Fight Aging!

Reprogramming of ordinary somatic cells into induced pluripotent stem cells (iPSCs) was initially thought to be a way to obtain all of the patient matched cells needed for tissue engineering or cell therapies. A great deal of work has gone towards realizing that goal over the past fifteen years or so; the research community isn't there yet, but meaningful progress has taken place. Of late, another line of work has emerged, in that it might be possible to use partial reprogramming as a basis for therapy, delivering reprogramming factors into animals and humans in order to improve tissue function, without turning large numbers of somatic cells into iPSCs and thus risking cancer or loss of tissue structure and function.

Reprogramming triggers some of the same mechanisms of rejuvenation that operate in the developing embryo, removing epigenetic marks characteristic of aged tissues, and restoring youthful mitochondrial function. It cannot do much for forms of damage such as mutations to nuclear DNA or buildup of resilient metabolic waste, but the present feeling is there is nonetheless enough of a potential benefit to make it worth developing this approach to treatments for aging. Some groups have shown that partial reprogramming - via transient expression of reprogramming factors - can reverse functional losses in cells from aged tissues without making those cells lose their differentiated type. But this is a complicated business. Tissues are made up of many cell types, all of which can need subtly different approaches to safe reprogramming.

Today's open access preprint is illustrative of the amount of work that lies ahead when it comes to the exploration of in vivo reprogramming. Different cell types behave quite differently, will require different recipes and approaches to reprogramming, different times of exposure, and so forth. It makes it very hard to envisage a near term therapy that operates much like present day gene therapies, meaning one vector and one cargo, as most tissues are comprised of many different cell types all mixed in together. On the other hand, the evidence to date, including that in the paper here, suggests that there are ways to create the desired rejuvenation of epigenetic patterns and mitochondrial function without the risk of somatic cells dedifferentiating into stem cells.

Partial reprogramming restores youthful gene expression through transient suppression of cell identity

Aging induces broad gene expression changes across diverse mammalian cell types, and these changes have been linked to many of the prominent hallmarks of aging. Cell reprogramming experiments have shown that young animals can develop from adult cells and aging features can be erased through complete reprogramming to pluripotency. Recent reports have further suggested that transient expression of the Yamanaka factors (SOKM) is sufficient to reverse features of aging and improve cell function. However, it was unclear whether these transient reprogramming interventions suppress somatic cell identities, activate late-stage pluripotency programs, or whether alternative reprogramming strategies could restore youthful gene expression.

Here, we investigated these questions using single cell measurements of gene expression to capture the phenotypic trajectory of transient reprogramming and evaluate the impact of alternative reprogramming methods. We found that transient reprogramming suppressed somatic cell identities and upregulated hallmark pluripotency programs, contrary to some previous reports but consistent with timecourse iPSC reprogramming experiments and lineage-tracing studies of transient SOKM expression. By inferring RNA velocity and applying numerical tools from dynamical systems, we also found that transiently reprogrammed cells transition back toward their original gene expression states after transit through an intermediate state. Our single cell profiles therefore revealed transient cell states that were likely masked in previous bulk measurements and support a model in which transient reprogramming suppresses somatic identities that are later reacquired through differentiation. Further experiments profiling single cell populations at multiple time-points during transient reprogramming will be necessary to confirm this hypothesis.

It remains unknown which of the Yamanaka Factors are required to restore youthful gene expression, or which subsets might exhibit distinct effects during transient reprogramming. Previous studies have explored only one set of factors at a time, preventing accurate comparisons to address these questions. Our pooled screens of all possible Yamanaka Factor subsets revealed that combinations of 3-4 Yamanaka Factors have remarkably similar effects, suggesting no single factor is required to restore youthful gene expression. Combinations of two Yamanaka Factors were also more similar to the full SOKM set than to control or single factor perturbations, and all reprogramming factor combinations reduced an aging gene expression score. Our screen demonstrates that no single pluripotency factor is required to mask features of aging and suggest oncogene-free reprogramming strategies may also restore youthful gene expression. Our multipotent reprogramming experiments in myogenic cells further support this suggestion, indicating that youthful gene expression may be restored even without activating the pluripotency factors.

Restoring youthful gene expression can improve tissue function, implying that transient reprogramming may be therapeutic. However, pluripotent reprogramming is well-known to be an oncogenic process, even when Myc is excluded from the reprogramming set. While it has been reported that transient reprogramming does not suppress somatic cell identities based on bulk measurements, our single cell results show that somatic cell identity is suppressed and late-stage pluripotency GRNs are activated in a transitional cell state in multiple cell types. This raises the possibility that even transient reprogramming may be oncogenic. Identifying alternative reprogramming strategies to restore youthful gene expression with lower neoplastic risk is therefore desirable. Toward this aim, we have shown that transient reprogramming with multiple subsets of the Yamanaka Factors induces highly similar transcriptional effects to the full set, and that a distinct multipotent reprogramming system can confer youthful expression. These results suggest the feasibility of disentangling the rejuvenative and pluripotency inducing effects of transient reprogramming and serve as a resource for further interrogation of transient reprogramming effects in aged cells.

Mitochondria are the power plants of the cell, responsible for constructing chemical energy store molecules, adenosine triphosphate (ATP). With age, mitochondria become increasingly dysfunction, performing less useful work while generating more reactive oxygen species (ROS) capable of damaging cellular machinery via inappropriate oxidative reactions. Raised levels of ROS, or oxidative stress, are just as much a feature of aging as mitochondrial dysfunction. Many researchers see oxidative damage to cells as important in age-related disease, but it is far from settled as to whether or not this mechanism is in fact important in comparison to others, such as, for example, reduced levels of the ATP needed to power cellular processes.

The exact mechanisms underlying Alzheimer's disease (AD) remain unclear despite comprehensive attempts to understand its pathophysiology. The most prominent theory postulates that, in AD, tau and amyloid-β negatively affect neuronal cells by compromising energy supply and the antioxidant response, causing mitochondrial and synaptic dysfunction. Neuronal activity is highly energy-dependent, and neurons are particularly sensitive to disruption in mitochondrial function. In addition, mitochondria produce cellular energy (adenosine triphosphate; ATP) and are also involved in many processes that are important for the life and death of the cell, including the control of second messenger levels, such as calcium ions (Ca2+) and reactive oxygen species (ROS).

Importantly, mitochondrial dysfunction contributes to reduced ATP production, Ca2+ dyshomeostasis, and ROS generation. Alterations in mitochondrial dynamics and mitophagy occur in early-stage AD, but the underlying mechanisms are poorly understood. Thus, studies elucidating the mechanisms of mitochondrial abnormalities in AD will facilitate a greater understanding of the pathogenesis of this neurodegenerative disease and potentially contribute to the advancement of therapeutic strategies to protect synaptic activity and subsequent cognitive function. Here, we review studies that suggest a role of mitochondrial dysfunction and the consequent ROS production in AD pathology and provide a context to explain current and future therapeutic approaches. We suggest that improving mitochondrial function should be considered an important therapeutic intervention against AD.

Link: https://doi.org/10.3389/fnagi.2021.617588

Senescent cells accumulate with age in tissues throughout the body. They secrete a mix of signals that provokes chronic inflammation, disruption of tissue maintenance, and changes in cell behavior that lead to pathology. Targeted clearance of senescent cells has been shown to produce rejuvenation in mice, a reversal of many different age-related conditions, particularly those strongly linked to the chronic inflammation of aging. In this context, researchers here discuss the presence of greater numbers of senescent cells in older tissues as an important mechanism determining outcomes for patients following organ transplantation.

Organ transplantation is the treatment of choice for end-stage-organ failure. The supply of organs, however, is limited, resulting in prolonged waiting times with many patients dying or becoming too ill to be transplanted. Aging demographics have incrementally affected the deceased donor population with older donors showing the by far largest proportional increase. Organs from older donors are, at the same time, underutilized, frequently discarded or not even considered.

The most obvious strategy that may close the gap between demand and supply may thus be an optimized utilization of older organs from deceased donors. Increased donor age, at the same time poses a significant risk for adverse outcomes including more frequent rejections due to an augmented immunogenicity in aging. Most relevantly, older organs have shown compromised long-term graft outcomes with inferior graft survival rates in addition to increased rates of chronic allograft dysfunction in kidney, heart, and lung transplantation.

Senescent cells accumulate with aging and have been identified as critical in driving the immunogenicity of older organs linked to the accumulation of cell-free mitochondrial DNA that accelerate alloimmune responses. Recent evidence also suggests that senescent cells can induce a senescent phenotype in adjacent cells, a potential mechanism on how the engraftment of older organs may facilitate the spread of senescence. Depletion of senescent cells, at the same time, has been shown to ameliorate a wide range of age-associated disabilities and diseases.

Characteristically, senescent cells secrete a myriad of pro-inflammatory, soluble molecules as part of their distinct secretory phenotype that have been shown to drive senescence and age-related co-morbidities. Preliminary data show that the transplantation of old organs limits the physical reserve of recipient animals. Here, we introduce potential mechanisms and consequences of prompting bystander senescence and discuss clinically relevant aspects of senescent cell spread when transplanting older organs. Although speculative, age-disparate transplantation may also provide unique opportunities as the transplantation of young organs may contribute to rejuvenation.

Link: https://doi.org/10.3389/fimmu.2021.671479

Senescent cells accumulate with age and cause a wide range of pathologies. They contribute in some way to near all of the common, ultimately fatal age-related conditions. Senescent cells secrete a mix of signals that produces chronic inflammation, disrupts tissue maintenance to encourage fibrosis, and changes the behavior of other cells for the worse in numerous ways. It is the signaling that allows the comparatively small fraction of senescent cells in any given aged tissue to cause such widespread harm.

Destroying senescent cells in a targeted fashion via the use of senolytic therapies has shown great promise in animal studies, and early human trials have show that at least some of those therapies can also destroy senescent cells in human patients. While scores of age-related conditions have been reversed in mice, and life span extended, via the use of senolytics, the clinical research community is initially focused on establishing efficacy for only a few conditions in human trials.

One of those conditions is chronic kidney disease, characterized by fibrosis, inflammation, and other effects likely caused in large part by senescent cells. Today's open access paper is a discussion of the science underlying this portion of the field.

Targeting Premature Renal Aging: from Molecular Mechanisms of Cellular Senescence to Senolytic Trials

Kidneys from elderly are associated with structural changes as the loss in renal mass, glomerulosclerosis, glomerular basement membrane thickening, tubular atrophy, interstitial fibrosis, and the arteriosclerosis. Furthermore, aged kidneys are characterized by functional impairments as reduced glomerular filtration rate (GFR), decrease in urine concentration, plasma flow, and sodium resorption. In healthy aging conditions, despite the gradual but constant drop in GFR (5-10% per decade after the age of 35 years), renal function can be preserved by compensatory mechanisms as hypertrophy of unaffected nephrons or by vasodilatory prostaglandins that can moderate excessive vasoconstriction.

However, beyond their functional reserve capacity, aged kidneys exhibit an increased susceptibility to "a second hit" damage as during acute kidney injury (AKI) occurrence, such as after a nephrotoxic drugs treatment (i.e., contrast agents) or during a bacterial induced systemic inflammatory response (i.e., sepsis or other infections). In the last few years, it has become extremely clear that maladaptive repair after an AKI episode can predispose to chronic kidney disease (CKD), and ultimately, depending on genetic, immunological, and environmental factors, to end-stage renal disease (ESRD).

The central mechanism underlying renal physiological and pathological aging is characterized by cellular senescence. Cellular senescence refers to a complex program that can be initiated by various cellular stresses and is characterized by cycle arrest despite the presence of growth stimuli. In renal aging-related diseases, senescent cells chronically accumulate in renal parenchyma, leading to tissue deterioration and to an aberrant signaling activation to different types of populations.

In the last few years, the development of compounds able to directly eliminate senescent cells or to target the effects of senescent cells has found a vivid interest in the complex field of age-related pathologies. Senotherapeutic agents hold promise for the utilization in treating disorders related to senescent cell accumulation such as neurodegenerative diseases, atherosclerosis, cancers, kidney injury, chronic obstructive lung disease, idiopathic pulmonary fibrosis, diabetes, as well as complications of organ transplantation, radiation, and chemotherapy. The term "senotherapeutic drugs" includes different molecules as the senolytics (compounds that kill senescent cells selectively), senomorphics (i.e., molecules that can inhibit SASP, modulate functions and morphology of senescence cells, or delay the progression of young cells to senescent cells), and senoinflammatory mediators (that are immune-system effectors of the clearance of senescent cells).

Senescent cell viability is strictly dependent on apoptosis resistance and anti-apoptotic signaling thus leading researchers in nephrology to extend the application of senotherapeutic strategies adopted in oncology also to prevent the complications of kidney aging.

For any given age-related condition, you will find papers in the literature that focus on one mechanism of aging and its contribution to that condition. Usually these are reviews covering the details of the mechanism and how it causes pathology, or the epidemiology of the mechanism in the field, as absent an effective means of intervention it is very challenging to establish just how large a contribution that mechanism actually has.

While looking through the work here on age-related mitochondrial dysfunction and atrial fibrillation, it is worth also taking a look at past work on senescent cell burden as a cause of atrial fibrillation, potentially via inflammatory, pro-growth signaling that leads to fibrosis in heart tissue. In both cases there are approaches to addressing the issue, mitochondrial replacement and senolytic drugs to destroy senescent cells, but those assessments have yet to be carried out rigorously. Until they have one, there is no way to predict which of these contributing causes is more or less important than the other.

Atrial fibrillation (AF) is the most common cardiac arrhythmia and contributes to a high prevalence of mortality and morbidity. The shortening of telomere length has been found to be common with age. Research efforts have argued that leukocyte telomere length (LTL) shortening is related to a variety of cardiovascular diseases, including atherosclerosis, left ventricular hypertrophy, and heart failure, but the relevance to AF is still controversial. In the Cardiovascular Health Study, researchers found no relationship between mean telomere length and AF in human atrial tissue.

The mechanisms of AF remain incompletely understood. Mitochondria play an important role in oxidative stress, calcium homeostasis, and energy metabolism. Studies have shown that mitochondrial dysfunction can cause insufficient ATP production and excessive reactive oxygen species (ROS), which damages the homeostasis of Ca2+ in myocardial cells and the excitability of membranes, in turn leading to AF.

Accumulating evidence has argued that PGC-1α is a key molecule of mitochondrial function because it participates in the regulation of mitochondrial biogenesis and energy metabolism and is closely related to oxidative stress and inflammation. It plays an important role in the occurrence and development of atherosclerosis, coronary heart disease, heart failure, and other cardiovascular diseases. Some researchers have put forward the concept of a "telomere-p53-PGC axis": that is, that the shortening of telomere will activate p53 expression, thereby inhibiting PGC-1 and causing mitochondrial dysfunction.

We measured the LTL, telomere-associated molecules, and mitochondrial membrane potential (MMP) of leukocytes to ascertain if they are correlated with aging-related AF and if they could be used as novel biomarkers for it. We found that LTL and serum PGC-1α are inversely correlated with the occurrence of aging-related AF and that the MMP of AF patients was significantly decreased, indicating that mitochondrial dysfunction plays a role.

Link: https://doi.org/10.1155/2021/5530293

Researchers here propose that the unifying underlying mechanism for lifestyle influences on dementia risk is chronic inflammation. That inflammation causes vascular degeneration and a consequent decline in the blood supply to the brain, which in turn contributes - to some degree - to all of the observed issues in the aging brain. When present to a large degree, these vascular issues are categorized as vascular dementia, a widely studied condition. But it is entirely plausible that subclinical vascular degeneration is an important mediating factor linking lifestyle and dementia. A competing hypothesis involves the role of persistent infection, and correlation between lifestyle factors and risk of suffering such infections. This also would be expected to proceed via raised levels of inflammation in the brain. The state of the immune system is indeed an important factor in aging.

The 2020 report of the Lancet Commission identified twelve potentially modifiable risk factors for dementia including less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, and low social contact, and suggested that 40% of worldwide dementias may be due to these factors. Research has also provided two additional important observations relevant to the etiology of dementia. The first was that drugs that successfully eliminated cerebral accumulations of beta amyloid have so far shown only modest impact on cognitive deficits, although trials are still ongoing. Ever since the original description that these proteins were present in the brains of individuals dying with dementia, they were considered to be etiologically significant in inducing dementia, and the modest impact they have had to date has forced a reappraisal of our approach to dementia.

The second landmark observation was that a decline in cerebral blood flow (CBF) was an early cerebral event that heralded the decline in cognitive function and may precede the appearance of the clinical syndrome by many years. This finding confirmed that vascular insufficiency is a major etiologic factor that anticipates the onset of cognitive deficits, and that the protein deposits found in the brain of demented individuals were more likely a consequence of the disease rather than its cause. While this was a major step forward in our understanding of the etiology of dementia, it left open the question: do all harmful lifestyles lead to cerebral hypoperfusion? If so, what are the physiological mechanisms that lead to the decline in CBF when a harmful lifestyle has persisted?

Several publications have proposed that inflammation may be the link between lifestyle, genetics, and Alzheimer's disease, but the mechanisms that link inflammation to this outcome are not clear. This review will focus on three lifestyle factors that negatively impact cognition, namely obesity, sedentary behavior, and insufficient sleep. In each case, a summary of the research associating the lifestyle to subsequent cognitive decline will be presented, and the impact of the lifestyle on cerebral vascular perfusion will be explored. The potential mechanisms linking the lifestyle to its eventual impact on perfusion will then be reviewed. A unifying hypothesis will be proposed, namely, that all lifestyles that negatively impact cognition do so through the activation of inflammatory factors, which then lead to small vessel disease, resulting in a reduction in cerebral perfusion and causing atrophy of structures essential for normal cognition.

Link: https://doi.org/10.3389/fnagi.2021.679837

Progeria, caused by loss of function mutations in the lamin A gene, is not accelerated aging. It is an example to demonstrate that many forms of cellular damage and disarray, when present to a greatly exaggerated degree, can in some ways mimic manifestations of aging. Aging is, after all, a process of cellular damage and disarray. It is, however, a specific balance of various forms of damage. Change that balance radically, or employ other forms of damage, as is the case in progeroid mice, and the outcome can no longer be called aging. It becomes a challenge to determine whether interventions that help ameliorate the harms of progeria would help meaningfully with normal aging; that depends strongly on the details of each case.

There is a growing interest in applying cellular reprogramming as an in vivo treatment. The goal is to deliver enough of the reprogramming factors to make a significant number of cells become more functional, by improving mitochondrial function and reversing a range of age-related epigenetic changes, but without forcing cells to abandon their roles to become induced pluripotent stem cells. A small number of such conversations is probably acceptable, given the outcome of stem cell therapies, but at some point too much of that will produce cancer or outright tissue failure. Thus initial explorations of reprogramming as a therapy are focused on short or otherwise limited exposure to the reprogramming agents.

A single short reprogramming early in life improves fitness and increases lifespan in old age

In 2006, it was shown that mouse somatic cells can be converted into pluripotent cells (iPSCs) by inducing the expression of four transcription factors: OCT4, SOX2, KLF4, and c-MYC (OSKM). This process of cellular reprogramming induces a global remodeling of epigenetic landscape to revert cell identity to a pluripotent embryonic-like state. Exploiting cell reprogramming offers an alternative route for cell therapy to restore organ and tissue function. Somatic cells can be reprogrammed into iPSCs, then modified or corrected in vitro before being re-differentiated into cells, tissues or organs for replacement in the donor or an immune-compatible patient.

Previous experiments using a reprogrammable mouse model demonstrated that a cyclic induction of OSKM two days a week, over the entire extremely short lifetime of a homozygous accelerated aging mouse model, increased longevity, through a potential chronically unstable epigenetic remodeling. These mice have a mutated Lmna gene that produces high level of the natural aging protein progerin.

In this study, we investigate a single short period of in vivo OSKM induction as pre-clinical proof of principle for a potential usage in clinic to prevent aging defects. We focused on heterozygous animals, which have moderate lifespan and levels of progerin, as these heterozygotes might be extremely sensitive to anti-aging therapies. As a short OSKM induction, was described to ameliorate immediate tissue regeneration after experimentally induced tissues injuries, we wondered whether a short period of OSKM genes induction might improve lifespan and tissues aging of heterozygotes mice.

Surprisingly, we found that many health measures, and longevity itself, were ameliorated in elderly mice, by a single two and a half weeks treatment earlier in life, at two months of age. This outcome was associated with a differential DNA methylation signature, suggesting that a "memorized effect" initiated by our short induction protocol early in life might be involved in a more juvenile physiology.

Low methionine intake has been shown, in animal studies, to mimic many of the same effects of calorie restriction, which is to say improved health and extended life span. A sizable fraction of the trigger mechanisms that produce improved metabolism as a result of lowered calorie intake appear to depend on methionine levels. Attempting a reduced methionine diet is about the hardest thing that any casual health enthusiast could choose to undertake when it comes to dietary self-experimentation. The sources of data on methionine content are incomplete and contradictory, and just about every common food stable is packed full of methionine. The specially formulated medical diets for people with conditions that require very low methionine intake in order to avoid pathology are expensive and unpleasant to consume in comparison to normal food. But perhaps there is a better way forward, and, given time, we may start to see low methionine options becoming more affordable and palatable.

"We've known for years that restricting the amino acid methionine in the diet produces immediate and lasting improvements in nearly every biomarker of metabolic health. The problem is that methionine-restricted diets have been difficult to implement because they taste so bad." Until now. Restricting methionine normally involves diets formulated with elemental (e.g., individual) amino acids. Individual amino acids are the building blocks of proteins. But diets made from elemental amino acids taste bad, and few are willing to tolerate the regimen.

A palatable solution emerged from the development of methods to selectively delete methionine from casein, the main protein in milk and cheese. Researches conducted proof-of-concept testing to establish that oxidized casein could be used to implement methionine restriction without the objectionable taste of the standard elemental diet. More than two-thirds of Americans are overweight or have obesity. More than 40 percent of adults have prediabetes or type 2 diabetes. A diet that offsets all the major components of metabolic disease would have an enormous impact.

A palatable, methionine-restricted diet could also ease a major frustration for those struggling to manage their weight. Each year, millions of people improve their metabolism and lose weight by reducing how much they eat. But eventually, most people gain back those pounds.

Link: https://www.eurekalert.org/pub_releases/2021-05/pbrc-smc052021.php

There is plenty of evidence to show that exercise improves memory, both very quickly and for a short time following any specific bout of exercise, and over the long term due to regular exercise. The mechanisms involved here are varied, likely a combination of cerebral blood flow changes and signaling molecules such as BDNF that are involved in the regulation of neurogenesis. Neurogenesis, the creation and integration of new neurons into the brain, is vital to memory function.

Researchers found that, despite only covering about one-third of the distance in high-intensity intermittent training (HIIT) compared with that covered in endurance training, similar improvements in exercise capacity and brain function were observed for both forms of exercise. In the experiment, rats were assigned to 1 of 3 groups - resting, endurance running, or alternating intervals (short sprints and rest) - during training sessions on treadmills 5 days/week for 4 weeks.

Both endurance running and HIIT resulted in weight loss, greater muscle mass, and the ability to exercise longer compared with controls; however, increased cellular aerobic capacity was found in the soleus (a muscle with predominantly slow-twitch fibers that makes it functionally well suited to endurance) and in the plantaris (a muscle with predominantly fast-twitch fibers for meeting high-energy functional demands) in the endurance-running and HIIT groups, respectively.

Rats in both groups demonstrated having better memory of spatial learning trials in searching for an escape platform in a water maze. In the hippocampus, increased cell development, neurogenesis, was also observed for both forms of exercise; however, levels of a signaling protein that promotes neurogenesis (BDNF) were increased by HIIT but not by endurance running, whereas the levels of its receptor (TrkB) were increased by both. Given that BDNF expression is known to be affected by exercise, why didn't endurance running increase BDNF expression? The answer may lie in the mediating role of stress on BDNF expression; exercise is a type of stress. While stress indicators in both exercise groups were found to be similar, this line of enquiry may lead to future studies:

Link: https://www.eurekalert.org/pub_releases/2021-05/uot-hit051721.php

The Methuselah Foundation is one of the formative non-profits focused on achieving progress towards the foreseeable technologies of human rejuvenation. The foundation was the original home of the first SENS research programs before they were spun out into the SENS Research Foundation, and is now focused on an eclectic range of activities that prominently features support for tissue engineering, as well as the formation of an investment fund for longevity industry startups, among other programs.

Vitalik Buterin, who founded the Ethereum blockchain initiative, and has become a high net worth philanthropist as a result, recently made a sizable gift of cryptocurrency to the Methuselah Foundation. Buterin has spoken publicly in support of rejuvenation therapies as an important goal for medical development, and this is the latest and largest in his donations in this space. When I noted this last week, I only mentioned the value of the Ether (ETH) that was donated, somewhere north of $2 million at the time of reporting, and not the very much larger amount of the Dogelon currency (ELON). I also said that I was not going to explain any of the general weirdness that comes along with the cryptocurrency space and events therein. Not my circus! However, if one wants to try to answer the question of how much funding the Methuselah Foundation now has, some explanation will be necessary.

It is easy to create a new cryptocurrency. There are a lot of them. Many of these are created as a joke, an act of Dadaist art, a get rich quick scheme, an altruistic cause, or some combination of all of these. It is also usually quite easy to convert ownership cryptocurrency A into ownership in cryptocurrency B, so all of the economic activity in the big currencies has a way of spilling over into the small ones, even the jokes. To the extent that the existence of Bitcoin and Ethereum is solving someone's large set of problems (such as, cynically, how to export funds from China), there will be traffic and value in currencies like Dogelon, which appears to have been created as, in essence, an altruistic joke, with a little of Dada thrown in by choosing to burn tokens by giving them to Vitalik Buterin rather than a null entity. Buterin is only playing along in the creation of art by giving all of those tokens to charitable causes, and in doing so throwing the system into upheaval.

Dogelon is, however, thinly traded. The present market price of any thinly traded asset is essentially a fiction. Manipulators can move it more or less as they like, one should assume that they already have, and it is otherwise unconnected from the reality of what the price might be for any sizable sale. Price is heavily dependent on what people think that the major holders are likely to do. If the major holder, for example, commits to only sell a little of their holdings over time in a structured and predictable way, then it is back to business as usual. Otherwise, other holders head for the exits and the price heads to zero. That process of immolation did get underway for Dogelon immediately following Vitalik's donation, and it is thus in the interest of the Methuselah Foundation to publicly suggest that this reaction is overblown.

Which is all to say that while the present value of the Methuselah Foundation Dogelon holdings is something like $80 million, if one is to trust the market price, which one shouldn't, in practice the foundation might turn out to have close to zero in value. There is a limited ability to turn any of that fictional thinly traded alleged value into actual funds for research programs without crashing the currency. It does seem plausible that a good, measured, well communicated strategy could extract millions to fund the non-profit over the years ahead, however, and the foundation staff appear to be taking the right steps towards that goal.

Our Promise to Steward Dogelon ($ELON) Value Long Term

Methuselah Foundation now controls 43% of the world's Dogelon Mars ($ELON) cryptocurrency and today announced in a press release that to maximize the $ELON's long-term value, the non-profit will steward the holdings for at least a year. Any future sales would be done to preserve the cryptocurrency's value while advancing the Foundation's mission.

The $ELON was received through a generous donation from Vitalik Buterin, co-founder of Ethereum and a visionary computer programmer. The gift was received on May 12, 2021 and surprised the rapidly growing Dogelon Mars community. It was expected that Buterin would permanently retain his $ELON holdings. The donation raised liquidity concerns for the $ELON, threatening its value and circulation.

"Because our mission to extend the healthy human lifespan requires a long-term view, Methuselah Foundation focuses on lasting achievements, not short-term rewards. We will take the same nurturing approach with our Dogelon Mars holdings because we understand that the cryptocurrency's value depends on maintaining the public's confidence and capturing its imagination, much like baseball cards or other collectibles. We want the $ELON to keep accruing value over the long term."

Vascular calcification is a feature of aging, a process in which cells in the blood vessel wall take on inappropriate identities and activities that are more appropriate to bone tissue. Evidence of recent years implicates chronic inflammation and the presence of senescent cells in this process. Senescent cells cause harm via their signaling, a good fraction of which is carried via forms of extracellular vesicle, such as exosomes. Here, researchers review what is known of the signaling that may be involved in changing the behavior of cells towards calcification processes. Whether or not it is necessary to understand all of this in order to find a way to block calcification is an interesting question: how much benefit will be produced by reducing inflammation and clearing senescent cells? If a sizable fraction of the problem remains, then a greater understanding will likely be required for further progress.

Vascular calcification (VC) is the abnormal deposition of calcium, phosphorus, and other minerals in the vessel wall in the form of hydroxyapatite. Over 60% of elderly people have calcium salt deposits in the vascular walls, and VC is closely associated with mortality from cardiovascular diseases in the aged population. Traditionally, calcification is considered as a degenerative disease associated with the aging process. However, increasing evidence has demonstrated that the occurrence and development of calcification is an active and highly regulated complex biological process, which is regulated by multiple factors, such as phenotypic conversion of vascular smooth muscle cells (VSMCs), metabolic homeostasis of calcium and phosphate, inflammation, oxidative stress, autophagy, and extracellular vesicle (EVs) release, among others.

Exosomes, as important intercellular message transporters, have recently been shown to participate in VC. Exosomes cargos include RNA, cytokines, proteins, and lipids. Studies have shown that the components of exosomes cargos differ significantly according to the cells that the exosomes origin. A large number of studies have focused on the role of exosomes in inducing mineral deposition during VC, but the role of exosomes in information transfer in VC has not yet been clarified.

Exosomes from different sources can participate in the regulation of VC by transporting miRNAs to recipient VSMCs. Exosomes released by mineralized osteoblasts contribute to the osteogenic differentiation of cells via a complex network of exosomal miRNAs. Bone marrow mesenchymal stem cell (MSC)-derived exosomes can alleviate high phosphorus-induced calcification in human aortic VSMCs through the modification of miRNA profiles. Exosomes derived from VSMCs are rich in miRNA-143 and proteins regulating cell adhesion and migration, which can participate in the regulation of cell proliferation and migration through autocrine and paracrine manners. An in vivo study showed that exosomes derived from melatonin-treated VSMCs could reduce VC in mice, while these effects were largely abolished by inhibition of exosomal miR-204 or miR-211.

The underlying mechanisms by which exosomes affect VC via transporting miRNA are still not fully understood and may vary among different conditions. Changes of miRNAs in exosomes can regulate osteogenic differentiation of cells by promoting the expression of Runx2 and activating related signaling pathways, for example, the Wnt/β-catenin pathways. Studies have shown that miRNAs with increased expression in the VC process can promote the osteogenic transformation of smooth muscle cells by targeting anti-calcification proteins or contractility markers, while miRNAs with decreased expression can inhibit the osteogenic transformation of SMCs by targeting osteogenic transcription factors. Further research on the characteristics of exosomes and their role in VC is needed and expected to provide novel ideas and targets for the clinical diagnosis and treatment of VC.

Link: https://doi.org/10.21037/atm-20-7355

Harvesting extracellular vesicles from cell cultures and then delivering them to patients is a way to obtain the benefits of first generation stem cell therapies with considerably fewer issues that delivery of cells. One doesn't have to worry about compatibility with the patient, for example. Logistically, vesicles are much easier to store, transport, and employ in therapy than cells. Since most of these first generation stem cell therapies achieve near all of their benefits via cell signaling in the short period before the transplanted cells die, the use of vesicles is a practical alternative, and an area in which considerable effort is going towards clinical development and application. Alongside the usual mix of companies working on therapies and researchers running animal studies, such as the one noted here, it is also quite possible for anyone in the US today to arrange extracellular vesicle injections given a little research into providers and a cooperative physician.

Recently, mesenchymal stem cell (MSC) transplantation has shown promising therapeutic potential in alleviating ageing-associated phenotypes. Despite their potential therapeutic applications, the direct use of stem cell transplantation still faces several hurdles, such as the risk of tumorigenesis and undesirable immune responses. Recent evidence has indicated the therapeutic potential of small extracellular vesicles (sEVs) secreted by MSCs derived from different tissues in alleviating cellular senescence, while avoiding the undesirable immune response and the risk of tumorigenesis. However, harvesting MSCs from different tissues, such as the bone marrow and adipose tissue, is invasive. In addition, limitations such as the decreased proliferative potential and therapeutic efficacy of MSCs during in vitro expansion have impeded the industrial production of sEVs.

Induced pluripotent stem cells (iPSCs) are a subpopulation of stem cells that can be reprogrammed from any tissue type in the body. iPSCs have a unique ability to proliferate indefinitely and display totipotency in vitro. Furthermore, induced pluripotent stem cell-derived MSCs (iMSCs) possess MSC-like therapeutic effects in tissue regeneration treatments. Along with the advantages of the acquisition and proliferation of iMSCs, compared with those of MSCs, sEVs can be abundantly obtained from iMSCs, which is convenient for industrial production.

Intervertebral disc degeneration (IVDD) models were established by puncturing discs from the tails of rats. Then, iMSC-sEVs were injected into the punctured discs. The degeneration of punctured discs was assessed. The age-related phenotypes were used to determine the effects of iMSC-sEVs on senescent nucleus pulposus cells (NPCs) in vitro. Western blotting was used to detect the expression of Sirt6. miRNA sequencing analysis was used to find miRNAs that potentially mediate the activation of Sirt6.

After injecting iMSC-sEVs, NPC senescence and IVDD were significantly improved. iMSC-sEVs could rejuvenate senescent NPCs and restore the age-related function by activating the Sirt6 pathway in vitro. Further, microRNA sequence analysis showed that iMSC-sEVs were highly enriched in miR-105-5p, which played a pivotal role in the iMSC-sEV-mediated therapeutic effect by downregulating the level of the cAMP-specific hydrolase PDE4D and could lead to Sirt6 activation. In conclusion, iMSC-sEVs could rejuvenate the senescence of NPCs and attenuate the development of IVDD.

Link: https://doi.org/10.1186/s13287-021-02362-1

The accumulation of senescent cells with age occurs throughout the body. The pace at which cells become senescent increases, thanks to growing levels of damage, and the pace at which senescent cells are destroyed slows down, largely due to immune system decline. Senescent cell secrete a mix of signals that provokes chronic inflammation, disruption of tissue structure and maintenance, and, further, detrimentally alters cellular behavior in a variety of other ways. This signaling environment actively creates and maintains dysfunction in the immune system and organs. Targeted removal of senescent cells in mice, using senolytic therapies, produces rapid and sizable rejuvenation of numerous aspects of aging.

Researchers are steadily exploring the enormous number of proven and potential connections between senescent cells in specific locations in the body and specific age-related conditions or aspects of degenerative aging. In today's example, researchers propose a direct link between the senescent cells that arise in the vascular system and the age-related decline of neurogenesis in the brain. Neurogenesis is the creation of new neurons that occurs in at least some parts of the mammalian brain, followed by the integration of those cells into established neural networks. It is vital to maintenance of brain tissue, memory, and other cognitive functions, and reversing its decline with age is an important goal for the regenerative medicine community.

Vascular Senescence: A Potential Bridge Between Physiological Aging and Neurogenic Decline

The adult mammalian brain contains distinct neurogenic niches harboring populations of neural stem cells (NSCs) with the capacity to sustain the generation of specific subtypes of neurons during the lifetime. However, their ability to produce new progeny declines with age. The microenvironment of these specialized niches provides multiple cellular and molecular signals that condition NSC behavior and potential. Among the different niche components, vasculature has gained increasing interest over the years due to its undeniable role in NSC regulation and its therapeutic potential for neurogenesis enhancement.

NSCs are uniquely positioned to receive both locally secreted factors and adhesion-mediated signals derived from vascular elements. Furthermore, studies of parabiosis indicate that NSCs are also exposed to blood-borne factors, sensing and responding to the systemic circulation. Both structural and functional alterations occur in vasculature with age at the cellular level that can affect the proper extrinsic regulation of NSCs. Additionally, blood exchange experiments in heterochronic parabionts have revealed that age-associated changes in blood composition also contribute to adult neurogenesis impairment in the elderly. Although the mechanisms of vascular- or blood-derived signaling in aging are still not fully understood, a general feature of organismal aging is the accumulation of senescent cells, which act as sources of inflammatory and other detrimental signals that can negatively impact on neighboring cells.

This review focuses on the interactions between vascular senescence, circulating pro-senescence factors, and the decrease in NSC potential during aging. Understanding the mechanisms of NSC dynamics in the aging brain could lead to new therapeutic approaches, potentially including senolysis, to target age-dependent brain decline.

Signatures built from the vast array of proteins found in the blood stream, including those encapsulated in extracellular vesicles, should in principle correlate with many health conditions. This includes those conditions, such as Alzheimer's disease, characterized by a long, slow preclinical stage in which damage and metabolic disarray builds up over time. Modern machine learning techniques allow the cost-effective construction of such signatures, given a large enough database work with, and as illustrated here.

Efforts to gauge people's Alzheimer's risk before dementia arises have focused mainly on the two most obvious features of Alzheimer's brain pathology: clumps of amyloid beta protein known as plaques, and tangles of tau protein. Scientists have shown that brain imaging of plaques, and blood or cerebrospinal fluid levels of amyloid beta or tau, have some value in predicting Alzheimer's years in advance. But humans have tens of thousands of other distinct proteins in their cells and blood, and techniques for measuring many of these from a single, small blood sample have advanced in recent years. Would a more comprehensive analysis using such techniques reveal other harbingers of Alzheimer's?

An initial analysis covered blood samples taken during 2011-13 from more than 4,800 late-middle-aged participants in the Atherosclerosis Risk in Communities (ARIC) study, a large epidemiological study of heart disease-related risk factors and outcomes, recording levels of nearly 5,000 distinct proteins in the banked ARIC samples. The researchers analyzed the results and found 38 proteins whose abnormal levels were significantly associated with a higher risk of developing Alzheimer's in the five years following the blood draw.

Researchers then measured protein levels from more than 11,000 blood samples taken from much younger ARIC participants in 1993-95. They found that abnormal levels of 16 of the 38 previously identified proteins were associated with the development of Alzheimer's in the nearly two decades between that blood draw and a follow-up clinical evaluation in 2011-13.

In a further statistical analysis, the researchers compared the identified proteins with data from past studies of genetic links to Alzheimer's. The comparison suggested strongly that one of the identified proteins, SVEP1, is not just an incidental marker of Alzheimer's risk but is involved in triggering or driving the disease. SVEP1 is a protein whose normal functions remain somewhat mysterious, although in a study published earlier this year it was linked to the thickened artery condition, atherosclerosis, which underlies heart attacks and strokes. Other proteins associated with Alzheimer's risk in the new study included several key immune proteins - which is consistent with decades of findings linking Alzheimer's to abnormally intense immune activity in the brain.

Link: https://www.jhsph.edu/news/news-releases/2021/researchers-identify-proteins-that-predict-future-dementia-alzheimers-risk.html

Calorie restriction promotes longevity, slowing the progression aging via sweeping metabolic changes across an entire organism. The metabolic changes it produces in cells are very similar in all species studied to date. This is one of the reasons why calorie restriction is so well studied: one can carry out low-cost experiments in yeast and nonetheless learn something that is likely relevant to human biochemistry. Still, it is well established that calorie restriction is much better at extending life in short-lived species. In humans there are clear improvements to long-term health, but nowhere near the same degree of life extension observed in calorie restricted mice.

Caloric restriction and the tor1Δ mutation are robust geroprotectors in yeast and other eukaryotes. Lithocholic acid is a potent geroprotector in Saccharomyces cerevisiae. Here, we used liquid chromatography coupled with tandem mass spectrometry method of non-targeted metabolomics to compare the effects of these three geroprotectors on the intracellular metabolome of chronologically aging budding yeast. Yeast cells were cultured in a nutrient-rich medium. Our metabolomic analysis identified and quantitated 193 structurally and functionally diverse water-soluble metabolites implicated in the major pathways of cellular metabolism.

We show that the three different geroprotectors create distinct metabolic profiles throughout the entire chronological lifespan of S. cerevisiae. We demonstrate that caloric restriction generates a unique metabolic pattern. Unlike the tor1Δ mutation or lithocholic acid, it slows down the metabolic pathway for sulfur amino acid biosynthesis from aspartate, sulfate, and 5-methyltetrahydrofolate. Consequently, caloric restriction significantly lowers the intracellular concentrations of methionine, S-adenosylmethionine, and cysteine. We also noticed that the low-calorie diet, but not the tor1Δ mutation or lithocholic acid, decreases intracellular ATP, increases the ADP:ATP and AMP:ATP ratios, and rises intracellular ADP during chronological aging.

These findings suggest a hypothetical model of how the observed CR-specific remodeling of cellular metabolism delays the chronological aging of yeast. The key aspects of this model are as follows: 1) a life-long decline in the intracellular concentrations of cysteine and methionine weakens tRNA thiolation, thus slowing down the pro-aging process of protein synthesis, 2) a decrease of intracellular methionine throughout the chronological lifespan attenuates a direct methionine-driven stimulation of the pro-aging Tor1 pathway, thereby lowering the inhibitory effect of Tor1 on autophagy and other anti-aging processes, 3) a deterioration in intracellular methionine concentration at diverse stages of chronological aging also weakens a methionine-dependent suppression of the proteasomal degradation of damaged and dysfunctional proteins, a known anti-aging process, 4) a decline in S-adenosylmethionine concentration throughout the chronological lifespan lowers the ability of the protein phosphatase Ppa2p to stimulate the pro-aging Tor1 pathway, and 5) a rise in the ADP:ATP and AMP:ATP ratios on most days of yeast chronological lifespan indirectly (i.e., independent of AMP or ATP binding to Snf1) stimulates the anti-aging protein kinase complex Snf1; Snf1 can also be activated directly, via an ADP binding-dependent protection of Snf1 from inactivating dephosphorylation.

Link: https://doi.org/10.18632/oncotarget.27926

A great deal of evidence shows that declining mitochondrial function is important to the aging process. This is directly downstream of various forms of damage, such as to mitochondrial DNA. It is also a long way downstream from a range of other forms of age-related disarray that lead to epigenetic changes that impact mitochondrial function - far enough downstream that it is unclear as to how exactly the causes of aging produce this outcome. One common view is that the quality control process of mitophagy suffers as the result of reduced production of necessary proteins, and thus damaged mitochondria accumulate.

Thus we come to mitochondrial replacement as a form of therapy. Cells do take up mitochondria from the surrounding medium, and so it is possible in principle to deliver large numbers of mitochondria into the body and expect to see results. Some progress has been made in this direction; see the biotech startup Cellvie, for example. The big unanswered question for those of us interested in rejuvenation is the degree to which the effects of this therapy will last. Will fresh mitochondria quickly succumb to the same issues of the aged environment that lead to loss of native mitochondrial function? The fastest way to find out is to try.

Mitochondrial Transplantation as a Novel Therapeutic Strategy for Mitochondrial Diseases

In recent years, advances in molecular and biochemical methodologies have led to a better understanding of mitochondrial defects and their mechanisms as the cause of various diseases, but therapies for mitochondrial disorders are still insufficient. Mitochondrial transplantation is an innovative strategy for the treatment of mitochondrial dysfunction to overcome the limitations of therapies using agents. Mitochondrial transplantation aims to transfer functional exogenous mitochondria into mitochondrion-defective cells for recovery or prevention of mitochondrial diseases. Simply put, replacing an old engine with a new one to regain its function.

Recently, a considerable number of studies demonstrated the effectiveness of mitochondrial transplantation in various diseases. There are many reports of mitotherapy in tissues, animal models and even in patients, as well as in vitro. These include neurological diseases, drug-induced liver toxicity and liver disease, including fatty liver and myocardial ischemia-reperfusion injury. Several studies have evaluated the improvement in mitochondrial function via mitochondrial transfer in neurological disease models. Researchers intravenously injected mitochondria isolated from human hepatoma cells (HepG2 cells) into neurotoxin-induced Parkinson's disease (PD) mouse brain. The recipient mouse suppressed PD progression by increasing the activity of the electron transport chain (ETC), and reduced free radical generation and apoptotic cells.

To increase mitochondrial delivery efficiency, more advanced techniques have been used. One study showed the enhanced delivery and functionality of allogenic exogenous mitochondria using peptide-mediated delivery by conjugating a cell penetrating peptide, Pep-1. The result of transplanting Pep-1-labeled mitochondria into brain tissues of a PD rat model demonstrated that mitochondrial complex I protein and mitochondrial dynamics were restored in dopaminergic neurons, which also improved oxidative DNA damage. The removal of dopaminergic neuron degeneration due to a neurotoxin was also observed in the PD rat model.

Research spawned by heterochronic parabiosis studies, in which an old and a young animal have their circulatory systems linked, continues to provide surprises. There is considerable debate over whether helpful factors in young blood versus a dilution of harmful factors in old blood provide the majority of the benefits to the older animal, with the evidence favoring the latter at the present time. Dilution of blood plasma has been shown to produce benefits in animal studies, but that involves adding albumin to avoid diluting that essential protein. Researchers recently showed that adding recombinant albumin, and skipping the dilution, still produces benefits to health in animal studies. This may change the understanding of what is going on here yet again.

Last year, two self-described "biohackers" in Russia had themselves hooked up to blood collection machines that replaced approximately half of the plasma coursing through their veins with salty water. Three days later, the men tested their blood for hormones, fats and other indicators of general well-being. The procedure, it seemed, had improved various aspects of immunity, liver function and cholesterol metabolism.

Irina and Michael Conboy initially tried taking the reductionist drug development approach. They identified two biochemical pathways implicated with aging, pharmacologically recalibrated both in old mice, and found that the animals' brains, livers and muscles showed signs of rejuvenation. But a more rudimentary intervention they tried did better still. In a series of experiments that inspired the Russian biohackers, the Conboys simply replaced half of the animals' plasma with saline. (They, like the biohackers, also added back albumin, a protein essential for maintaining the proper fluid balance in the blood.) The dilution of pro-aging factors proved sufficient to activate a series of molecular changes in the mice that unleashed age-defying factors, leading to cognitive improvements and reduced inflammation in the brain.

Although other researchers saw many of the same effects when they administered young blood to mice, Irina Conboy suspects that those benefits had more to do with the dilution of old plasma than any enrichments provided by the young plasma. On balance, her research suggests that the detrimental effects of circulatory proteins in old blood - which include the suppression of youthful factors - are far stronger than any rejuvenating qualities of molecules added via young blood.

Many age-elevated factors have been identified, but finding drugs for each one is a challenge. Plasma dilution, by comparison, knocks them all down - and others as yet unknown - in one fell swoop. The Conboys founded a company to develop the plasma exchange strategy further. Others feel similarly dubious about young blood as a therapeutic. "This approach reminds me of trying to refresh sour milk by pouring fresh milk into it," says Iryna Pishel, who previously tested the anti-aging effects of young plasma on old mice and saw little impact on lifespan or immunological markers of aging.

Link: https://www.smithsonianmag.com/innovation/in-search-to-stall-aging-biotech-startups-are-out-for-blood-180977728/

Building better scaffolding materials for tissue regrowth is one important line of work in the regenerative medicine. The idea is to better mimic necessary characteristics of the natural extracellular matrix, to make the cells inhabiting the scaffold material behave in ways that are conducive to regrowth and regeneration. The open access paper noted here is an example of this sort of ongoing research and development, tackling one small aspect of scaffold materials for one tissue type.

To achieve rapid skeletal muscle function restoration, many attempts have been made to bioengineer functional muscle constructs by employing physical, biochemical, or biological cues. Here, we develop a self-aligned skeletal muscle construct by printing a photo-crosslinkable skeletal muscle extracellular matrix-derived bioink together with poly(vinyl alcohol) that contains human muscle progenitor cells.

To induce the self-alignment of human muscle progenitor cells, in situ uniaxially aligned micro-topographical structure in the printed constructs is created by a fibrillation/leaching of poly(vinyl alcohol) after the printing process. The in vitro results demonstrate that the synergistic effect of tissue-specific biochemical signals, obtained from the skeletal muscle extracellular matrix-derived bioink, and topographical cues, obtained from the poly(vinyl alcohol) fibrillation, improves the myogenic differentiation of the printed human muscle progenitor cells with cellular alignment. Moreover, this self-aligned muscle construct shows the accelerated integration with neural networks and vascular ingrowth in vivo, resulting in rapid restoration of muscle function.

Thus we demonstrate that combined biochemical and topographic cues on the 3D bioprinted skeletal muscle constructs can effectively reconstruct the extensive muscle defect injuries.

Link: https://doi.org/10.1063/5.0039639

There is some interest in the research community in targeting first generation stem cell therapies to the skin in order to reverse skin aging. These stem cell therapies use cells obtained from fat tissue or other well established sources, and in near all cases the transplanted cells near all die quite quickly following their introduction into the patient. Methods of cell production and sources of cells vary widely, and so do the observed benefits. Increased regeneration is widely claimed, but only intermittently proven. Benefits realized by patients largely derive from reductions in systemic inflammation and other effects on cell behavior resulting from the signaling provided briefly by the transplanted stem cells.

Today's open access paper on stem cell therapy in the context of the treatment of photoaging in the skin is an interesting companion piece to a recent review and earlier report on the use of mesenchymal stem cells in aging skin. Treatment of skin aging is an field of medicine almost swamped by the nonsense put out by the "anti-aging" marketplace, but there is some evidence for treatment with stem cells to be helpful. Caveat emptor, of course.

The Paracrine Effect of Adipose-Derived Stem Cells Orchestrates Competition between Different Damaged Dermal Fibroblasts to Repair UVB-Induced Skin Aging

Human dermal fibroblasts (HDFs) are the primary cell type in the dermis and are responsible for extracellular matrix (ECM) deposition and remodeling, supplying skin with structural integrity and elasticity. In the process of skin aging, the quantity and proliferation rates of HDFs are declined, and collagen is reduced. On the other hand, matrix-degrading metalloproteinases (MMPs) are increased, degrading and changing the structure of the ECM, which accelerates the breakdown of connective tissue. All of these changes result in the thinning of the dermis, enhancement of wrinkles, and loss of elasticity.

Skin aging is caused by intrinsic factors (e.g., time, genetic factors, and hormones) and extrinsic factors (e.g., ultraviolet (UV) exposure and pollution). Eighty percent of skin aging primarily results from exposure to UV light, which is known as photoaging. Ultraviolet B (UVB) radiation penetrates the epithelial layer and causes DNA damage in the dermis of the skin. However, most UVB radiation directly affects cells in the upper dermis. Compared with HDFs in the lower dermis, more HDFs in the upper dermis suffer UVB-induced DNA damage. Failure of aged-cellular repair results in cell death. Healthy cells are gradually generated to replace the damaged cells to keep homeostasis.

Currently, some clinical studies have shown that autologous fat grafting, nanofat, and adipose stromal cells reduce wrinkles, increase dermal thickness, improve skin elasticity, and whiten skin. Adipose-derived stem cells (ASCs) play an important role in these therapies. ASCs have the ability to differentiate into different cell lineages, such as adipocytes, endothelial cells (ECs), osteocytes, cardiomyocytes, and neurons. In addition, ASCs secrete various biologically active molecules to repair damaged neighboring cells and influence the surrounding microenvironment. ASCs are considered a promising tool for cell-based therapy, especially in skin rejuvenation, wound healing, and scar remodeling. Because ASCs are usually injected into the subcutaneous fat layer, the paracrine effect of ASCs is the main mechanism by which skin rejuvenation occurs. However, the role of the paracrine effect of ASCs on the repair of different UVB-induced damaged HDFs is still unknown.

We hypothesized that ASCs could repair different UVB-damaged HDFs to various degrees via paracrine factors. To induce photoaging and natural aging in vitro and in vivo, HDFs and nude mice were irradiated with UVB light, and the control group received no irradiation. We found that ASCs enhanced HDF cell function. However, nonirradiated HDFs were more robust than UVB-irradiated HDFs after coculture with ASCs. This finding suggests that ASC treatment may more strongly impact HDFs in the lower dermis.

One of the many frontiers of development in regenerative medicine is the delivery of cells engineered to overexpress one or more specific proteins in order to adjust cell function and activity in a favorable direction. Here, researchers demonstrate that making cardiomyocytes express cyclin D2 before transplantation into an animal model of a heart attack produces beneficial regeneration. The heart is a poorly regenerative organ, and any injury results in scarring and reduced capacity at best. The engineered cardiomyocytes survive following transplantation to some degree, but also produce signaling that provokes greater regeneration activity in native heart cells.

An enduring challenge for bioengineering researchers is the failure of the heart to regenerate muscle tissue after a heart attack has killed part of its muscle wall. That dead tissue can strain the surrounding muscle, leading to a lethal heart enlargement. Heart experts thus have sought to create new tissue - applying a patch of heart muscle cells or injecting heart cells - to replace damaged muscle. Similarly, they have tried to stimulate division of existing heart muscle cells near the damaged area.

After an experimentally induced heart attack in a pig model, heart tissue around the infarction site was injected with about 30 million bioengineered human cardiomyocytes that were differentiated from induced pluripotent stem cells. These cells also overexpress cyclin D2, part of a family of proteins involved in cell division. Compared to control human cardiomyocytes, the cyclin D2-cardiomyocytes showed enhanced potency to repair the heart. They proliferated after injection, and by four weeks, the hearts had less pathogenic enlargement, reduced size of dead muscle tissue and improved heart function.

Intriguingly, the cyclin D2-cardiomyocytes stimulated not only their own proliferation, but also proliferation of existing heart muscle cells around the infarction site of the pig heart, as well as showing angiogenesis, the development of new blood vessels. This ability of the graft cyclin D2-cardiomyocytes to stimulate the proliferation of nearby existing heart cells suggested paracrine signaling, a type of cellular communication where a cell produces a signal that induces changes in nearby cells.

Link: https://www.uab.edu/news/research/item/12041-heart-attack-recovery-aided-by-injecting-heart-muscle-cells-that-overexpress-cyclin-d2

Researchers here mine a very large data set to establish whether age-related diseases linked to a specific underlying single causative mechanism of aging will show up together in patients more often than not. One would expect that they will. To pick one example, multiple age-related diseases appear likely to be primarily caused by the increased presence of senescent cells in old tissues. A patient's senescent cell burden will thus largely determine the risk of suffering from all of those conditions. Patients exhibiting one condition, most likely because they have more senescent cells than their healthier peers, should be more likely to also exhibit other conditions in that set.

Age-associated accumulation of molecular and cellular damage leads to an increased susceptibility to loss of function, disease, and death. Aging is the major risk factor for many chronic and fatal human diseases, including Alzheimer's disease, multiple cancers, cardiovascular diseases, and type 2 diabetes mellitus (T2DM), which are collectively known as age-related diseases (ARDs). However, genetic, environmental, and pharmacological interventions can ameliorate loss of function during aging and confer resistance to multiple age-related diseases in laboratory animals. Age-related multimorbidity, the presence of more than one ARD in an individual, is posing a major and increasing challenge to health care systems worldwide. An important, open question, therefore, is whether mechanisms of aging in humans contribute to multimorbidity in patients, and hence whether intervention into these mechanisms could prevent or treat more than one ARD simultaneously.

Specific biological mechanisms begin to fail as an individual ages. Individual aging hallmarks are present in the development or disordered physiology of specific ARDs. For example, loss of proteostasis appears to have a prominent role in neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases, which are associated with protein aggregates composed of amyloid-beta and α-synuclein, respectively.

The role of genes in individual human ARDs and ARD multimorbidity has been studied extensively, as has the link between aging hallmarks and individual ARDs. For example, previous studies have demonstrated that multiple, individual human ARDs share gene ontology (GO) terms linked to mechanisms of aging, specifically aging hallmarks. However, whether these underlying mechanisms of aging contribute to the occurrence of multimorbidity in patients has not previously been investigated. Here, we explore the notion that the same aging hallmark may contribute to risk of multiple ARDs and, therefore, results in their co-occurrence in the same individual (i.e., ARD multimorbidity).

To address this question, we text mined 917,645 literature abstracts followed by manual curation, and found strong, non-random associations between age-related diseases and aging mechanisms, confirmed by gene set enrichment analysis of genome-wide association study data. Integration of these associations with clinical data from 3.01 million patients showed that age-related diseases associated with each of five aging mechanisms were more likely than chance to be present together in patients.

Link: https://doi.org/10.1101/2021.05.04.442567

In today's open access paper, the authors report on inroads in counting senescent immune cells in blood samples from human patients of different ages. Accurate determination of senescence status isn't cut and dried for many types of immune cell, but the researchers believe they have produced good numbers for cytotoxic T cells, showing that older people have many more senescent cells in this category. I'd like to see more of this sort of research, establishing some sort of baseline of expectations for levels of cellular senescence in various tissues by age, leading towards assays that can be used to directly the measure the outcome of treatment with senolytic drugs to selectively destroy senescent cells.

The results here suggest surprisingly high levels of cellular senescence in some important immune cell populations, more than half of the cells in a sample being senescent by the criteria used. In the broader context, it would make sense for numbers to be high relative to tissues. After the thymus atrophies significantly in late life, near all new T cells - needed to maintain the observed constant T cell population across a lifetime - are created by replication of existing T cells. Eventually cells hit the Hayflick limit and either self-destruct or become senescent.

Will treatment with senolytics produce benefits to immune function in this scenario? It will kill senescent T cells, and more cells will become senescent in the course of replicating to make up the numbers. The outcome will most likely be a lower count of senescent immune cells than existed prior to treatment, and the benefits of clearing senescent cells throughout the body should be sizable, but it is something to consider. Replication stress on the immune system is to be avoided if possible. One would have to test this scenario in larger mammals than mice: one big difference between mice and people is that mice do not rely on replication of existing T cells to maintain overall T cell population size, so there is little to be learned from existing mouse data.

Senescence-associated β-galactosidase reveals the abundance of senescent CD8+ T cells in aging humans

Aging leads to a progressive functional decline of the immune system, rendering the elderly increasingly susceptible to disease and infection. The degree to which immune cell senescence contributes to this decline remains unclear, however, since markers that label immune cells with classical features of cellular senescence accurately and comprehensively have not been identified.

Using a second-generation fluorogenic substrate for β-galactosidase and multi-parameter flow cytometry, we demonstrate here that peripheral blood mononuclear cells (PBMCs) isolated from healthy humans increasingly display cells with high senescence-associated β-galactosidase (SA-βGal) activity with advancing donor age. The greatest age-associated increases were observed in CD8+ T-cell populations, in which the fraction of cells with high SA-βGal activity reached average levels of 64% in donors in their 60s. CD8+ T cells with high SA-βGal activity, but not those with low SA-βGal activity, were found to exhibit features of telomere dysfunction-induced senescence and p16-mediated senescence, were impaired in their ability to proliferate, developed in various T-cell differentiation states, and had a gene expression signature consistent with the senescence state previously observed in human fibroblasts.

Based on these results, we propose that senescent CD8+ T cells with classical features of cellular senescence accumulate to levels that are significantly higher than previously reported and additionally provide a simple yet robust method for the isolation and characterization of senescent CD8+ T cells with predictive potential for biological age.

Researchers here use animal models to argue that raised levels of O-GlcNAcylation observed in heart failure patients are more important than thought as a contributing cause to the progression of this condition, rather than being further downstream as an end consequence. One must always be careful, however, in analysis of work where researchers break some important mechanism, causing problems, and then fix it. It is always possible to produce harm by causing unnatural disarray to a specific mechanism in animal metabolism. Removing that unnatural disarray will always help. That doesn't mean that the model necessarily has relevance to a condition in which the specific mechanism appears - relevance strongly depends on the specific details.

Proteins within living cells can be modified with the addition of small chemical groups that coax the proteins to change their shape or function. Among those modifications is O-GlcNAcylation, the addition of the sugar molecule O-GlcNAc (O-linked N-acetylglucosamine). The modification is controlled by two other molecules: O-GlcNAc transferase (OGT), an enzyme that adds the sugars to proteins, and O-GlcNAcase (OGA), an enzyme that facilitates their removal. Researchers have long known that proteins in the cells of people with heart failure have more O-GlcNAc than usual. But whether increased levels of the sugar were a cause or consequence of heart failure - or an attempt by the body to ward off heart failure - has been unclear.

Researchers genetically engineered mice with higher than usual levels of OGT or OGA in heart muscle cells. The animals with high OGT - and therefore more O-GlcNAc in these cells - developed severe heart failure. Their hearts began to weaken and pump less blood at just 6 weeks old. By 25 weeks of age, more than half of all mice with high OGT had died, while no control animals with normal levels of OGT had died. "These mice developed really stunning heart failure. Similar to many patients with cardiomyopathy, the mice developed enlarged hearts, abnormal electrical rhythms and died very early."

Animals with high OGA - and therefore lower than usual O-GlcNAc in their heart cells - remained healthy, however, and showed no signs of heart failure, even when challenged with an operation that constricts one of the heart's blood vessels. To test whether high levels of O-GlcNAc could be reversed to help prevent end-stage heart failure, the researchers next cross-bred the two strains of mice, engineering animals to have both high OGT and OGA levels. These animals no longer developed heart failure or died early, presumably because while OGT led them to add excessive O-GlcNAc sugars to proteins in the heart cells, the high levels of OGA reversed that excessive modification.

Link: https://www.hopkinsmedicine.org/news/newsroom/news-releases/molecular-alteration-may-be-cause--not-consequence--of-heart-failure

The biggest problem I see with the Hallmarks of Aging paper is not really the fault of its authors, but rather that a sizable part of the research community now takes that list of aging associated mechanisms as a guide to points of intervention in aging. Unlike the SENS view of aging, a list of mechanisms in aging that preceded the Hallmarks paper by more than a decade, the Hallmarks were not established to be a list of root causes of aging, and were never intended to be taken as such.

In the case of SENS, wherein a great deal of thought has gone into identifying mechanisms that are root causes of aging, one can proceed logically from the mechanisms to building treatments that target those mechanisms. In the case of the Hallmarks, that a specific hallmark exists does not in and of itself justify a strong focus on targeting it; it can be a downstream consequence of the underlying causes of aging, and thus targeting it will not yield meaningful results.

As the main cause of disease and death in the modern world, senescence (i.e. aging; not to be confused with replicative or cellular senescence) is one of the major biological and medical challenges of the 21st century. It would therefore be invaluable to understand the central biological mechanisms of senescence and how they give rise to late-life disease, including cardiovascular disease, many forms of cancer, chronic obstructive pulmonary disease (COPD), dementia, and many other maladies.

With the goal of representing common denominators of aging in different organisms, in 2013 researchers described nine hallmarks of aging. Since then, this representation has become a major reference point for the biogerontology field. The template for the hallmarks of aging account originated from landmark papers defining first six and later ten hallmarks of cancer. Here we assess the strengths and weaknesses of the hallmarks of aging account.

As a checklist of diverse major foci of current aging research, the hallmarks of aging has provided a useful shared overview for biogerontology during a time of transition in the field. It also seems useful in applied biogerontology, to identify interventions (e.g. drugs) that impact multiple symptomatic features of aging. However, while the hallmarks of cancer provide a paradigmatic account of the causes of cancer with profound explanatory power, the hallmarks of aging do not.

A worry is that as a non-paradigm the hallmarks of aging have obscured the urgent need to define a genuine paradigm, one that can provide a useful basis for understanding the mechanistic causes of the diverse aging pathologies. We argue that biogerontology must look and move beyond the hallmarks to understand the process of aging.

https://doi.org/10.1016/j.arr.2021.101407

Today's question: are we at the point at which it make sense to run a great many short human trials of potential interventions to slow or reverse aging? The answer tends to be quite conditional on the details. If the trials cost little, meaning that they can run for a year or less, and involve low-cost assays conducted before and after, then exploration sounds more viable. If the potential interventions have sizable, reliable effects in mice, then that makes it more attractive to devote funding to the project. Testing senolytics such as the dasatinib and quercetin combination in old human volunteers, with assessments of epigenetic age and blood markers of inflammation and disease, for example. There is no reason to leave that entirely to the Mayo Clinic, as they certainly won't be covering all of the bases any time soon. The wheels of the formal clinical trial system turn very slowly.

Use of the immunosuppressant drug rapamycin is a reliable way to slow aging in mice, with data that is far better than that for metformin. It triggers some of the mTOR related pathways that are involved in the calorie restriction response. The outcomes in mice are not as impressive as those for senolytics, but at some cost, testing rapamycin against potential biomarkers of aging makes sense. Biomarkers based on blood samples are becoming quite cheap. Volunteer organizations can run viable, useful studies of a few hundred volunteers at a tiny fraction of the millions of dollars it would cost a major institution to conduct the same work. And so Lifespan.io is doing just that. They have crushed down the cost of a rapamycin trial of 200 people or so, and are looking to raise $75,000 to perform the minimum version of that trial. I encourage you to take a look at this project: we'll be seeing a lot more of this sort of thing, as the community grows and more people ask why there is a lack of human data for existing approaches and biomarkers.

Pearl: Participatory Evaluation of Aging with Rapamycin for Longevity

The medicine rapamycin has been shown to extend the healthspan of all organisms it has been tested on - mice, warms, yeast - for decades, and yet to date there has been no trial to sufficiently demonstrate safety and proper dosing for this purpose in humans. It is now time for this to change. With your help, we will be conducting a large clinical trial named Participatory Evaluation (of) Aging (with) Rapamycin (for) Longevity Study, or PEARL, to find out. This will be the first study to see if Rapamycin works as well in humans as it does in mice (for longevity).

Rapamycin works through the mTOR signaling pathway, one of the master regulators of cell metabolism and a key controller of autophagy (recycling in cells). Basically, it tells our cells to switch from growth to repair, and to clean out all the garbage. Not only that, but the quality of the proteins our cells produce increases, which means that there is less garbage in the first place. What all this amounts to is improved health and lengthened life for worms, flies and mice - now it's our turn!

The PEARL trial will follow up to 200 participants over 12 months testing four different rapamycin dosing regimens. It will be double-blind, randomized, placebo-controlled and registered with clinicaltrials.gov. The principal investigator is Dr. James P Watson at UCLA, who was also a PI for the famous TRIIM trial. To ensure safety the participants' blood will be regularly monitored and side effects noted.

A battery of tests and measurements will be taken, both after 6 and 12 months. These will include autonomic health tests, blood tests, body composition tests, fecal microbiome testing, immune and inflammation health tests, methylation age clock testing and skeletal muscle tests. With your help we will find out if and how well rapamycin works to combat human aging. And, armed with a positive result, we will finally be able to help slow down onset of age related damage for you and those who you love and care about.

Telomerase gene therapy is an aspirational goal for a number of companies and research groups, and may presently be available via medical tourism in a limited, expensive, and probably not very efficient fashion. Groups such as Telocyte would like to run human trials of telomerase gene therapy for neurodegenerative conditions. Much of this is focused on the primary activity of telomerase, lengthening of telomeres and thus increased cell activity in older tissues. Telomerase, however, has other functions, not as well explored, that may still be relevant to aging and age-related disease. It may act to protect mitochondrial function in an environment of increased oxidative stress, for example. The paper here takes a look at what is know of these other mechanisms in the context of telomerase-based therapies for neurodegenerative disease.

Telomerase is an enzyme that in its canonical function extends and maintains telomeres, the ends of chromosomes. This reverse transcriptase function is mainly important for dividing cells that shorten their telomeres continuously. However, there are a number of telomere-independent functions known for the telomerase protein TERT (Telomerase Reverse Transcriptase). This includes the shuttling of the TERT protein from the nucleus to mitochondria where it decreases oxidative stress, apoptosis sensitivity, and DNA damage.

Recently, evidence has accumulated on a protective role of TERT in brain and postmitotic neurons. This function might be able to ameliorate the effects of toxic proteins such as amyloid-β, pathological tau and α-synuclein involved in neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). However, the protective mechanisms of TERT are not clear yet. Recently, an activation of autophagy as an important protein degradation process for toxic neuronal proteins by TERT has been described.

This review summarises the current knowledge about the non-canonical role of the telomerase protein TERT in brain and shows its potential benefit for the amelioration of brain ageing and neurodegenerative diseases such as AD and PD. This might form the basis for the development of novel strategies and therapies against those diseases.

Link: https://doi.org/10.3390/biomedicines9050490

Myostatin inhibition, strength training, and forms of amino acid supplementation, such as leucine supplementation, all have data to show that they can improve muscle mass. They have all been used in human trials as possible treatments for sarcopenia, the age-related loss of muscle mass and strength that ultimately leads to frailty. That strength training works, and works fairly well, to both improve muscle mass and reduce age-related mortality suggests that a sizable fraction of the problem is the pervasive lack of activity and exercise in older populations. Myostatin inhibition could in principle produce larger effects, based on the outcome of loss of function mutations, in which the affected individuals are very heavily muscled. In human trials of anti-myostatin antibodies, the gains have been much smaller.

It has been frequently reported that myostatin inhibition increases muscle mass, but decreases muscle quality (i.e., strength/muscle mass). Resistance exercise training (RT) and essential amino acids (EAAs) are potent anabolic stimuli that synergistically increase muscle mass through changes in muscle protein turnover. In addition, EAAs are known to stimulate mitochondrial biogenesis.

We have investigated if RT amplifies the anabolic potential of myostatin inhibition while EAAs enhance muscle quality through stimulations of mitochondrial biogenesis and/or muscle protein turnover. Mice were assigned into ACV (myostatin inhibitor), ACV+EAA, ACV+RT, ACV+EAA+RT, or control over 4 weeks. RT, but not EAA, increased muscle mass above ACV. Despite differences in muscle mass gain, myofibrillar protein synthesis was stimulated similarly in all versus control, suggesting a role for changes in protein breakdown in muscle mass gains.

There were increases in MyoD expression but decreases in Atrogin-1/MAFbx expression in ACV+EAA, ACV+RT, and ACV+EAA+RT versus control. EAA increased muscle quality (e.g., grip strength and maximal carrying load) without corresponding changes in markers of mitochondrial biogenesis and neuromuscular junction stability.

In conclusion, we showed that addition of resistance exercise training, but not dietary EAAs, to the myostatin inhibition further increased muscle mass through the attenuation of muscle protein breakdown with proportionate improvements in muscle strength. Interestingly, addition of dietary EAAs to the myostatin inhibition with or without resistance exercise training improved muscle quality. Thus, dissection of the underlying mechanisms behind the combined positive effect of dietary EAAs and resistance exercise training on muscle mass and quality can shed light on the discovery of effective therapeutics against muscle wasting such as sarcopenia.

Link: https://doi.org/10.3390/nu13051508

The concept of a neatly packaged definition of a disease works well when dealing with the realm of infectious conditions. There is a pathogen, the pathogen causes certain symptoms, and one works towards intervention based on, for example, getting rid of the pathogen or interfering in its ability to do harm. Since medicine was largely concerned with tackling infectious disease until comparatively recently, the disease model has become very ingrained in the medical and regulatory community.

Unfortunately, this model doesn't work well for age-related disease. The situation is completely different. Aging involves a network of interacting, layered, underlying processes of molecular damage and consequent tissue dysfunction. Senescent cells and cross-links and calcification contribute to arterial stiffening, which causes hypertension, which harms the kidneys and the brain, joining the other forms of harm to the kidneys and the brain, and at some point in time the symptoms in any given organ cross over the line in the sand from "not a disease" to "we'll call this a disease". But calling it a disease really doesn't help to clarify what should be done about it.

That the disease model, formed in the era of the dominance of infectious disease in medical concerns, hasn't been helpful when it comes to guiding researchers towards the best strategies to treat age-related conditions is illustrated by the very slow progress made to date, across a lifetime of radical advances in all of the underlying technologies, such as materials science and computing, that enable the development of greater capabilities in medicine and life science research.

A different approach is needed for aging and its consequences, which is to largely abandon the idea of treating a specific disease, identified by a specific cluster of symptoms, and instead focus on treating a specific mechanism of aging. Identify a form of damage, such as the accumulation of senescent cells, and repair it, such as by selectively destroying those cells. Then assess the outcome.

The plasticity of ageing and the rediscovery of ground-state prevention

Disease is considered the most fundamental unit of analysis in medicine. The definition of disease is the object of ongoing philosophical debate between naturalistic, constructivist, and instrumentalist accounts. While there is no consensus on the concept of disease, the notion of disease is central to medicine. Until recently, the function of disease as the focus of medicine has gone unchallenged, due to its intuitive appeal as an obviously plausible target of medical intervention. However, the complexity of most age-related ailments, the fact that elders are affected by concomitant conditions (multimorbidity), and the fact that a great number of age-related symptomatic states escape clear nosological determination, have led some to question the utility of disease as the central focus of medical care.

In a provoking 2004 paper on the "end of the disease era," the authors explicitly criticized disease-centric medicine. They instead propose a more individualized approach that revolves around the clinical trade-offs necessary to manage a complexity of concomitant affections. Instead of treating each disease individually, medicine should strive to treat an individual patient's unique combination of diseases, and the way they affect physical and psychological functioning, as well as daily activities, goals, and life plans. The focus is less on discrete pathologies and survival, than on the reality of how an individual organism becomes diseased and weakened over time.

This post-disease paradigm is an example of a very general explanatory framework: one that considers multimorbidity, as opposed to discrete pathological states, to be the central focus of geriatric medicine. In this account, the health of the ageing person is best understood as the result of multiple concomitant pathologies.

In contrast, understanding health as the absence of disease is not compatible with the idea of measuring and protecting functional trajectories as the focus of geriatric care. From an epistemological point of view, this vision clearly resonates with the explanatory framework of ageing as a plastic phenotype. For researchers working on intrinsic capacity, the disease construct is inadequate for capturing how an individual fares in her environment in functional terms. Function, not disease, is the object of care in this clinical perspective on ageing.

The same applies to the molecular version of the explanatory framework. Researchers in this domain are not interested in linking alterations in metabolic pathways to the manifestation of a given discrete pathology. Their focus is rather on the role of those pathways in maintaining organ functionality over time. This, in turn, can translate into the delayed onset and slowing down of multiple diseases of old age. The longitudinal focus of intrinsic capacity emphasizes prevention over reaction even in the absence of a specific clinical phenotype.

A growing body of evidence points to the inflammatory activity of microglia in the aging brain as an important contributing cause of neurodegenerative conditions. Some of these microglia have become senescent, and like other types of senescent cell, drive chronic inflammation and tissue dysfunction via the senescence-associated secretory phenotype (SASP). Others are merely activated, pushed into an inflammatory state by the presence of increasing levels of molecular waste and other forms of damage in brain tissue. Clearing out microglia and allowing them to repopulate has been shown to produce benefits in mice, as has the selective destruction of senescent microglia. This all points to inflammatory signaling as an important mechanism in age-related neurodegenerative conditions.

Microglia are immune cells of the brain, representing the neural tissue's defense system. A large body of evidence shows that microglia have a significant neuroprotective role, and that impaired and over activated microglial phenotypes are present in brains of Parkinson's disease (PD) patients. Thereby, PD progression is potentially driven by a vicious cycle between dying neurons and microglia through the instigation of oxidative stress, mitophagy and autophagy dysfunctions, α-synuclein accumulation, and pro-inflammatory cytokine release.

In the central nervous system (CNS), microglia constitute up to 12% of all cells, and their density changes depending on the brain region. Early studies in mice showed that bone-marrow-derived hematopoietic cells move to the CNS, where they differentiate into microglia-like cells. With innovative conditional cell depletion techniques, it was recently shown that microglia have the ability to self-renew, and that interleukin-1 (IL-1) signaling is enabling this process.

Just like the abundance of microglia is region-specific, microglial morphology varies from brain area to brain area. In a resting state, microglia survey the brain microenvironment and show ramified morphology. Surveillance encompasses multiple functions: clearance of accumulated or deteriorated neuronal and tissue elements, dynamic interaction with neurons whilst regulating the synaptic pruning process, and maintaining overall brain homeostasis. Once activated upon brain damage and certain host or non-host stimuli, microglia are quickly undergoing a morphology change into an ameboid-like form, coupled with the release of inflammatory molecules, cytokines and chemokines. With regard to their activation, microglia are commonly divided into two classes: M1 (pro-inflammatory) or M2 (anti-inflammatory). Even though, by now, it is known that the states of activation are much more heterogeneous and diverse.

New approaches are being developed to determine sub-populations of microglia, mostly through single-cell gene expression studies and by determining fine morphological differences using computational methods. With age, microglia tend to express more IL-1β and they become more phagocytic in nature compared to microglia from younger brains. These phenotypic changes over time can influence their ability to function normally and attain the neuronal homeostasis and support. Eventually, an accumulation of non-functional, senescent microglia could contribute to irreversible and progressive neurodegeneration in PD.

Link: https://doi.org/10.3390/ijms22094676

There is a fair amount of epidemiological data to suggest that vegetarians have, on balance, better long-term health prospects than people who consume meat. The usual caveats apply, in that vegetarianism in many wealthier study populations is correlated with a range of other potentially relevant line items, such as education, wealth, and better lifestyle choices. Further, the average vegetarian may well be mildly calorie restricted in comparison to the average meat eater, and that may be enough in and of itself to explain health effects. Other suggested contributing factors include dietary advanced glycation end-products, but as is usual in these matters the research community has yet to provide firm, line by line data on the relative importance of each of the underlying mechanisms in humans.

Vegetarians appear to have a healthier biomarker profile than meat-eaters, and this applies to adults of any age and weight, and is also unaffected by smoking and alcohol consumption, according to a new study. To understand whether dietary choice can make a difference to the levels of disease markers in blood and urine, researchers performed a cross-sectional study analysing data from 177,723 healthy participants (aged 37-73 years) in the UK Biobank study, who reported no major changes in diet over the last five years.

Participants were categorised as either vegetarian (do not eat red meat, poultry or fish; 4,111 participants) or meat-eaters (166,516 participants) according to their self-reported diet. The researchers examined the association with 19 blood and urine biomarkers related to diabetes, cardiovascular diseases, cancer, liver, bone and joint health, and kidney function.

Even after accounting for potentially influential factors including age, sex, education, ethnicity, obesity, smoking, and alcohol intake, the analysis found that compared to meat-eaters, vegetarians had significantly lower levels of 13 biomarkers, including: total cholesterol; low-density lipoprotein (LDL) cholesterol - the so-called 'bad cholesterol; apolipoprotein A (linked to cardiovascular disease), apolipoprotein B (linked to cardiovascular disease); gamma-glutamyl transferase (GGT) and alanine aminotransferase (AST) - liver function markers indicating inflammation or damage to cells; insulin-like growth factor (IGF-1), a hormone that encourages the growth and proliferation of cancer cells; urate; total protein; and creatinine (marker of worsening kidney function).

However, vegetarians also had lower levels of beneficial biomarkers including high-density lipoprotein 'good' (HDL) cholesterol, and vitamin D and calcium (linked to bone and joint health). In addition, they had significantly higher level of fats (triglycerides) in the blood and cystatin-C (suggesting a poorer kidney condition).

Link: https://www.eurekalert.org/pub_releases/2021-05/eaft-vhh050621.php

The blockchain and cryptocurrency space is known to produce events that require more than a little explanation for an outsider to even begin to understand what exactly has taken place. I will not attempt to do that here. In the midst of one of those events, involving dog themed joke currencies that are nonetheless somehow magically worth real money, albeit to some highly variable degree depending on who has control of them, and what everyone else thinks that controller will do with them, well known entrepreneur Vitalik Buterin, founder of Ethereum, donated 1,000 Ether to the Methuselah Foundation. That amounts to more that $2 million at the present time, a sizable fraction of the yearly budget of that organization.

Buterin has made substantial philanthropic donations to advance the state of longevity in the past, such as to the SENS Research Foundation, and has spoken on the desirability of producing therapies to treat aging as a medical condition. The Methuselah Foundation is the parent organization of the SENS Research Foundation, and organized some of the first research programs to work on mechanisms of aging that were insufficiently supported by the broader research community. Since then, the Methuselah Foundation has undertaken a range of projects, many of which aim to advance the state of the art in tissue engineering, and launched the Methuselah Fund to invest in early stage startups in the longevity industry.

Vitalik Buterin donates more than $60M to charity after selling meme tokens including Shiba Inu

Ethereum creator Vitalik Buterin sold large amounts of three meme tokens on Wednesday that he was given for free. Buterin then used proceeds of the sales to support a range of charities, according to public blockchain data. Buterin was given the tokens through a rather unusual token distribution strategy. The developers behind at least three dog-themed tokens - based around the Shiba Inu breed of dog - decided to send half of their tokens to his publicly known Ethereum address. These tokens included Shiba Inu (SHIB), Akita Inu (AKITA) and Dogelon Mars (ELON).

The theory behind this was that the approach was akin to burning the tokens. Presumably, the idea was that Buterin - who owns 333,500 ETH worth around $1.3 billion - wouldn't need the cash and would just sit on the tokens. Buterin appears to have had other ideas, however. Starting a few hours ago, Buterin began sending the tokens in batches to Uniswap and selling them for ETH, creating a total of 15,719 ETH, an amount worth about $63 million.

Following the sales, Buterin sent large amounts of ETH to various charities that support different causes. He gave out more than 16,000 ETH along with some of the dog-themed tokens. The largest tranche - 13,292 ETH - was sent to Givewell, a non-profit charity assessment organization. The Ethereum creator also sent 1,000 ETH and 430 billion ELON tokens (the latter worth $215,000) to the Methuselah Foundation, which focuses on making people live longer. He sent 1,050 ETH to the Machine Intelligence Research Institute, which focuses on ensuring AI has a positive impact.

Researchers here use the properties of a subset of natural killer T cells of the immune system in order to provoke these cells into greater activity without rousing the rest of the immune system into action. The outcome is that the activated natural killer T cells then destroy more senescent cells than would otherwise have been the case. Destroying senescent cells by any means leads to a dose-dependent degree of rejuvenation in older individuals, and that result is achieved here. This is an intriguing approach to the challenge of clearing senescent cells, and it will be interesting to watch its further development.

In a healthy state, these immune cells - known as invariant Natural Killer T (iNKT) cells - function as a surveillance system, eliminating cells the body senses as foreign, including senescent cells, which have irreparable DNA damage. But the iNKT cells become less active with age and other factors like obesity that contribute to chronic disease. The iNKT cells have two attributes that make them an especially appealing drug target. First, they all have the same receptor, which does not appear on any other cell in the body, so they can be primed without also activating other types of immune cells. Second, they operate within a natural negative feedback loop that returns them to a dormant state after a period of activity.

Researchers found they could remove senescent cells by using lipid antigens to activate iNKT cells. When they treated mice with diet-induced obesity, their blood glucose levels improved, while mice with lung fibrosis had fewer damaged cells, and they also lived longer. The results presented for iNKT cells in a mouse model of lung fibrosis offer hope for a potentially fatal disease that often leads to lung transplants. "I think this is a potential immune therapy for senescence and fibrosis. It's a fairly well tolerated therapy, and we just have to get around dosing and trials."

Link: https://www.eurekalert.org/pub_releases/2021-05/uoc--sfm050621.php

This popular science article covers some of the high points of the past few decades of research into the comparative biology of aging. Why are some mammals exceptionally long-lived for their size? What are the mechanisms of interest, and can any of those mechanisms inform the development of therapies to extend healthy human life spans? Answers remain to be determined in a concrete fashion for these and other, related questions. Metabolism and its relationship to aging is a very complex area of study, a great deal of the space remains poorly mapped, and as of yet it is hard to say as to whether any of the work in progress is even in principle capable of yielding useful paths to near term implementations in human medicine.

Perhaps the most remarkable animal Methuselahs are among bats. One individual of the species Myotis brandtii, a small bat about a third of the size of a mouse, was recaptured, still hale and hearty, 41 years after it was initially banded. "It's equivalent to about 240 to 280 human years, with little to no sign of aging. So bats are extraordinary. The question is, why?" There are two ways to think about this question. First: What are the evolutionary reasons that some species have become long-lived while others have not? And second: What are the genetic and metabolic tricks that allow them to do that?

The outline of an answer is beginning to emerge as researchers compare species that differ in longevity. Long-lived species, they've found, accumulate molecular damage more slowly than shorter-lived ones do. Naked mole rats, for example, have an unusually accurate ribosome, the cellular structure responsible for assembling proteins. It makes only a tenth as many errors as normal ribosomes. And it's not just mole rats: In a follow-up study comparing 17 rodent species of varying longevity, researchers found that the longer-lived species, in general, tended to have more accurate ribosomes.

One of the principles beginning to emerge from comparative studies of aging is that different species may follow different paths to longevity. All long-lived mammals need to delay the onset of cancer, for example. Elephants do this by having multiple copies of key tumor-suppressing genes, so that every cell has backups if one gene breaks during the wear and tear of life. Naked mole rats, on the other hand, gain cancer resistance from an unusual molecule involved in sticking cells together, while bowhead whales have amped up their DNA-repair pathways.

Link: https://www.theatlantic.com/science/archive/2021/05/worlds-oldest-animals-whale-bats/618824/

That the brain has a lymphatic system that drains into the body is a comparatively recently discovery, a development of the last decade of research. It isn't the only way in which fluids drain from the brain - see, for example, the work on the cribriform plate path for drainage of cerebrospinal fluid - but there are a limited number of such pathways outside the vascular system. The vascular system itself is separated from the brain by the blood-brain barrier that surrounds every blood vessel that passes through the central nervous system. This barrier controls the entry and exit of molecules and cells, limiting the degree to which forms of undesirable molecular waste can be removed.

Cerebrospinal fluid and lymphatic fluid leaving the brain can carry away molecular waste, such as the protein aggregates of various forms (amyloid-β, tau, α-synuclein, and so on) that are associated with the development of neurodegenerative conditions. These pathways of drainage decline in effectiveness with age. This is coming to be seen as a meaningful contribution to the buildup of protein aggregates in the brain, and thus consequent pathology. This makes mechanisms of drainage an important consideration in the development of neurodegeneration, and a potential target for therapies.

Brain's waste removal system may offer path to better outcomes in Alzheimer's therapy

Abnormal buildup of amyloid-beta is one hallmark of Alzheimer's disease. The brain's lymphatic drainage system, which removes cellular debris and other waste, plays an important part in that accumulation. A 2018 study showed a link between impaired lymphatic vessels and increased amyloid-beta deposits in the brains of aging mice, suggesting these vessels could play a role in age-related cognitive decline and Alzheimer's. The lymphatic system is made up of vessels which run alongside blood vessels and which carry immune cells and waste to lymph nodes. Lymphatic vessels extend into the brain's meninges, which are membranes that surround the brain and spinal cord.

For this new study, the research team sought to determine whether changing how well the lymphatic drainage works in the brain could affect the levels of amyloid-beta and the success of antibody treatments that target amyloid-beta. Using a mouse model of early-onset Alzheimer's, researchers removed some of the lymphatic vessels in the brains of one group of mice. They treated these mice, as well as a control group, with injections of monoclonal antibody therapies, including a mouse version of aducanumab.

Mice with less functional lymphatic systems had greater buildup of amyloid-beta plaques and of other immune cells that cause inflammation, which is another factor in Alzheimer's pathology. Moreover, when the researchers compared immune cells in the brains of human Alzheimer's patients with those of the mice whose meningeal lymphatic system had been diminished, they found that the genetic fingerprints of certain immune cells in the brain, the microglia, were very similar between people with the disease and mice with defective lymphatic vessels. These mice also performed more poorly on a test of learning and memory performance, suggesting that dysfunctional lymphatic drainage in the brain contributes to cognitive impairment and increases difficulties for antibodies that target amyloid-beta.

Meningeal lymphatics affect microglia responses and anti-Aβ immunotherapy

Alzheimer's disease (AD) is the most prevalent cause of dementia. Although there is no effective treatment for AD, passive immunotherapy with monoclonal antibodies against amyloid beta (Aβ) is a promising therapeutic strategy. Meningeal lymphatic drainage has an important role in the accumulation of Aβ in the brain, but it is not known whether modulation of meningeal lymphatic function can influence the outcome of immunotherapy in AD.

Here we show that ablation of meningeal lymphatic vessels in 5xFAD mice (a mouse model of amyloid deposition that expresses five mutations found in familial AD) worsened the outcome of mice treated with anti-Aβ passive immunotherapy by exacerbating the deposition of Aβ, microgliosis, neurovascular dysfunction, and behavioural deficits. By contrast, therapeutic delivery of vascular endothelial growth factor C improved clearance of Aβ by monoclonal antibodies. Notably, there was a substantial overlap between the gene signature of microglia from 5xFAD mice with impaired meningeal lymphatic function and the transcriptional profile of activated microglia from the brains of individuals with AD.

Overall, our data demonstrate that impaired meningeal lymphatic drainage exacerbates the microglial inflammatory response in AD and that enhancement of meningeal lymphatic function combined with immunotherapies could lead to better clinical outcomes.

Researchers here attempted a combination gene therapy using BDNF and TrkB in order to provoke growth of axons in the mouse optic nerve and brain. The hope is to produce enough repair and regrowth to outpace for a time the disease process that causes damage. This seemed to have positive results in the optic nerve, but less so when applied to a mouse model of tauopathy. The regenerative medicine community might argue that sufficiently comprehensive regenerative will help, and functional recovery following treatment is a matter of the balance between degree of regeneration versus degree of harm caused by the disease process. It remains the case that addressing the causes of the condition may also be necessary to achieve positive results in patients.

A common feature of neurodegenerative diseases is disruption of axonal transport, a cellular process responsible for movement of key molecules and cellular 'building blocks' including mitochondria, lipids, and proteins to and from the body of a nerve cell. Axons are long fibres that transmit electrical signals, allowing nerve cells to communicate with other nerve cells and muscles. Scientists have suggested that stimulating axonal transport by enhancing intrinsic neuronal processes in the diseased central nervous system might be a way to repair damaged nerve cells. Two candidate molecules for improving axonal function in injured nerve cells are brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin receptor kinase B (TrkB).

Researchers have now shown that delivering both of these molecules simultaneously to nerve cells using a single virus has a strong effect in stimulating axonal growth compared to delivering either molecule on its own. They tested their idea in two models of neurodegenerative disease known to be associated with reduced axonal transport, namely glaucoma and tauopathy (a degenerative disease associated with dementia).

Glaucoma is damage to the optic nerve often, but not always, associated with abnormally high pressure in the eye. In an experimental glaucoma model, the researchers used a tracer dye to show that axonal transport between the eye and brain was impaired in glaucoma. Similarly, a reduction in electrical activity in the retina in response to light suggested that vision was also impaired. The gene therapy restored axonal transport between the retina and the brain, as observed by movement of the dye. The retinas also showed an improved electrical response to light, a key prerequisite for visual restoration.

Next, the team used transgenic mice bred to model tauopathy, the build-up of 'tangles' of tau protein in the brain. Tauopathy is seen in a number of neurodegenerative diseases including Alzheimer's disease and frontotemporal dementia. Once again, injection of the dye showed that axonal transport was impaired between the eye and the brain - and that this was restored using the viral vectors. The team also found preliminary evidence of possible improvement in the mice's short-term memory, but those results did not quite achieve statistical significance.

Link: https://www.cam.ac.uk/research/news/gene-therapy-technique-shows-potential-for-repairing-damage-caused-by-glaucoma-and-dementia

In this open access commentary, the authors discuss efforts to uncover the mechanisms by which microglia in the aging brain are primed to undertake inflammatory responses, more so than those in the young brain. This may be due in part towards increased numbers of senescent microglia, secreting pro-inflammatory signals. This tendency towards an exaggerated response to potential threats causes harm to neural and cognitive function. The age-related dysfunction of microglia is thought to be an important contributing factor to the progression of neurodegeneration in later life, particular given the growing evidence for chronic inflammation in the brain to be involved in the development of neurodegenerative conditions.

The inflammatory response that occurs systemically and in the brain is exacerbated as a result of aging. The underlying inflammation, which is actually heightened with age, is believed to be a precursor to neurodegenerative diseases like Alzheimer's disease. Moreover, in diseases in which inflammation plays a critical role, the aging population seems to be more vulnerable.

Previous research has shown that systemic infection can affect the central nervous system (CNS); studies have shown evidence of cognitive decline following systemic inflammation. Cognitive decline seems to occur more frequently in the aged population after infection, likely due to the microglial priming that occurs with age. Primed microglia have a heightened pro-inflammatory gene profile and a decrease in neuroprotective factors, which causes an exaggerated response to stimuli. Based on this evidence, it was hypothesized that systemic infection would produce a greater pro-inflammatory response in the brain of aged mice, and that this heightened response occurs because aged mice are lacking in the expression of microglial-specific anti-inflammatory genes.

In a mouse model of systemic infection, researchers observed an increase in microglial cell count and a more pro-inflammatory environment in middle-aged infected mice. This study is consistent with previous evidence showing that inflammaging, or age-related inflammation, is naturally heightened in the nervous system. Moreover, the authors disproved their hypothesis that anti-inflammatory microglia-specific genes are responsible for the elevated inflammatory response in aged brains since the expression of anti-inflammatory mediators was elevated in middle-aged brains following infection. Thus, the cause for the increase in pro-inflammatory genes remains to be elucidated.

Link: https://doi.org/10.3390/cells10051037

The "anti-aging" marketplace has long been a pit of fraud, lies, hopes, and dreams, and blatantly so. Whatever the supplement sellers and cosmetics companies that dominate that industry have to say about the capabilities of their products is essentially nonsense, and this play-acting is accepted by the public as just another part of the backdrop of everyday life. Scientific studies are cherry-picked, and outright lies are told. Whatever works and can pass muster to move products from shelves.

It used to be the case that we could draw a bright line between what worked what didn't work when it came to interventions targeting the mechanisms of aging. If someone was selling something, then it didn't work. That was a simpler era. Now that the first rejuvenation therapies exist, in the form of senolytic drugs, and numerous other approaches are under development, it becomes somewhat harder to pick apart the snake oil from the legitimate science. One actually has to look at the details, and become a knowledgeable consumer.

Ultimately, the therapies that work will largely drive out the therapies that do not work. At this point, however, it remains the case that all too many new entries into the longevity industry are following the old supplement sellers' playbook, in which marketing is much more important than effect size, and science only exists to provide a thin cloak of legitimacy.

Two Industries in One Field

Our field is divided into two groups of people. The first group consists of the snake oil salesmen peddling unproven supplements and therapies to whoever is foolish enough to buy and take things on faith without using the scientific method. The hucksters have long been a plague on our field, preying on the gullible and tainting legitimate science with their charlatanry and nonsense. One example is a "biotech company" evading the FDA by setting up shop in countries with few or no regulations. They make bold claims yet never deliver on those claims in practice, using poorly designed experiments and tiny cohorts that are statistically irrelevant.

Another example is the supplement peddler selling expensive supplement blends with flashy names, which, on inspection, turn out to be commonly available herbs and minerals that are mixed and sold at a high markup with questionable or no supporting data. These sorts of people have plagued our community and given the field a reputation of snake oil.

The second group are the credible scientists, researchers, and companies who have been working on therapies for years and sometimes more than a decade or two. Some of these therapies are following the damage repair approach advocated by Dr. Aubrey de Grey of the SENS Research Foundation over a decade ago. The basic idea is to take an engineering approach to the damage that aging does to the body and to periodically repair that damage in order to keep its level below that which causes pathology. Others including Dr. David Sinclair are focusing on partial cellular reprogramming and believe it may be possible to reset the cells in our bodies to a younger state using reprogramming factors.

While it will be some years yet before all therapies to end age-related diseases are here and available, and the hucksters are still peddling their wares, you can arm yourself with knowledge and protect yourself and our community from these people. Learn to evaluate science rather than taking things at face value, and avoid expensive scams and bad science. Here is a useful checklist to consider when reading an article, looking at claims made by supplement makers, or evaluating any science in general.

There is enthusiasm in the research community for in vivo cellular reprogramming as a path to treat aging. Reprogramming somatic cells to pluripotency recaptures some of the processes that take place in the developing embryo, and has been shown to restore youthful patterns of gene expression, leading to improved mitochondrial function. Reprogramming can't do much for DNA damage or forms of persistent molecular waste in long-lived cells, but forms of reprogramming may be able to improve tissue function to a sizable enough degree to be worth the effort. Early results in mice are promising. There is a long way to go in order to produce systems of reprogramming that are safe enough and sophisticated enough to be used systemically, however, rather than in comparatively small and isolated areas of the body, such as the retina.

As we age, we become increasingly vulnerable to age-related diseases. The progressive aging of the population makes this issue one of, if not the, major current scientific concern in the field of medicine. Aging is an intricate process that increases the likelihood of cancer, cardiovascular disorders, diabetes, atherosclerosis, neurodegeneration, and age-related macular degeneration. The regenerative capacity of cells and tissues diminishes over time and they thus become vulnerable to age-related malfunctions that can precipitate death.

Developing prophylactic strategies to increase the duration of healthy life and promote healthy aging is challenging, as the mechanisms causing aging are poorly understood, even if great progress has been made from studying naturally occurring or accelerated-aging phenomena. We now know that aging inculcates many changes, or 'hallmarks': genomic instability, telomere shortening, epigenetic alterations, loss of proteostasis, cellular senescence, mitochondrial dysfunction, deregulated nutrient sensing, altered intercellular communication, and stem cell compromise and exhaustion. These various hallmarks of aging are all active fields of molecular mechanistic study with much promise but relatively few tangible results have been translated into therapy.

Perhaps the most effective strategies so far have been those that focus on the removal of senescent cells with 'senolytic' drugs. In some ways, however, we feel this is too focused on the symptoms of aging whereas perhaps the most promising strategy for the future would be to focus on the causes of aging and its corollary, the rejuvenative capacity of stem cells.

Simply expressing four transcription factors, OCT4, SOX2, KLF4 and c-MYC (OSKM), converts somatic cells into induced pluripotent stem cells (iPSCs). Reprogramming occurs through a global remodeling of the epigenetic landscape that ultimately reverts the cell to a pluripotent embryonic-like state, with properties similar to embryonic stem cells (ESCs). This cellular reprogramming allows us to imagine cell therapies that restore organ and tissue function. Indeed, by reprogramming a somatic cell, from a donor into iPSCs, these cells can then be modified or corrected before redifferentiation, to produce 'rejuvenated' cells, tissues or organs, for replacement in the same donor or an immune-compatible person.

In recent years, emerging results have led to new ideas demonstrating that the mechanics of cellular reprogramming can be used to reduce the deleterious effects of aging and to delay these effects by increasing regenerative capacity, either at the cellular or the whole-organism level.

Link: https://doi.org/10.3390/ijms22083990

The progressive age-related dysfunction of microglia in the aging brain is implicated in the progression of neurodegenerative disease, as well as the increased inflammation and forms of pathology found in the brain tissue of older individuals. In mice, clearance of microglia can be efficiently achieved and leads to a rapid repopulation of the brain with new microglia, as well as improvements in measures of brain function. Similarly, targeted destruction of senescent microglia and other supporting cells in the brain via the use of senolytic drugs that can pass the blood-brain barrier has been shown to reduce chronic inflammation and pathology in mouse models of neurodegeneration.

Microglia, far from being simply 'brain glue', play an important role as the brain's resident immune cells. There is some precedent for the toxicity of senescent cells, with several studies identifying that the elimination of senescent cells as potential mechanisms for countering their deleterious effects. In the case of microglia, senescence as a descriptor is sometimes used interchangeably with dystrophic. 'Dystrophy' now tends to refer more to morphological changes, whereas 'senescence' may be used to refer to specific secretory phenotypes, particularly associated with ageing. These features have been observed in healthy but aged brains, although it has also been suggested by a study using human brain tissue that senescent microglia are exclusively a disease-associated phenotype.

Specific depletion of microglia by targeting of Colony Stimulating Factor 1 Receptor (CSF1R) has been utilised in mouse models, for the purpose of impeding the propagation of phospho-tau, such as is observed in Alzheimer's disease. However, even as this demonstrates the principle of specifically targeting microglia, such a large scale depletion of the cell type is likely to be of limited practical benefit in a clinical setting. CSF1R inhibition in mouse models has been shown to eliminate 99% of CNS microglia. Inhibition of CSF1R, then removal of this inhibition for 1 week, was demonstrated to allow 'repopulation' of microglia, while triggering no cognitive, motor function, or behavioural deficits.

It remains to be seen if this approach would be so successful in the larger, more complex human brain, where cell volume is substantially greater than in the mouse. Microglial elimination and repopulation in an aged mouse model was shown to improve cognition, particularly spatial memory, concurrently increasing density of synaptic spines and neurogenesis. These processes are diminished in the aged brain, demonstrating benefit not only to the microglia but also to the surrounding neurons.

Targeting and eliminating or reprogramming aged or senescent microglia clearly holds potential for reversing the impact of ageing on the brain, and much has already been learned from such techniques. However, at the present time, it remains unclear how these techniques might be translated into benefit in human patients. An ideal outcome would be the ability to target specifically aged, senescent, and neurotoxic microglia and eliminate them from the brain without the requirement for genetic manipulation and transgene expression. Efficacy of such a technique may well be improved by more specific identification and targeting of senescent microglia, which would require the identification of a unique, specific marker.

Link: https://doi.org/10.3390/ijms22094402

Researchers here report on DNA sequencing carried out in a (necessarily small) number of supercentenarians (age 110 and over) and semi-supercentenarians (age 105 to 109), and identification of genetic variants associated with DNA repair and clonal hematopoiesis that are more common in these survivors to late old age. We should treat this all as being highly speculative, however.

Firstly, near all genetic variants that have been found to correlate with age in one study population fail to replicate in other study populations, and this is true of studies with cohorts consisting of thousands of individuals. The study here used a primary cohort of less than 100 individuals over the age of 100. This is ever the challenge in research focused on extreme old age: very few people make it that far. There was a secondary validation cohort of a few hundred centenarians, but I'm not sure that should increase our confidence in the data, given the existence of other studies that did much the same thing and still failed to replicate.

Secondly, given the identification of a genetic variant, near everything one can say about it is quite speculative in advance of much more detailed research into how exactly that variant changes cell behavior. Lastly, the most robust data established to date on the contributions of genetic variants to human longevity, with studies pulling from very large national databases such as the UK Biobank, suggests that genetics has only a minor role to play. Lifestyle choices and exposure to pathogens are the dominant factors. In the case of long-lived families, cultural transmission of lifestyle choices relating to longevity seems a more plausible explanation than genetics, given the rest of the literature as it presently stands.

Whole-genome sequencing analysis of semi-supercentenarians

The study of human extreme longevity constitutes a model useful to assess the impact of genetic variability on this trait according to the following considerations. First, researchers showed that, considering individuals surviving to age 105 years, the relative risk of sibling surviving to 105 years is 35 times the chance of living to age 105 of the control population. These data suggest a more potent genetic contributions if samples are recruited in the last percentile of survival - the power to detect association with longevity is greater for centenarians versus nonagenarians samples of the same birth cohort. Second, despite different definitions and opinion regarding the concept of healthy aging, the clinical and biochemical data on centenarians showed that they can be considered as a paradigm of healthy aging as they avoid or largely postpone all major age-related diseases. Thus, healthy aging and exceptional longevity (people who live more than 100 years) are deeply related.

Cardiovascular diseases (CVDs) constitute the first cause of death globally and many studies highlighted the intersection between CVDs and aging as cardiac and vascular aging are considered the major risk factor for CVDs. Many molecular mechanisms have been described as hallmarks of this process such as cellular senescence, genomic instability, chromatin remodeling macromolecular damage, and mitochondrial oxidative stress, perturbed proteostasis, vascular and systemic chronic inflammation, among others. An emerging common mechanism between aging and CVD is the accumulation with age of somatic mutations. An age-related expansion of hematopoietic clones characterized by disruptive somatic mutations in few recurrent genes (such as DNMT3A, TET2, ASXL1, PPM1D, TP53), conferring to the mutated cells a selective proliferative advantage. The expansion of such mutated clones ('clonal hematopoiesis of indeterminate potential', CHIP), has been associated to an acceleration of the atherosclerotic process, an increased risk of haematological malignancies, ischemic stroke, coronary heart disease, and all-cause mortality.

In this study, we generated and analyzed the first whole genome sequencing data with high coverage (90X) in a cohort of 81 semi-supercentenarians and supercentenarians [105+/110+] (mean age: 106.6 ± 1.6) recruited across the entire Italian peninsula together with a control cohort of 36 healthy geographically matched individuals (Northern, Central, and Southern Italy) (mean age 68.0 ± 5.9). Data recently published with a second independent cohort of 333 centenarians (100+ years) and 358 geographically matched controls (Northern, Central, and Southern Italy) were used to replicate our results.

We identified five common variants (rs7456688, rs10257700, rs10279856, rs69685881, and rs7805969), all in the same region located between COA1 gene and STK17A gene. The gene-based analysis of sequencing data identified STK17A gene as the most significant gene that is validated in the second cohort.

STK17A is involved in DNA damage response and positive regulation of apoptotic process and regulation of reactive oxygen species (ROS) metabolic process. Moreover, it has been suggested that STK17A can be activated in response to external stimuli such as UV radiation and drugs. Data suggests a possible role of this gene in DNA damage response as the variants associated to an increase of SKT17A expression (in-silico prediction) were found more frequent in 105+/110+ than controls. Researchers have proposed the following sequence of events that occurs during aging: (i) mutation impairs function of genes involved in stress response and DNA repair; (2) DNA repair became more error-prone leading to accumulation of DNA damage; (3) this process accelerates age-related decline. In this model, genetic variants in STK17A may maintain DNA damage responses in 105+/110+, favoring healthy aging.

Greater longevity tends to be accompanied by better late life health and a slower progression of measurable aspects of aging. Researchers are very interested in uncovering the genetic contribution to variations in the pace of aging in our species, but the harder they look, the more it appears that genetic differences provide only a small contribution at best. Variance in pace of aging must then largely result from better lifestyle choices and lesser exposure to damaging circumstances such as persistent infections. Even in the case of long-lived families, there is the argument that a slower pace of aging is far more a matter of culture, rather than of genetics.

The Long Life Family Study (LLFS) has enrolled over 5,000 participants from almost 600 families and has been following them for the past 15 years. The study is unique in that it enrolls individuals belonging to families with clusters of long-lived relatives. Since 2006, the LLFS has recruited participants belonging to two groups: the long-lived siblings (also called the proband generation) and their children. Since they share lifestyle and environmental factors, the spouses of these two groups have also been enrolled in the LLFS as a referent group.

To assess cognitive performance, the researchers administered a series of assessments to the study participants meant to test different domains of thinking, such as attention, executive function and memory, over two visits approximately eight years apart. This allowed researchers to ask whether individuals from families with longevity have better baseline cognitive performance than their spouses do and whether their cognition declines more slowly than does that of their spouses.

Individuals from long-lived families performed better than their spouses on two tests: a symbol coding test, which has participants match symbols to their corresponding numbers and provides insight into psychomotor processing speed, attention, and working memory, and a paragraph recall test, which asks participants to remember a short story and assesses episodic memory. Individuals in the younger generation (participants born after 1935) exhibited a slower rate of cognitive decline on the symbol coding test than did their spouses.

"This finding of a slower decline in processing speed is particularly remarkable because the younger generation is relatively young at an average age of 60 years and therefore these differences are unlikely to be due to neurodegenerative disease. Rather we are detecting differences in normal cognitive aging."

Link: https://www.eurekalert.org/pub_releases/2021-05/buso-pwf050421.php

The relationship between age-related kidney failure and neurodegeneration is interesting to consider in the context of research into the longevity-associated gene klotho. Overexpression of klotho slows aging, while loss of expression accelerates aging. Klotho also affects cognitive decline; more klotho slows age-related neurodegeneration. Klotho, however, appears to act in the kidney, not the brain. This is a point of emphasis on the importance of the kidneys to long term health; loss of kidney function leads to deterioration of tissue function throughout the body, due to the failure to clear waste products from the bloodstream.

A new study has found that people with reduced kidney function may have an increased risk of developing dementia. Chronic kidney disease affects approximately 15% of adults in the United States and it is more common as people age. However, since many people don't experience symptoms until later stages, it is estimated that 90% of people with chronic kidney disease don't know they have it. "Even a mild reduction in kidney function has been linked to an increased risk of cardiovascular disease and infections, and there is growing evidence of a relationship between the kidneys and the brain."

Researchers used a database to identify nearly 330,000 people 65 years and older who received health care in the city of Stockholm and were followed for an average of five years. None of the participants had dementia or had undergone kidney transplants or dialysis at the start of the study. Over the course of the study 18,983 people, or 6% of participants, were diagnosed with dementia.

Researchers found as kidney function decreased, the rate of dementia increased. In people with a normal kidney filtration rate of 90 to 104 mL per minute, there were seven cases of dementia per 1,000 person-years. In people with severe kidney disease, or a filtration rate of less than 30 mL per minute, there were 30 cases of dementia per 1,000 person-years.

After adjusting for other factors that could affect dementia risk like smoking, alcohol use, hypertension and diabetes, researchers determined that people with filtration rates of 30 to 59 mL per minute, which indicates moderate chronic kidney disease, had a 71% higher risk of developing dementia compared to those with normal kidney function, and people with filtration rates of less than 30 mL per minute had a 162% higher risk.

Link: https://www.eurekalert.org/pub_releases/2021-05/aaon-rkf042921.php

The individual members of a very small number of species are functionally immortal. These are all lower animals that exhibit a profound capacity for regeneration and lack sophisticated nervous systems, such as hydra or jellyfish. A hydra is essentially a hunger-motivated bundle of stem cells, at least from the perspective of the mammalian world of limited and regimented tissue regeneration. Absent predation or accident these animals do not exhibit any increase in mortality rate over time. Proving that to be the case is actually quite challenging. For hydra, for example, researchers conducted a long-running experiment to assess mortality that involved hundreds of carefully tended animals kept for years.

We mortal individuals are offshoots of an immortal germline cell lineage; it isn't that much of a stretch to envisage one of those offshoots, such as hydra, extending the germline concept to a mass that consists of a few tens of thousands of cells. That transition happens during embryonic development for higher species, after all. Loss of immortality appears to arise once a species starts in on larger cell counts in the body, or a complex nervous system that stores state. Something about those characteristics is largely incompatible with an exceptional regenerative capacity, a body that is largely stem cells.

Returning to the theme of it being a time-consuming exercise to establish whether or not a species has a lifespan, let alone putting definitive numbers to that lifespan, we might look at how little is known of lobsters. Like many marine species, far less is known about lobster aging and lobster lifespan than most people might guess, given the size of the industries focused on farming lobsters. Until very recently, it wasn't even possible to measure the age of a lobster reliably. This is one of many species that exhibit negligible senescence: the appearance of few to none of the usual evident signs of aging over their life span. There is a rapid decline at the end, but up until that point there is little sign of that impending fate. Individuals remain vigorous and capable of reproduction all the way through. None of these species are expected to be actually ageless, given what is known of the biochemistry and physiology of higher animals (they are not roving bundles of stem cells, after all), but proving that hypothesis that becomes ever harder as species life span increases. After a certain point it becomes impractical to sit around and wait, and lobster life span, what we know of it, is well past that line in the sand.

Most research into animal aging proceeds at the sedate pace of a poorly funded field of study. This slowly progressing community is one in which scientists intermittently establish that, yes, yet another higher species - usually a marine species, as that is where the biggest gaps in knowledge are to be found - appears to be negligibly senescent. Today's example is the bigmouth buffalo, a well known freshwater fish species. Beyond reinforcing the point that evolution produces strange and interesting outcomes, what could result from this field? It tells us that in the very long term, re-engineering humans to have a better cellular metabolism that is less prone to degenerative aging is a viable project. If an outcome exists, that outcome can in principle be replicated. But in the near term, meaning the next few decades in this context, it is very unclear that understanding any of this biochemistry and its interactions with aging will (or could) lead to medical technology that will help unmodified humans resist or reverse aging.

No evidence of physiological declines with age in an extremely long-lived fish

Although the pace of senescence varies considerably, the physiological systems that contribute to different patterns of senescence are not well understood, especially in long-lived vertebrates. Long-lived bony fish (i.e., Class Osteichthyes) are a particularly useful model for studies of senescence because they can readily be aged and exhibit some of the longest lifespans among vertebrates. In this study we examined the potential relationship between age and multiple physiological systems including: stress levels, immune function, and telomere length in individuals ranging in age from 2 to 99 years old in bigmouth buffalo (Ictiobus cyprinellus), the oldest known freshwater teleost fish.

Contrary to expectation, we did not find any evidence for age-related declines in these physiological systems. Instead, older fish appeared to be less stressed and had greater immunity than younger fish, suggesting age-related improvements rather than declines in these systems. There was no significant effect of age on telomeres, but individuals that may be more stressed had shorter telomeres. Taken together, these findings suggest that bigmouth buffalo exhibit negligible senescence in multiple physiological systems despite living for nearly a century.

Impressive results have been produced in mice via clearance of senescent cells: rejuvenation, extension of life, and reversal of numerous different age-related conditions. This has provoked an increasing number of research groups to focus on the mechanisms of cellular senescence, in search of novel ways to identify and destroy these cells, or to suppress the senescence-associated secretory phenotype (SASP) that they produce. The secreted signal molecules of the SASP alter surrounding cell behavior and rouse the immune system to chronic inflammation. This is the means by which the comparatively small number of lingering senescent cells present in late life can produce such a sweeping disruption of tissue function and health.

One of the key stumbling blocks in the field of senescence is the lack of a single, universal, robust, biomarker that allows identification of senescent cells with high sensitivity and specificity and is capable of differentiating them from terminally differentiated, quiescent, and other non-dividing cells. Growth arrest is a key feature which can be readily demonstrated in vitro using assays that measure DNA synthesis. However, DNA synthesis measurement is not totally specific since DNA repair may still be active. Measuring the expression levels of p16INK4A and p21WAF1/CIP1 are key to detecting cell cycle arrest but are not expressed persistently particularly p21WAF1/CIP1 by senescent cells. Accumulation of high levels of p16INK4A is required to maintain the senescent state enabling it to be extensively used as a marker for senescence in most normal untransformed cells and tissues. However, p16INK4A is also expressed in non-senescent cells and cells that are transiently arrested, and senescence can also occur independently of p16INK4A. Coupled with the lack of specific antibodies, this limits its use as a biomarker for senescence.

Accumulating evidence has demonstrated that both anti-senescence and pro-senescence therapies could be beneficial depending on the context. Pro-senescence therapies help limit damage by restraining proliferation and fibrosis during carcinogenesis and active tissue repair whereas anti-senescence agents enable elimination of accumulated senescent cells to restore tissue function, and potentially aid organ rejuvenation. It has been found that cells which escape from senescence post-chemotherapy re-enter the cell cycle, are highly aggressive, chemo-resistant, and exhibit stem cell characteristics and can contribute to cancer recurrence. Since several therapeutic modalities trigger senescence in tumors, it is important to decipher the mechanisms involved in the escape from senescence as a more detailed understanding may allow the development of better therapies and also help to reduce the off-target effects contributing to unwanted toxicity.

A thorough understanding of SASP regulation is required to exploit it for therapeutic purposes. There is a growing need for further research to investigate how the different signaling pathways regulating SASP such as p38MAPK, mTOR, GATA4, TAK1, cGAS/cGAMP/STING are interconnected and how SASP manifests the age-related pathologies. Inhibition of SASP without perturbing the stable growth arrest would allow reduction of the deleterious effects while maintaining tissue homeostasis and other physiological roles. However, targeting SASP for therapeutic purposes has to be undertaken with great care since it has both beneficial and deleterious roles due to the plethora of components.

Identification of key SASP factors secreted by senescent cells in aged tissues and residual tumors in the post-treatment period might have potential as biomarkers for real-time medical surveillance. The advent of powerful genetic and pharmacological tools to dissect the relationship between accumulated senescent cells and aging should improve our understanding of how accumulated senescent cells lead to age associated decline.

Link: https://doi.org/10.3389/fcell.2021.645593

Occupations involving physical labor tend to be associated with lower life expectancy. Researchers here show that this is the effect of those occupations correlating with lower socioeconomic status and accompanying lifestyle choices. The physical activity is, as one might expect, associated with a modestly higher life expectancy where one can control for other factors. It is well established in other literature that greater physical activity correlates with reduced mortality and a longer life expectancy. The human data on activity and mortality cannot go far beyond mere correlation, but animal data makes it very clear that physical activity causes improvements in long-term health and life expectancy.

In this prospective cohort study, we linked data from Norwegian population-based health examination surveys, covering all parts of Norway with data from the National Population and Housing Censuses and the Norwegian Cause of Death Registry. 437,378 participants (aged 18-65 years; 48.7% men) self-reported occupational physical activity (mutually exclusive groups: sedentary, walking, walking and lifting, and heavy labour) and were followed up from study entry (between February, 1974, and November, 2002) to death or end of follow-up on Dec 31, 2018, whichever came first. We estimated differences in survival time (death from all causes, cardiovascular disease, and cancer) between occupational physical activity categories using flexible parametric survival models adjusted for confounding factors.

During a median of 28 years from study entry to the end of follow-up, 74 ,203 (17.0%) of the participants died (all-cause mortality), of which 20,111 (27.1%) of the deaths were due to cardiovascular disease and 29,886 (40.3%) were due to cancer. Crude modelling indicated shorter mean survival times among men in physically active occupations than in those with sedentary occupations. However, this finding was reversed following adjustment for confounding factors (birth cohort, education, income, ethnicity, prevalent cardiovascular disease, smoking, leisure-time physical activity, body-mass index), with estimates suggesting that men in occupations characterised by walking, walking and lifting, and heavy labour had life expectancies equivalent to 0.4, 0.8, and 1.7 years longer, respectively, than men in the sedentary referent category. Results for mortality from cardiovascular disease and cancer showed a similar pattern. No clear differences in survival times were observed between occupational physical activity groups in women.

Our results suggest that moderate to high occupational physical activity contributes to longevity in men. However, occupational physical activity does not seem to affect longevity in women. These results might inform future physical activity guidelines for public health.

Link: https://doi.org/10.1016/S2468-2667(21)00032-3

It is a strange world that we live in, in which we have to argue - actually debate with people who earnestly hold the opposing view - that more of us living for longer, in better health than is the case today, is a good outcome. That it is worth aiming for, a great good, a sign of progress, a cause worth devoting a life to. That less suffering and less death in this world of ours would be a good outcome. How is this not self-evidently true in everyone's eyes? After all, you won't find many people out there arguing for the reinstatement of the shorter, less healthy lives that our ancestors lived. Few of the world's advocates are earnestly interested in rolling back the medical progress that has been achieved to date, with the aim of making more people ill, and reducing life expectancy.

Every death is a tragedy, and aging and its consequences kill far, far more people than any other cause. More than all of the other causes lumped together, in fact. Dealing with the mechanisms of aging should at this point be the primary focus of the efforts of our species to improve our lot in the world. That it isn't demonstrates that we are not particularly rational, either individually or as a collective.

So why is it so hard to obtain support for straightforward progress in medicine, where that progress implies longer, healthier lives? The entire point of medicine is to evade death and illness, to improve health. This is also a primary rationale and outcome in numerous other sizable human industries, such as farming. Success in cancer research implies cancer patients becoming cancer survivors, living longer in good health. The same is true of any other well-supported and publicly approved field of medicine for age-related disease. And yet bring up the lengthening of human life as a direct goal, and suddenly there is opposition.

After watching this behavior in puzzlement for more than two decades, I'm still little closer to understanding it. At this point, I think it has much to do with a bias towards the status quo, rather than any of the details of the situation. It is the fear of change that leads to rejection of all change, whether or not it is beneficial.

How Long Can We Live?

Longevity scientists who favor the idea of living for centuries or longer tend to speak effusively of prosperity and possibility. As they see it, sustaining life and promoting health are intrinsically good and, therefore, so are any medical interventions that accomplish this. Biomedically extended longevity would not only revolutionize general well-being by minimizing or preventing diseases of aging, they say, it would also vastly enrich human experience. It would mean the chance for several fulfilling and diverse careers; the freedom to explore much more of the world; the joy of playing with your great-great-great-grandchildren; the satisfaction of actually sitting in the shade of the tree you planted so long ago. Imagine, some say, how wise our future elders could be. Imagine what the world's most brilliant minds could accomplish with all that time.

In sharp contrast, other experts argue that extending life span, even in the name of health, is a doomed pursuit. Perhaps the most common concern is the potential for overpopulation, especially considering humanity's long history of hoarding and squandering resources and the tremendous socioeconomic inequalities that already divide a world of nearly eight billion. There are still dozens of countries where life expectancy is below 65, primarily because of problems like poverty, famine, limited education, disempowerment of women, poor public health and diseases like malaria and H.I.V./AIDS, which novel and expensive life-extending treatments will do nothing to solve. Lingering multitudes of superseniors, some experts add, would stifle new generations and impede social progress.

Altering T cells of the adaptive immune system to enable recognition of cancerous cells is a mainstream area of research these days. The approach of adding chimeric antigen receptors to T cells, tailored to a cancer, is well established for blood cancers, but still challenging for solid tumors, characterized a wide variety of cancerous cells and signatures. Researchers here show that genetic modification of T cells to produce IL-24 allows these immune cells to effectively destroy cancerous cells that lack recognizable surface features, so long as they are close to cancerous cells that can be recognized. Further, the process of cancer cell destruction via IL-24 leads to the ability of the immune system to later recognize those cells as cancerous, suppressing the possibility of recurrence of the cancer.

A protein called IL-24 attacks a variety of cancers in several different ways. Researchers now deliver the gene coding for IL-24, which is called MDA-7, to solid tumors using T cells. This isn't the first time T cells have been engineered for cancer immunotherapy. Chimeric antigen receptor T (CAR-T) cell therapy - which is designed to destroy cancer cells expressing specific surface molecules - has shown tremendous success for treating advanced cancers of the blood and lymphatic systems. But CAR-T has made limited progress on solid tumors, such as prostate cancer or melanoma, because the cells that make up those tumors aren't all the same, which blocks the engineered T cells from recognizing and attacking. Researchers armed T cells with MDA-7/IL-24 to target cancer more broadly.

At the sub-cellular level, MDA-7/IL-24 binds to receptors on the surface of cells and instructs them to make and release more copies of the MDA-7/IL-24 protein. If the cell is normal, the protein is simply secreted and no damage occurs. But if the cell is cancerous, MDA-7/IL-24 causes oxidative stress damage and ultimately cell death, not only within the primary tumor but also among its distant metastases - the cause of death in 90% of patients. As a result of this process, the immune system generates memory T cells that can theoretically kill the tumor if it ever comes back. At the whole tumor level, IL-24 also blocks blood vessel formation, starving tumors of the nutrients so badly needed to sustain their unchecked growth.

In mice with prostate cancer, melanoma, or other cancer metastases, MDA-7/IL-24-expressing T cells slowed or stopped cancer progression better than unmodified T cells. The researchers also discovered that arming T cells with MDA-7/IL-24 allowed them to survive better and multiply in the tumor microenvironment - the space right around the cancerous mass. In the clinic, this approach would involve extracting the patient's own T cells from tumor samples, genetically engineering them to express MDA-7/IL-24, growing millions of copies of the cells in the lab and finally transplanting them back into the patient. CAR-T cells could also be engineered to express MDA-7/IL-24.

Link: https://www.masseycancercenter.org/news/engineering-t-cells-to-attack-cancer-broadly

Researchers here show that intermittent fasting alters the gut microbiome in ways that likely increase the production of butyrate. This metabolite is known to produce beneficial downstream effects, such as upregulation of BDNF and neurogenesis. As research into the gut microbiome in health and aging continues, an increased knowledge of the mechanisms by which fasting and calorie restriction act to improve health will be one of the outcomes.

Experiments in experimental rodents and observations in human volunteers or patients suggest that the beneficial effects of intermittent fasting can only partly be explained by reduced calorie intake. A plethora of alternative mechanisms mediating the effects of intermittent fasting have been brought forward and can roughly be grouped in three categories involving mechanisms involving circadian biology, altered lifestyle, and remodeling of the gut microbiome.

The notion that the latter is especially instrumental for mediating the beneficial effects of intermittent fasting is supported by many observations in experimental animals, including that white adipose tissue browning provoked by intermittent fasting requires an intestinal flora, or that restructuring of the gut microbiome by intermittent fasting counteracts retinopathy in diabetic mice. The effects of intermittent fasting on the human microbiome remain, however, largely uncharacterized, and in view of the problems associated with extrapolating data in experimental rodents to humans, it would be important to establish the effects of intermittent fasting in our species as well.

Prompted by the above mentioned considerations, we decided to characterize the effects of a monthly episode of intermittent fasting on the human gut microbiome and to contrast the results with nonfasting controls and with the effects of cessation of intermittent fasting following the intervention.

We observed in two independent cohorts, sampled in two different years, that Ramadan-associated intermittent fasting induces substantial remodeling of the gut microbiome. Importantly, we established that intermittent fasting in humans is especially associated with an upregulation of butyric acid-producing Lachnospiraceae in a manner that correlates to improvement in human physiologic surrogate markers such as blood glucose and BMI. Intermitting fasting-provoked upregulation of Lachnospiraceae thus may provide a rational explanation for at least some of the beneficial effects reported for intermittent fasting in humans.

Link: https://doi.org/10.1093/ajcn/nqaa388

The membrane pacemaker hypothesis suggests that the lipid composition of membranes, and particularly mitochondrial membranes, is an important determinant of species longevity in at least some clades, such as mammals and birds. Membrane composition determines the degree of resistance to lipid oxidation and consequent loss of function for component parts of a cell. Aging is associated with a rise in oxidative stress placed upon cells and their structures, related to chronic inflammation and mitochondrial dysfunction.

Over the years, a fair amount of supporting evidence has been gathered for this view of species longevity, but the paper here stands in opposition to that work, at least for bird species. It is worth noting that birds, and other flying species, are metabolically quite different from near relative non-flying species. The high metabolic demands of flight lead to adaptations that clearly impact aging in many cases, such as for some bat species with noted longevity, perhaps largely through mitochondrial function, perhaps not. That said, the membrane pacemaker hypothesis was thought to be relevant in both mammals and birds. As usual, all too little is simple, straightforward, and a settled matter when it comes to the details of cellular metabolism and aging.

No Evidence for Trade-Offs Between Lifespan, Fecundity, and Basal Metabolic Rate Mediated by Liver Fatty Acid Composition in Birds

The fatty acid composition of biological membranes has been hypothesised to be a key molecular adaptation associated with the evolution of metabolic rates, ageing, and life span - the basis of the membrane pacemaker hypothesis (MPH). MPH proposes that highly unsaturated membranes enhance cellular metabolic processes while being more prone to oxidative damage, thereby increasing the rates of metabolism and ageing. MPH could, therefore, provide a mechanistic explanation for trade-offs between longevity, fecundity, and metabolic rates, predicting that short-lived species with fast metabolic rates and higher fecundity would have greater levels of membrane unsaturation.

However, previous comparative studies testing MPH provide mixed evidence regarding the direction of covariation between fatty acid unsaturation and life span or metabolic rate. Moreover, some empirical studies suggest that an n-3/n-6 PUFA ratio or the fatty acid chain length, rather than the overall unsaturation, could be the key traits coevolving with life span. In this study, we tested the coevolution of liver fatty acid composition with maximum life span, annual fecundity, and basal metabolic rate (BMR), using a recently published data set comprising liver fatty acid composition of 106 avian species.

While statistically controlling for the confounding effects of body mass and phylogeny, we found no support for long life span evolving with low fatty acid unsaturation and only very weak support for fatty acid unsaturation acting as a pacemaker of BMR. Moreover, our analysis provided no evidence for the previously reported links between life span and n-3 PUFA/total PUFA or MUFA proportion.

Our results rather suggest that long life span evolves with long-chain fatty acids irrespective of their degree of unsaturation as life span was positively associated with at least one long-chain fatty acid of each type (i.e., SFA, MUFA, n-6 PUFA, and n-3 PUFA). Importantly, maximum life span, annual fecundity, and BMR were associated with different fatty acids or fatty acid indices, indicating that longevity, fecundity, and BMR coevolve with different aspects of fatty acid composition. Therefore, in addition to posing significant challenges to MPH, our results imply that fatty acid composition does not pose an evolutionary constraint underpinning life-history trade-offs at the molecular level.

The term "mesenchymal stem cell therapy" covers a very broad range of cell sources and cell capabilities. Arguably the category needs to be thrown out and replaced with a more detailed taxonomy. The results of mesenchymal stem cell therapy in one clinic can be wildly different from those in another due to small differences in protocol, even given a similar source of cells.

Taken as a whole, this class of therapy appears to fairly reliably suppress chronic inflammation for a time, while unreliably provoking increased regeneration and tissue maintenance. Transplanted cells near all die rapidly rather than integrating into tissues, and results are thus achieved via the signaling generated for a brief time by the transplanted stem cells.

In this review paper, researchers discuss some of the evidence for mesenchymal stem cell therapies to improve structure and function in aged skin, which is an area of clinical practice in which one needs to follow references somewhat more carefully than is usually the case, given the sizable contingent at that end of the community that likes to play fast and loose with the truth.

Aged skin is highly associated with loss of function and structural degeneration. With aging, the skin naturally loses its collagen content and elastic fibers become deranged. Additionally, aged skin demonstrates an increase in oxidant activity, and an increase in the production of matrix metalloproteases (MMP), which are typically involved in matrix degradation. Additionally, exposure to UV light is known to promote premature aging of the skin, namely photoaging. Thus, rejuvenation therapies, which focus on the prevention and reversal of skin aging are in high demand in our society, which increasingly aims to maintain a youthful appearance and improve their health.

Adipose derived MSCs (AD-MSCs) have been gaining attention in skin antiaging therapy because of their efficient re-epithelization and secretion of several growth factors necessary for skin regeneration. In recent years, researchers observed histological and structural modifications in aged facial skin after the injection of expanded AD-MSCs, collected from fat removed by liposuction. Treatment with AD-MSCs caused an increase in elastic fibers in the superficial layer of the dermis and modified the collagen and reticular fiber networks, which became more arranged. Subsequently, AD-MSCs were observed to induce complete regeneration of solar elastosis in photoaged skin.

The transplantation of AD-MSCs leads to complete regeneration of dermal elastic matrix components, including oxytalan, elaunin, and elastin fibrillary networks. In solar-aged skin, the normal elastin matrix is usually lost, and AD-MSC-mediated treatment successfully reversed the inhibition of precursor molecules involved in neoelastinogenesis.

Another way to use AD-MSCs in antiaging therapy, in a "cell-free" method of treatment, is by using extracellular vesicles (EVs), which have several advantages over stem cells and their safety issues. Adipose-derived mesenchymal stem cells extracellular vesicles (AD-MSCs-EVs) have anti-photoaging potential and were analyzed as subcutaneous injections in photoaged mice models. The treatment resulted in a decrease in skin wrinkles and promotion of epidermal cell proliferation. Additionally, macrophage infiltration and reactive oxygen species (ROS) production were reduced, which inhibited MMP activation and collagen degradation.

Link: https://doi.org/10.3390/ijms22052410

A sizable fraction of sarcopenia, the loss of muscle mass and strength with age, is avoidable. Not all of it, of course, at least not without advances in therapies targeting the underlying mechanisms of aging. But it is in part the consequence of a lack of physical activity, with other contributions arising from diet, changes to the gut microbiome, and chronic inflammation. There is extensive data on the ability of structured exercise programs, such as strength training, to reverse measures of sarcopenia in older individuals. A more comprehensive set of lifestyle changes is assessed in this study, with varying outcomes. Physical activity still appears to come out ahead.

Few studies have comprehensively described changes in blood biomarkers of the physiological responses underlying sarcopenia reduction associated with lifestyle interventions. In this study, we performed secondary analyses of data in a randomized controlled trial of multi-domain lifestyle interventions (6-month duration physical exercise, nutritional enrichment, cognitive training, combination and standard care control) among 246 community-dwelling pre-frail and frail elderly, aged ≥65 years, with and without sarcopenia.

We observed that multi-domain physical, nutritional, and cognitive interventions among pre-frail and frail older adults were associated with favorable changes in sarcopenia and blood biomarkers underlying the muscle mass and physical functional response to intervention. As previously reported, the data are highly consistent with previous studies in showing that physical exercise alone or in combination with cognitive and nutritional intervention was most efficacious in improving muscle mass, lower limb strength, and gait speed. The physical exercise in this study was of moderate and gradually increasing intensity and well tolerated with high adherence rate (85%).

Perhaps unsurprisingly, there was limited effect observed with nutritional intervention delivered with a traditional oral nutrition supplement and not with a formulation with high content of leucine or whey protein or vitamin D, which have been shown in more recent studies to increase muscle mass and muscle function in sarcopenic and malnourished older patients.

Chronic low-grade inflammation associated with oxidative stress is believed to be a major underlying mechanism of aging and aging-related diseases including sarcopenia. Inflammatory markers such as CRP and IL-6 are reported to be associated with decreased muscle mass and strength, and the reduction of inflammation is believed to directly or indirectly ameliorate age-related muscle loss. In the present study, inflammatory levels are observed to be reduced especially by combined intervention, as evidenced by the significant drops in CRP and TNF-α levels. However, the levels of these inflammatory markers were not associated with sarcopenia status or reduction. Thus, the reduction of inflammation may not be the primary underlying mechanism of the response of sarcopenic elderly to lifestyle interventions.

Link: https://doi.org/10.18632/aging.202705

Michael Greve, you might recall, is a strong supporter of the Strategies for Engineered Negligible Senescence (SENS) rejuvenation biotechnology approach to aging, first put forward twenty years ago by Aubrey de Grey and collaborators. Five years ago Michael Greve pledged $10 million to be split between SENS-focused research and investment in startup companies arising from that research. His venture firm, Kizoo Technology Ventures, has invested in companies that are developing potential rejuvenation therapies, such as the cross-link breaking enzymes of Revel Pharmaceuticals, and the senolytic suicide gene therapy of Oisin Biotechnologies. He founded a non-profit, Forever Healthy Foundation, that, among other things, runs the Undoing Aging conference series and publishes serious, sober, detailed technical reviews of approaches to treating aging. Now Michael Greve is greatly expanding his efforts to support the new and growing longevity industry.

In the SENS viewpoint, which is itself a synthesis of evidence gathered over past decades of scientific research, aging is caused by the accumulation of fundamental forms of well-known cell and tissue damage that arise as a side-effect of the normal operation of metabolism. The best approach to intervention is to periodically repair that damage. Repair is explicitly rejuvenation.

Scientists and supporters of SENS advocated for removal of the senescent cells that accumulate in old tissues a decade before the rest of the scientific community came around to supporting that idea. The animal data produced since then shows that clearance of senescent cells produces profound reversals of aging and age-related disease in old mice. It is even capable of reversing the detrimental restructuring of the heart in old individuals that leads to heart failure. Now, a good fraction of the growing longevity industry is pursuing the development of senolytic therapies capable of selective destruction of senescent cells. Thus to my eyes, the more support there is for the SENS approach to the challenge of aging the better. It is clearly the right way forward towards meaningful control over aging within our lifetimes.

Kizoo commits €300 million to advance rejuvenation startups

Michael Greve, founder of the Forever Healthy Foundation and owner of Kizoo Technology Ventures, announced today that he will make available an additional €300 million to be invested in rejuvenation biotech. The funds, to be deployed via Kizoo, will be used to create and support more startups in the rejuvenation space. They will also allow Kizoo to maintain a strong commitment to its key startups during follow-up rounds and to advance the therapies from clinical development to public availability.

With this €300 million commitment, Greve and Kizoo double down on their mission to accelerate the advent of rejuvenation biotechnology by doing lighthouse investments in entirely new, repair-based approaches that treat the root causes of aging and thus overcome age-related diseases. Through the creation of successful companies, they seek to inspire scientists, investors, and the general public by demonstrating that human rejuvenation is not science fiction anymore and that the resulting therapies are affordable and uncomplicated.

Technologies pioneered by Kizoo's startups include removal of arterial plaque, decalcification of aged tissue, breaking of protein-glucose cross-links, and delivery of new mitochondria to aged cells - all aiming to prevent and repair common age-related conditions such as myocardial infarction, stroke, high blood pressure, tissue stiffening, skin aging, and loss of muscle function.

"I am really grateful that we can use the funds we have created with our highly successful technology ventures to contribute to the quest to get aging under full medical control and to make age-related diseases a thing of the past. For me, it is a worthy cause that is exciting in a technological, commercial, and above all, a humanitarian way." Greve expects that the new funds, in combination with the strong, multi-round commitment of Kizoo to its key startups, should trigger co-investments of up to 3-4 times the initial amount, resulting in a significant acceleration of the development and public availability of the therapies.

Researchers have recently proposed a taxonomy of subtypes of Alzheimer's disease based on differences in the spread of tau protein aggregation through the brain that is characteristic of the later stages of the condition. Tau aggregation caused dysfunction and cell death in neurons. It is interesting to speculate as to the underlying reasons why there are four such classes of progression of tau pathology. Why only four? Why so clearly four? One might suggest - with absolutely no evidence to hand as of yet - that this has something to do with differing rates of age-related failure among the few drainage pathways by which cerebrospinal fluid leaves the brain, for example. This drainage allows the removal of molecular waste from the brain, its loss is implicated in Alzheimer's disease, and it is possible that drainage rates falter more or less rapidly in different parts of the brain for different people.

Alzheimer's disease is characterized by the abnormal accumulation and spread of the tau protein in the brain. An international study can now show how tau spreads according to four distinct patterns that lead to different symptoms with different prognoses of the affected individuals. "In contrast to how we have so far interpreted the spread of tau in the brain, these findings indicate that tau pathology in the brain varies according to at least four distinct patterns. This would suggest that Alzheimer's is an even more heterogeneous disease than previously thought. We now have reason to reevaluate the concept of typical Alzheimer's, and in the long run also the methods we use to assess the progression of the disease."

Researchers used a study population of 1,143 individuals who were either cognitively normal or individuals who had developed Alzheimer's in various stages. An algorithm was applied to the data from the tau PET images from the 1,143 individuals, the so-called SuStaIn (Subtype and Staging Inference) algorithm. As expected, many individuals did not show any abnormal tau PET signal, and these were therefore automatically assigned to a tau-negative group. By then cross-validating the tau PET images with a sixth independent cohort, and following up the individuals for about two years, the researchers were able to develop four patterns that best represented the data from the remaining individuals.

"We identified four clear patterns of tau pathology that became distinct over time. The prevalence of the subgroups varied between 18 and 30 percent, which means that all these variants of Alzheimer's are actually quite common and no single one dominates as we previously thought."

Link: https://www.lunduniversity.lu.se/article/alzheimers-disease-composed-four-distinct-subtypes

Researchers here provide evidence for alterations in the gut microbiome to be an important contributing case of raised blood pressure, or hypertension. Fasting reduces blood pressure, and here it is demonstrated that this is due in part to improvements in the state of the microbial populations of the gut. It is well known that the gut microbiome changes with age, losing beneficial populations and gaining harmful populations. This study suggests that some of those changes contribute to age-related hypertension, providing yet another reason to put resources into the near term development of therapies that can reverse the aging of the gut microbiome, such as flagellin vaccination or fecal microbiota transplantation.

"Previous studies from our lab have shown that the composition of the gut microbiota in animal models of hypertension, such as the SHRSP (spontaneously hypertensive stroke-prone) rat model, is different from that in animals with normal blood pressure. Further, transplanting dysbiotic gut microbiota from a hypertensive animal into a normotensive one results in the recipient developing high blood pressure. This result told us that gut dysbiosis is not just a consequence of hypertension, but is actually involved in causing it. This ground work led to the current study in which we proposed to answer two questions. First, can we manipulate the dysbiotic microbiota to either prevent or relieve hypertension? Second, how are the gut microbes influencing the animal's blood pressure?"

Researchers drew on previous research showing that fasting was both one of the major drivers of the composition of the gut microbiota and a promoter of beneficial cardiovascular effects. Working with the SHRSP model of spontaneous hypertension and normal rats, the researchers set up two groups. One group had SHRSP and normal rats that were fed every other day, while the control group had SHRSP and normal rats with unrestricted food availability. Nine weeks after the experiment began, the researchers observed that, as expected, the rats in the SHRSP control had higher blood pressure than the normal control rats. Interestingly, in the group that fasted every other day, the SHRSP rats had significantly reduced blood pressure when compared with the SHRSP rats that had not fasted.

The researchers transplanted the microbiota of the rats that had either fasted or fed without restrictions into germ-free rats, which have no microbiota of their own. The germ-free rats that received the microbiota of normally fed SHRSP rats had higher blood pressure than the germ-free rats receiving microbiota from normal control rats, just like their corresponding microbiota donors. Additionally, germ-free rats that received microbiota from the fasting SHRSP rats had significantly lower blood pressure than the rats that had received microbiota from SHRSP control rats.

Link: https://blogs.bcm.edu/2021/04/29/from-the-labs-fasting-lowers-blood-pressure-by-reshaping-the-gut-microbiota/

The composition of the gut microbiome changes with age, becoming less helpful and more inflammatory as the proportion of actively harmful bacteria grows. There are many contributing causes with plausible supporting evidence in the scientific literature, including dietary changes characteristic of late life, immune aging, intestinal tissue dysfunction that is downstream of stem cell aging or senescent cell accumulation, and so forth. As is often the case in these matters, it remains unclear as to which of these causes are the most relevant targets for the development of therapies.

That said, it is possible to produce some reversal of aspects of microbiome aging in mice by innoculation with flagellin. This spurs the immune system to more aggressively destroy problematic gut microbes that manufacture flagellae in order to move into gut tissue. That this intervention is beneficial to a meaningful degree suggests that immune aging is an important cause of harmful shifts in gut microbiome populations. In fact, one can argue for a bidirectional relationship, in which the immune system falters in its gardening of the microbiome with advancing age, but a part of that faltering is caused by the activities of inflammatory microbes.

The aging gut microbiome and its impact on host immunity

The microbiome plays a fundamental role in the maturation, function, and regulation of the host immune system from birth to old age. In return, the immune system has co-evolved a mutualistic relationship with trillions of beneficial microbes residing our bodies while mounting efficient responses to fight invading pathogens. As we age, both the immune system and the gut microbiome undergo significant changes in composition and function that correlate with increased susceptibility to infectious diseases and reduced vaccination responses. Emerging studies suggest that targeting age-related dysbiosis can improve health- and lifespan, in part through reducing systemic low-grade inflammation and immunosenescence - two hallmarks of the aging process. However, a cause and effect relationship of age-related dysbiosis and associated functional declines in immune cell functioning have yet to be demonstrated in clinical settings.

Given the ever-growing impact of the gut microbiome on the host immune system, it is reasonable to speculate that restoring age-related declines in gut microbial richness and function - be it through personalized nutrition or supplements - may represent a prophylactic measure to fight functional declines in immune fitness. In this context, prebiotics, probiotics, and postbiotics or synbiotics with the ability to reinforce immunity through supporting intestinal barrier integrity or by regulating inflammatory processes have been tested in clinical settings. However, a lack of consistency between studies, strain specific differences or doses, prebiotic nature and quantity, or age and medical conditions of the subjects have made it difficult to validate the effectiveness of such approaches to reinforce age-associated declines in host-immune fitness.

None the less, mining the gut microbiome is a treasure trove waiting to be unlocked, and gerontology is no exception here. As exemplified by numerous preclinical studies, restoration of a youthful microbiome has rejuvenating potential for the aged host through sustaining immunity and health-span. Thus, a better understanding of the dynamic age-related changes in gut microbial community structures and associated metabolome, how such alterations affect cellular immune networks and how these pathways can be therapeutically targeted will have wide-reaching implications for future strategies to reinforce or even rejuvenate the aging immune system.

It has been more than a decade since researchers demonstrated that genetic engineering of mice to boost LAMP2A levels in the liver produced a sizable rejuvenation of liver function in old animals. This happens because increased levels of LAMP2A cause an upregulation of chaperone-mediated autophagy, a cellular maintenance process responsible for removing damaged molecules and structures in the cell. This makes cells more functional, and thus the tissue more functional. Since then, work on LAMP2A and autophagy has continued. Nowadays, the same research group that produced the liver results is a part of Selphagy Therapeutics within Life Biosciences, developing a small molecule approach to LAMP2A upregulation. This will inevitably be far less effective than gene therapy, but small molecules are still the way that most research programs move to the clinic, a function of the very conservative nature of venture funding and regulation in the biotech space.

All cells maintain a network of cleaning systems that remove and recycle unwanted proteins. One school of thought holds that when the process, called autophagy, malfunctions in neurons, the toxic buildup of proteins can promote neurodegenerative diseases such as Alzheimer's. Now, scientists have shown that a drug designed to invigorate a specialized cellular garbage disposal mechanism ameliorated symptoms in two mouse models of Alzheimer's.

The system the drug targets is called chaperone-mediated autophagy (CMA), in which single proteins are selected and escorted to spherical vesicles in cells called lysosomes, where they are then degraded. Once at the lysosome, the protein-chaperone complex binds to receptors called lysosome-associated membrane protein type 2A (LAMP2A) to trigger the destruction process. The drug, called CA, works by ramping up LAMP2A to boost CMA activity.

CMA activity normally drops as people age, but neurodegenerative disease can make it worse, further affecting the normal protein balance in the brain. The researchers tested whether a CMA activator like CA could protect against Alzheimer's. They gave the oral drug to mice that either had a tau abnormality or a combination of toxic tau and beta-amyloid protein clumps. The drug significantly reduced levels of tau and beta-amyloid, as well as plaques, in the brains of the animals. The treatment also normalized the animals' walking ability and improved visual memory, anxiety- and depression-like behaviors, and neuromuscular strength.

Link: https://www.fiercebiotech.com/research/treating-alzheimer-s-disease-by-invigorating-cell-s-specialized-garbage-cleaning-system

Putting stem cells back to work is the theme of a great of the research that takes place in the regenerative medicine community. Stem cells are responsible for producing a supply of daughter somatic cells, required to replace losses and maintain functional tissue. Stem cell activity throughout the body declines with age, however. Much of this decline is not caused by intrinsic cell and tissue damage that would prevent activity, but is rather an evolved reaction to the presence of that damage.

Suppressing stem cell activity likely serves to reduce cancer risk in later life. The more cell activity there is in a damaged environment, the greater the odds that cancerous cells will arise. Unfortunately, the consequence of a reduced rate of rapid death by cancer is the certainty of a slow and drawn out decline due to organ failure. Thus, there are projects such as the one noted here, in which scientists search for ways to force stem cells into greater activity, despite the presence of damage.

By tracing individual neural stem cells (NSCs) in mice over the course of several months, researchers identified "short-term NSCs" that quickly differentiate into more specialized neurons, and "long-term NSCs" that continually divide and replicate themselves to maintain an ongoing reserve of stem cells with the ability to generate many different cell types in the brain. This key population of long-term NSCs divided less often and failed to maintain their numbers as the mice aged.

The scientists next examined thousands of genes in the long-term NSCs, which were dividing less often and had slipped into an inactive state known as quiescence. The gene activity of the quiescent NSCs varied greatly in young versus middle-aged animals. As expected, there were changes in genes that control how long-term NSCs divide, as well as generate new neurons and other brain cells. Remarkably, there were many important changes in gene activity related to biological aging at younger ages than anticipated. These pro-aging genes make it more difficult for cells to repair damage to their DNA, regulate their genetic activity, control inflammation, and handle other stresses. Among the pro-aging genes, the scientists were most intrigued by Abl1, which formed the hub of a network of interrelated genes.

Using an existing, FDA-approved chemotherapy drug called Imatinib, scientists could easily inhibit the activity of the gene Abl1. The scientists gave older mice doses of Imatinib for six days. After the drug blocked the activity of the gene Abl1, the NSCs began to divide more and proliferate in the hippocampus, the part of the brain responsible for learning and memory. We've succeeded in getting neural stem cells to divide more without depleting, and that's step one. Step two will be to induce these stem cells to make more neurons. Step three will be to demonstrate that these additional neurons actually improve learning and memory."

Link: https://www.genengnews.com/news/neural-stem-cells-decline-during-aging/

Much pearl-clutching is in evidence in a recent article on the existence of groups, such as Libella Gene Therapeutics, attempting to prototype telomerase gene therapies via patient paid trials, or such as Integrated Health Systems and BioViva, trying to develop markets for such therapies via medical tourism. The gatekeepers of medical regulation stand in opposition to the idea that patients and their supporters can make responsible decisions about risk, based on the available data. Medicine is somehow a privileged space, different from every other human endeavor, in which only the anointed priesthood are allowed to determine what is and is not allowed. It is reprehensible. Analysis has shown that this attitude, and the system of regulation that accompanies it, costs a great many lives by slowing the development of new therapies and limiting the opportunities for treatment.

Medicine, like every form of service, works best in an environment of review organizations, competition, and due diligence by customers. At the end of the day, it is always a matter of caveat emptor. And this already happens, as anyone who has been through a scheduled surgery can tell you. Patients absolutely shop the market to the degree that present regulation allows them to do so, and there is a robust system of legal culpability by which fraud and harm can be prosecuted. As is the case in every other industry, providers of medical services have financial and other incentives to produce good results for patients.

I personally do not have a strong opinion on whether the telomerase gene therapy that is the subject of this article will help with Alzheimer's disease; it seems indirect and compensatory, improving cell function rather than striking directly at the known causes. That said, several noted research groups are very much in favor of developing telomerase based therapies for human use, and at least one company in the longevity industry, Telocyte, is seeking to raise funding to run a formal trial of telomerase gene therapy for Alzheimer's disease within the existing regulatory system. It is an entirely mainstream goal.

At some point all new medical technologies must be tried for the first time in humans. Is that to be left to the anointed priesthood, with its impossible goal of zero patient risk, ever increasing costs of certification, and ever fewer approvals with each passing year? Or should we live in a more reasonable world in which more sensible and cost-effective choices regarding risk, pace of development, and availability of treatments are made by patients, supporters, and networks of review organizations, rather than by uncaring bureaucrats? I would vote for the latter of these two options.

Six patients with dementia went to Mexico for an unproven gene therapy, a biotech CEO claims

Six patients with dementia traveled to Mexico last year to be injected with a gene therapy not authorized for use in the U.S., according to the CEO of a Seattle-area startup that wants to accelerate testing of unproven anti-aging medicines and views U.S. drug safety regulations as a hindrance. At the heart of the project is a controversial biotech called BioViva, whose CEO had herself injected with an experimental gene therapy in Colombia and whose advisory board includes renowned Harvard geneticist George Church. It is part of a growing ecosystem of entrepreneurs and scientists, dreamers and schemers, who believe aging is not inevitable and aim to develop treatments to extend the human life span.

Last month, during a talk hosted by the National University of Singapore, the CEO, Elizabeth Parrish, divulged that she was eagerly awaiting data from a human study involving six patients who received an experimental gene therapy. On Friday, she told STAT the procedures were done last year in Mexico. If true, it would be the first known attempt to use the technique to treat age-related dementia, which is most often caused by Alzheimer's disease.

STAT set out to independently verify the accuracy of Parrish's claims. While many key details could not be confirmed, including the identities of these six patients and how the purported treatment affected them, STAT found evidence that BioViva and partners were recruiting patients. A newsletter emailed by BioViva in 2019 said 10 patients over age 50 with mild to moderate Alzheimer's were needed for a study of a gene therapy. The one-hour procedure, according to an FAQ linked from the email, would be done in Mexico City and involved a one-time injection. The effort raises the specter of an overseas medical tourism industry targeting patients desperate to lengthen their lives and offering unproven treatments that would permanently alter the genetic code inside recipients' cells.

The authors here tout a discussion of diet and cellular senescence, but in fact deliver a discussion on obesity, calorie restriction, and cellular senescence. One of the mechanisms by which excess visceral fat tissue causes chronic inflammation and pathology is by increasing the pace at which senescent cells are produced. The number of lingering senescent cells increases with age, and these cells disrupt the function of the immune system and surrounding tissue via their inflammatory secretions. Calorie restriction, on the other hand, upregulates stress response mechanisms that can slow the pace at which senescent cells are created. It also preserves the function of the immune system into later life, thereby increasing the pace at which they are destroyed by the immune system at any given age.

Normal human cells do not divide indefinitely. When cultured in vitro, cells can undergo only a finite number of divisions before entering in a nondividing state, the so-called replicative senescence. Senescence has been suggested both as contribute and a consequence of the ageing process and is involved in the development of many age-related chronic diseases. Cellular senescence is a state of an irreversible growth arrest that occurs in response to various forms of cellular stress and is characterized by a pro-inflammatory secretory phenotype.

Multiple studies showed that cellular senescence occurs in both physiological and pathophysiological conditions. Senescent cells accumulate with ageing and can contribute to age-related decline in tissue function. Obesity is a metabolic condition that can accelerate the ageing process by promoting a premature induction of the senescent state of the cells. In contrast, caloric restriction without malnutrition is currently the most effective non-genetic intervention to delay ageing, and its potential in decreasing the cellular senescent burden is suggested.

The precise mechanisms underlying the effect of obesity in the induction of premature cellular senescence are poorly understood and warrant further investigation. Moreover, more studies are required to understand how lowering calories intake reduces cellular senescence burden, and whether this can directly lower levels of molecules involved in the inflammation process, like interleukins, which, for instance, could also be promoted by other variables independently altered by senescence. Plus, in obesity and ageing studies, the researchers tend to focus on one specific organ or pathology type, which limits the information that may be collected about the temporal biological order of senescence induction. Thus, more in vitro studies are required especially in cellular model systems that can replicate the alterations seen during in vivo progression in the ageing process.

Link: https://doi.org/10.1097/j.pbj.0000000000000120

In heterochronic parabiosis, the circulatory systems of an old and young animal are connected. The young animal exhibits some aspects of accelerated aging, while the old animal exhibits some degree of rejuvenation. Early investigations focused on the supply of factors in young blood to the old animal as the causative mechanism, and GDF11 was one of the first such factors identified for further research and development. There has been some controversy over the published works on this topic, however, stemming initially from technical issues involved in working with GDF11, then later from investigations that point to dilution of harmful factors in old blood being the dominant mechanism in heterochronic parabiosis. The company Elevian claims to have resolved these issues, and is advancing therapies based on delivering GDF11, but it will probably be at least a few more years before there is a clear view into the details of their work.

Growth differentiation factor 11 (GDF11), a member of the TGF-β superfamily, has recently received attention because of its numerous functions in modulating the development and differentiation of various tissues and organs. Studies regarding the role of GDF11 in the development of various diseases have been conducted in recent decades. GDF11 is reportedly beneficial with respect to controlling age-related cardiac hypertrophy, improving muscle tone, preventing degeneration in the central nervous system, enhancing cognitive function, and promoting tissue regeneration.

Important parabiosis experiments involving two animals of different ages, performed in 2013 and 2014, revealed that GDF11 levels were disrupted in an age-related manner in vascular, neurogenic, and skeletal muscle tissues. Those findings suggested that GDF11 may be regarded as an honorable "rejuvenation" factor that could restore regenerative function, thus resisting aging and extending longevity. A study in fish revealed that GDF11 has rejuvenation capacity to extend the lifespan. In 2020, a plasma proteomic dataset demonstrated that the GDF11 protein can significantly extend the lifespan.

These studies demonstrated critical roles for GDF11 in the inhibition of aging. However, recent studies have yielded conflicting data regarding the ability of GDF11 to alleviate dysfunction in age-related diseases. Thus, the regeneration ability of GDF11 with respect to age-related dysfunction requires further investigation. This review provides an overview of GDF11 and its functions in age-related diseases. It also discusses potential underlying mechanisms for the effects of GDF11 in age-related diseases.

Link: https://doi.org/10.18632/aging.202881

The aging of the immune system causes a great deal of damage, and in many different ways. There are many varieties of immune cell in the innate and adaptive portions of the immune system, and pathological subsets are known to arise with age. Take age-associated B cells, for example, or the misconfigured T cells that contribute to varieties of autoimmune disorder, or the regulatory T cells that contribute to the pathology of heart failure, or the macrophages that become foam cells to accelerate atherosclerosis. There are many more examples.

To a first approximation, the immune system of the central nervous system is distinct from that of the rest of the body. The blood-brain barrier separates the two sides, allowing only some traffic to pass between. When looking closer, this is not entirely true, however. T-cells of the adaptive immune system can cross into the cerebrospinal fluid in small numbers, particularly in disease states, and there is evidently some mode of communication between the immune systems of the central nervous system and the rest of the body, given that they both respond to threats that occur on only one side of the blood-brain barrier.

Researchers here present evidence for aggressive, cell-killing T cells to make their way to the brain in increasing numbers with age, and there cause problems that contribute to neurodegeneration and cognitive decline. Whether this is an extension of the existing and better regulated traffic that takes place in youth, or the consequence of blood-brain barrier dysfunction, or some other collection of mechanisms to allow passage, remains an open question.

Accumulation of cytotoxic T cells in the aged CNS leads to axon degeneration and contributes to cognitive and motor decline

Aging is a major risk factor for the development of nervous system functional decline, even in the absence of diseases or trauma. The axon-myelin units and synaptic terminals are some of the neural structures most vulnerable to aging-related deterioration, but the underlying mechanisms are poorly understood. In the peripheral nervous system, macrophages - important representatives of the innate immune system - are prominent drivers of structural and functional decline of myelinated fibers and motor endplates during aging. Similarly, in the aging central nervous system (CNS), microglial cells promote damage of myelinated axons and synapses.

Here we examine the role of cytotoxic CD8+ T lymphocytes, a type of adaptive immune cells previously identified as amplifiers of axonal perturbation in various models of genetically mediated CNS diseases but understudied in the aging CNS. We show that accumulation of CD8+ T cells drives axon degeneration in the normal aging mouse CNS and contributes to age-related cognitive and motor decline. We characterize CD8+ T-cell population heterogeneity in the adult and aged mouse brain by single-cell transcriptomics and identify aging-related changes.

Mechanistically, we provide evidence that CD8+ T cells drive axon degeneration in a T-cell receptor- and granzyme B-dependent manner. Cytotoxic neural damage is further aggravated by systemic inflammation in aged but not adult mice. We also find increased densities of T cells in white matter autopsy material from older humans. Our results suggest that targeting CD8+ CNS-associated T cells in older adults might mitigate aging-related decline of brain structure and function.

A fair number of researchers consider cellular reprogramming to be a promising path forward for the treatment of aging. Some of these think that epigenetic change is an important cause of of aging, while others see the epigenetic changes characteristic of aging as a downstream consequence of underlying processes of damage, but consider reprogramming to be a potentially useful point of intervention regardless. Reprogramming as a basis for therapy entails at least partially pushing cells towards pluripotency, in the same manner as the production of induced pluripotent stem cells, but not so far down this path that they lose their differentiated identity and ability to function. As a side-effect, the epigenetic patterns of gene expression are reset to a more youthful configuration. Mitochondrial function improves, cell function improves. This cannot repair DNA damage, and will likely also struggle with some of the other issues of aging, such as the accumulation of waste products in long-lived cells. It does, however, appear to produce benefits in animal models, in early exploratory studies.

Multicellular life evolved from simple unicellular organisms that could replicate indefinitely, being essentially ageless. At this point, life split into two fundamentally different cell types: the immortal germline representing an unbroken lineage of cell division with no intrinsic endpoint and the mortal somatic cells, which age and die. In this review, we describe the germline as clock-free and somatic cells as clock-bound and discuss aging with respect to three DNA-based cellular clocks (telomeric, DNA methylation, and transposable element). The ticking of these clocks corresponds to the stepwise progressive limitation of growth and regeneration of somatic cells that we term somatic restriction. Somatic restriction acts in opposition to strategies that ensure continued germline replication and regeneration. We thus consider the plasticity of aging as a process not fixed to the pace of chronological time but one that can speed up or slow down depending on the rate of intrinsic cellular clocks.

The initiation of the DNA methylation aging clock, the telomeric clock, and perhaps other clocks at the beginning of development suggests an intimate relationship between development and aging. Indeed, the adaptation of developmental clock rate to environmental pressure could account for the wide variation in lifespan observed between species. For example, humans and naked mole-rats exhibit neoteny, where slowing the rate of development correlates with an extension of lifespan. The application of germline strategies in somatic stem cells has resulted in the remarkable regenerative capacity of lower life forms that are capable of indefinite lifespans, such as sponges, planarians, and hydra. This regenerative capacity has become increasingly restricted as more complex life forms evolved, being confined prior to the embryonic to fetal transition period in mammals. However, retention of extensive capacity for regeneration is observed in lower vertebrates, including fishes, amphibians, and reptiles, which also exhibit remarkable phenotypic plasticity in their capacity for metamorphosis and in certain cases of remarkable reversals of developmental stage and sexual development.

Finally, reprogramming using germline factors can uncover a similar but latent phenotypic plasticity in mammals by reverting both the developmental state and cellular age. Indeed, both natural phenotypic plasticity in the blue wrasse and partial reprogramming involve the repression of DNA methyl transferases and induction of demethylases which, by a yet-to-be-determined mechanism, may enable the DNA methylation clock to tick backward. The discovery that partial reprogramming can reverse the aging clock without permanent alteration of cellular identity has led to initial studies that demonstrate the potential to reverse organismic aging. Although there are many challenges ahead, our current understanding of cellular clocks and our ability to reprogram them using germline factors opens the door to many promising therapeutic approaches to slowing down, preventing, or reversing aging itself and thus treating the many age-related diseases that burden society. Indeed, if these approaches can be made practical and scalable, we may find ourselves in a future in which we have no time to age.

Link: https://doi.org/10.3390/genes12050611

There is an interesting history of accidental discoveries regarding exceptional regeneration in mammals, such as the MRL mice that are capable of regenerating the ear tags and notches that researchers use to track mice through experiments, thereby causing some confusion. Researchers have since then spent time on attempts to identify important mechanisms by which mammalian regeneration takes the path of scarring, rather than the path of regrowth. The discovery noted here is an interesting one. The scientists involved have established a good proof of concept based on a regulator of scarring, EN1. When suppressed this leads to the complete regeneration of skin injuries without scar formation.

Skin wounds generally heal by scarring, a fibrotic process mediated by the Engrailed-1 (En1) fibroblast lineage. Scars differ from normal unwounded skin in three ways: (i) They lack hair follicles, sebaceous glands, and other dermal appendages; (ii) they contain dense, parallel extracellular matrix fibers rather than the "basket-weave" pattern of uninjured skin; and (iii) as a result of this altered matrix structure, they lack skin's normal flexibility and strength. A successful scar therapy would address these three differences by promoting regrowth of dermal appendages, reestablishment of normal matrix ultrastructure, and restoration of mechanical robustness. However, little is known about the cellular and molecular mechanisms blocking a regenerative healing response in postnatal skin, or whether these mechanisms can be bypassed by modulating specific fibroblast lineages.

We asked whether scarring fibroblasts are derived purely from expansion of existing En1 lineage-positive fibroblasts present in unwounded skin, or whether En1 scar fibroblasts could arise de novo by activation of En1 expression in postnatal, En1 lineage-negative fibroblasts within the wound niche. We used fibroblast transplantation as well as transgenic mouse models to trace En1 expression in a spatiotemporally defined fashion. Next, we studied fibroblast responses to mechanical forces in vitro and in vivo to establish a mechanotransduction mechanism linking skin tension to postnatal En1 expression. Finally, we used chemical (verteporfin) and transgenic inhibition of mechanotransduction signaling to modulate En1 expression during wound healing.

Fibroblast transplantation and lineage-tracing studies reveal that En1 lineage-negative fibroblasts (ENFs) of the reticular (deep) dermis activate En1 in the wound environment, generating ~40 to 50% of scar fibroblasts. This phenomenon depends on mechanical cues. Comparison of ENFs with En1-expressing and En1 knockdown fibroblasts by RNA sequencing suggests that En1 regulates a wide array of genes related to skin fibrosis. In healing wounds, YAP inhibition by verteporfin blocks En1 activation and promotes ENF-mediated repair, yielding skin regeneration in 30 days with recovery of functional hair follicles and sebaceous glands. This suggests that modulation of En1 activation, whether direct or indirect, can yield wound regeneration.

Link: https://doi.org/10.1126/science.aba2374