya Yamanaka. Starting in 2006, Yamanaka demonstrated how adding just four proteins to human adult cells could reprogram them so that they look and act like those in a newly formed embryo. To many scientists, Yamanaka's discovery was promising mainly as a way to manufacture replacement tissue for use in new types of transplant treatments. Researchers at the Spanish National Cancer Research Centre took the technology in a new direction when they studied mice whose genomes harbored extra copies of the Yamanaka factors. Turning these on, they demonstrated that cell reprogramming could actually occur inside an adult animal body, not only in a laboratory dish. The experiment suggested an entirely new form of medicine. You could potentially rejuvenate a person's entire body. But it also underscored the dangers. Clear away too many of the methylation marks and other footprints of the epigenome and "your cells basically lose their identity."

To others, however, the evidence for rejuvenation is plainly in its infancy. Jan Vijg, chair of the genetics department at the Albert Einstein College of Medicine in New York City, says aging consists of "hundreds of different processes" to which simple solutions are unlikely. Theoretically, he believes, science can "create processes that are so powerful they could override all of the other ones. We don't know that right now." An even broader doubt is whether the epigenetic changes that Izpisúa Belmonte is reversing in his lab are really the cause of aging or just a sign of it - the equivalent of wrinkles in aging skin. If so, Izpisúa Belmonte's treatment might be like smoothing out wrinkles, a purely cosmetic effect. "We have no way of knowing, and there is really no evidence, that says the DNA methylation is causing these cells to age," says John Greally, another professor at Einstein. The notion that "if I change those DNA methylations, I will be influencing aging has red flags all over it."

The issue with first generation cell therapies for regenerative medicine is that transplanted cells near entirely fail to engraft into tissue. There are exceptions, but for the most part, the cells used in therapy die rather than take up productive work to enhance tissue function. Where benefits occur, they are mediated by the signals secreted by the transplanted cells in the brief period they remain alive. Mesenchymal stem cell therapies that reduce chronic inflammation for some period of time are an example of the type. They are good at that outcome of reduced inflammation, but highly unreliable when it comes to any other desired result, such as increased regeneration.

Thus an important goal in regenerative medicine and tissue engineering circles is to solve the issue of engraftment, and enable the reliable delivery of cells that survive to participate in improving tissue function. Numerous strategies have been tried, with varying degrees of success. The best to date is to provide cells with a surrounding biodegradable scaffold that incorporates supporting nutrients and signals. This can work quite well when cells are allowed to form a pseudo-normal tissue like structure prior to transplantation, for example in heart patches or retina patches. The research noted here offers quite a different and much simpler strategy to improve engraftment rates, the removal of lower quality cells from the cell population created for transplantation.

Biomedical engineers believe they can aid the failing heart by using pluripotent stem cells to grow heart muscle cells outside of the body, and then injecting those muscle cells or adding a patch made from those cells, at or near the site of the dead heart tissue. Experimental and clinical trial evidence with this approach has shown moderate improvement of the pumping ability of the heart's left ventricle. However, the ability of the delivered cells to remuscularize the heart and improve cardiac function depends on the quality of those cells. A challenge has been low rates of engraftment by the transplanted cells.

Researchers now report a simple method to improve the quality of the delivered cells, and they found that this method - tested in a mouse heart attack model - doubled the engraftment rate of the injected stem cell-derived cardiomyocytes. The robust approach to select functionally competent, intact-DNA cells from a heterogeneous population can be easily adopted in clinical settings to yield cells that are better able to repopulate the ischemic myocardium and improve the performance of a failing heart.

Cardiac cell transplantation requires millions of stem cells or their differentiated derivatives. Cell propagation under accelerated growth conditions is a common way to get these large numbers of cells; but accelerated growth causes culture stress, including lethal DNA damage. These DNA-damaged cells are not suitable for cell transplantation and have to be removed from cell preparations. The researchers found they could activate transcription factor p53 in induced pluripotent stem cells to selectively induce programmed cell death, or apoptosis, specifically in DNA-damaged cells, while sparing DNA damage-free cells. They used Nutlin-3a, an MDM2 inhibitor, to activate the p53. After Nutlin-3a treatment, the dead cells were washed from the culture, and the remaining DNA damage-free cells were cultured normally and differentiated into cardiomyocytes.

The researchers then injected 900,000 of the derived cardiomyocytes into the border zone in the left ventricle of the mouse heart attack model. Four weeks later, the researchers found a significantly higher engraftment rate, about 14 percent, in hearts that received the DNA damage-free cardiomyocytes. Engraftment of the control derived cardiomyocytes was about 7 percent. "As this is a small molecule based approach to select DNA damage-free cells, it can be applied to any type of stem cells, though selection conditions would need to be optimized and evaluated. Other stem cell approaches for diseases such as neurodegenerative diseases, brain and spinal cord injuries, and diabetes might benefit by adopting our method."

Link: https://www.uab.edu/news/research/item/10661-a-simple-method-to-improve-heart-attack-repair-using-stem-cell-derived-heart-muscle-cells

Researchers here suggest that infection plays an important role in cardiovascular disease in later life, and that the chronic inflammation of aging is a factor in allowing infection to cause significant harm to the heart. This is one of countless issues that could be mitigated through rejuvenation of the aging immune system, fixing the underlying issues that cause the immune system to become less functional and more inflammatory. These include atrophy of the thymus, the loss of thymic tissue where T cells of the adaptive immune system mature, loss of hematopoietic stem cell capacity, leading to reduced generation of new immune cells, the structural aging of lymph nodes, preventing immune cells from efficiently coordinating with one another, and the accumulation of senescent and otherwise dysfunctional immune cells.

Infection and infectious disease associated pathologies are often complicated by delays in immune response generation and excess inflammation that impact infection resolution. The term "inflammaging" was coined to denote the multifaceted dysregulation of homeostatic processes that over time culminates in quantifiable, organism-wide shifts towards inflammation in old age. As we shift our focus towards understanding the impact of inflammaging, we have recently determined that inflammaging may also accelerate the decline in cardiovascular fitness.

Age is a major prognostic factor for the development of non-tuberculous mycobacteria (NTM) disease, with recent clinical data reflecting increased incidence of NTM infection in elderly individuals. It is also known that tuberculosis (TB) caused by Mycobacterium tuberculosis (M.tb) can cause pericarditis, endocarditis, and myocarditis leading to sudden deaths. TB is a major global killer and it is estimated that 57% of all TB deaths globally occur in individuals older than 65. Based upon abundant circumstantial evidence, a direct link between mycobacterial infections, aging, and cardiac dysfunction was hypothesized by our group.

We examined how mycobacterial infection and inflammaging catalyze the decline in cardiovascular function in the elderly. Young (3 months) and old (18 month) female C57BL/6 mice were infected with a sub-lethal dose of Mycobacterium avium (M. avium), an NTM. We observed no differences in the M. avium bacterial numbers in the lung, liver, or spleen between young and old M. avium infected mice. However, through the course of M. avium infection, old mice developed severe dysrhythmia and developed pericarditis. Moreover, the hearts of M. avium infected old mice had increased cardiac hypertrophy, fibrosis, expression of pro-inflammatory genes, and infiltration of immune cells, which are hallmarks of myocarditis.

Since these cardiac abnormalities only manifested in old mice, we investigated several factors that contribute to this form of age dependent infectious myocarditis. Independent of M. avium infection, old mice had increased levels of pro-inflammatory cytokines in their serum, which may have predisposed old mice to infectious myocarditis. The reasons for increased inflammation in old age are multifaceted, and future studies will be needed to identify the principal sources of increased inflammation and whether ameliorating inflammation prevents NTM associated cardiac complications in old mice. This highlights how even low or what we may generally consider as insignificant bacterial loads can profoundly impact cardiovascular health.

Link: https://doi.org/10.18632/aging.102128

Today's open access paper is a review of present progress towards regenerative therapies that can reverse hearing loss. Progressive hearing loss is pervasive in old age, and accelerates considerable in the later stages of life. Hearing loss correlates with cognitive decline, and while it is plausible that this is because of degeneration of central nervous system function, there is also the consideration that loss of hearing isolates people and deprives them of interactions that stimulate brain activity. It is well demonstrated in mice that environment richness has a strong impact on the brain and its pace of aging.

Much of the research into age-related hearing loss is focused on the sensory hair cells of the inner ear. These detect the pressure waves of sound and in response pass impulses into nervous system connections leading to the brain. There is some evidence for loss of these cells to be the problem, and some evidence for the cells to survive in sufficient numbers, but lose their connections to the brain. Numerous research teams over the past decade or more have worked on producing regenerative therapies to regrow functional hair cells in the aged inner ear. Numerous strategies have been attempted, such as adapting mechanisms from regenerative species that can regrow hair cells as adults, or direct stimulation of pathways such as Notch that are associated with growth. Varying degrees of success have been demonstrated in mice, but as is often the case, progress towards the clinic remains frustratingly slow.

Hearing regeneration and regenerative medicine: present and future approaches

More than 5% of the world population lives with some degree of hearing impairment. The main factors behind hearing degeneration are ototoxic drugs, aging, continued exposure to excessive noise and infections. After an injury, the auditory system is damaged irreversibly, because the regeneration system is inhibited or deactivated in higher mammals, oppositely to other non-mammalian vertebrates. The pool of adult stem cells in the inner ear drops dramatically after birth. Therefore, an endogenous cellular source for regeneration is absent. In mammals, hair cells (HCs) are only generated during a short embryonic period; hence, their loss in adults produces an irreversible hearing defect. Similarly, the spiral ganglion neurons (SGNs) degeneration is unrecoverable and in the case of synaptic loss, recovery has been shown to be limited.

Because of the drastic reduction in the number of stem cells in the inner ear after the neonatal period, the autonomous regenerating capacity is almost depleted. Therefore, many research groups have focused their efforts on developing stem cell-based treatments to restore HC, SGN, and SC populations. The auditory regeneration field is mainly focus on embryonic stem cells, adult stem cells, or induced pluripotent stem cells (iPSCs). However, nowadays the main issues to be solved are the obtaining of a proper efficiency in the production of auditory stem cells and to demonstrate the utility and safety of these cells in a clinical context. Experimentation in animal models with regenerative capacity, such as zebrafish or avian models, has shown that their auditory regeneration is guided by the same genetic pathways activated during embryonic development. That mechanism leads to HC or stereocilia regeneration by different mechanisms, that have aroused great interest for the development of novel therapies that can reconstruct these pathways in humans.

In our opinion, the important discoveries in this area are mainly focused on the development of methods for stem cell transplantation, improving migration, survival, and new genetic systems for cell fate monitoring. Different routes for stem cell transplantation to the cochlea have been tested, such as through the perilymph or the endolymph. Although these techniques are promising, their results show a low cell survival rate, with only small populations of new cells at the target tissue. Transplantation of cells into the modiolus (bone lamina inside the cochlea) or in the cochlear nerve, showed a higher cell survival rate and increased migration to the target. However, the transplantation process involves potential hearing damage. The direct transplantation of stem cells on the side wall tissue of the cochlea seems to achieve efficient results. The abundance of tissue and blood supply to the area, may be responsible for the increased survival of grafted cells in the wall.

In our opinion, hearing regeneration should be considered from a multidisciplinary point of view, not only focused on stem cells, but also considering molecular mediators as a strategy to improve the outcome. Some combined therapies have been shown to be a better approach to treat some diseases than singular therapies, for instance, stem cell delivery with gene therapy to treat critical limb ischemia. The transplantation of stem cell-derived otic progenitors or adult stem cells (as neural stem cells), results in a significant improvement in hearing, which is especially noticeable in neuronal regeneration. However, the cells have to properly migrate to the damaged area and promote the establishment of functional synaptic connections between HCs and SGNs, which could be improved with molecular mediators or genetic engineering.

The open access editorial noted here serves as an introduction to some of the current thinking on the role of cytomegalovirus (CMV) in the age-related decline of the immune system. CMV infection is pervasive throughout the population, particularly in the old. This persistent viral infection cannot be effectively cleared by the immune system, and an ever greater percentage of immune cells become uselessly specialized to fight CMV. This leaves ever fewer immune cells ready to tackle other threats. This seems an important component of immune dysfunction, one that can perhaps be addressed by selectively destroying these immune cells to free up space for replacements. The research community is by no means unified on this view of CMV, however, as illustrated here.

Aging represents a paradox of immunodeficiency and inflammation (inflammaging) and autoimmunity. Over the lifespan there are changes in the architecture and functioning of the immune system, often termed immunosenescence. Recently, there have been major developments in understanding the cellular and molecular bases, and genetic and epigenetic changes, in the innate and the adaptive immune system during aging, and the interactions between these separate arms of vertebrate immunity. Limited longitudinal studies have begun to reveal biomarkers of immune aging, which may be considered to constitute an "immune risk profile" (IRP) predicting mortality and frailty in the very elderly. Hallmark parameters of the IRP may also be associated with poorer responses to vaccination.

The usually asymptomatic infection with the widespread persistent cytomegalovirus, CMV, has an enormous impact on immune biomarkers, but according to the circumstances and depending on what is measured, this can translate into a detrimental or a beneficial effect. The prevalence of CMV infection in populations in industrialized countries increases with age, and within individuals the degree of immune commitment to anti-CMV responses also increases with age. This may cause pathology by maintaining higher systemic levels of inflammatory mediators ("inflammaging") and decreasing the "immunological space" available for immune cells with other specificities, or it may exert beneficial "adjuvant-like" effects. Modalities to prevent or reverse immunosenescence may therefore need to include targeting infectious agents such as CMV in a robustly personalized manner.

Because of the increasing recognition that CMV has a marked impact on immune parameters commonly associated with age, it is crucial to dissect out whether age or CMV is responsible for altering biomarkers predictive of health status (e.g., frailty) or other important parameters such as response to vaccination (especially seasonal influenza). Researchers have investigated whether T cell responsiveness to a range of CMV proteins is different in younger and older healthy people and whether relaxation of anti-CMV immunosurveillance in later life could contribute to disease. They found that CMV-specific CD4+ T cells secreting the anti-inflammatory cytokine IL 10 were predominantly directed to latency-associated CMV proteins and that these responses were not greater in the elderly than the young. However, the frequency of IFN-γ-secreting CD4+ T cells correlated with latent viral genome copy number in monocytes. They conclude that viremia is rare in the elderly due to the maintenance of T cell responsiveness but that CMV can be an important comorbidity factor in people who are not perfectly healthy.

Further complications in analyzing the impact of CMV may arise because most human data are derived from studies using peripheral blood. However, the bone marrow harbors large amounts of late-stage differentiated CD8 T cells possibly because the production of IL 15 is greater in CMV-infected individuals. Also, expression of the NK-associated receptor CD161 is similar in CMV-seropositive and seronegative young subjects but is different in the elderly, illustrating that CMV effects may be different at different ages. The large accumulations of CMV-specific T cells, also in the bone marrow, may contribute to the state of inflammaging, but it is likely that other immune (and non-immune) cells are also major contributors. Cells of the innate immune system far outnumber those of adaptive immunity and may also be heavily influenced by the presence of CMV, contributing to inflammaging.

Link: https://doi.org/10.3389/fimmu.2019.01614

Given the newfound acceptance of cellular senescence as an important cause of aging, many more research groups are assessing the impact of senescent cells in their research into aging. Here, the focus is on chromatin organization, a collection of nuclear structures and processes in the cell that appear to have some influence over the pace of aging over a lifetime. The researchers discover that the gene DGCR8 accelerates the appearance of senescent cells and dysfunction when mutated, and thus producing broken protein machinery, but slows the accumulation of lingering senescent cells when overexpressed in its correct form. This touches on some of the same machinery of the cell as the mir-122 findings discussed a few days ago, and that work is worth comparing with the notes here, as an example of just how complicated this all is.

Stem cell aging is newly recognized as an important culprit in organismal aging. For example, aging of mesenchymal stem cells (MSCs) has been shown to drive aging-associated tissue degeneration. MSCs, which have the potential to differentiate into mesodermal lineages like osteoblasts, chondrocytes, and adipocytes, can be isolated from various tissues including bone marrow, cord blood, adipose tissue, and dental pulp. Premature depletion of MSCs is observed in patients with Hutchinson-Gilford progeria syndrome (HGPS) and Werner syndrome (WS), two premature aging diseases that are associated with accelerated atherosclerosis, osteoporosis, and osteoarthritis. Despite numerous studies showing that MSCs play pivotal roles in tissue rejuvenation, regeneration, and repair by differentiating into various somatic cell types, little is known about the key regulators of MSC aging.

Aging-associated declines in stem cell functionality are often accompanied by epigenetic changes, such as changes in genomic DNA methylation, histone modifications, and chromatin remodeling enzymes. Heterochromatin domains are structurally inaccessible and usually transcriptionally inactive. These domains are established during early stages of embryogenesis and are gradually lost with aging, resulting in the de-repression of normally silenced genes. Whereas heterochromatin loss drives human MSC (hMSC) aging, the re-establishment of heterochromatin alleviates premature aging and promotes longevity in Drosophila and human cells, suggesting that the maintenance of heterochromatin organization could be an effective therapeutic intervention against aging.

DiGeorge syndrome critical region 8 (DGCR8) is a critical component of the canonical microprocessor complex for microRNA biogenesis. Here, we demonstrate that DGCR8 plays an important role in maintaining heterochromatin organization and attenuating aging. A truncated version of DGCR8 accelerated senescence in human mesenchymal stem cells (hMSCs) independent of its microRNA-processing activity. Further studies revealed that DGCR8 maintained heterochromatin organization. DGCR8 was downregulated in pathologically and naturally aged hMSCs, whereas DGCR8 overexpression alleviated hMSC aging and mouse osteoarthritis. Taken together, these analyses uncovered a novel, microRNA processing-independent role in maintaining heterochromatin organization and attenuating cellular senescence by DGCR8, thus representing a new therapeutic target for alleviating human aging-related disorders.

Link: https://doi.org/10.1038/s41467-019-10831-8

Atherosclerosis is a condition in which fatty lesions form to narrow and weaken blood vessels. It causes a sizable percentage of all deaths in old age, via stroke or heart attack when lesions rupture. Much of the focus in the medical and research communities is on cholesterol in the bloodstream as a contributing factor to the condition, but atherosclerosis should be thought of as being primarily caused by the dysfunction of the macrophage cells responsible for removing cholesterol from blood vessel tissues, handing it off to HDL particles to return to the liver. In youth these cells function just fine, and young people don't develop lesions. In old age, however, it is a different story.

Macrophages are vulnerable to oxidized cholesterol and to the signaling of chronic inflammation. Both can degrade their ability to transport cholesterol, and they can develop into senescent foam cells that make the local environment even more inflammatory. They also die in large numbers, overwhelmed by cholesterol, and the debris of cell death expands the lesion that the macrophages should be helping to remove. It is because oxidized cholesterol is important in this process that reductions in overall cholesterol in the bloodstream can slow the progression of atherosclerosis. Treatments such as statins have become widely used as a result, but they do not lead to significant reversal of existing lesions.

Scientists here note that most of the work on atherosclerosis to date focuses on reducing LDL cholesterol in the bloodstream, which is to say cholesterol attached to an LDL particle. But other forms of cholesterol are also present in the blood stream, the so-called remnant cholesterol, and the research community has underestimated its presence and contribution to atherosclerosis. This has implications for the various approaches taken to try to control the condition, and further demonstrates that perhaps it is a better idea to focus on the macrophages rather than on the cholesterol. If macrophages can be made resilient to oxidized cholesterol, either by removing that cholesterol in a targeted way, by preventing it from being created in the first place, or by giving the macrophages additional capabilities, as we're working on at Repair Biotechnologies, then this should go a long way towards the goal of reversal of atherosclerosis.

Levels of 'Ugly Cholesterol' in the Blood are Much Higher than Previously Imagined

Three quarters of the Danish population have moderately elevated levels of cholesterol. If cholesterol levels are too high, risk of cardiovascular disease is increased. Often, LDL cholesterol, the so-called bad cholesterol, is considered the culprit. However, new research shows that a completely different type of cholesterol may be more responsible than previously assumed. What we are talking about is remnant cholesterol To their surprise, the researchers have discovered that the amount of remnant cholesterol in the blood of adult Danes is much higher than previously believed. From the age of 20 until the age of 60, the amount in the blood is constantly increasing, and for many people it remains at a high level for the rest of their lives.

"Our results show that the amount of remnant cholesterol in the blood of adult Danes is just as high as the amount of the bad LDL cholesterol. We have previously shown that remnant cholesterol is at least as critical as LDL cholesterol in relation to an increased risk of myocardial infarction and stroke, and it is therefore a disturbing development." The results are based on data from people from the Copenhagen General Population Study. A total of 9,000 individuals had cholesterol in their fat particles in the blood measured by metabolomic techniques. "Previous studies from the Copenhagen General Population Study show that overweight and obesity are the main cause of the very high amount of remnant cholesterol in the blood of adult Danes. In addition, diabetes, hereditary genes and lack of exercise play a part."

In 2018, a large international, controlled clinical trial was published that clearly showed that when triglycerides and thus remnant cholesterol were reduced by the help of medication in people with elevated levels in the blood, the risk of cardiovascular disease was reduced by 25%. "Our findings point to the fact that prevention of myocardial infarction and stroke should not just focus on reducing the bad LDL cholesterol, but also on reducing remnant cholesterol and triglycerides. So far, both cardiologists and GPs have focused mostly on reducing LDL cholesterol, but in the future, the focus will also be on reducing triglycerides and remnant cholesterol."

A third of nonfasting plasma cholesterol is in remnant lipoproteins: Lipoprotein subclass profiling in 9293 individuals

Increased concentrations of calculated remnant cholesterol in triglyceride-rich lipoproteins are observationally and genetically, causally associated with increased risk of ischemic heart disease; however, when measured directly, the fraction of plasma cholesterol present in remnant particles is unclear. We tested the hypothesis that a major fraction of plasma cholesterol is present in remnant lipoproteins in individuals in the general population.

We examined 9293 individuals from the Copenhagen General Population Study using nuclear magnetic resonance spectroscopy measurements of total cholesterol, free- and esterified cholesterol, triglycerides, phospholipids, and particle concentration. Fourteen subclasses of decreasing size and their lipid constituents were analysed: six subclasses were very low-density lipoprotein (VLDL), one intermediate-density lipoprotein (IDL), three low-density lipoprotein (LDL), and four subclasses were high-density lipoprotein (HDL). Remnant lipoproteins were VLDL and IDL combined.

Mean nonfasting cholesterol concentration was 72 mg/dL for remnants, 78 mg/dL for LDL, and 71 mg/dL for HDL, equivalent to remnants containing 32% of plasma total cholesterol. Of 14 lipoprotein subclasses, large LDL and IDL were the ones containing most of plasma cholesterol. The plasma concentration of remnant cholesterol was from 54 mg/dL at age 20 to 74 mg/dL at age 60. Corresponding values for LDL cholesterol were from 58 mg/dL to 81 mg/dL. Thus, using direct measurements, one third of total cholesterol in plasma was present in remnant lipoproteins, that is, in the triglyceride-rich lipoproteins IDL and VLDL.

Senescent cells are an important cause of degenerative aging. Lingering senescent cells accumulate over time and disrupt tissue function and immune function via their secretions. An insidious part of this is that the signals secreted by senescent cells cause other nearby cells to be more likely to become senescent. Thus once they start to accumulate the result is an accelerating feedback loop of dysfunction and degeneration. There are many such feedback loops in aging, which is why the process starts slow and then speeds up considerably in later life.

Aging is a major risk factor in the development of chronic diseases, especially cardiovascular diseases. Age-related organ dysfunction is strongly associated with the accumulation of senescent cells. Cardiac mesenchymal stromal cells (cMSCs), deemed part of the microenvironment, modulate cardiac homeostasis through their vascular differentiation potential and paracrine activity. Transcriptomic analysis of cMSCs identified age-dependent biological pathways regulating immune responses and angiogenesis. Aged cMSCs displayed a senescence program characterized by Cdkn2a expression, decreased proliferation and clonogenicity, and acquisition of a senescence-associated secretory phenotype (SASP).

Increased CCR2-dependent monocyte recruitment by aged cMSCs was associated with increased IL-1ß production by inflammatory macrophages in the aging heart. In turn, IL-1ß induced senescence in cMSCs and mimicked age-related phenotypic changes such as decreased CD90 expression. The CD90+ and CD90- cMSC subsets had biased vascular differentiation potentials, and CD90+ cMSCs were more prone to acquire markers of the endothelial lineage with aging. These features were related to the emergence of a new cMSC subset in the aging heart, expressing CD31 and endothelial genes.

These results demonstrate that cMSC senescence and SASP production are supported by the installation of an inflammatory amplification loop, which could sustain cMSC senescence and interfere with their vascular differentiation potentials.

Link: https://doi.org/10.1111/acel.13015

Naked mole-rats live something like ten times longer than similarly sized mice, show few signs of aging until very late life, and are near immune to cancer. These two species are used as models by researchers to try to understand how, in detail, differences in metabolism can lead to the observed large differences in life span across mammalian species. Since metabolism is ferociously complex, this is very much a work in progress; in the grand scheme of things, only small inroads and starting points have been established. I fully expect investigations of the detailed interactions of metabolism and aging to be ongoing and nowhere near complete thirty years from now, when rejuvenation therapies based on repair of the well-known root causes of aging are a going concern. While it is of course the right thing to do to attempt to fully understand metabolism, this work is not the fast path to new medical technologies that will have significant impacts on human health and longevity.

Although biological and chronological time can be dissociated to some extent by experimental manipulation, aging appears to be the most important risk factor for the deterioration of normal physiological functions. One species that - to a certain degree - escapes from the rule that natural life expectancy declines with body mass is the naked mole-rat (Heterocephalus glaber). Although this rodent has a similar size as the laboratory mouse (Mus musculus), it lives 10-20 times longer without showing any visible signs of aging. Furthermore, the naked mole-rat can live for over 32 years in captivity, without facing any increased age-related risk of mortality, challenging Gompertz's mortality law, and thus establishing the naked mole-rat as a non-aging mammal.

Not only naked mole-rats can live an extremely long life, but they also show a remarkably long healthspan associated with almost no decline in physiological or biochemical functions for more than 20 years. For example, cardiac functions are well preserved in aged naked mole-rats, cognitive functions do not decline with age and the naked mole-rat brain seems to be naturally protected from neurodegenerative processes, and also very little pathologic alterations have been found in the kidneys of aged naked mole-rats. In addition, typical signs of aging, such as loss of fertility, muscle atrophy, bone loss, changes in body composition or metabolism are mostly absent in the naked mole-rats. Finally, the incidence of age-related diseases such as cancers or metabolic disorders is extremely low in the naked mole-rat.

We used mass spectrometric metabolomics to analyze circulating plasma metabolites in both species at different ages. Interspecies differences were much more pronounced than age-associated alterations in the metabolome. Such interspecies divergences affected multiple metabolic pathways involving amino, bile and fatty acids as well as monosaccharides and nucleotides.

The most intriguing metabolites were those that had previously been linked to pro-health and antiaging effects in mice and that were significantly increased in the long-lived rodent compared to its short-lived counterpart. This pattern applies to α-tocopherol and polyamines (in particular cadaverine, N8-acetylspermidine and N1,N8-diacetylspermidine), all of which were more abundant in naked mole-rats than in mice. Moreover, the age-associated decline in spermidine and N1-acetylspermidine levels observed in mice did not occur, or is even reversed (in the case of N1-acetylspermidine) in naked mole-rats. In short, the present metabolomics analysis provides a series of testable hypotheses to explain the exceptional longevity of naked mole-rats.

Link: https://doi.org/10.18632/aging.102116

Senescent cells are a cause of aging. While near all senescent cells are destroyed shortly after entering that state, either by their own programmed cell death processes or by the immune system, the few that linger accumulate over the years to cause considerable harm. While it is true that even in late life senescent cells are far outnumbered by non-senescent, functional cells, senescent cells secrete a potent mix of inflammatory and other signals known as the senescence-associated secretory phenotype (SASP). The SASP disrupts tissue function, encourages nearby cells to also become senescent, and produce a state of chronic inflammation that accelerates many age-related conditions.

On the bright side, this means that near all age-related conditions can be turned back to some degree by the targeted removal of senescent cells, using senolytic therapies. The more such cells that are destroyed by a treatment, the larger the benefit. Since this produces such a broad range of beneficial effects, and there are only so many scientists in the world, the research community has yet to fully investigate even all of the most compelling, urgent uses of senolytic treatments to reverse specific age-related disease, let alone all of the other, lesser opportunities.

Today's open access paper on the prospects for senolytic therapies to effectively treat chronic kidney disease is an example of the sort of work we'll be seeing on a regular basis in the years ahead. Research teams will make slow inroads on assessing the use of senolytics as a rejuvenation therapy that can benefit patients with age-related condition A, B, or C, and so forth through a long, long list of diseases. It is a measure of just how new this field is, assessed in the grand scheme of things, that even the most widespread and severe conditions such as chronic kidney disease, those with no good therapeutic options at present, and wherein senolytic treatments might plausibly turn back much of the disease, are still not well investigated.

Cellular Senescence and the Kidney: Potential Therapeutic Targets and Tools

Chronic kidney disease (CKD) is defined by the persistent loss of kidney function and currently affects approximately 13.4% of the global population. The progressive nature of CKD often leads to end-stage renal disease (ESRD), requiring renal replacement therapy. To date, there are no curative therapeutic options for CKD/ESRD. An as yet untreatable final common pathway irrespective of the etiology in CKD is kidney fibrosis, characterized histologically by glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Numerous compounds directly targeting factors involved in fibrosis driving pathways are currently being studied with varying results. Apart from the use of the renin-angiotensin-aldosteron pathway interfering agents such as ACE inhibitors or angiotensin receptor blockers to reduce the progressive remodeling of renal parenchyma, no therapeutics addressing pathophysiological mechanisms underlying CKD are used clinically. However, increasing effort is currently put into investigating the efficacy of targeting senescent cells during renal disease.

Aging is associated with the decline of kidney function. During aging, increased renal p16 expression is most notably seen in tubular epithelium and to a lesser extent in glomerular (podocytes and parietal epithelium) and interstitial cells. Changes in p16 were more pronounced in the cortex compared to the medulla. In rodents, the amount of senescent proximal tubular cells increases with age, whereas no increase of senescent cells is seen in the glomeruli. Renal tubular cell senescence correlates with tubular atrophy, interstitial fibrosis, and glomerulosclerosis. Furthermore, the removal of senescent tubular cells leads to decreased glomerulosclerosis.

Eliminating senescent cells through transgenic depletion and pharmaceutical inhibition reduces kidney dysfunction and long-term kidney injury in experimental models of kidney damage, obesity-induced metabolic dysfunction, and during aging. These promising results have spurred interest in the development of clinically applicable therapeutic compounds that target senescence-associated pathways. Eliminating senescent cells (dubbed as senolysis) is just one of the various potential interventional approaches to target the adverse effects of cellular senescence (so-called "senotherapy"), including the prevention of senescence, modulation of SASP (termed senomorphics), and stimulation of immune system-mediated clearance of senescent cells.

The removal of senescent cells with so-called "senolytics" may be the most feasible and most attractive approach for clinical application, as the prevention of senescence and modulation of SASP would require chronic treatment with prolonged exposure to therapeutics. Several chemotherapeutics and checkpoint inhibitors currently used in daily oncological practice show senolytic properties. However, the applicability of such senolytic compounds for the treatment of renal diseases has hardly been investigated.

Research regarding senescence in the kidney has pointed to the proximal tubular epithelium as the culprit, and the removal of senescent tubular epithelial cells is therefore a promising approach to the attenuation of fibrosis in CKD. Due to the specific nature of proximal tubular epithelium, several specific targeting options are available, by which therapeutic drug efficacy can be potentiated and side effects can be reduced. Repurposing senolytic drugs that have been tested in clinical trials for other, mostly oncological, indications by functionalization for targeted delivery is a promising method to make a fast translation to clinical nephrology practice.

There is a great deal of hype surrounding the use of compounds that increase NAD+ levels in mitochondria, thereby improving the function of old tissue. This doesn't address the underlying molecular damage that leads to reduced NAD+ levels in later life, and thus might be thought of as something akin to pressing the accelerator harder in a car with a worn engine, but there is a slow accumulation of evidence for some degree of benefit to result. For example, reduced blood pressure in older hypertensive individuals, suggesting improved function of smooth muscle tissue in blood vessel walls. The example today is quite different, as the focus is on the function of cochlear tissue of the inner ear that is vital to hearing, and which suffers the loss of cells and cell function with age.

Age-related hearing loss (ARHL) or presbycusis is the most common cause of hearing loss and sensory disability, characterized by gradual deterioration of auditory sensitivity at all frequencies, with increasing age. ARHL still remains largely untreated. Despite the fact that the mechanism of ARHL has remained elusive, multiple studies have demonstrated that age-dependent oxidative stress, reactive oxygen species (ROS) metabolism, up-regulation of inflammatory responses, and mitochondrial dysfunction in parallel with cellular signaling and gene expression changes are implicated in this process. Particularly, structural changes and degeneration of inner ear cells, such as sensory hair cells, spiral ganglion neurons, and stria vascularis, are characteristics of aged mammals.

NAD+ and NADH are crucial mediators of energy metabolism and cellular homeostasis, as they act as cofactors for NAD+-dependent enzymes, including sirtuins (SIRTs), histones, and poly (ADP-ribose) polymerases (PARPs). Notably, cytosolic-free NAD+ levels decrease under various pathological conditions, including aging. There is strong evidence to support a role for SIRT1 in the process of aging and cell death, through deacetylation of targets such as NF-κB and p53. In addition, it has been proven that SIRT3 plays key roles in mitochondrial functions through deacetylation of mitochondrial proteins. Therefore, we hypothesize that long-term induction of high cellular NAD+ levels may produce protective effects against ARHL.

We investigated the effect of β-lapachone (β-lap), a known plant-derived metabolite that modulates cellular NAD+, on ARHL in C57BL/6 mice. We elucidated that the reduction of cellular NAD+ during the aging process was an important contributor for ARHL; it facilitated oxidative stress and pro-inflammatory responses in the cochlear tissue through regulating sirtuins that alter various signaling pathways, such as NF-κB, p53, and IDH2. However, augmentation of NAD+ by β-lap effectively prevented ARHL and accompanying deleterious effects through reducing inflammation and oxidative stress, sustaining mitochondrial function, and promoting mitochondrial biogenesis in rodents. These results suggest that direct regulation of cellular NAD+ levels by pharmacological agents may be a tangible therapeutic option for treating various age-related diseases, including ARHL.

Link: https://doi.org/10.1111/acel.13016

Calorie restriction improves near all measures of metabolic health, mitochondrial function included. Mitochondria are the power plants of the cell, and they accumulate damage and dysfunction with age, in part because the processes of quality control intended to remove worn and broken mitochondria falter. Calorie restriction improves the situation, but, characteristically, does so in a very broad way that makes it challenging to pick out the important mechanisms from the many other sweeping changes in cellular activity. Researchers here suggest that upregulation of miR-122 is noteworthy, but it is just one of many changes noted in the paper.

Both caloric restriction (CR) and mitochondrial proteostasis are linked to longevity, but how CR maintains mitochondrial proteostasis in mammals remains elusive. MicroRNAs (miRNAs) are well known for gene silencing in cytoplasm and have recently been identified in mitochondria, but knowledge regarding their influence on mitochondrial function is limited.

Here, we report that CR increases miRNAs, which are required for the CR-induced activation of mitochondrial translation, in mouse liver. The ablation of miR-122, the most abundant miRNA induced by CR, or the retardation of miRNA biogenesis via Drosha knockdown significantly reduces the CR-induced activation of mitochondrial translation. Importantly, CR-induced miRNAs cause the overproduction of mitochondrial DNA encoded proteins, which induces the mitochondrial unfolded protein response (UPRmt), and consequently improves mitochondrial proteostasis and function.

These findings establish a physiological role of miRNA-enhanced mitochondrial function during CR and reveal miRNAs as critical mediators of CR in inducing UPRmt to improve mitochondrial proteostasis.

Link: https://doi.org/10.1016/j.isci.2019.06.028

Much of the proceedings at Undoing Aging in Berlin earlier this year were recorded, but of course it takes a few months for everything to process through the queue. I briefly escaped from the conference for an ad hoc, unstructured discussion with Adam Ford of Science, Technology, and the Future, who, like the Life Extension Advocacy Foundation folk, was interviewing as many people as he could during the event. It wound up a monologue on topics that were at the top of my mind at the time, particularly the present state of funding and the transformation of our community from a primary focus on advocacy and academic research to one in which a great deal of important work is now carried out in startup companies, and the utilitarian ethics of treating aging as a medical condition. The resulting video is now up at YouTube, and is here accompanied by a transcript for those who prefer text.

I'm Reason. I've been around in this community for quite the long time, going on I guess twenty years now, rather shockingly. I seem to have become old in my own lifetime; I'm not as young as I look, unfortunately. I run Fight Aging!, the blog, which I've used as a platform for advocacy for some time, the aforementioned going on twenty years, though more like fifteen now for that site. Recently, last year, I cofounded Repair Biotechnologies with Bill Cherman to actually jump into the industry and do some things. Prior to that I was investing as an angel in a few biotech startups focused on aging, where I felt it was a better choice than giving to the SENS Research Foundation or other groups to do the research, because companies have the chance to attract a great deal more funding more rapidly than non-profits do, unfortunately - that is just the way of the world.

That is very much the transition of our community right now. And as that happens, I think it becomes much more important to think about why the hell are we doing this thing? Sudden influxes of vast amounts of funding are consequential. There are several hundred million dollar funds right now, focused on longevity, and there will be more next year, because it is a land rush right now. If you lose sight of why you are doing this, and thus what is the most effective approach, then you wind up with a bunch of idiots doing stupid things that won't work, and the upshot of that is that funding will be wasted. It is to a certain degree unavoidable, I mean look at the dot com era; every new industry has its peak of hype, a bunch of stupid things happen, a bunch of charlatans come in and take funding from investors who don't know any better. It will happen, but I think that those of us who are here now, and have been here in this community, have something of a duty to try to reduce the size of that problem, down to some nominal minimum, to the degree that that is possible to achieve.

So why do we do this? The fundamental philosophy of the problem is that death is bad. Suffering is bad. That death is bad is the more debatable of those two. It is quite possible to construct an ethical position in which we say it is fine to be dead, you didn't exist for quite a long time prior to existing, and you will not exist for quite a long time after you cease to exist. That is the way of the universe; the Stoics were good with this position. But I think it is very hard to argue that suffering is acceptable, at least above the sort of "maybe I should get out of bed and do something today" level of suffering needed to motivate the human animal to go and do something constructive. Anything much more than that level of angst I think should go away - and certainly that includes the level of pain, physical decrepitude, loss of function, and horrible things happening to the people around you that comes with aging. That should go away.

The world just hasn't quite got there yet in terms of thinking about this in the right way. People think about malaria in the right way. Malaria is something like one six hundredth of the cost to humanity of aging, depending on how you want to measure all the little fripperies around the edges. So if we really feel up in arms about malaria, willing to spend billions on getting rid of it, which some people clearly are, then we should be spending trillions on getting rid of aging. We should be, but we are not, and that is why the advocacy community came into being. We have this weird mismatch between our capabilities and our goals. The world is a crazy place, I think everyone acknowledges that; there are many, many insanities that the human condition contains, be that politics, be that the way that some people like peanut butter, pick your poison. The present relationship with aging is just another one of these insanities: the world is insane with respect to aging, because accepting aging is insane. Why would anybody accept that he or she is going to crumble and die, and not want to do something about it? Plain, basic utilitarianism says that we should do something about it if we can do something about it. And we can do something about it!

So is the population of the world asleep at the switch because next to no-one realizes that we can do something about it? That will change pretty soon. Senolytics will wake up everybody. What if you can take one pill that makes your arthritis go away? That is basically what senolytics will do, when they are truly effective. The ones we have right now, that are available right now, appear to be fairly good at getting rid of arthritis, based on the results of trials yet to be published. Once this realization happens, I think there will be an interesting phase change. People will start to somewhat wake up from this business of "oh well, aging is just a fact of life, wherein we're all going to die horribly, let's just get on and try to paper over that." So no, instead let us go full on utilitarian and try to do something about it. That is essentially the philosophy of action here. It is that aging is so terrible that there is really no amount of effort that humanity could spend on this problem that would be too great. Of course we're so far away from anything that even approaches a reasonable amount of effort, given the level of death and suffering caused by aging, that for the foreseeable future we can keep on advocating and building hundred million dollar funds. If investors build another hundred of those hundred million dollar funds, that would be a nice start, but by no means the right amount of funding in order to reasonably address the problem, given what it actually costs.

The cost is enormous, and, sadly, most discussions about aging, when they do get going, really skate over the utilitarianism of it in favor of "wow, we're spending a lot of money on entitlements, we need to do something about this." That latter expression seems to be what passes for ethical thought in policy circles these days. It is a matter of "well, we're spending a bunch of funds, we should find a way to stop doing that." Then of course, the nihilists seems to be mostly in charge now, because their idea of spending less is to not treat old people for their conditions, rather than building rejuvenation therapies that stop old people from getting those conditions. As I said, it is insanity. This really just needs to change. So this is why the advocacy, and now that we're at the point at which funding can be raised for startup companies working on rejuvenation biotechnologies, these startups are just another form of advocacy, really, if you look at the bigger picture. We're not building therapies because we can do something with our small slice of the pie of aging, we're building therapies because if we show people that we can do something with our small slice of the pie of aging, then soon enough there will be another hundred companies over the next decade, working on their small slices. People will see success and attempt to replicate it themselves.

There are a hundred, two hundred, three hundred programs out there languishing in the research community that could be turned into companies, turned into therapies, doing useful things in and around aging. As you know, the research community is just not good at raising funding. They are not good at translating their research to the clinic. They are poor at a lot of things other than just advancing the science. I think it falls to the rest of us, where "the rest of us" means anyone who might be an entrepreneur, or in the venture industry, or an advocate, to set forth and sift through these programs, the output of the scientific community, and say "look, we should do something with these things." If the research community isn't pushing a program forward, well, this is a time in which anyone can wrap a company around a project, say "I think we can do something with this," go to the venture industry and get a few million dollars in seed funding.

That will be the case for the next twenty years, on and off, as the market cycles up and down. So we should have a thousand startup companies working on a thousand projects related to aging. While there are only seven categories of fundamental causative damage, per SENS, some of those categories are very, very broad in terms of their little individual components. We have to fix all of lipofuscin, and we don't even have a good catalog of everything that is in lipofuscin, just the major pieces of it. We have to get rid of all the amyloids, and that is a good few dozen projects right there. Replacing aged stem cells: a different cell population, different recipes for therapy for every tissue. And so on and so forth all the way down the list.

Then after we've worked through the SENS list of causative damage as it exists today, there will be all the things about aging that are problematic but are hidden by the fact that people presently die before they become problematic. Such as nuclear pore proteins in long-lived neurons. Some of those molecules never change after they are initially created. It is the same molecule for your entire life, and if it gets damaged, well, that is kind of a problem. How do we build the nanotechnology to go fix our nuclear pore proteins? That is a problem that no-one should much care about today, because there are fifty other things that will kill you before that will become an issue. But it will become an issue, eventually. If we come to live to 150, I'm willing to believe that your nuclear pore proteins becoming corroded and corrupted and reacted with is actually a serious issue, at least in neurons.

We can in principle replace everything except the brain. So the worst case scenario for the ultimate future is that they open your skull, take out your brain, and put it into a new body. I'm sure it will actually be somewhat more sophisticated than that, but this is just a thought experiment - what is the most radical thing you can make work in terms of replacement, in principle? That is moving the brain to a new body. What will probably happen instead is that your new body will be rebuilt from your old body: regeneration and rejuvenation by delivery of cells and therapies and control over cell behavior. But the brain itself? A really challenging problem, because you have to fix it without breaking it. I think we are along the way towards understanding the mechanisms to target for the early, preventative reductions in inflammation, to avoid supporting cells in the brain going crazy, to get rid of the protein aggregates. To try to keep things the way they were during your 30s. But that is just a starting point. There is so much to do after that. It is a big project. When I say trillions in funding, I'm serious. This is a very big thing, this is reinventing architecture when you are a caveman, going all the way up to the Renaissance, and building huge palaces. That is the scope of the project for us. I don't think it will take as long as it took the cavemen, but I think that we're definitely in for the long haul. To the extent that we can incrementally build meaningful rejuvenation therapies along the way, then many of us will also be in for the long haul, and this turns into someone's life's work. That life might be rather long.

I don't know how long people will live. I am in my late 40s, and if you can just run the thought experiment of the biotechnologies that will be available to me in my 80s, I won't look anything like an 80 year old person today. I will have no chronic inflammation; no senescent cells; probably no cross-links in my body; my stem cells will have been replaced; my immune system gardened; and so on and so forth through a long list of treatments that are going to happen in the next few decades, and are very plausible right now. So you can add these things up and say, right, if an 80 year old has no inflammation, no senescent cells, no cross-links, no atherosclerosis, what does that do to health? Do you still look like an 80 year old? Can you go run a mile? No-one knows, and we get to find out by doing it. That is the great adventure.

The big problems in aging are all comparatively simple to solve, and it is all benchwork in the lab to get your programs going. You don't need the massive computational, big data, machine learning projects that are popular right now. The only place where present artificial intelligence might be useful is in improving the state of small molecule drug discovery, and my belief is that small molecule drug discovery will go away, largely, in favor of gene therapy. So maybe your AI is looking for genes or proteins that are of useful effect, but the present process of finding genes that have useful effects is not terrible. It is having good results. The upshot is, ok, where do you use AI in this process outside of small molecule development? And I don't see anything in which AI is absolutely necessary, useful in any way other than incrementally improving the infrastructure, reducing costs. Targeting senescent cells with senolytics, that is where small molecules might be useful, but the best projects there don't involve small molecules. Dealing with mitochondrial DNA damage? No, that is benchwork, and it seems unlikely that small molecules can do anything meaningful there - that is gene therapy territory. Stem cells? Again, it is just a matter of developing the methodologies that can lead to successful therapies, and deep down under that development, you find a role for AI in anything where there is a lot of data to be analyzed, but it is only incremental improvement in cost and efficacy.

Infrastructure makes the world turn, and incremental improvement is not to be sneezed at, but it is just a part of the technology background. You can't just jump up and say "we're going to do AI for longevity", no. You are going to do AI for biotechnology in general, and biotechnology is then applied to longevity. So AI will vanish into the tool space. It won't be a major category that is up there on its own in the fight against aging. Right now it is because it is novel and because investors throw funding at AI like there's no tomorrow, and entrepreneurs and scientists follow the funding. So you get In Silico Medicine, for example, and they are doing small molecule discovery AI, which is what most other people are now following on to do nowadays, because that is where the funding is in the present phase. But I think this will just fade into the background, it will be another tool in the toolkit. It isn't exciting, it is not category changing. It is an incremental advance, using computers a little bit more to help you do things when there is a lot of data involved.

Let's talk about Effective Altruism. That community is doing smart things, in the sense that Big Philanthropy is thoroughly corrupt, and one should ask the question: if I want to do good in the world, versus conning myself into thinking that I did good in the world, what should I in fact do? You don't give to the Red Cross, because the Red Cross is a thoroughly corrupt organization. The same for most large entities in philanthropy; they have enormous overheads, and most donated funding doesn't go to the projects you would want it to go to. The Effective Altruism movement in that sense is great, and a very overdue examination and critique of philanthropy as a whole. Secondly, if the effective altruists can find convincing ways to convince high net worth individuals to actually give sensibly, this will be a good thing. I suspect that reason many of high net worth individuals don't give sensibly is because they have absolutely no idea how to do good, and it is a big project to figure out how to do good at scale. If Effective Altruism can lead to more people in the high net worth category putting their funds into projects that actually have a good chance of improving the human condition, then that is a public good.

The third strand is obviously that the Effective Altruism community includes people who are quite concerned about which projects to fund from a utilitarian point of view, and to the extent that anyone takes even a cursory look at aging, it is obviously the case that aging is far worse than anything else that happens anywhere. Pick your favorite cause in the third world, and I can tell you that those people are suffering more from aging than from the target of your favored cause. Even for war, even for famine, it is still the case that aging is much, much worse. This is a sad thing, because we could be dealing with all of these issues, but when it comes to prioritization, yes, if you want to solve famine because it is terrible and causes people to suffer, then you also be willing to work on solving aging in that same population, because it causes a far worse outcome to far more people. So the Effective Altruism community should logically work its way to advocacy for the treatment of aging as a medical condition, because it is undeniably the case that it is the worst problem facing humanity, and it is the most cost effective point of intervention to reduce suffering and death in the world. Even when intervening in tiny ways, the outcome is an enormous return on philanthropic investment in the cause.

So I think that the effective altruists do good, and I think that there are not enough of them, and I think that they are not talking about aging to the degree that they should. But they are coming at it largely from an outsider perspective, and except for a few, they don't understand the science, they don't understand the degree to which rejuvenation is possible. Effective Altruism is a young movement, it has a way to go yet, but it has the potential to be very important. We shall see how it develops. In terms of our community engaging with effective altruists, it is all just advocacy at the end of the day. To the extent that the aging research and development community needs funding, then we set forth and engage the effective altruists to the extent that they have funds, or can influence sources of funding. If it is more effective to talk to effective altruists, then we aging advocates will do that, trust me.

That might be challenging as an argument right now, as right now it is clearly more effective to talk to the venture capitalists, because they are very incentivized to put funding into these projects. Very large amounts of funding, in fact, to the point at which it would be very hard to raise that level of funding through any sort of philanthropic program. Unless of course you are talking to high net worth individuals. But convincing high net worth individuals to go and put funds into work on treating aging is Effective Altruism, whether or not you are cloaking it in that name. Certainly, I and others are guilty of poking high net worth individuals to say "have you thought about this a little bit? Do you want to get old? You can do something about it. So go do something about it." But it is an incremental process. You can't just flip a switch and have all of the trooping masses of the Effective Altruism community go off and spread the desired message. So we shall see. It will go where it goes.

There is an enormous waste right now in development and deployment of ineffective ways to treat age-related disease, those that don't target the causes of aging. Further it will cost a great deal to develop functional rejuvenation therapies that do target causes of aging. But if you look at the enormous amounts that are spent on merely coping with the consequences of aging, then making it go away is highly efficient. But of course it is not just about funding and cost, it is about effective reduction of suffering. Funding spent on anti-aging research is an enormously cost-effective way to reduce suffering, providing it is spent on the right anti-aging research, rather than the programs that are not likely to produce more than a small effect. So mTOR inhibitors are great compared to previous technologies for dealing with age-related diseases, because they influence a lot of processes, but the effect size is really not large in the grand scheme of things. If you are going to put funding into developing mTOR inhibitors, then fine, that is happening, then you should spend that same level of funding on aspects of the SENS program that can actually repair underlying damage, rather than trying to tweak the body to be a little more resilient to damage. People taking mTOR inhibitors are still going to die on the same schedule as the rest of us. That aren't that much more resilient. People with senescent cells removed, on the other hand, well, who knows. We will see what that does to life span. I think that the pensions and insurance companies are going to be in for a rude awakening. Personally, I think that five years of additional life is not an unreasonable guess, and that will break a lot of insurance companies if they haven't prepared successfully.

Regarding what will convince the world that meaningful progress is happening and further meaningful progress is possible, I think that recent developments in the laboratory, particularly around senolytics, are convincing to scientists. That is helpful. But I don't think that it convinces the world at large in a useful way. Things have to leave the lab for that to happen. The thing about senolytics is that even those initial compounds available now seem to be quite good at making a sizable impact on quality of life in older people, and possibly for autoimmune diseases, and a bunch of other things. To the degree that we can say "guys, we're giving you a rejuvenation pill, your arthritis is probably going to go away" and then if even half of the patients lose their arthritis, or their symptoms are greatly minimized, and they lose their other inflammatory conditions, and we turn back early Alzheimer's disease - and all of these are plausible things that senolytics should accomplish, based on the mouse studies - then if that happens, then suddenly rejuvenation therapies are a real thing, and people can stop saying it is impossible to rejuvenate humans. Then we can go from there to explain that this is just one part of a larger program. We're just doing one tiny thing, and not even that well, and look how good it is.

Senolytics will be the point at which an awful lot of things change. The early stages are happening right now. The self-experimentation community is doing interesting things with senolytics. Once the first studies that actually have large effects are published, it will be hard for regulators to keep these early senolytic drugs out of peoples' hands. There are 60 million people in the US alone who would benefit from senolytics because they are old enough to have conditions that are inflammatory. This should happen. It will happen. And that would be the moment, I think. Senolytics, not anything else. Aging is a huge burden. Effectively treating aging will solve many problems. Old people are old people because they are aged. If you rejuvenate them, then they are no longer old. They will have a better time of it, and if you have an aging population of 80 year olds who are physiologically like 65 year olds, then you have an aging population of 65 year olds, effectively. After that it is very easy.

This short open access review is a good introduction to what is known of the changes to the microbial population of the gut that take place over the course of aging. Collectively, the activity of gut microbes is influential on health, arguably to a similar degree as exercise, though far less well quantified at this time. Altering the distribution of bacterial populations in older animals, to better resemble what is observed in young animals, leads to benefits to health, for example. Some of the specific mechanisms by which beneficial gut microbes improve health are being uncovered, such as the secretion of propionate, a compound now being developed as a dietary supplement. Much more remains to be established, of course; this is a part of the broader field still in its comparative infancy.

Dwelling at the interface between host epithelia and the external environment, commensal microbes actively modulate development, nutrient absorption, and disease onset in the host. Host metabolism is significantly modulated by commensal microbes, and the gut microbial composition significantly affects blood metabolite composition. Just as the composition of the microbiota varies within and between tissues, microbial consortia do also vary through time within individual tissues. Although individual gut microbiota are largely unstable in the first years of life, they become more stable during adulthood and undergo dramatic changes in richness and composition upon onset of disease and frailty. The onset of specific diseases, such as cancer, obesity, diabetes, or inflammatory bowel disease, is associated with specific microbial signatures.

Studies in humans and laboratory model organisms, such as flies, fish, and mice, have additionally shown that the composition of the gut microbiota dramatically changes during aging and is associated with host health and life span. In mice, e.g., lipopolysaccharide (LPS) from gut microbiota can accelerate age-dependent inflammation ("inflammaging"), and mice lacking Toll-Like receptor 4 (TLR4), which is the LPS receptor, are protected from age-dependent inflammation, showing that a microbial-specific substrate induces aging-specific phenotypes. Inflammaging can be further exacerbated in germ-free mice by gut microbiota transfers from aged donor mice, showing a direct causal relation between age-specific microbial communities and host aging.

Using deep learning to analyze human microbiome data helped build a human microbiome aging clock, which predicts host age with an accuracy of about four years. While during adulthood microbial composition contributes to cellular and tissue homeostasis, age-dependent changes in the microbial composition may contribute to increasing frailty and disease onset in later life. The causes leading to the changes in microbiota composition and function during host aging are still poorly understood and possibly include direct or indirect microbial selection by the host and microbe-microbe interactions, as well as microbial evolution.

Link: https://doi.org/10.1371/journal.ppat.1007727

Shift Bioscience is working on a way to improve mitochondrial function in old tissues. Mitochondria, as you might recall, are the power plants of the cell, responsible for producing chemical energy store molecules used to power cellular processes. Every cell has a herd of hundreds of mitochondria that replicate like bacteria and are culled when damaged by the quality control process of mitophagy. Mitochondrial function nonetheless declines with age, and this affects all cell activities. It is particularly relevant to age-related disease in energy hungry tissues such as the brain and muscles, but the detrimental effects are global throughout the body.

Aging degrades mitochondrial function via several mechanisms, and an important one is the loss of quality control, allowing broken mitochondria to overtake cells. Systematically removing those broken mitochondria on a consistent, ongoing basis should be beneficial, but the question has always been how to manage this feat. The present Shift Bioscience candidate small molecule drug enables functional, undamaged mitochondria to better outcompete their damaged peers for the limited supply of proteins needed to function. This can in principle tip the balance back towards healthy rather than dysfunctional mitochondria in a tissue.

You are proposing to search for small molecules that could potentially slow down progression of the epigenetic clock. Can you tell us a little bit more about your drug screening process?

It is very difficult to implement high-throughput drug screening for biological aging, since contemporary assays of biological age are cell based and can take months to complete. This would require millions of cell lines to be maintained in parallel for months, and this is simply too cost prohibitive. To overcome this challenge, we plan to utilize an approach called 'protein interference', where a library of protein fragments is delivered by virus to a population of cells containing a biological age-reporter. Each cell receives a unique protein fragment that may bind to any protein at any position, and through this binding, we could discover peptides that slow down, stop, or reverse biological aging. These protein fragments could be used as therapeutics or guide the design of small molecules.

Many of the hallmarks of aging influence the epigenetic aging clocks; what makes you consider the mitochondria the optimal target for therapeutic interventions?

The discovery of epigenetic aging clocks had particular significance to our company, as they provided the opportunity to audit our key hypothesis (e.g. mitochondrial dysfunction is an important part of aging). To do this, we measured the clock in human cells without a functional citric acid cycle, which severely reduces energy production by mitochondria. This caused a 16-year acceleration of the clock compared to control cells, which, to our knowledge, is the largest acceleration reported.

So far you claim to have identified one family of small molecules that appear to slow the epigenetic clock by at least 50% by restoring mitochondrial function in aged cells. Does this mean that the mitochondria are being repaired or replaced?

In mice, we have preliminary data indicating a deceleration of biological aging by 40% in the brain and 60% in the heart due to the small molecules (as defined by the epigenetic clock). Current evidence suggests that under such conditions, functional mitochondria are able to 'outbreed' dysfunctional mitochondria and become the dominant population. This is an example of overcoming damage by dilution, in contrast to conventional repair.

Cells have the unfortunate habit of favoring mutated mitochondria over healthy ones, and these damaged mitochondria can take over a cell in a relatively short time. How might we prevent the cells from making this poor choice so that they retain their healthy mitochondria?

Though our small molecule approach is closest to clinical development, there are other exciting approaches to combating mutated mitochondria in development. Aubrey de Grey has proposed transferring the mitochondrial DNA to the safety of the nucleus, an approach called 'allotopic expression'. This is not as far-fetched as it might seem, since evolution has already encouraged the vast majority of mitochondrial DNA to transfer to the relative safety of the nucleus. Why not finish off the job that evolution started? The second approach is to deliver endonucleases to mitochondria that specifically target and digest mutated mitochondrial DNA. Researchers have recently validated this approach in mouse models of mitochondrial disease.

So where are you now in terms of development of a therapy and potential human trials?

We are currently creating an enhanced molecule that overcomes some of the limitations of this small molecule family (e.g. they are quickly cleared out of the bloodstream). Once validated in cellular and animal models, we plan to target rare inherited mitochondrial diseases with this enhanced molecule because they provide the fastest route to the clinic.

Link: https://www.leafscience.org/an-interview-with-dr-daniel-ives-of-shift-bioscience/

Exceptional regeneration can be found in some higher animals, such as zebrafish and salamanders. These species are capable of completely regenerating non-lethal injuries and large loss of tissue from internal organs and limbs, producing an organ that is indistinguishable in function from the original, and doing so repeatedly. In mammals, with very few exceptions that occur in only a few species and a few tissues, such injuries only scar with no proficient regeneration. Why is this case? That is the question that many research groups seek to answer, as finding a way to spur regeneration of organs and limbs in our species is obviously a very desirable goal.

The authors of today's paper argue for the use of garfish as an animal model for the investigation of regeneration, based on the fact that they can regrow fins and have a genome that is closer to that of humans than is the case for zebrafish. The question all along regarding proficient regeneration is whether all of the relevant mechanisms are still in place in humans, just dormant and waiting for the right cues to be activated. Some research makes this seem plausible, but the scientific community is still some unknown distance from a definitive understanding of what needs to be accomplished in human biochemistry to allow limb or organ regrowth. It seems likely that cellular senescence and macrophage function are quite different in highly regenerative species, and some cancer suppression genes are similarly important. We can only speculate at this point as to whether any of these items can be safely changed in human biochemistry.

Fish Reveal Limb-Regeneration Secrets

Researchers have studies how gar and other fish regenerate entire fins. More importantly, the researchers focused on how they rebuild the endochondral bones within their fins, which are the equivalents of human arms and legs. Garfish has been called a "bridge species," as its genome is similar to both zebrafish - often used as a genetic model for human medical advances - and humans. Gar evolve slowly and have kept more ancestral elements in their genome than other fish. This means that along with serving as a bridge species to people, gar also are great connectors to the deep past.

So, by studying how fish regenerate fins, researchers pinpointed the genes and the mechanisms responsible that drive the regrowth. When they compared their findings to the human genome, they made an interesting observation. "The genes responsible for this action in fish also are largely present in humans. What's missing, though, are the genetic mechanisms that activate these genes in humans. It is likely that the genetic switches that activate the genes have been lost or altered during the evolution of mammals, including humans."

Evolutionary speaking, this suggests that the last common ancestor of fish and tetrapods, or four-legged vertebrates, had already acquired a specialized response for appendage regeneration, and that this program has been maintained during evolution in many fish species as well as salamanders. Continuing research into these key genes and missing mechanisms could eventually lead to some revolutionary medical advances. "The more we study these commonalities among vertebrates, the more we can home in on prime targets for awakening this program for regenerative therapies in humans."

Deep evolutionary origin of limb and fin regeneration

Salamanders and lungfishes are the only sarcopterygians (lobe-finned vertebrates) capable of paired appendage regeneration, regardless of the amputation level. Among actinopterygians (ray-finned fishes), regeneration after amputation at the fin endoskeleton has only been demonstrated in polypterid fishes (Cladistia). Whether this ability evolved independently in sarcopterygians and actinopterygians or has a common origin remains unknown. Here we combine fin regeneration assays and comparative RNA-sequencing (RNA-seq) analysis of Polypterus and axolotl blastemas to provide support for a common origin of paired appendage regeneration in Osteichthyes (bony vertebrates).

We show that, in addition to polypterids, regeneration after fin endoskeleton amputation occurs in extant representatives of 2 other non-teleost actinopterygians: the American paddlefish (Chondrostei) and the spotted gar (Holostei). Furthermore, we assessed regeneration in 4 teleost species and show that, with the exception of the blue gourami (Anabantidae), three species were capable of regenerating fins after endoskeleton amputation: the white convict and the oscar (Cichlidae), and the goldfish (Cyprinidae).

Our comparative RNA-seq analysis of regenerating blastemas of axolotl and Polypterus reveals the activation of common genetic pathways and expression profiles, consistent with a shared genetic program of appendage regeneration. Comparison of RNA-seq data from early Polypterus blastema to single-cell RNA-seq data from axolotl limb bud and limb regeneration stages shows that Polypterus and axolotl share a regeneration-specific genetic program. Collectively, our findings support a deep evolutionary origin of paired appendage regeneration in Osteichthyes and provide an evolutionary framework for studies on the genetic basis of appendage regeneration.

Vadim Gladyshev's team has put online the new GENtervention database that shows gene expression profile data for mouse livers, assessed across a range of interventions known to slow aging in that species. Since many or even near all these interventions work through a similar collection of stress response and cellular maintenance mechanisms, such as macroautophagy, proteasomal function, and so forth, there are many commonalities in the profiles. The paper is not open access, though the usual approaches work if you want to read it, but the database is freely available.

We collected and characterized RNA-seq data on several lifespan-extending interventions, including three that had never been analyzed at the level of gene expression, across sexes, doses, and age groups. We observed a significant feminizing pattern of gene expression changes in males in response to genetic and dietary interventions at both transcriptomic and metabolomic levels. This effect was associated with perturbations of common genes and molecular pathways including those regulated by growth hormone. The feminizing effect could not explain lifespan extension but was associated with the diminution of sex-associated differences pointing to the converging effect of lifespan-extending interventions on hepatic transcriptome and metabolome across sexes.

Expanding this analysis with available microarray data allowed us to define gene expression signatures associated with individual interventions (rapamycin, calorie restriction, and growth hormone deficiency) as well as shared across longevity interventions. We observed that despite some differences, most of them perturb similar genes and pathways, including upregulation of xenobiotic metabolizing enzymes regulated by NRF2, TCA cycle, oxidative phosphorylation, and ribosome protein genes and downregulation of complement and coagulation cascades. Many of these functions turned out to be affected across tissues. Moreover, some genes involved in stress response, apoptosis, glucose metabolism, and immune response, as well as certain pathways, such as oxidative phosphorylation, were found to be commonly perturbed across interventions and, at the same time, associated with the degree of lifespan extension effect, serving as both qualitative and quantitative predictors of longevity. These genes and processes seem to be most persistent and reliable determinants of longevity in mice and deserve further exploration. We further developed a publicly available web application GENtervention that can be used to interrogate this dataset.

Finally, we employed gene expression signatures to identify new lifespan-extending interventions based on gene expression data. Here, our algorithm could distinguish two mouse strains of the same age with different expected lifespans. We have also found that hypoxia and hepatocyte-specific Keap1 knockout are positively associated with longevity signatures at the level of gene expression, and therefore appear to be strong candidates for experimental validation. In addition, we demonstrated the applicability of this method to predict new candidate lifespan-extending compounds and validated the detected positive association of gene expression induced by mTOR inhibitor KU-0063794 and ascorbyl-palmitate, making them appealing candidates for further investigation and survival studies.

Link: https://doi.org/10.1016/j.cmet.2019.06.018

It has for some years now been possible to reprogram adult somatic cells into pluripotent stem cells that are functionally equivalent to embryonic stem cells. This is achieved by overexpressing some or all of the Yamanaka transcription factors, Oct4, Sox2, Klf4, and c-Myc (OSKM) proteins. One of the most interesting outcomes of this process is that cells so treated reverse epigenetic markers of aging to some degree, and repair their mitochondrial damage. Thus the research community has started to induce this same reprogramming in living animals to observe the results. If done haphazardly, the outcome is unrestrained cancer and tissue dysfunction, as one might expect. The surprise is that there are approaches that can lead to benefits with no such issues.

The discoveries of recent years in this part of the field have given rise to the company Turn.bio, who are attempting an implementation of transient partial reprogramming to rejuvenate cells throughout the body, as well as numerous research groups working on their own approaches to a basis for therapies capable of enhancing regeneration and function in old tissues. The work noted here is an example of the type, and is quite interesting for the further evidence that it is possible, given suitable methodologies, to deliver reprogramming factors to mice over a long period of time without causing noticeable harm.

Reversal of ageing- and injury-induced vision loss by Tet-dependent epigenetic reprogramming

In mammals, progressive DNA methylation changes serve as an epigenetic clock, but whether they are merely an effect or a driver of ageing is not known. In cell culture, the ectopic expression of the four Yamanaka transcription factors, namely Oct4, Sox2, Klf4, and c-Myc (OSKM), can reprogram somatic cells to become pluripotent stem cells, a process that erases most DNA methylation marks and leads to the loss of cellular identity. In vivo, ectopic, transgene-mediated expression of these four genes alleviates progeroid symptoms in a mouse model of Hutchison-Guilford Syndrome, indicating that OSKM might counteract normal ageing. Continual expression of all four factors, however, induces teratomas or causes death within days, ostensibly due to tissue dysplasia.

Ageing is generally considered a unidirectional process akin an increase in entropy, but living systems are open, not closed, and in some cases can fully reset biological age, examples being "immortal" cnidarians and the cloning of animals by nuclear transfer. Having previously found evidence for epigenetic noise as an underlying cause of ageing, we wondered whether mammalian cells might retain a faithful copy of epigenetic information from earlier in life, essentially a back-up copy of the original signal to allow for its reconstitution at the receiving end if information is lost or noise is introduced during transmission.

To test this hypothesis, we introduced the expression of three-gene OSK combination in fibroblasts from old mice and measured its effect on RNA levels of genes known to be altered with age, including H2A, H2B, LaminB1, and Chaf1b. We excluded the c-Myc gene from these experiments because it is an oncogene that reduces lifespan. OSK-treated old fibroblasts promoted youthful gene expression patterns, with no apparent loss of cellular identity or the induction of Nanog, an early embryonic transcription factor that can induce teratomas.

Next, we tested if a similar restoration was possible in mice. To deliver and control OSK expression in vivo, we engineered a tightly regulated adeno-associated viral (AAV) vector under the control of tetracycline response element (TRE) promoter. To test if ectopic OSK expression was toxic in vivo, we infected 5 month-old C57BL/6J mice with the vector delivered intravenously, then induced OSK expression by providing doxycycline in the drinking water. Surprisingly, continuous induction of OSK for over a year had no discernable negative effect on the mice, ostensibly because we avoided high-level expression in the intestine, thus avoiding the dysplasia and weight loss seen in other studies.

Post-mitotic neurons in the central nervous system are some of the first cells in the body to lose their ability to regenerate. Using the eye as a model tissue, we have shown that expression of OSK in mice resets youthful gene expression patterns and the DNA methylation age of retinal ganglion cells, promotes axon regeneration after optic nerve crush injury, and restores vision in a mouse model of glaucoma and in normal old mice. Thus we have shown that in vivo reprogramming of aged neurons can reverse DNA methylation age and allow them to regenerate and function as though they were young again.

The requirement of the DNA demethylases Tet1 and Tet2 for this process indicates that altered DNA methylation patterns may not just a measure of age but participants in ageing. How cells are able to mark and retain youthful DNA methylation patterns, then in late adulthood OSK can instruct the removal of deleterious marks is unknown. Youthful epigenetic modifications may be resistant to removal by the Tets by the presence of a specific protein or DNA modification that inhibits the reprogramming machinery. Even in the absence of this knowledge, these data indicate that the reversal of DNA methylation age and the restoration of a youthful epigenome could be an effective strategy, not just to restore vision, but to give complex tissues the ability to recover from injury and resist age-related decline.

Most of the interventions and genetic alterations shown to slow aging in laboratory species are operating through some combination of the same set of underlying stress response mechanisms, the quality control and repair systems that step up their operation in response to nutrient deprivation and other stresses. Therefore is isn't surprising that the research community continues to discover shared mechanisms and regulators that, if disabled, will prevent numerous interventions from working to extend life in animal studies.

The research here, in which the gene ATGL-1 is identified as vital to such a shared mechanism, is interesting from a pure science perspective. It is another step forward in understanding how stress responses systems interact with the pace of aging. It isn't, however, going to be all that useful in the process of building therapies to extend human life. In our species, unlike short-lived species such as flies, worms, and mice, greater activity of stress response mechanisms does not greatly alter length of life. That said, the data obtained from the practice of calorie restriction shows that it has a large enough positive impact on health to be well worth considering as a lifestyle choice - larger than near any medical technology is so far proven to provide to basically healthy individuals.

Still, even given sizable health benefits, relative to the present bounds of the possible, producing therapies that mimic the response to calorie restriction or other stresses is not the path forward to meaningful rejuvenation of the old. These approaches do not do enough to address the underlying damage that causes aging. They don't reverse it to a great enough degree, and they don't slow it down enough to escape the current limits on the human life span. We need means of deliberate repair of the underlying damage that causes aging in order to produce rejuvenation, not means of adjusting metabolism into a somewhat more resilient state, that little more able to resist the damage.

ATGL-1 mediates the effect of dietary restriction and the insulin/IGF-1 signaling pathway on longevity in C. elegans

In metazoans, the insulin/IGF1 signaling pathway (IIS) coordinates nutrient and energy availability with growth, metabolism, and longevity. Two major "signaling nodes", FoxO- and TORC1-centered, are responsible for the effect of nutrients and IIS on the lifespan. Transcription factor FoxO1 that adapts mammalian organisms to starvation is negatively regulated by IIS via Akt-mediated phosphorylation and nuclear exclusion. At the same time, TORC1 (Target Of Rapamycin Complex 1) is activated by Akt and nutrients and promotes anabolic processes while inhibiting catabolism.

The downstream targets of FoxO and TORC1 that transmit longevity signals remain largely unknown. Given that both FoxO and TORC1 are ubiquitously expressed and regulate a plethora of important biological responses, identification of the specific pathways that control longevity is challenging. In fact, we do not even know whether FoxO and mTORC1 are involved in the same pathway or mediate different pathways of the longevity control.

We have recently found that FoxO1 and mTORC1 control the rates of lipolysis in mammalian cells by regulating expression of adipose triglyceride lipase (ATGL). Although complete hydrolysis of triglycerides to glycerol and fatty acids is performed jointly by tri-, di-, and monoacylglyceride lipases, ATGL represents the rate-limiting lipolytic enzyme. In other words, in every mammalian experimental system tested thus far, elevated ATGL expression increases, while attenuated ATGL expression decreases, lipolysis.

Since known biochemical pathways that control longevity converge on the regulation of ATGL expression, we have hypothesized that ATGL may represent the long sought after target of the nutrient and insulin/IGF1 signaling pathways that regulate life span. Here, we utilize the nematode C. elegans, a well-characterized and widely used model for longevity studies, and show that expression of the C. elegans ATGL homologue ATGL-1 is controlled by nutrients and the DAF-2/DAF-16 pathway. Moreover, we find that the partial loss-of-function ATGL-1 mutant blocks the life-extending effects of dietary restriction (in the eat-2 loss-of-function model) and DAF-2 deficiency, whereas over-expression of ATGL-1 increases C. elegans lifespan.

Researchers here analyze markers in mice that are reflective of the decline of the immune system into the state of inflammaging, in which chronic inflammation disrupts normal cell and tissue function throughout the body. Unsurprisingly, some of these markers are predictive of life span. A faster decline of the immune system, for whatever underlying reason, will tend to lead to a shorter life expectancy. The immune system is vital in defense against pathogens, destruction of cancerous cells, and clearance of senescent cells. When these functions decline, the result is increased risk of age-related disease and mortality.

Several theories have been proposed to explain the aging process. The oxidative-inflammatory theory of aging links the age-related increase in oxidative stress with the chronic low-grade inflammation, the so-called "inflammaging", through the interplay of the immune system. It is known that the age-related increase in oxidative stress impairs the correct functioning of cells. Given that oxidation and inflammation are interlinked processes, the increase in oxidative stress in immune cells results in an increased release of proinflammatory mediators, giving as a result the age-related establishment of a chronic oxidative and inflammatory stress.

According to this theory, a relationship has been found between the oxidative and inflammatory states of immune cells, their functional capacity, and the lifespan of a subject. In this regard, it has been demonstrated that centenarians have immune cell function and redox parameters similar to those in adults, despite their advanced age. However, if they maintain this optimal functionality during their whole lifespan or they undergo some remodelling of these parameters during aging is unknown. Therefore, a deep understanding of these subjects would require their follow-up throughout the aging process to shed light into which changes or adaptations are the "successful ones." Since a longitudinal study is impossible to carry out in human subjects throughout the whole aging process, mice, which have a mean longevity of two years, were used for this work.

Thus, a longitudinal study was performed analysing several functions (macrophage chemotaxis and phagocytosis, natural killer activity, lymphocyte chemotaxis, and lymphoproliferation capacity), redox parameters (catalase, glutathione peroxidase, and glutathione reductase activities, reduced and oxidized glutathione, and superoxide anion and malondialdehyde concentrations), and inflammatory mediators (basal release of IL-6, IL-1β, TNF-α, and IL-10) in peritoneal leukocytes throughout the aging process of mice. This approach allowed us to address three important questions: (i) which markers are the most important predictors of remaining longevity in adult or middle life? (ii) Are the same parameters predictive of successful aging at very advanced age? (iii) Which changes or adaptations an individual experiences throughout his/her lifetime that allow the attainment of extreme longevity?

The results reveal that some of the investigated parameters are determinants of longevity at the adult age (lymphoproliferative capacity, lymphocyte chemotaxis, macrophage chemotaxis and phagocytosis, glutathione peroxidase activity, and glutathione, malondialdehyde, IL-6, TNF-α, and IL-10 concentrations), and therefore, they could be proposed as markers of the rate of aging. However, other parameters are predictive of extreme longevity only at the very old age (natural killer activity, catalase, and glutathione reductase activities, and IL-6 and IL-1β concentrations), and as such, they could reflect some of the adaptive mechanisms underlying the achievement of high longevity.

Link: https://doi.org/10.1155/2019/4574276

UNITY Biotechnologies is the furthest ahead of the growing number of companies working on the development of senolytic therapies capable of selectively destroying senescent cells in old tissues. Senescent cells are generated constantly in the body, but are near all destroyed by programmed cell death processes or by the immune system. The few that linger, however, accumulate to cause serious issues via their inflammatory secretions. They disrupt tissue structure and function and provoke a sizable fraction of the chronic inflammation of aging.

Because senescent cells have systemic effects throughout the body, not just local effects in the tissue they reside in, and because the whole point of the exercise is to produce therapies that can be used off-label to produce rejuvenation for all aspects of aging, not just the very narrow aspect being trialed, the UNITY Biotechnology principals are thought by many in the community to be taking a poor approach to their first trials. They are using local injections to target arthritic joints, while it has already been shown that systemic administration in animal models is beneficial to not just arthritis but also near all other aspects of aging physiology. Nonetheless, the effect size for removal of senescent cells is so large that even this technically worse approach produced decent results in an earlier trial.

UNITY Biotechnology, Inc., a biotechnology company developing therapeutics to extend healthspan by slowing, halting or reversing diseases of aging, today announced details for the planned Phase 2 study of UBX0101 in patients with osteoarthritis (OA) of the knee. "In June, we announced promising results from our Phase 1 study of UBX0101 in patients with OA of the knee showing that our senolytic molecule had a dose-dependent response across multiple clinical endpoints. We look forward to substantiating the promising results we observed in Phase 1 in a larger Phase 2 study. We will also be gathering additional information on duration of effect out to 24 weeks, validating early safety and dose-finding, and characterizing potential disease-modifying effects on bone and cartilage."

In June 2019, UNITY announced results from its first-in-human Phase 1 study of UBX0101 in patients with moderate-to-severe OA of the knee. In this study, UBX0101 was well-tolerated. Improvement in several clinical outcomes, including pain and function, as well as modulation of certain senescence-associated secretory phenotype (SASP) factors and disease-related biomarkers was observed after a single dose of UBX0101.

UNITY plans to initiate a Phase 2 study of UBX0101 in patients with painful, moderate-to-severe OA of the knee. The study is expected to enroll approximately 180 patients with initiation expected in the fourth quarter of 2019 and initial 12-week results expected in the second half of 2020. This will be a randomized, double-blind, placebo-controlled study evaluating three doses (0.5mg, 2mg and 4mg) of UBX0101 administered via a single intra-articular injection. The primary measure will be an assessment of pain at 12 weeks using the WOMAC-A instrument. Secondary measures will include safety and tolerability, pain (by 10 point Numerical Rating Scale, or NRS) and function (by WOMAC-C) at 12 weeks, as well as similar measures at 24 weeks.

Link: http://ir.unitybiotechnology.com/news-releases/news-release-details/unity-biotechnology-inc-announces-plan-phase-2-clinical-study