Fight Aging!

Mitochondrial function declines with age throughout the body. One of the better explored lines of investigation of this phenomenon focuses on changes in gene expression causing a reduction in mitochondrial fission, leading to impaired mitophagy, in turn leading to a build up of worn and dysfunctional mitochondria. Mitochondria are the descendants of ancient symbiotic bacteria, and they divide (fission) and join together (fusion) like bacteria. Mitophagy is the quality control mechanism responsible for removing damaged mitochondria, and it requires mitochondrial fission in order to operate efficiently, as larger mitochondria are more resistant to mitophagy.

Are there ways to provoke a restoration of youthful levels of mitochondrial fission and thus mitophagy? In one sense yes, in that all of the established approaches to boosting mitochondrial function improve the situation to some degree, such as NAD+ upregulation and mitochondrially targeted antioxidants. In another sense no, as none of those options are definitively better than regular exercise. In a final sense yes, in that researchers have identified various proteins that change in expression with age, affecting mitochondrial fission. It is a long road from identifying a protein to finding a small molecule drug that can safely affect its expression, however, and gene therapies to precisely achieve this sort of outcome throughout the body are still not a going concern.

Today's research materials are an example of this type of work, investigating the mechanisms of mitochondrial fission in search of targets that might improve it in old tissues. It remains to be see what the next generation of therapies aimed at improving mitochondrial function will look like, but it is plausible that transplantation of functional mitochondria, an approach already in preclinical development in several companies, will prove to be a good way to work around the need for a great deal of further research and understanding of mechanisms.

Researchers show protein controls process that goes awry in Parkinson's disease

As scientists work toward finding a cure for Parkinson's disease, one line of research that has emerged focuses on mitochondria, the structures within cells that make energy. The health of those structures is maintained through a quality control system that balances two opposite processes: fission - one mitochondrion splitting in two - and fusion - two becoming one. When there's a problem with fission, that system is thrown out of balance. The consequences can include neurodegenerative diseases, such as Parkinson's disease, and other serious conditions.

A new study found that a protein in humans called CLUH acts to attract Drp1 to mitochondria and trigger fission. In experiments with fruit flies that were genetically engineered with an analog for Parkinson's disease, the team showed that damage from the disease could be reversed by increasing the amount of a protein that scientists call "clueless," which is the fruit fly equivalent of CLUH. "With a critically important pathway such as Drp1, there might be multiple proteins we could use to intervene and ultimately control Parkinson's disease. When we modified clueless in flies, symptoms analogous to Parkinson's disease improved substantially."

The team further showed that both clueless in flies and CLUH in human cells recruit free-floating Drp1 from within a cell to attach to receptors on the surface of mitochondria. In addition, the researchers discovered that CLUH in human cells helps translate the genetic instructions found in messenger RNA into the protein for Drp1 receptors on the surface of mitochondria. More available Drp1 receptors means that more Drp1 can be recruited in order to trigger fission.

Clueless/CLUH regulates mitochondrial fission by promoting recruitment of Drp1 to mitochondria

Mitochondrial fission is critically important for controlling mitochondrial morphology, function, quality and transport. Drp1 is the master regulator driving mitochondrial fission, but exactly how Drp1 is regulated remains unclear. Here, we identified Drosophila Clueless and its mammalian orthologue CLUH as key regulators of Drp1. As with loss of drp1, depletion of clueless or CLUH results in mitochondrial elongation, while as with drp1 overexpression, clueless or CLUH overexpression leads to mitochondrial fragmentation.

Importantly, drp1 overexpression rescues adult lethality, tissue disintegration, and mitochondrial defects of clueless null mutants in Drosophila. Mechanistically, Clueless and CLUH promote recruitment of Drp1 to mitochondria from the cytosol. This involves CLUH binding to mRNAs encoding Drp1 receptors MiD49 and Mff, and regulation of their translation. Our findings identify a crucial role of Clueless and CLUH in controlling mitochondrial fission through regulation of Drp1.

Telomeres are caps of repeated DNA sequences at the ends of chromosomes. Telomere length is reduced with each cell division, and when telomeres become too short cells become senescent and either undergo programmed cell death or are removed by the immune system. This ensures cell turnover in tissues, and acts to reduce the risk of cell lineages becoming damaged enough to become cancerous.

Researchers here present evidence for the onset of this replicative senescence to be a slow process, changes assembling and growing as telomeres become shorter. The implication is that while senescent cells are known to be harmful when they accumulate with age, perhaps the burden of pre-senescent cells in old tissues is also meaningfully harmful. Whether or not this is the case has yet to be determined; the challenge is never in identifying a mechanism, the challenge lies in determining how important it is.

In 1961, researchers discovered that human fibroblast cells cultured in the laboratory could only divide a limited number of times, after which they stopped multiplying but remained metabolically active. This state was termed replicative senescence and was found to occur in a range of cell types. Further research revealed that senescence is caused by the shortening of caps, or 'telomeres', on the end of chromosomes. Every time a cell divides, its telomeres shrink until they reach a critical length that stops the cell from multiplying. New evidence showed that senescence is induced by cell stress as well as successive divisions, and that the number of senescent cells increases as tissues age.

Despite almost 60 years of research, many questions still remain about senescence; for instance, what happens to cells as they transition in to the senescent state? How does their metabolism change during this shift, and do they take on a new cell identity? Now researchers report the results of experiments that exquisitely profile the roadmap cells take on their path to senescence.

The team used a new experimental design to survey the entire genome and repertoire of RNAs, proteins, and metabolites present in fibroblasts cultured in the laboratory. These patterns were traced over time as the cells grew until they stopped dividing. The data revealed that RNAs known to be expressed in fully senescent cells progressively accumulate throughout the cell cycle. This suggests that senescent cells in vivo may be slowly amassing these features, but not yet expressing the classic biomarkers associated with the end-point of senescence, such as the beta-galactosidase enzyme.

The findings suggest that cells gradually acquire a number of changes on the path to replicative senescence: they express different genes, rewire their metabolic reactions and take on a new identity similar to mesenchymal cells. Previous studies have shown that removing senescent cells can increase the health- and life-span of mice. Therefore, interventions that target these early changes could help improve the well-being of individuals by stopping the cascade of events that lead to replicative senescence.

Link: https://doi.org/10.7554/eLife.77749

Senescent cells are created and destroyed constantly throughout life, but their numbers accumulate with age, a growing imbalance that is probably primarily caused by immune system aging. The immune system is responsible for removing those senescent cells that do not undergo programmed cell death, but it becomes ever less competent with age. A lingering population of senescent cells is clearly responsible for causing significant harm to cell and tissue function, largely via the secretion of inflammatory, pro-growth factors. Here, researchers think a little more deeply about how this harm progresses.

Here, based on recent research evidence from our laboratory and others, we propose a mechanism - Senescence-Associated Cell Transition and Interaction (SACTAI) - to explain how cell heterogeneity arises during aging and how the interaction between somatic cells (SomCs) and senescent cells, some of which are derived from aging somatic cells, results in cell death and tissue degeneration. Recent genomic analysis reveals a remarkable heterogeneity of cell types during aging. Such cell heterogeneity gives rise to not only senescent cells but also other types of cells including progenitor and stromal cells.

Adult mesenchymal stem cells (MSCs) constitute a small percentage of cells responsible for repair upon tissue damage. The increase in senescent cells is tightly associated with repeated activation of adult MSCs, where they reach replication capacity and become senescent. In response to stress signals, differentiated SomCs may lose their identity and de-differentiate into MSC-like cells for repair. Such epigenetically re-programmed MSCs are subject to cell senescence triggered by replicative, mechanical, and inflammatory stress signals. Although in small numbers, senescent MSCs manifest the senescence-associated secretory phenotype (SASP), spread inflammation, and signal surrounding somatic cells in the tissue microenvironment. Thus, senescent MSCs may accumulate during aging by cell proliferation, transition, and senescence, and accelerate catabolism and death of somatic cells through cell interactions. Important signaling molecules mediating the SACTAI process include pro-inflammatory cytokine IL-1β, IL-6, IL-8, growth factor TGF-β, and morphogen Sonic Hedgehog, which at least partially overlap with SASPs.

SACTAI is a proposed two-step mechanism for aging-associated tissue degeneration and somatic cell death. In the first step, a few adult SomCs, in response to mechanical, inflammatory, or replicative stress signals, undergo proliferation, MSC transition, and senescence, resulting in senescent MSCs (snMSCs). This cell transition and senescence process results in a heterogenous cell population, which enables heterotypic cell interactions with each other. During the second step, snMSCs interacts with SomCs via SASPs. Such cell senescence-associated signaling contributes to cell death and tissue degeneration in age-related diseases. The newly discovered SomC transition to snMSC during aging may explain the fibrosis, abnormal ossification (calcification), and inflammaging phenotypes often associated with aging tissues. The identification of the multi-step mechanism of SACTAI provides an opportunity to develop potential drugs to intervene during different stages of age-related disease pathogenesis.

Link: https://doi.org/10.3390/cells11071089

The effective altruism community is concerned with practical utilitarianism and efficiency in the matter of philanthropy. This can range from avoidance of inefficient charities, and the infrastructure needed for more people to find out which organizations are in fact efficient in their chosen field, to comparisons between philanthropic causes with the aim of finding the greatest gain for a given donation. Since the greatest cause of human suffering, by far, is aging, it is naturally the case that effective altruists frequently discuss rejuvenation biotechnology. A related field is that of the cryonics industry and cryopreservation, low-temperature storage of at least the brain on death, to save lives that cannot otherwise be saved because rejuvenation technologies will not arrive rapidly enough.

A cryopreserved individual is only clinically dead. The data of the mind still exists, the tissue structure still exists. It is possible to envisage in great detail the future technological capabilities needed to bring a cryopreserved patient back to active life - and people have, such as in the recently published Cryostasis Revival. Given the choice between tens of millions of minds lost to oblivion every year, or taking a chance of preservation, it seems obvious that cryopreservation should be far more widespread and better supported than it is. Yet this is an argument yet to be accepted by anything more than a small, fringe community.

Today I'll point out an opinionated summary of discussions on cryopreservation from the effective altruism community. The cryonics industry is small and lacks funding for efficient progress towards the virtuous cycle of technological advances that convince people this is real, greater attention, rising membership, and thus more funding for further technological advances. This is the type of problem that philanthropy excels at solving, provided those directing the funding know what they are doing. Clear and demonstrable technological progress in reversible cryopreservation of organs, a capability that has immediate application to the transplantation industry, is an important goal that could be greatly accelerated by philanthropy, for example. Alas, many people have yet to be convinced that saving lives in this way is desirable, or that present approaches give a good enough chance of success to be funded.

Brain preservation to prevent involuntary death: a possible cause area

Note that prior effective altruism discussions primarily focus on cryonics, although I prefer the term brain preservation because it is also compatible with non-cryogenic methods and anchors the discussion around the preservation quality of the brain. I'm not discussing whether individuals should sign themselves up for brain preservation, but rather whether it is a good use of altruistic resources to preserve people and perform research about brain preservation. It seems to me that:

(a) Most current technical arguments against brain preservation, to the extent that there are any at all, don't grapple with the possibility of structural inference. Because of the correlated nature of structural information in the brain, it is likely that there are numerous topological maps of the biomolecule-annotated connectome that could retain the information needed for long-term memories. Even if many of these maps were damaged or destroyed by aspects of the brain preservation procedure, if at least one could still be inferred, then the information content would still be present.

(b) Most extant arguments in the effective altruism community against brain preservation as a cause area don't grapple with QALY improvement/extension, and for unclear reasons treat humans as replaceable units, neglecting relational and psychological factors. If people think humans are replaceable, I think they should justify this, and also consider whether they are being consistent about it.

(c) With today's methods, brain preservation may already be among the best altruistic investments available from a QALY improvement/extension perspective, given reasonable estimates about the probability of success.

(d) With more research, substantially cheaper methods for structural brain preservation could potentially be developed, which could further improve the cost/benefit calculus. With more research, our uncertainty about different aspects of the brain preservation project could also be better clarified.

As a result of the above, and given its neglectedness, I think brain preservation for the prevention of involuntary death is one of the best areas for people interested in helping others to work in. I also think it is a great place for people who are interested in helping others to donate money. If you disagree, I would love to hear from you why that is. If you agree, I would love to discuss with you practical topics of how to best improve the field. Thanks for reading!

Is it useful to think of cancer as a stem cell disease, a condition that (largely) arises because stem cells become dysfunctional? The evidence seems to suggest that at least some cancers arise from somatic cells taking on stem cell properties, while a body of work indicates that at least some cancerous tissues are supported by small populations of cancer stem cells that might be targeted for destruction. Here researchers are interested in the bigger picture, the nature of the relationship between stem cell function, stem cell resilience, cancer, and aging. In an era that will soon enough seen the widespread use of regenerative medicine and rejuvenation therapies that, by their nature, will increase stem cell function in older people, it is perhaps worth thinking about how cancer risk fits into all of this.

A stem-cell theory of cancer predicates that not only does the cell affect the niche, the niche also affects the cell. It implicates that even though genetic makeup may be supreme, cellular context is key. When we attempt to solve the mystery of a long cancer-free life, perhaps we need to search no further than the genetics and epigenetics of the naked mole-rat. When we try to unlock the secrets in the longevity and quality of life, perhaps we need to look no further than the lifestyle and habits of the super centenarians. We speculate that people with Down's syndrome and progeria age faster but have fewer cancers, because they are depleted of stem cells, and, as a consequence, have fewer opportunities for stem cell defects that could predispose them to the development of cancer. We contemplate whether these incredible experiments of nature may provide irrefutable evidence that cancer is a stem-cell disease-fewer aberrant stem cells, fewer cancers; no defective stem cells, no cancer.

A stem-cell theory of aging and cancer reiterates a fundamental oncological principle: although genetic makeup may be pivotal, cellular context is paramount. When the genome and epigenome that regulate aging and malignancy are also stemness genes and stem-like properties, they reaffirm the key role that stem-cell quality and quantity play in longevity and cancer. We suspect that long-lived, cancer-spared mammals maintain a youthful genome and epigenome because they are equipped with a larger and healthier pool of stem cells. We contemplate that people with Down's syndrome and progeria age faster but have fewer cancers because they are depleted of stem cells and therefore have fewer opportunities for stem-cell defects that render one prone to cancer formation.

Therefore, the benefit of longevity needs to be balanced against the risk of malignancy. Intuitively, how we manage to conserve stemness and delay senescence is key.

Link: https://doi.org/10.3390/cancers14051338

Researchers here assess the state of muscle stem cells and neuromuscular junctions, both known to decline in function with advancing age. This leads to sarcopenia, the loss of muscle mass and strength. This is a universal phenomenon, but some people are more affected than others. Many underlying mechanisms contribute to these issues, with the chronic inflammation of aging being an important one, but a perhaps surprising degree of muscle aging in our modern world is a consequence of lack of exercise. The study noted here is an example of this point, showing the degree to which fitness slows core aspects of muscle degeneration.

Muscle fibre denervation and declining numbers of muscle stem (satellite) cells are defining characteristics of ageing skeletal muscle. The aim of this study was to investigate the potential for lifelong recreational exercise to offset muscle fibre denervation and compromised satellite cell content and function, both at rest and under challenged conditions. Sixteen elderly lifelong recreational exercisers (LLEX) were studied alongside groups of age-matched sedentary (SED) and young subjects. Lean body mass and maximal voluntary contraction were assessed, and a strength training bout was performed. From muscle biopsies, tissue and primary myogenic cell cultures were analysed by immunofluorescence and RT-qPCR to assess myofibre denervation and satellite cell quantity and function.

LLEX demonstrated superior muscle function under challenged conditions. When compared with SED, the muscle of LLEX was found to contain a greater content of satellite cells associated with type II myofibres specifically, along with higher mRNA levels of the beta and gamma acetylcholine receptors (AChR). No difference was observed between LLEX and SED for the proportion of denervated fibres or satellite cell function, as assessed in vitro by myogenic cell differentiation and fusion index assays. When compared with inactive counterparts, the skeletal muscle of lifelong exercisers is characterised by greater fatigue resistance under challenged conditions in vivo, together with a more youthful tissue satellite cell and AChR profile. Our data suggest a little recreational level exercise goes a long way in protecting against the emergence of classic phenotypic traits associated with the aged muscle.

Link: https://doi.org/10.1113/JP282677

Chronic inflammation is a feature of aging, and causes disruption of cell and tissue function throughout the body. Short term inflammation is a necessary feature of regeneration from injury and defense against pathogens, but when inflammatory signaling is maintained for the long term it becomes very harmful. The risk of suffering all of the common diseases of aging is strongly connected to raised inflammation. Given this, we might ask what causes age-related systemic inflammation, and thus where should the research community seek to intervene, in order to reverse this undesirable aspect of degenerative aging.

A growing burden of senescent cells is one noteworthy cause, actively encouraging inflammation via the senescence-associated secretory phenotype. The metabolic activity of excess visceral fat tissue is another. Disruption of the intestinal barrier is also an area of focus for the research community, and the subject of today's open access review paper.

The intestinal barrier is made up of mucus, epithelial cells connected by tight junctions that prevent the passage of unwanted pathogens and molecules, and patrolling immune cells, intended to maintain a separation between the gut and tissues surrounding the gut. Unfortunately, like all structures and systems in the body, the barrier becomes dysfunctional with age. The result is greater inflammation, as unwanted materials leak into tissue.

The Intestinal Barrier Dysfunction as Driving Factor of Inflammaging

In recent years, the function of the intestinal barrier has received increasing scientific attention as more and more intra- and extra-intestinal diseases, such as irritable bowel syndrome, inflammatory bowel diseases such as Crohn's disease, type 1 diabetes, colorectal cancer, acute inflammation-related diseases such as sepsis, and allergic diseases, were found to be associated with a dysfunctional intestinal barrier. The results of various animal studies demonstrated a link between intestinal barrier dysfunction and aging. For instance, aged monkeys had poorer intestinal barrier function, increased systemic inflammation, and higher microbial translocation compared to young animals. In Drosophila models, intestinal barrier dysfunction has been shown to predict the approaching death of flies.

In this review, we want to explore whether intestinal barrier dysfunction and the accompanying alterations to the intestinal microbiota composition are driving factors for the increasing proinflammatory status during aging known as inflammaging. Inflammaging was first described as a combination of a reduced ability to deal with stressors and the resulting increase in proinflammatory milieu. More recently, inflammaging was defined as a "chronic, sterile, low-grade inflammation" that occurs during aging. A similar concept is metaflammation, describing a metabolically driven inflammation caused by nutrient excess.

Due to the major role of the intestinal barrier in preventing bacterial toxins and pathogens from the intestinal lumen entering into circulation, an impaired barrier function or even minor changes in the regulation of the epithelial, microbial, biochemical, or immunological barrier might contribute to aging-associated decline as well as disease development.

The alterations found at the level of intestinal microbiota composition and intestinal barrier function in aging have been proposed to be interlinked with aging-associated decline in other organs, such as the liver. Due to its anatomical location receiving a more or less 'unfiltered' blood from the gut, the liver is confronted not only with nutrients, but also many xenobiotics, as well as bacterial toxins and metabolites stemming from the intestinal microbiota, along with endocrine mediators. This allows for a rather direct communication between the gut and the liver.

In summary, the gastrointestinal epithelial barrier, with its multiple layers and its various function, is affected by the physiological aging process. However, as its role in healthy aging or disease development becomes increasingly evident, attempts to restore the barrier function, e.g., through modulation via microbiota modifications, supplementing strains such as Lactobacillus plantarum or their metabolites, are of special interest. Besides microbiota modulation through probiotic strains or postbiotics, the current and future treatment of epithelial barrier dysfunction could include nutritional interventions and also bioactive pharmaceutical molecules, biologicals, or mucoprotectants.

Atherosclerosis is in part an inflammatory condition, drive by the chronic inflammation of aging. It arises from dysfunction in the macrophage cells responsible for clearing out lipids from blood vessel wall, and inflammatory signaling makes those macrophages less able to perform that maintenance. There are other issues affecting the macrophages, not least of which being that they become overwhelmed by the large amount of cholesterol present in established atherosclerotic lesions, but inflammation is a noteworthy contribution to the problem.

The association between inflammation and atherosclerosis is well established, and mechanistic studies have demonstrated that inflammation is an essential mediator of all stages of atherosclerosis, from initiation to progression and the development of thrombotic complications. Circulating immune cells play a critical role in the build-up of atherosclerotic plaques by adhering to activated endothelium and infiltrating the arterial wall to become lesional cells. This association has led to the study of various anti-inflammatory therapies in the last years.

The bone marrow (BM) is the primary site of haematopoiesis, and the proliferation and migration of haematopoietic progenitors are regulated by various physiological and pathological stimuli. Experimental studies suggest that increased BM haematopoietic activity may be a central link between cardiometabolic risk factors and exacerbated inflammation in atherosclerosis. In mice, hypercholesterolaemia and low HDL-cholesterol levels associated with elevated haematopoietic activity with increased monocytosis and neutrophilia. Hypertension, driven by an overactive sympathetic activation, deteriorates haematopoietic cell niche in the BM which can contribute to atherosclerosis. In humans, it has been suggested that chronic stress accelerates haematopoiesis, giving rise to higher levels of inflammatory cells that might contribute to the atherosclerotic process. In addition, haematopoietic stem cell division rates are increased in subjects with atherosclerosis, and it has been suggested that the haematopoietic system might be chronically affected in these subjects.

However, human data to support this association are sparse. Our purpose was to study the association between cardiovascular risk factors, BM activation, and subclinical atherosclerosis. Whole body vascular 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI) was performed in 745 apparently healthy individuals (median age 50.5) from the Progression of Early Subclinical Atherosclerosis (PESA) study. Bone marrow activation (defined as BM 18F-FDG uptake above the median maximal standardized uptake value) was assessed. Systemic inflammation was indexed from circulating biomarkers.

Bone marrow activation was significantly associated with high arterial metabolic activity (18F-FDG uptake). The co-occurrence of BM activation and arterial 18F-FDG uptake was associated with more advanced atherosclerosis, i.e. plaque presence and burden.

Link: https://doi.org/10.1093/eurheartj/ehac102

Mitophagy is the cellular maintenance process responsible for removal of damaged mitochondria, the vital power plants of the cell. With age, mitophagy becomes less effective, allowing mitochondrial function to decline, an important contribution to age-related degeneration in energy-hungry tissues such as muscle and the brain. A variety of dysfunctions contribute to this issue. Many arise from age-related changes in gene expression, such as loss of production of proteins necessary for mitochondrial fission, leading to larger mitochondria that are resistant to mitophagy. Researchers here focus on the effects of the BNIP3 protein on mitophagy and mitochondrial function, as well as downstream effects on inflammation and loss of muscle mass and strength with age.

Sarcopenia is one of the main factors contributing to the disability of aged people. Among the possible molecular determinants of sarcopenia, increasing evidences suggest that chronic inflammation contributes to its development. However, a key unresolved question is the nature of the factors that drive inflammation during aging and that participate in the development of sarcopenia. In this regard, mitochondrial dysfunction and alterations in mitophagy induce inflammatory responses in a wide range of cells and tissues. However, whether accumulation of damaged mitochondria in muscle could trigger inflammation in the context of aging is still unknown.

Here, we demonstrate that BNIP3 plays a key role in the control of mitochondrial and lysosomal homeostasis, and mitigates muscle inflammation and atrophy during aging. We show that muscle BNIP3 expression increases during aging in mice and in some humans. BNIP3 deficiency alters mitochondrial function, decreases mitophagic flux and, surprisingly, induces lysosomal dysfunction, leading to an upregulation of TLR9-dependent inflammation and activation of the NLRP3 inflammasome in muscle cells and mouse muscle. Importantly, downregulation of muscle BNIP3 in aged mice exacerbates inflammation and muscle atrophy, and high BNIP3 expression in aged human subjects associates with a low inflammatory profile, suggesting a protective role for BNIP3 against age-induced muscle inflammation in mice and humans.

Taken together, our data allow us to propose a new adaptive mechanism involving the mitophagy protein BNIP3, which links mitochondrial and lysosomal homeostasis with inflammation and is key to maintaining muscle health during aging.

Link: https://doi.org/10.1111/acel.13583

Nicotinamide adenine dinucleotide (NAD) in the context of aging and mitochondrial function has turned into a fairly energetic area of study. NAD is a crucial element in the mitochondrial production of the chemical energy store molecule adenosine triphosphate (ATP), but levels decline with age for a variety of reasons, and this contributes to loss of mitochondrial function. The characteristic changes in gene expression that take place with age lead to reduced production and recycling of NAD via various pathways. Further, CD38 acts to break down NAD and levels of CD38 increase with age.

Why does CD38 production increase with age? Research suggests that this is a consequence of inflammatory signaling, the chronic inflammation of aging, driven in part by a growing burden of senescent cells, but also by molecular damage and debris that triggers similar immune reactions to those produced by infection.

In today's open access paper, researchers report on the effects of partial inhibition of CD38 in mice. In principle, the effect of this inhibition is to disconnect the relationship between inflammation and impaired mitochondrial function mediated by loss of NAD. This disconnection enables improved health and life span. This is an effect likely also possible to achieve via exercise, though not to the same magnitude when it comes to gains in maximum life span; in mice exercise only improves healthspan and medial life span.

Mouse lifespan is more plastic than that of humans in response to interventions that improve metabolism. It isn't clear at this point as to whether a 10-20% increase in lifespan should be seen as interesting. I am starting to lean towards reversal of age-related pathology in later life as a more interesting metric. Regardless of my opinion, clearly there will be considerable further effort devoted towards the clinical translation of ways to increase NAD levels or interfere in the activities of CD38. We shall see how well it does in humans at the end of the day, with structured exercise programs as the bar to beat.

CD38 inhibitor 78c increases mice lifespan and healthspan in a model of chronological aging

NAD is a cofactor of oxidation-reduction reactions and is a substrate for enzymes involved in cellular homeostasis. NAD levels decrease with aging and progeroid states, which is associated with metabolic abnormalities and fitness decline. The NAD-consuming enzymes such as CD38 and PARP1 have been shown to play a major role in this process. The accumulation of CD38+-inflammatory cells decreases NAD levels in aging. The small molecule 78c is a specific and potent inhibitor of CD38 that boosts NAD levels, improves survival of progeroid mice, and ameliorates several metabolic, structural, and molecular features of aging. However, to date the effect of CD38 inhibition on natural aging and longevity has not been explored. Here, we demonstrate that 78c increases the lifespan and healthspan of naturally aged male mice.

When offered the food to young mice ad libitum, 78c significantly boosted NAD, validating the 78c treatment. We then placed 1-year-old C57BL/6 male and female mice on either a control or 78c diet and closely followed their healthspan and longevity. When both sexes were grouped, treatment with 78c significantly improved longevity, with a maximal survival increase of 9%. When analyzing survival for males and females separately, a sex-specific effect of 78c was observed. The 78c-treated males had a 17% increase in median survival and a 14% increase in maximal lifespan compared with control. In females, no significant survival benefit was observed

We then evaluated the effect of 78c on the frailty in a cohort of old male mice. Frailty scores were derived from clinical examination. Changes in frailty index after 3 months were plotted in comparison with the baseline index. All animals in the control group had a significantly higher frailty index than that was 3 months earlier. By contrast, 78c showed a protection against age-related frailty increase.

There are many potential approaches to interfere in the sweeping age-related chances to immune function. Of these, many stem from epigenetic changes characteristic of age, causing dysregulation via too much or too little production of a given protein, rather than more structural issues relating to reduced production of immune cells and increasing wear and tear of populations of immune cells lacking reinforcements. In this arena, a more efficient small molecule drug discovery process can allow for incremental improvement in immune function, assuming one can find a single point of intervention that has a high yield outcome in one or more populations of immune cells.

As we age, a biochemical pathway involving the signaling molecule PGD2 becomes more active, impairing immunity in two major ways: First, antigen-presenting cells called dendritic cells migrate less efficiently, slowing the adaptive T-cell and antibody responses. Second, white blood cells called neutrophils infiltrate infected tissues more aggressively, leading to damaging inflammation. Thus, the aged immune system is both slower to respond to new infections and more likely to overreact once it does mount a response. Bioage's drug BGE-175 inhibits this pathway by blocking the interaction between PGD2 and its receptor, a protein called DP1.

In the study, daily doses of BGE-175 protected aged mice from a lethal dose of SARS-CoV-2, the virus that causes COVID-19. Ninety percent of mice that received the drug survived, whereas all untreated control mice died. BGE-175 treatment was initiated two days after infection, when the mice were already ill, a time-frame relevant to real-life clinical situations in which patients would receive medication only after becoming symptomatic.

BGE-175 is currently in a Phase 2 clinical trial to test whether it can prevent disease progression and mortality in older patients hospitalized with COVID-19. "The promising preclinical data in this paper show that BGE-175 almost completely protects aged mice from lethality in a compelling model of human COVID-19. By reversing age-related declines in critical immune mechanisms, BGE-175 could allow older patients to more effectively fight off this disease."

Link: https://www.eurekalert.org/news-releases/946865

One comparatively unexplored path to clearing senescent cells from the aged body is to coerce portions of the immune system into working harder. In youth, the immune system is adept at removing senescent cells, and does so at a fast enough page to prevent accumulation. In old age, this process slows down. Here, researchers report on an in vitro demonstration of the potential for natural killer cells to clear senescent cells, marking their function as a potential target for the development of novel senolytic therapies capable of rejuvenation through the selective removal of senescent cells. Deciduous Therapeutics is a startup biotech company currently pursuing this path.

Previous experiments have shown that natural killer (NK) cells are partially responsible for the clearance of senescent cells from the human body. While some senescent cells have ways of avoiding detection and clearance, NK cells are attracted to certain parts of the senescence-associated secretory phenotype (SASP), which trigger them to kill the cells expressing it. Techniques are being developed to use this senolytic ability of NK cells as a potential therapy.

After taking NK cells out of whole blood, researchers sought to change the distribution of these cells. NK cells express different amounts of CD56 and CD16. NK cells that express high CD56 but low CD16 are immature and secrete interferon-γ; NK cells with low CD56 and high CD16 are responsible for cytotoxicity: the actual killing of other cells. The enrichment process, which involved activating the cells through the cytokine IL-2, substantially increased the percentages of both of these cell types.

These enriched cells were found to be very good at selectively eliminating senescent cells after 16 hours. In an experiment with one NK cell for every senescent cell, 15% of normal fibroblasts and 43% of senescent fibroblasts died. These numbers remained largely the same regardless of how senescence was induced, and endothelial cells yielded similar results to fibroblasts. Doubling or tripling the number of NK cells did kill more senescent cells; however, it also increased the number of normal cells being killed in the process. Therefore, instead of using more NK cells, the researchers increased the time in co-culture; while the number of normal fibroblasts dying remained low, only 10% of senescent cells survived after four days' exposure to fresh, enriched NK cells.

Link: https://www.lifespan.io/news/sens-researchers-culture-immune-cells-to-fight-senescence/

My attention was recently drawn to Cryopets, a newly formed cryonics provider that has a novel approach to nudging the cryonics industry closer to the mainstream. As regular readers know, cryonics is the low-temperature storage of patients immediately following death, aimed at preservation of the fine structure of brain tissue that stores the data of the mind. Given a high quality preservation, and then indefinite maintenance at low temperature, at some point the societies of the high-tech future will have the capability to revive those patients. There is nothing magical about it; it "just" requires mature molecular nanotechnology and its application to biological systems, as well as a very comprehensive control over biology. That is over the horizon now, but preserved individuals have all the time in the world to wait.

The challenge for the cryonics industry is that it remains small, a very niche concern, with limited funding for progress. Both it and the rejuvenation industry were once alike in this respect, but in the latter case sufficient technological progress was bootstrapped on limited funding, particularly recent work on senolytic therapies, in order to convince the world that there is a viable approach to treating aging as a medical condition. Cryonics has yet to have that moment, despite some early demonstrations of vitrification, thawing, and subsequent implantation and functioning of organs in animals.

How does one bootstrap an industry? Funding depends on interest, which depends on convincing people with viable technology demonstrations, which depends on funding. It is a slow and incremental process, and the only shortcuts usually involve philanthropic funding for research. The latest generation of initiatives include those trying to produce technology demonstrations and those trying to modernize the marketing of cryopreservation services and thus obtain a larger paying membership. The Cryopets principals, on the other hand wants to try building normal, everyday self-sustaining hospital businesses that offer cryopreservation as an additional service. Since it is far cheaper to start that effort in the veterinary industry, the initial focus is on building self-sustaining veterinary hospitals that offer cryopreservation of pets as an additional service.

The soft landing here, in event of failure of the primary goal, is a functioning business. In principle that makes this more attractive to investors than some of the other options on the table for advancing the cryonics industry. Though it really is the case that someone should fund one of the paths to reversible vitrification of organs! That is a very promising prospect, with immediate application to the large medical industry for transplantation, xenotransplantation, and future creation of universal organs from cell banks. In any case, Cryopets has an interesting idea at the core of its business plan, and a greater diversity in efforts to expand the cryonics industry is always a good thing.

The immune system reacts to damaged and dying cells, as well as their debris. As the level of tissue damage rises with age, this pattern recognition contributes to increasing levels of chronic inflammation. That in turn causes further harm, changing cell behavior for the worse, degrading tissue structure and function. Inflammation in aging is an example of a process that is beneficial in the short term becoming harmful when sustained for the long term, a process that is beneficial in the youthful environment becoming actively harmful in the age-damaged environment.

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of the damaged tissue or dead cells. DAMPs are (i) rapidly released following necrosis; (ii) produced by the activated immune cells via specialized secretion systems or by the endoplasmic reticulum (ER)-Golgi apparatus secretion pathway; (iii) known to activate the innate immune system by interacting with pattern-recognition receptors (PRRs), and thereby directly or indirectly promote adaptive immunity responses; (iv) inclined to contribute to the host's defense and pathological inflammatory responses in non-infectious diseases; and (v) responsible for restoring homeostasis by promoting the reconstruction of the tissue.

Accumulating evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, hyperglycemia, oxidative stress, ischemia, mechanical trauma, stress, environmental condition, and genetic defects during retinal development. Recent studies suggested that DAMPs that include extracellular matrix (ECM)-proteins are increased; this suggests a protective or pathogenic role in different retinal disorders. In retinal disorders DAMPs function through multiple specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs), and the NOD-like receptor (NLRs) family.

The diverse nature of the retinal cell types and their neuronal circuitry complicates our understanding of the cell-specific immune responses and the release of DAMPs in various retinal disorders. Therefore, future studies are warranted to identify the DAMPs involved in the molecular mechanisms of retinal diseases, employing single-cell or cell-specific proteomic signatures to identify/design or repurpose next generation therapeutics for retinal disorders.

Link: https://doi.org/10.3390/ijms23052591

Researchers here suggest that mixing mitochondrial DNA haplotypes in the same individual has long-term negative consequences to health, though the precise mechanisms by which this happens have yet to be determined. This has the most relevance to ongoing work on mitochondrial transplants as a way to restore mitochondrial function in old people. Fortunately mitochondrial DNA is not completely unique to the individual. There is a large but limited number of haplotypes, so matching to a patient would be more akin to blood type matching for transfusions than having to produce a distinct set of material for each patient. It does raise the question of whether the goal of producing optimized, hyperefficient mitochondria to enhance human capabilities will be as readily achievable as hoped, however.

The presence of more than one mitochondrial DNA (mtDNA) genetic variant in the cell is called heteroplasmy. Although very rare, heteroplasmy sometimes occurs naturally as a result of mtDNA mutations and can cause several diseases. New therapeutic approaches proposed in recent years and aimed at preventing disease or treating infertility can generate a new form of heteroplasmy in people. "This new form of heteroplasmy, involving distinct non-mutated mtDNA variants, is produced when an individual's cells contain both the original recipient mtDNA and the donor mtDNA transferred during the intervention."

Researchers generated mice with a single nuclear genome but with all their cells simultaneously containing two distinct mtDNA variants. This mouse strain was fertile, and young animals showed no related disease. But long-term analysis over the full lifetime of these mice showed that the coexistence of two mtDNA variants in the same cell compromised mitochondrial function. "We observed that cells rejected the presence of two mitochondrial genomes, and most of them progressively eliminated one of the mtDNA variants. Surprisingly, however, major organs like the heart, lungs, and skeletal muscle were unable to do this."

Organs that could eliminate one of the mtDNA variants, like the liver, recovered their mitochondrial metabolism and cellular health, but those that could not progressively deteriorated as the animals aged. Thus the animals, which appeared healthy in their youth, in later life suffered from heart failure, pulmonary hypertension, loss of muscle mass, frailty, and premature death. The researchers conclude that the dangerous effects of mitochondrial therapeutic interventions identified in the new study show the need for caution in the selection of the donor mtDNA genotype.

Link: https://www.eurekalert.org/news-releases/946412

Partial reprogramming exposes cells to the Yamanaka factors for long enough to reset their epigenetic patterns to those of a youthful cell, but not so long as to force a change of state into induced pluripotent stem cells. This is an active area of research, not yet an exact science in practice, and the long-term risk of cancer via current techniques remains unknown, but animal studies have produced promising results in the short term when it comes to improved function following the application of a partial reprogramming therapy.

What will partial reprogramming do to senescent cells? In today's open access paper, researchers discuss the prospects of using partial reprogramming therapies targeted to senescent cells to minimize their harmful metabolic activity. As is usually the case, this sort of approach compares unfavorably with the proven senolytic strategy of destroying lingering senescent cells. At least some senescent cells are senescent for a good reason, meaning damage, potential for cancer, and so forth, and giving these cells a new lease on life seems a bad idea.

Synergistic Anti-Ageing through Senescent Cells Specific Reprogramming

In this review, we seek a novel strategy for establishing a rejuvenating microenvironment through senescent cells specific reprogramming. We suggest that partial reprogramming can produce a secretory phenotype that facilitates cellular rejuvenation. This strategy is desired for specific partial reprogramming under control to avoid tumour risk and organ failure due to loss of cellular identity. It also alleviates the chronic inflammatory state associated with ageing and secondary senescence in adjacent cells by improving the senescence-associated secretory phenotype (SASP).

Senescence-specific phenotypes are manifested by increased expression of senescence-associated genes and altered metabolic state, while cell cycle (cell cycle withdrawal) and protein synthesis also appear to be characteristically altered. Of these, the SASP is an essential component of the senescence microenvironment. The multiple cytokines, enzymes, and extracellular vesicles (EVs) that make up the SASP can interact with young cells through the senescence microenvironment, a balance that generally promotes senescence. Still, the rejuvenating microenvironment of immature cells can also improve the metabolic state of senescent cells at the tissue level and thus break the senescence signature within senescent cells through the remodelling of protein synthesis and gene expression. It is possible that the vicious cycle of senescence within senescent cells can be broken through the remodelling of protein synthesis and gene expression patterns.

This may be an opportunity left by evolution to combat senescence with controlled reprogramming of local tissues (based on the Yamanaka factors, which essentially create a persistent young environment in a controlled manner), in turn, radically improving the overall senescence homeostasis of senescent cells through metabolic reprogramming and epigenetic remodelling, and this deadlock-breaking anti-ageing strategy is autonomously regulated by the ageing microenvironment, depending on the degree of senescence (the more the microenvironment is inclined to senescence, the easier the local reprogramming, metabolic reprogramming, and epigenetic remodelling). In summary, the phenomena we expect to see in future research and clinical translation are as follows: As rejuvenation becomes more pronounced, local reprogramming loses the promotion from SASP and combines with a controlled induction system to avoid tumours and loss of cellular function.

One might think of the retina as an exposed part of the central nervous system, available for inspection, unlike the rest of it. One of the major challenges in the diagnosis, prevention, and treatment of neurodegenerative conditions is that it is difficult to establish what exactly is going on inside a living individual's brain. Even modern imaging systems have considerable limitations in what can be seen. Thus a number of research groups, such as the one noted here, are attempting to find ways to make use of retinal structure as a readout for the broader state of the aging brain.

In almost 3,000 participants of the Rhineland Study aged between 30 and 94 years, the retina was assessed using "spectral domain optical coherence tomography" (SD-OCT) - a technique that provides detailed images of the retina and its various layers. In addition, brain scans were performed by magnetic resonance imaging (MRI). The data were analyzed using sophisticated software algorithms. This allowed for automated identification and determination of thickness and volumes, of both the different retinal layers and the different structures of the brain. Next, researchers looked for associations between the volume of the retina and the volume of certain brain structures.

There was a close relation between layers of the inner retina and the white matter in the brain. The thinner these retinal layers, the smaller the volume of the brain's white matter. By contrast, sections of the outer retina were mainly associated with the gray matter of the cerebral cortex. In the brain's occipital lobe, where visual processing happens, these associations were particularly pronounced. And the researchers found further relationships. The thickness of different retinal layers correlated closely with the volume of the hippocampus. This is an area of the brain that plays a central role in memory and is often affected in dementia.

"Imaging of the retina using SD-OCT is relatively simple, non-invasive and inexpensive. The current results suggest that SD-OCT measurements of the retina could potentially serve as biomarkers for brain atrophy and to monitor progression of certain neurodegenerative diseases. Further population-based studies as well as studies in patient groups and over a longer period of time are now needed to verify these results in a clinical setting."

Link: https://www.dzne.de/en/news/press-releases/press/the-retina-as-a-potential-biomarker-for-reduced-brain-matter/

Senescent cells accumulate with age, causing tissue dysfunction throughout the body via their inflammatory secretions. One of those dysfunctions is the age-related imbalance in bone remodeling, favoring the osteoclasts that break down bone tissue at the expense of the osteoblasts that rebuild it. The result is osteoporosis, the characteristic loss of bone mass and resilience that takes place with age. It has been clear for some years now that clearing senescent cells in aged individuals is a potential basis for the treatment of osteoporosis, producing a reversal of the condition in animal models treated in this way. This outcome is accompanied by a range of supporting evidence, as discussed here.

Osteoporosis is a frequent age-related disease that results from a dysregulation of the activities of osteoclasts and osteoblasts. As in other age-related diseases, research in the last decade has clearly provided evidence for a role of senescence in age-related osteoporosis. In pioneering work the expression of the senescent cell biomarker p16Ink4 was shown to increase in bone-derived B cells, T cells, myeloid cells, osteoprogenitors, osteoblasts, and osteocytes from young versus old male and female mice. Moreover, osteocytes and myeloid cells were identified as the cell populations with the most pronounced upregulation of senescence-associated secretory phenotype (SASP) factors within the bone environment.

Accumulation of senescent cells in the context of age-related and radiotherapy-related bone loss was since then confirmed by others, and was also shown in bone biopsy samples from older postmenopausal compared to younger premenopausal women. A causative role of senescent cells in mediating age-related bone loss was finally evidenced by pharmacological clearance of senescent cells in old mice or genetic clearance of senescent cells by inducible elimination of p16Ink-4a-expressing senescent cells using INK-ATTAC transgenic mice. The positive effect on bone microarchitecture and bone strength observed in these models after clearance of senescent cells was shown to be mediated partly by the elimination of senescent osteocytes. Moreover, increased bone formation by osteoblasts and a reduction in bone marrow adipose tissue was seen, and thereby supported a shift in bone marrow-derived mesenchymal stem cell (BMSC) differentiation from osteoblasts to adipocytes as mechanism of senescence mediated age-related bone loss

Taken together, a major focus in recent research has been on the role of senescence in BMSC proliferation and differentiation, and major progress has been made in elucidating potential regulators of senescence-mediated bone loss in age-related osteoporosis. This knowledge provides an important foundation for an in-depth understanding of the application of already existing senescence-based therapeutic options in the treatment of osteoporosis. Furthermore, by closing the gaps, in future, novel therapeutic options with a more specific and individualized approaches may arise.

Link: https://doi.org/10.3390/ijms23052701

Senescent cells accumulate with age. They are never a very sizable proportion of all cells in a tissue, but they causes a great deal of harm via their inflammatory signaling, changing the behavior of surrounding cells for the worse, and contributing to chronic inflammation throughout the body. All of the common age-related diseases appear to be driven by the presence of senescent cells to a significant degree. Over the past decade, a great deal of progress has been made in learning more about the role of cellular senescence in aging, thanks to the development of senolytic therapies capable of selectively destroying these senescent cells.

A number of human trials have been conducted or are underway for the first generation senolytic treatment of dasatinib and quercetin in combination, with promising results so far. Quercetin is a readily available supplement, and dasatinib can in principle be prescribed off label by any physician, so obtaining more human data is an important goal in order to enable widespread use in the populations that may benefit. Unfortunately, since dasatinib is an existing approved drug, there is little incentive for the pharmaceutical industry to underwrite the sizable cost of running the necessary trials. The small number of trials that have been conducted to date arise from academic research. There is an opportunity here for philanthropists to advance the field and the state of knowledge by running informal trials at a lower cost.

Meanwhile, data trickles in slowly from the academic trials. Today's paper describes an interesting result, in that senolytic treatment increases circulating α-klotho in mice and humans, implicating senescent cells in the age-related decline in α-klotho levels. The klotho gene is one of the few robustly establishing longevity genes: in mice, more klotho means a longer life, less klotho means accelerated aging. Klotho levels in humans correlate with longevity and better later life health. The evidence to date suggests that klotho likely acts primarily via improved kidney function. Any decline in kidney function has detrimental effects throughout the body.

Orally-active, clinically-translatable senolytics restore α-Klotho in mice and humans

α-Klotho is a geroprotective protein that can attenuate or alleviate deleterious changes with ageing and disease. Declines in α-Klotho play a role in the pathophysiology of multiple diseases and age-related phenotypes. Pre-clinical evidence suggests that boosting α-Klotho holds therapeutic potential. However, readily clinically-translatable, practical strategies for increasing α-Klotho are not at hand. Here, we report that orally-active, clinically-translatable senolytics can increase α-Klotho in mice and humans.

We examined α-Klotho expression in three different human primary cell types co-cultured with conditioned medium (CM) from senescent or non-senescent cells with or without neutralizing antibodies. We assessed α-Klotho expression in aged, obese, and senescent cell-transplanted mice treated with senolytics. We assayed urinary α-Klotho in patients with idiopathic pulmonary fibrosis (IPF) who were treated with the senolytic drug combination, Dasatinib plus Quercetin (D+Q).

We found exposure to the senescent cell secretome reduces α-Klotho in multiple nonsenescent human cell types. This was partially prevented by neutralizing antibodies against the senescence-associated secretory phenotype (SASP) factors activin A and Interleukin 1α (IL-1α). Consistent with senescent cells' being a cause of decreased α-Klotho, transplanting senescent cells into younger mice reduced brain and urine α-Klotho. Selectively removing senescent cells genetically or pharmacologically increased α-Klotho in urine, kidney, and brain of mice with increased senescent cell burden, including naturally-aged, diet-induced obese (DIO), or senescent cell-transplanted mice. D+Q increased α-Klotho in urine of patients with IPF, a disease linked to cellular senescence.

In summary, senescent cells cause reduced α-Klotho, partially due to their production of activin A and IL-1α. Targeting senescent cells boosts α-Klotho in mice and humans. Thus, clearing senescent cells restores α-Klotho, potentially opening a novel, translationally-feasible avenue for developing orally-active small molecule, α-Klotho-enhancing clinical interventions. Furthermore, urinary α-Klotho may prove to be a useful test for following treatments in senolytic clinical trials.

The number of healthy years of life, or life lived free from disability, is increasing over time in much the same way as overall human life span. The dynamics of the process are somewhat different, but the causes are much the same, some combination of public health measures and advances in medical technology. When considering healthspan rather than lifespan, there are also more marked differences between the consequences of age-related diseases. As noted here, neurodegeneration produces more of a burden than other classes of condition.

There have been advances in healthcare over recent decades that mean many people with chronic health conditions are living longer. In the new study, researchers wanted to determine whether this extension to life involves an increase in years with or without disability. The team analyzed data from two large population-based studies of people aged 65 or over in England. The studies, the Cognitive Function and Aging Studies (CFAS I and II) involved baseline interviews with 7,635 people in 1991-1993 and with 7,762 people in 2008-2011, with two years of follow-up in each case.

For both healthy people and those with health conditions, the average years of disability-free life expectancy (DFLE) increased from 1991 to 2011. Overall, men gained 4.6 years in life expectancy and 3.7 years in DFLE. Men with conditions including arthritis, coronary heart disease, stroke, and diabetes gained more years in DFLE than years with disability. The greatest improvements in DFLE in men were seen for those with respiratory difficulties and those living post-stroke. Between 1991 and 2011, women experienced an increase in life expectancy at age 65 years of 2.1 years, and an increase in DFLE of 2.0 years. Similar to men, most improvement in life expectancy for women with long-term conditions was in disability-free years.

However, women with cognitive impairment experienced an increase in life expectancy with disability (1.6 years) without any improvement in DFLE. Men with cognitive impairment experienced only a small increase in DFLE (1.4 years) with an increase in life expectancy with disability that was comparable in magnitude (1.4 years). Therefore, at age 65, the percentage of remaining years of life which were spent disability-free decreased for men with cognitive impairment and women with cognitive impairment.

Link: https://www.eurekalert.org/news-releases/945732

Age-related diseases arise from common causes, but aging is a multifaceted process of numerous interacting forms of damage and disarray, and it is usually challenging to assign a weight to any given part of aging in the causation of any given age-related disease. Still, a great deal of theorizing takes place. Here, researchers discuss the causes of hearing loss and Alzheimer's disease, given that the two conditions tend to co-occur more often than mere chance would lead to. Some underlying process contributes meaningfully to both, and in the treatment of aging, it is best to aim as close to the root causes as possible. That is where the greatest benefit will be achieved.

Epidemiological studies show a strong independent association between age-related hearing loss (ARHL) and Alzheimer's disease (AD). Actually, recent data link 9% of sporadic AD to hearing loss starting at mid-life. Thus, ARHL emerges as the main preventable risk factor of AD, at least in this life period, even with causal implications. Comorbidity between ARHL and AD will further aggravate the condition of the patients, multiplying health, social, economic, and sanitary impact. In sum, epidemiological data link ARHL with cognitive impairment and dementias, in particular AD, pointing to dynamic association between these two neurodegenerative conditions. Besides ARHL contributing to the pathogenesis of AD, the converse may also be the case. However, at present, the biological or mechanistic foundations of such interplay are unknown.

Several hypotheses/mechanisms have been put forth. These include existence of shared underlying pathologies, such as those of vascular origin; diminished auditory input that directly triggers brain atrophy as an expression of the complex chain of cellular events leading to dementia; overload of cognitive resources, diverted to process diminished auditory input; existence of amyloid plaques (AP), intraneuronal neurofibrillary tangles (NFT) and cytoskeletal pathology in the cochlea, dorsal cochlear nucleus, superior olive, central nucleus of the inferior colliculus, medial geniculate body, primary auditory cortex and association area of the auditory cortex. These or another related hypothesis/mechanism do not exclude each other mutually. Whether such interplay is unidirectional from ARHL to AD, or bidirectional is also unknown. The challenge of testing such intricate and open-end hypotheses scenery, is the complexity and multiplicity of factors involved in the genesis and development of both neurodegenerative conditions.

Frailty and related oxidative stress have recently drawn considerable attention. In this review, we discuss the possibility that the oxidative stress linked to frailty, could be, at least in part, primarily involved in the interplay between ARHL and AD.

Link: https://doi.org/10.3389/fnins.2021.816300

In today's open access paper, researchers note that the characteristic loss of maintainance of heterochromatin structure that occurs with age appears sufficient to produce signatures of aging in female germline cells, oocytes, accompanied by a rising level of transposon activity. Along with thymic involution, loss of function in female germline cells is one of the more rapid aspects of aging. This is the subject of a range of research programs, investigating the causes, and potential means of addressing the issue, ranging from tissue engineered ovaries to the usual panoply of pharmacological approaches to slow the mechanisms of aging.

Heterochromatin is the packaged form of nuclear DNA, tended by complex protein machinery and various decorating molecules that keep it folded in such a way as to hide away most genes from the expression machinery that would otherwise jump in and start to produce RNA molecules from their genetic blueprints. When heterochromatin is correctly packaged and maintained, most of the genome is silenced, including parasitic transposon sequences, the remnants of ancient viral infections. Most cellular systems are impacted with age, and heterochromatin packaging is no exception. As it becomes more ragged, transposons can begin to replicate themselves, causing harm. The cause of this disarray in heterochromatin machinery may result from stochastic DNA damage, in that double strand break repair depletes necessary resources - but this is a fairly recent discovery that needs more validation.

Loss of heterochromatin and retrotransposon silencing as determinants in oocyte aging

Reproductive aging is defined as the age-related loss of fertility due to increasing damage to the reproductive and other systems. Oocytes themselves accumulate damage in an age-related manner and deteriorate to the point where they are non-functional. In human, females this occurs at a relatively early age, before the onset of aging in other organs and tissues. In our era of increased rate of delayed childbearing, it is becoming crucial to understand the mechanisms underlying the compromised quality of oocytes with age.

Changes in epigenetic regulation of gene expression and chromosome structure have been recognized as contributors to aging, and epigenetic changes during aging have been listed among the "hallmarks of aging". The loss of heterochromatin histone marks has been associated with the aging process in many systems and tissues. It was shown that epigenetic changes occur in mouse oocytes of advanced maternal age, at ages where aneuploidy is considerable. However, the mechanisms that are altered by these changes, and the ways they affect the different aspects of oocyte aging are yet to be explored. The consequences of heterochromatin de-regulation in aging may be related to the activated transcription of transposable elements (TE) in the genome, and their subsequent effect on genome stability and cellular integrity. This was shown to occur in several organisms and systems. Currently, it is unclear whether TE are activated in older oocytes, and whether, and when exactly, TE expression is involved in oocyte aging and epigenetics.

In this work, we study the role of heterochromatin loss in the aging of oocytes. We show that heterochromatin loss in oocytes can be detected at an age of 9 months in mice, when low aneuploidy rates are present, but a decrease in oocyte quality is evident, as previously reported. We show that these changes are characterized by the loss of repressive histone marks, elevation of specific retrotransposon mRNA transcription, elevated processing of repeated sequences and retrotransposons, and increased activation of the DNA repair machinery. Treatment of oocytes with chemical compounds that inhibit heterochromatin formation can mimic the effect of aging and cause a decrease in oocyte maturation rates and elevation in L1 retrotransposon activity and DNA damage.

Importantly, we find that the effect of heterochromatin loss and L1 retrotransposon activity on oocyte maturation with age is partially reversible through treatment of oocytes with AZT, a SIRT1 activating molecule-SRT-1720, or overexpression of Sirt1 or Ezh2 in older oocytes. Treatment with AZT does not prevent epigenetic failure in older oocytes while the other interventions do. This fact demonstrates that the epigenetic effect is upstream to retrotransposon activation at this stage of the aging process.

Senescent cells are created and destroyed constantly in the body, but their numbers accumulate with age, an imbalance that is a consequence of raised rates of creation due to an age-damaged environment, and the failure of the immune system to rapidly clear these errant cells. Senescent cells actively secrete a pro-inflammatory, pro-growth mix of signals, useful in the short term in contexts such as suppression of precancerous lesions and coordination of wound healing. When present for the long term, senescent cell signaling is very harmful to cell and tissue function, however. It is an important contributing cause of chronic inflammation and many age-related conditions.

Cellular senescence is a state of stable cell-cycle arrest despite continued metabolic activity, which usually occurs in response to many endogenous and exogenous stresses during aging processes. Historically, senescence was first identified half a century ago, with the discovery that human diploid fibroblasts displayed a finite capacity for cell division because of telomere shortening (replicative senescence). Conversely, the telomere length-independent senescence was then observed in many aged or damaged tissues. Such stress-induced premature senescence (SIPS) can be triggered by distinctive stressful stimuli, including persistent DNA damage, oncogene activation, oxidative stress, and mitochondrial dysfunction in the cardiovascular system.

Eminently characterized by a proliferation arrest, the senescent cells are differed from other non-dividing cells (such as quiescent cells) with specific morphological and functional features. Growing evidences demonstrated that the senescent cardiovascular cells, including endothelial cells, vascular smooth muscle cells, fibroblast cells, cardiomyocytes, T cells and et al., were accumulated in the culprit lesions of cardiovascular system and act to improve or exacerbate the onset and outcome of cardiovascular diseases. While cellular senescence imposes an important role in suppressing tumorigenesis. There is strong evidence that cellular senescence also participates in the progression of heart regeneration, cardiac remodeling, atherosclerosis, and heart failure.

In this review, we first discuss the mechanisms and the features underlying cellular senescence. Then, we summarize the different types of senescent cells that present in cardiovascular systems and describe the pathophysiological implications of cellular senescence in cardiovascular disease. Moreover, we highlight the role of SIRT1 and mTOR in regulating senescence during age-related cardiovascular diseases. Finally, we focus on the emerging pro-senescent and anti-senescent therapies and discuss their therapeutic potential for cardiovascular diseases.

Link: https://doi.org/10.14336/AD.2021.0927

One of the more interesting findings of recent years, emerging from the use of accelerometers in epidemiological studies, is that even quite modest levels of physical activity have a meaningful impact on mortality in later life. There is a big difference between being inactive and being somewhat active. One of the ways of visualizing this part of the dose-response curve for exercise is to look at the relationship between steps taken per day and mortality.

A meta-analysis of 15 studies involving nearly 50,000 people from four continents offers new insights into identifying the amount of daily walking steps that will optimally improve adults' health and longevity - and whether the number of steps is different for people of different ages. Taking more steps a day helps lower the risk of premature death.

More specifically, for adults 60 and older, the risk of premature death leveled off at about 6,000-8,000 steps per day, meaning that more steps than that provided no additional benefit for longevity. Adults younger than 60 saw the risk of premature death stabilize at about 8,000-10,000 steps per day. "So, what we saw was this incremental reduction in risk as steps increase, until it levels off. And the leveling occurred at different step values for older versus younger adults."

Interestingly, the research found no definitive association with walking speed, beyond the total number of steps per day. Getting in your steps - regardless of the pace at which you walked them - was the link to a lower risk of death. The new research supports and expands findings from another study, which found that walking at least 7,000 steps a day reduced middle-aged people's risk of premature death.

Link: https://www.umass.edu/news/article/meta-analysis-15-studies-reports-new-findings-how-many-daily-walking-steps-needed

Manipulation of cellular biochemistry in order to provoke beneficial stress responses, in a similar way to the outcome of calorie restriction, heat and cold stress, oxidative stress, and so forth, is a popular area of development in aging research. It dovetails well with the established infrastructure for discovering and vetting small molecule drugs, and there are many potential points of intervention in signaling pathways in a cell. Unfortunately the effect sizes leave something to be desired; few pharmacological approaches to stress response upregulation come with evidence to suggest that they are an improvement over exercise or the practice of calorie restriction.

One of the better explored approaches to inducing a stress response in cells is the selective inhibition of mitochondrial function. Mitochondria are the power plants of the cell. Given that mitochondrial function is of great importance to health, and declines with age, mitochondrial inhibition is a counterintuitive path to therapy, but it works. Some forms of partial impairment of the operation of the electron transport chain in mitochondria, a collection of protein complexes responsible for producing chemical energy store molecules to power cellular processes, lead to a stress response that produces a net benefit in older individuals. In particular mitochondrial function can be diminished in aging by a faltering of the quality control mechanism of mitophagy, responsible for removing worn and damaged mitochondria. If partial inhibition then provokes more effective mitophagy, the result is a net gain.

Mitochondrial complex I as a therapeutic target for Alzheimer's disease

Partial inhibition of complex I with small molecules emerged as a promising strategy to induce beneficial mitochondrial induced stress response. Complex I inhibitors are in clinical trials for various human conditions, including type 2 diabetes, cancers, metabolic disorder, obesity, inflammatory and infectious diseases. Only metformin, resveratrol, berberine, and epigallocatechin-3-gallate were trialed in a limited number of studies for neurodegenerative diseases, including Alzheimer's disease (AD). Metformin improved cognitive function in patients with amnestic MCI, while resveratrol, berberine and epigallocatechin-3-gallate did not show statistically significant improvements in cognitive performance in patients with AD, Huntington's disease, or MCI. While all four complex I inhibitors penetrate the blood-brain barrier (BBB), the therapeutic effect of resveratrol, berberine and epigallocatechin-3-gallate was limited, probably due to a poor stability, short half-life, and a very low bioavailability in contrast to metformin. Therefore, modifications of current complex I inhibitors or the development of new small molecules with improved drug-like properties and bioavailability are needed to increase therapeutic efficacy for neurodegenerative diseases.

We recently identified a small molecule tricyclic pyrone compound (CP2) that penetrates the BBB and accumulates in mitochondria where it mildly inhibits the activity of complex I. CP2 is bioavailable, has low toxicity in vitro and in vivo, and has good drug-like properties and safety profile. CP2 increased mitochondrial respiratory control ratio and reduced proton leak, suggesting better coupling efficiency of the neuronal electron transport chain (ETC), greater bioenergetic reserve, and enhanced ability to withstand stress. In vivo efficacy of chronic CP2 administration was examined in independent cohorts of male and female mouse models of AD. In all studies, chronic CP2 treatment did not induce toxicity or affect development. Remarkably, in all treatment groups, CP2 improved energy homeostasis in the brain and periphery (glucose uptake and utilization, glucose tolerance, and insulin resistance), synaptic activity, long-term potentiation, dendritic spine maturation, cognitive function and proteostasis (reduced amyloid-β and phosphorylated Tau levels), and reduced oxidative stress and inflammation in the brain and periphery, ultimately blocking the ongoing neurodegeneration.

In conclusion, we summarized here evidence for a novel therapeutic approach to exploit the incredible ability of mitochondria to engage multifaceted neuroprotective stress response triggered by partial complex I inhibition. This approach promises relief for multiple human conditions, and to promote healthy aging to delay the onset of neurogenerative diseases, AD in particular, where age is the greatest risk factor. There is a mounting body of evidence generated in model organisms and humans in support of the safety of chronic application of complex I inhibitors. However, a better understanding of the molecular mechanisms is required to establish safety in translation to humans, including the development of biomarkers that inform on mitochondrial function and the capacity to induce the beneficial stress response. Further therapeutic developments should produce selective and specific complex I inhibitors capable of penetrating the BBB with excellent safety profile.

The various geroprotective drugs capable of upregulating cellular maintenance processes in order to modestly slowing aging in short-lived laboratory species are a mixed bunch, ranging from the only technically geroprotective, including well characterized, and well used drugs such as aspirin, to drugs with very mixed data for small effects, such as metformin, through to the better end of the range such as mTOR inhibitors like rapamycin that reliably slow aging. Even in the case of rapamcyin, it remains unclear that the benefits in long-lived species such as our own are all that much better than a good exercise program or the practice of calorie restriction. Senolytic drugs are technically also lumped under the geroprotective heading, but as an actual rejuvenation therapy, and one that produces profoundly greater reversal of age-related diseases in animal models than is the case for other geroprotectives, this has always seemed to me to be a very different class of treatment.

Recent work has shown that it is possible to prevent or even reverse the dysregulation of oxidative stress, autophagy, and the occurrence of senescence using a new class of drugs called geroprotectors. Geroprotectors are drugs that delay or reverse ageing processes and in doing so target the major risk factors for age-related diseases. They promise to promote health span of more than one organ system at the same time in animal models. Studies in model organisms or retrospective studies in patients show that they can ameliorate tissue dysfunction and reduce the onset and severity of many diseases. Over 200 compounds have been classified as geroprotectors, each reported to slow ageing and/or extend lifespan in a variety of organisms.

Such drugs could have distinct advantages over present treatments in osteoporosis (OP) and offer new opportunities for osteoarthritis (OA) due to the fact that they may be able to prevent both OP and OA and their co-morbidities. However, the effects of geroprotectors on skeletal health have received little attention compared to other organ systems with the assumption that these drugs will work equally well for all tissues. Here we review the evidence available to address whether geroprotectors have potential for the care of skeletal age-related diseases and their co-morbidities. We focus on drugs with a good safety profile, which have been shown to target ageing pathways, extend the lifespan and healthspan in animal models and have some evidence of improving health in humans by demonstrating protection from multiple-age-related diseases and for which there are well designed studies in animal models of OP and OA or clinical data available.

Geroprotectors potentially have additional benefits to treat OA and OP and their co-morbidities. However, few studies focus on skeletal health despite their burden of disease. Only one study with the combination of senolytics dasatinib and quercetin shows signs of improvement in a model of bone loss and no improvement has been demonstrated so far in aged models of OA. These studies highlight that extension of lifespan cannot be considered a surrogate marker for extension of health span in all tissues and thorough studies in aged models of OP and OA are required to assess the real benefit of geroprotectors to improve skeletal health.

Link: https://doi.org/10.3389/fcell.2022.682045

Age-related diseases will tend to cluster because they arise from specific underlying processes of aging. If one process of aging is more advanced in a given individual, then that individual is more at risk of suffering the panoply of age-related diseases that are most driven by that process of aging. This is easy enough to say, and seems self-evident. Here, researchers mine human medical databases in order to map clusters of age-related diseases to the hallmarks of aging, visualizing this relationship between mechanisms of aging and disease co-occurrence in real data.

Genetic, environmental, and pharmacological interventions into the aging process can confer resistance to multiple age-related diseases in laboratory animals, including rhesus monkeys. These findings imply that individual mechanisms of aging might contribute to the co-occurrence of age-related diseases in humans and could be targeted to prevent these conditions simultaneously. 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 in humans, confirmed by gene set enrichment analysis of GWAS 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. Genetic evidence revealed that innate and adaptive immunity, the intrinsic apoptotic signaling pathway, and activity of the ERK1/2 pathway were associated with multiple aging mechanisms and diverse age-related diseases. Mechanisms of aging hence contribute both together and individually to age-related disease co-occurrence in humans and could potentially be targeted accordingly to prevent multimorbidity.

Link: https://doi.org/10.1111/acel.13524

Mitochondria are the power plants of the cell, deeply integrated into many core cellular processes, but most importantly, responsible for generating the energy store molecule adenosine triphosphate (ATP), used to power cellular processes. Mitochondria are descended from ancient symbiotic bacteria, and act like bacteria in many ways, fusing and dividing, and passing around component parts promiscuously. Every cell contains a herd of hundreds of these organelles, monitored by quality control processes that destroy worn mitochondria in order to maintain overall function.

Importantly, mitochondria contain their own small circular genome. Mitochondrial DNA is less well protected than that of the cell nucleus, and more prone to stochastic mutational damage. There are clearly types of mitochondrial DNA damage, large deletion mutations that remove genes essential to the electron transport chain, central to mitochondrial function, that result in pathological damage to cells. But mitochondria throughout the body undergo a declining function with age that seems to have more to do with altered dynamics and the failure of mitophagy to keep up with worn mitochondria, a consequence of age-related changes in gene expression of crucial proteins.

Yet mutational damage other than deletions, such as point mutations, is widespread across mitochondria in aged tissues. To what degree is this stochastic mutational damage important as a contribution to age-related mitochondrial decline? Is it as relevant as loss of mitophagy? Unimportant in comparison? Today's open access paper reviews what is known on this topic. It is a complicated situation, still much debated, with mixed evidence on all sides.

The Complicated Nature of Somatic mtDNA Mutations in Aging

With only a few noted exceptions, mitochondria are the main source of cellular energy in eukaryotes. These organelles process dietary reducing equivalents and oxygen through the electron transport chain (ETC) to produce ATP via oxidative phosphorylation (OXPHOS). Mitochondria are involved in other important cellular functions. To varying extents, different cell types rely on these different functions, which, in turn, determines their intracellular localization, dynamics, number, and respiratory flux. As organisms age, these different mitochondrial processes degrade to differing extents and in tissue specific ways. A lingering question in the field of aging biology concerns the source of this dysfunction.

As a consequence of an endosymbiotic event ∼2 billion years ago that gave rise to mitochondria, these organelles have retained a small rudimentary genome that, in animals, is comprised of a circular double-stranded DNA molecule (mtDNA) present in dozens to thousands of copies per cell. The relatively small genome is extremely compact and encodes a total of 37 genes: 22 tRNAs, two mitochondrial ribosomal RNAs, and 13 peptides that comprise essential components of the ETC. As such, proper maintenance of the genetic information is essential for energy production and therefore maintaining cell homeostasis. One long-standing hypothesis in aging research is that the loss of genetic information encoded by the mtDNA is an important driver of aging.

With limited DNA repair capacity and higher replicative index, mtDNA has a substantially higher de novo mutation rate compared to nuclear DNA. The mitochondrial genome is maternally inherited, with most mtDNA within a cell and organism being an exact copy of the original maternal mtDNA pool, a phenomenon known as homoplasmy. However, mtDNA is susceptible to mutations within the germline, which can result in a number of devastating maternally inherited diseases. In addition to causing overt disease, mtDNA mutations can be present at lower levels, a condition known as heteroplasmy. The heteroplasmic allele fraction can range from very low levels to near homoplasmy and can be inherited or occur de novo within somatic tissues during aging and development.

Because of the multi-copy nature of mtDNA, it is estimated that the phenotypic threshold for pathogenic heteroplasmies is ∼60-90% of mitochondrial genomes within a cell. To add more complexity to the condition of heteroplasmy, the occurrence and frequency of mtDNA mutations may have different outcomes depending on the timing of their occurrence, the specific tissue in which they arise, and the total mtDNA content of the cell. Despite decades of study, the complex nature of mitochondrial genetics has made the exact role of somatic mtDNA mutations in aging difficult to discern.

In this review, we focus on the complicated observational and experimental evidence suggesting that, at least in some capacity, somatic mtDNA mutations are involved in the aging process with an emphasis of when, where, and how these mutations arise during aging. Additionally, we highlight current limitations in our knowledge and critically evaluate the controversies stemming from these limitations. Lastly, we highlight new and emerging possibilities that offer potential ways forward to increase our understanding of somatic mtDNA in the aging process.

Systems of measuring biological age are multiplying rapidly. There are many ways of going about this, from epigenetic clocks to weighted combinations of simple measures such as grip strength. Researchers here build their own assessments for the purpose of looking at aging in younger adults, 20s to 40s, a part of aging that is not well studied at all. The interesting outcome is that there appears to be a significant variation in assessed biological age between different organs and systems in the body. It is a little early to talk about why this arises, whether an artifact of the tools used, or reflects some underlying truth about the nature of aging.

Investigators recruited 4,066 volunteers to supply blood and stool samples and facial skin images and to undergo physical fitness examinations. The volunteers were between the ages of 20 and 45 years; 52% were female and 48% were male. "Most human aging studies have been conducted on older populations and in cohorts with a high incidence of chronic diseases. Because the aging process in young healthy adults is largely unknown and some studies have suggested that age-related changes could be detected in people as young as their 20s, we decided to focus on this age range."

In total, 403 features were measured, including 74 metabolomic features, 34 clinical biochemistry features, 36 immune repertoire features, 15 body composition features, 8 physical fitness features, 10 electroencephalography features, 16 facial skin features, and 210 gut microbiome features. These features were then classified into nine categories, including cardiovascular-related, renal-related, liver-related, sex hormone, facial skin, nutrition/metabolism, immune-related, physical fitness-related, and gut microbiome features.

Because of the difference in sex-specific effects, the groups were divided into male and female. The investigators then developed an aging-rate index that could be used to correlate different bodily systems with each other. Based on their findings, they classified the volunteers either as aging faster or aging slower than their chronological age. Overall, they discovered that biological ages of different organs and systems had diverse correlations, and not all were expected. Although healthy weight and high physical fitness levels were expected to have a positive impact, the investigators were surprised by other findings. For example, having a more diverse gut microbiota indicated a younger gut while at the same time having a negative impact on the aging of the kidneys, possibly because the diversity of species causes the kidneys to do more work.

Link: https://www.eurekalert.org/news-releases/945229

Many studies of exercise and health support the view that older people typically undertake far less exercise than they should. Exercise improves function and lowers mortality risk, and therefore the less active segment of the older population are only harming themselves. We evolved to be active throughout life, and we suffer when that is not the case. As researchers note here, the dose-response curve for exercise results in sizable benefits when moving from little exercise to some exercise, and diminishing returns with further increases. Evidence suggests that the optimal level is probably still somewhat more than the established 150 minutes per week, however.

The study followed 51 older adults, tracking their physical activity and fitness measurements. The participants performed tests specifically designed to measure cognitive functioning and underwent MRIs to assess brain functioning. They also wore a device that measured the intensity of the wearer's physical activity, number of steps taken and distance covered. The researchers assessed fitness through a six-minute walking test, during which participants walked as quickly as they could to cover the most distance possible within the time limit.

The brain is made up of a bunch of distinct networks. Different parts of the brain are active at different times. While one of these networks is active, the other should be shut off. If it's not, that's a sign that a person's brain isn't functioning as well as it should be. These networks are the key to being able to perform basic tasks in daily life, such as remembering important information and exhibiting self-control. But as people age, these tasks often become more difficult. This study was the first to examine how these networks interact with physical activity and fitness to impact how the brain functions.

"This paper is exciting because it gives us some evidence that when people whose brain networks aren't functioning optimally engage in physical activity, we see improvement in their executive function and their independence. Maybe just take the stairs on the way to work. Stand up and walk around a little bit more. That's where you get the most bang for your buck, not crazy, high-intensity exercise."

Link: https://news.uga.edu/physical-activity-may-protect-your-brain-as-you-age/

In today's open access paper, researchers discuss the influence of metabolism on the aging of stem cells. Stem cells maintain tissue by providing a supply of daughter somatic cells to replace losses. Animals have evolved to minimize the risk of cancer by limiting the ability of near all cells to replicate. Somatic cells operate under the Hayflick limit, driven by loss of telomere length with each cell division, leading to senescence or self-destruction when telomeres are short. Stem cells use telomerase to maintain long telomeres and thus continually produce replacement somatic cells with long telomeres.

Unfortunately stem cell activity is reduced with advancing age, leading to a reduced production of somatic cells and the steady decline of tissue maintenance and function. The causes of this are complex, even while being energetically explored by a large portion of the broader research community. At the very high level, damage to stem cells, damage to the supporting cells of the stem cell niche, and changes in the signaling environment that cause stem cells to become more quiescent, even if undamaged. The balance of these issues appears different for different stem cell populations. Aged muscle stem cells appear functional when given a youthful environment, for example.

Metabolic Regulation of Stem Cells in Aging

Somatic stem cells integrate critical environmental inputs that inform decisions on self-renewal, differentiation, and subsequent tissue turnover. Aging is a risk factor for many diseases, and recent studies are starting to uncover the molecular mechanisms of how environmental factors, such as diet, can influence stem cell behavior over time. With aging, many adult stem cell populations accumulate damage and become impaired in their function, which leads to inefficient tissue repair and may predispose to age-associated diseases such as cancer. Although numerous studies have shown that dietary restriction confers beneficial effects on overall organismal lifespan, we are just starting to uncover the complexities of metabolic dependencies in stem cells and how the availability of specific nutrients are sensed within a heterogeneous population of stem, progenitor, and niche cells and communicated between each other. The advent of new single cell technologies has already begun to enhance our ability to resolve the complex metabolic heterogeneity and interactions that exist in certain niches, such as in the gut crypt and bone marrow.

Recent studies using single cells technologies have also revealed that seemingly uniform, terminally differentiated cells in the liver and intestinal villus have specific transcriptional metabolic profiles that are driving cell function. These differences among hepatocytes and enterocytes were largely influenced by location, proximity to nutrients, and oxygen supply within their respective tissues. In the upcoming years, as multiple single cell -omic technologies advance and integrate, we will begin to see more advanced tissue maps of transcriptional, proteomic, and metabolomic signatures of stem and progenitor cells and their corresponding niches, both under homeostatic conditions as well as during aging and other pathological states. These types of studies will also likely layer dietary patterns with other environmental factors to expand our understanding of how nutrients and systemic metabolism impact tissue homeostasis. Finally, the constant improvement and engineering of primary 3D organoid cultures will allow us to more precisely examine intrinsic and extrinsic age-associated changes, as well as measure the activity of metabolic pathways, in response to defined nutrient conditions. We will be able to incorporate and study other signals in these systems, such as cytokines, hormones, and microbial metabolites. All of these advances will conceivably lead to better strategies and therapies for tissue repair with age, while carefully avoiding interventions that may accelerate age-dependent diseases such as cancer.

A good deal of evidence points to increased inflammatory activation of microglia in the brain, and consequent chronic inflammation of brain tissue, as an important component of neurodegenerative conditions. Some of these inflammatory microglia are senescent, and their clearance has been shown to be helpful in animal models, but the broader problem is an imbalance between pro-inflammatory M1 microglia and anti-inflammatory M2 microglia. A number of options exist if the goal is to shift the balance, from clearance and regeneration of all microglia via CSFR1 inhibition to various mechanisms that might encourage microglia to preferentially adopt the M2 state.

Microglia-mediated neuroinflammation is a common feature shared by various neurodegenerative diseases. Neuroinflammatory includes microglial activation, and microglia could polarize into either M1 pro-inflammatory phenotype or M2 anti-inflammatory phenotype in response to different micro-environmental disturbances, which are called classical activation and alternative activation, respectively. M1 microglia release inflammatory cytokines and chemokines, resulting in inflammation and neuronal death. However, tissue maintenance and repair are associated with alternative activation of M2 microglia. M1 microglia induce inflammation and neurotoxicity, while M2 microglia induce anti-inflammatory and neuroprotection, both of which are involved in the pathogenesis of neurodegenerative diseases, therefore microglia act as a double-edged sword in neurodegenerative diseases.

It's impossible to repair or regenerate damaged neurons by current drugs nowadays once neurodegenerative diseases occur or even before the onset of diseases, but current drugs could alleviate disease-related symptoms by restricting the extent of neuroinflammation. Fortunately, the balance between microglia M1/M2 polarization has a promising therapeutic prospect in the pathogenesis of neurodegenerative diseases. However, previous studies have shown that several M1 inhibitive agents are unhelpful.

As inhibiting M1 microglia alone is not enough, promoting M2 microglia activation simultaneously might also be required for treating neurodegenerative diseases. Promoting microglia polarization shift from M1 to M2 phenotype may be a more prospective strategy in the therapy of neurodegenerative diseases. Activated microglia is also a double-edged sword in other central nervous system diseases such as ischemic stroke, spinal cord injury, and traumatic brain injury. There have been many studies about modulation of microglia polarization from M1 to M2 in these diseases, which may provide many interesting ideas in neurodegenerative diseases.

Link: https://doi.org/10.3389/fnagi.2022.815347

Continuing the recent run of interesting observations arising from the ability to assess epigenetic age, researchers here show that a hibernating species shows no uptick in epigenetic age over the period of hibernation. The metabolism of hibernation has been a topic of minor interest for some years in the context of aging and mechanisms of aging. The metabolic state of hibernation seems favorable in many of the same ways that are observed in states like calorie restriction, but perhaps for distinct reasons.

Yellow-bellied marmots are able to virtually halt the aging process during the seven to eight months they spend hibernating in their underground burrows. The study, the first to analyze the rate of aging among marmots in the wild, shows that this anti-aging phenomenon kicks in once the animals reach 2 years old, their age of sexual maturity. The researchers studied marmot blood samples collected over multiple summer seasons in Colorado, when the animals are active above ground, to build statistical models that allowed them to estimate what occurred during hibernation. They assessed the biological aging of the marmots based on what are known as epigenetic changes - hundreds of chemical modifications that occur to their DNA.

This process, the researchers said, helps explain why the average life span of a yellow-bellied marmot is longer than would be expected from its body weight. Hibernation, an evolutionary adaptation that allows animals to survive in harsh seasonal environments where there is no food and temperatures are very low, is common among smaller mammals, like marmots. The marmots' hibernation alternates between periods of metabolic suppression that last a week or two and shorter periods of increased metabolism, which generally last less than a day. During metabolic suppression, their breathing slows and their body temperature drops dramatically.

All of these hibernation-related conditions - diminished food consumption, low body temperature and reduced metabolism - are known to counter the aging process and promote longevity. This delayed aging is likely to occur in other mammals that hibernate, because the molecular and physiological changes are similar.

Link: https://newsroom.ucla.edu/releases/marmots-and-the-secret-to-longevity

A large portion of research into senescent cells in the context of degenerative aging is focused on how these cells fail to destroy themselves. Senescent cells are primed to enter the programmed cell death process of apoptosis, but various mechanisms hold this off. Sabotaging some of those mechanisms is an effective way to clear a sizable fraction of senescent cells in many old tissues, as demonstrated by the initial small molecule senolytic treatments, such as the dasatinib and quercetin combination.

As the authors of today's open access paper note, the fact that these apoptosis-inducing senolytics are only partially effective raises questions about the diversity of anti-apoptosis mechanisms and varieties of senescent cell. It is a fertile area of research, in which scientists are uncovering new ways to provoke senescent cells into apoptosis, with different degrees of effectiveness on senescent cells of different origins. There are many more areas of cellular biochemistry yet to explore, and likely many more effective senolytic small molecules yet to be identified.

Why Senescent Cells Are Resistant to Apoptosis: An Insight for Senolytic Development

Cellular senescence is a process that leads to a state of irreversible growth arrest in response to a variety of intrinsic and extrinsic stresses. Initially, the phenomenon was found when cultured cells were shown to undergo a limited number of cell divisions in vitro. Cellular senescence is different from cell quiescence which represents a transient and reversible cell cycle arrest. Cellular senescence can be a physiologically or pathologically relevant program depending on the specific situation. It normally functions as a vital tumor suppressive mechanism and also plays an important role in tissue damage repair. However, senescent cells (SnCs) have been implicated in various age-related diseases.

Accordingly, selective elimination of SnCs has been exploited as a novel strategy to treat the diseases. In addition, SnCs have also been implicated in infectious diseases. For example, virus infection can induce cellular senescence, which was found to be a pathogenic trigger of cytokine escalation and organ damage, and recently found to be associated with the COVID-19 severity in the elderly. Clearance of virus-induced SnCs was considered as a novel treatment option against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and perhaps other viral infections.

One of the characteristics of SnCs is their ability to resist apoptosis. Until now, small molecules that can selectively kill SnCs, termed senolytics, were developed to target the proteins in the SnC anti-apoptotic pathways (SCAPs). However, due to the high heterogeneity in gene expression and their diverse origins, SnCs may use different SCAPs to maintain their survival, making it difficult to use a single senolytic to kill all types of SnCs. Although significant progresses on the development of senolytics have been made, some proteins involved in the SCAPs have been overlooked, their potential of being senolytic targets have not been investigated. Therefore, gaining more insights into the apoptosis-resistant mechanism of SnCs may greatly help to design or screen more effective senolytics that can be used to treat SnC-associated disorders.

In this review, we discussed the latest research progresses and challenge in senolytic development, described the significance of regulation of senescence and apoptosis in aging, and systematically summarized the SCAPs involved in the apoptotic resistance in SnCs.

Now that cost-effective epigenetic age assessment is a going concern, we will see all sorts of interesting correlations, such as the one noted here in patients with obstructive sleep apnea, before and after treatment. Since it remains unclear as to what exactly is being measured by epigenetic age, which aspects of aging and consequent metabolic dysfunction contribute to the outcome, a good deal of speculation is involved when thinking about why and how what is known of the consequences of sleep apnea relates to what is known of degenerative aging.

Obstructive sleep apnea (OSA) affects 22 million people in the U.S. and is linked to a higher risk of hypertension, heart attacks, stroke, diabetes, and many other chronic conditions. Age acceleration testing involves a blood test that analyzes DNA and uses an algorithm to measure a person's biological age. The phenomenon of a person's biological age surpassing their chronological age is called "epigenetic age acceleration", and is linked to overall mortality and to chronic diseases.

Researchers studied 16 adult nonsmokers who were diagnosed with OSA and compared them to eight control subjects without the condition to assess the impact of OSA on epigenetic age acceleration over a one-year period. After a baseline blood test, the OSA group received continuous positive airway pressure (CPAP) treatment for one year before being tested again.

"Our results found that OSA-induced sleep disruptions and lower oxygen levels during sleep promoted faster biological age acceleration compared to the control group. However, the OSA patients who adhered to CPAP showed a deceleration of the epigenetic age, while the age acceleration trends did not change for the control group. Our results suggest that biological age acceleration is at least partially reversible when effective treatment of OSA is implemented."

Link: https://www.eurekalert.org/news-releases/945630

GlyNAC supplementation means addition of glutathione precursors to the diet, glycine and N-acetylcysteine. Glutathione is a natural antioxidant, protective against oxidative stress and able to improve mitochondrial function. Levels of glutatione decline with age, but this can be compensated for via providing increased levels of precursor compounds that will lead to greater manufacture of glutathione. Delivering glutathione directly has been attempted, but doesn't work, for reasons that likely relate to how glutathione ends up in the parts of the cell where it does its work. The interesting data is of course the human data, showing a reduction in chronic inflammation and improvements in other markers, but here find evidence for life extension in mice resulting from this approach.

Determinants of length of life are not well understood, and therefore increasing lifespan is a challenge. Cardinal theories of aging suggest that oxidative stress (OxS) and mitochondrial dysfunction contribute to the aging process, but it is unclear if they could also impact lifespan. Glutathione (GSH), the most abundant intracellular antioxidant, protects cells from OxS and is necessary for maintaining mitochondrial health, but GSH levels decline with aging. Based on published human studies where we found that supplementing glycine and N-acetylcysteine (GlyNAC) improved/corrected GSH deficiency, OxS, and mitochondrial dysfunction, we hypothesized that GlyNAC supplementation could increase longevity.

We tested our hypothesis by evaluating the effect of supplementing GlyNAC vs. placebo in C57BL/6J mice on (a) length of life; and (b) age-associated GSH deficiency, OxS, mitochondrial dysfunction, abnormal mitophagy and nutrient-sensing, and genomic damage in the heart, liver, and kidneys. Results showed that mice receiving GlyNAC supplementation (1) lived 24% longer than control mice; (2) improved/corrected impaired GSH synthesis, GSH deficiency, OxS, mitochondrial dysfunction, abnormal mitophagy and nutrient-sensing, and genomic damage. These studies provide proof-of-concept that GlyNAC supplementation can increase lifespan and improve multiple age-associated defects. GlyNAC could be a novel and simple nutritional supplement to improve lifespan and healthspan, and warrants additional investigation.

Link: https://doi.org/10.3390/nu14051114

Mitochondria are the power plants of the cell. They are deeply integrated into many core cellular processes, but their primary responsibility is to generate adenosine triphosphate (ATP), an energy store molecule used to power cellular activities. Mitochondria are the evolved descendants of ancient symbiotic bacteria, and carry a small remnant genome encoding a handful of genes vital to ATP production. Each cell contains hundreds of mitochondria. Worn mitochondria are destroyed by the quality control process of mitophagy, while other mitochondria replicate much like bacteria to make up numbers.

The mitochondrial genome is less well protected than the nuclear genome, and some forms of mutational damage can cause mitochondria to become both dysfunctional and in some way able to outcompete their peers, either resistant to mitophagy or better able to replicate, or both. It is an open question as to how much of the age-related decline in mitochondrial function is a result of stochastic mitochondrial DNA damage, both modest and severe, versus the characteristic epigenetic changes of age that impair mitophagy and mitochondrial function in other ways.

To answer that question, it would be necessary to repair mitochondrial DNA damage in isolation of other processes. This is the goal of the MitoSENS project at the SENS Research Foundation, and their approach is to place mitochondrial genes into the nuclear genome, suitably altered such that the proteins produced are transported into the mitochondria where they are needed. This has been achieved for a few of the necessary genes, and if achieved for all it would, in principle, make mutational damage to the mitochondrial genome a non-event. It would then be possible to observe the outcome of this intervention in animal models, to see how much of a gain in health and life span was achieved.

SRF Publication on Mitochondrial Genome in Aging and Disease and the Future of Mitochondrial Therapeutics

The MitoSENS team continue to make progress in developing rejuvenation biotechnologies to prevent, reverse, or remove mutant mitochondria from aging cells. The center of their work continues to be allotopic expression, placing "backup copies" of the mitochondrial DNA into the nucleus, which would supply the proteins that mutation-bearing mitochondria can no longer produce for themselves, and thus keep them (and our cells) functioning normally over time. The MitoSENS team's 2016 breakthrough with allotopic expression of the mitochondrial genes ATP8 and ATP6 marked an important milestone. Since then, they've continued to work to advance the field, including showing how the distinct way that mitochondria encode genetic instructions into their DNA can be better "translated" for use in the nuclear genome, resulting in robust but transient protein production for all of the 13 genes. The team is now working on creating stable expression for these proteins and in achieving functional relevance.

In a new peer-reviewed scientific paper, the MitoSENS team gives an overview of where the field is at and the obstacles that are holding us back. They first highlight some of the drugs, supplements, and stem cell treatments that have been tried and failed (or only had modest effects) to treat inherited mitochondrial diseases. But then they get to the heart of the matter: the challenges that now need to be overcome in order to move allotopic expression towards the clinic. These include mastering the targeting of allotopically-expressed proteins to the right place in the mitochondria; modifying either the protein products themselves or the way we deliver them to prevent these proteins being incorrectly assembled in places other than their intended location; and controlling the level of protein production and its regulation by the cell (since too little protein production wouldn't have a therapeutic effect, and too much might be harmful).

The Mitochondrial Genome in Aging and Disease and the Future of Mitochondrial Therapeutics

Mitochondria are at the interface between several critical functions in the cell, including metabolism, signaling, and immune surveillance. Advances in our understanding of mitochondrial biology and function have illuminated the role of mitochondrial dysfunction in pathology and aging. The unique properties of the organelle predispose its genome to mutations and compromised functions leading to several diseases collectively called mitochondriopathies. Researchers have exploited various technologies, including small-molecule drugs, allogeneic hematopoietic stem cell transplantation, mitochondrial replacement, as well as gene-editing tools, such as nucleic acid therapy and mitochondria-targeted restriction endonucleases, in alleviating these diseases. While modulating organelle function using small molecules is attractive at the outset and benefits from ease of administration, few leads have been identified that hold curative promise, and this treatment modality leaves the root cause of pathology unaddressed.

Recent gene editing approaches, such as targeted restriction endonucleases and base-editing enzymes show promise, though they are limited by their narrow specificity and may require patient-to-patient customization. Gene therapy in the form of allotopic expression has received the most attention for its potential as a robust method for reversing the symptoms of mitochondrial DNA (mtDNA) mutations. Synchronizing allotopic expression for the 13 mtDNA genes with the nuclear-mitochondrial transcription and translation machinery can overcome limitations in competing with pre-existing mutant proteins in the respiratory chain complexes due to heteroplasmy, a condition commonly observed in known mtDNA pathologies. Furthermore, advances in technologies capable of inserting large DNA cargos into the nuclear genome, such as safe harbor expression or mini chromosomes, will allow for testing multiple allotopic genes simultaneously. While validating the technology in vivo has its challenges due to inadequate animal models for all the protein coding genes, the ease of generating precise human iPSCs, particularly from patients with specific mtDNA mutations, may allow us to test these gene therapy approaches on a case-by-case basis in vitro.

One of the potential paths to regenerative therapies for the aging brain is to reprogram supporting cells to produce neurons that can then integrate into existing neural networks, a supplemental form of neurogenesis. One has to be a little cautious in reading new research on this topic, given that some past work has proven to be a dead end, the victim of difficulties in determining exactly what is going on inside the brain. Nonetheless, a number of different groups are pursuing a number of different possibilities; one might hope that at least one approach will bear fruit. The example here is at a comparatively early stage of discovery.

During development, mammalian stem cells readily proliferate to produce neurons throughout the brain and cells - called glia - that help support them. Glia help maintain optimal brain function by performing essential jobs like cleaning up waste and insulating nerve fibers. However, the mature brain largely loses that stem cell capacity. Only two small regenerative zones, or niches, remain in the adult brain, leaving it with extremely limited capacity to heal itself following injury or disease.

Looking for a way to spur this "multipotent" regeneration, researchers used a genetic engineering technique in adult mouse brains to induce astrocytes, a subset of glia, to produce different transcription factors, proteins pivotal for controlling cell identity. These experiments showed that a single transcription factor - a protein known as DLX2 - appeared to reprogram astrocytes into neural stem-like cells capable of producing neurons and multiple subtypes of glial cells.

The researchers confirmed these findings both using a technique called lineage tracing, in which they followed progeny of the altered astrocytes as they multiplied, as well as marker analysis that showed that these new cells had the expected identities of neurons or glia. Researchers suggest that DLX2 might someday be used as a tool to treat traumatic brain injuries, strokes, and degenerative conditions .

Link: https://www.utsouthwestern.edu/newsroom/articles/year-2022/single-protein-prompts-mature-brain-cells.html

Gene therapies delivering mRNA produce a temporary production of proteins. An RNA molecule acts as a blueprint for a ribosome to assemble many copies of a specific protein, but this doesn't last long, and a few days of protein expression from a single treatment is a reasonable expectation in practice. This make RNA therapies suitable to produce partial reprogramming in an animal or patient. The Yamanaka factors are delivered for a long enough period of time to rejuvenate epigenetic patterns and restore mitochondrial function, but (hopefully) not long enough to convert any meaningful number of somatic cells into induced pluripotent stem cells. The former outcome is desirable, while the latter outcome would damage tissue function and create the risk of cancer.

Induced pluripotent stem cells (iPSCs) reprogrammed from replicative senescing or centennial cells had restored the telomere and mitochondrial functions with a gene expression profile similar to embryonic stem cells (ESCs). This and other avenues of research confirm that cellular age can be reversed. These seminal results led the scientific community to ask whether cellular rejuvenation due to reprogramming could take place in vivo.

To answer this question, researchers generated transgenic mouse models, expressing Yamanaka factors (OSKM) under the control of doxycycline. Strikingly, they observed the emergence of teratomas in several organs, thus demonstrating the feasibility of in vivo reprogramming. However, to prevent deterioration related to aging or to rejuvenate the organism, it is important not to generate fully dedifferentiate cells, as this leads to a deterioration of the animal's health or tumor formation. Consequently, it was judicious to think to trigger the reprogramming process and stop it before obtaining pluripotent cells, hoping that it might erase cellular aging marks instead of favoring senescence. Researchers envisioned such a strategy and proposed a protocol to induce partial reprogramming in a homozygous progeria transgenic mouse model. They induced OSKM expression for 2 days per week during the lives of the animals with doxycycline and observed a significant increase in the lifespan of these animals, as well as the improvements in age-related hallmarks.

The use of strategies based on mRNA to express the factors needed for cell reprogramming has rapidly emerged as a promising technology to achieve the goal of partial reprogramming. Hence, in this review, after a brief revisiting of the state-of-the-art various technologies, we will focus on methods based on RNA that induce the conversion of somatic cells into pluripotent cells. We will frame these technological advances in the context of recent cutting-edge approaches to reverse age-related cell and tissue phenotypes by reprogramming them towards pluripotency.

Link: https://doi.org/10.3390/pharmaceutics14020317

Elastin is a vital component of the complex structure of the extracellular matrix in flexible, elastic tissues, such as skin and blood vessel walls. It is the extracellular matrix that determines physical tissue properties, such as strength, elasticity, and so forth. This structure becomes disarrayed with age for a variety of reasons: photoaging that breaks down molecules or encourages alterations; cross-linking between molecules that restricts their range of motion; changes in the behavior of cells that maintain the structure.

Today's open access paper looks at a different aspect of this issue. The researchers discuss what happens to the debris from elastin that is broken down, and how cells react to this signal of damage. Unfortunately, further harms resulting from initial damage are very much a characteristic of aging. It isn't just that molecules become broken, but cells then change their behavior as a result, often in maladaptive ways.

Restoration of the extracellular matrix in aged tissues is one of the areas of rejuvenation research in which there is little forward motion, and there are too many goals here for which there are, as of yet, no good, obvious approaches to therapy ready to move into preclinical development. Cross-links can in principle be broken, but only one biotech company is working on a plausible approach applicable to the whole body at present. Cells can be reprogrammed to more youthful function, but it is unclear as to whether that will result in improved maintenance of skin extracellular matrix in the context of damage and disarray that is not present in youth. Cells can be coerced into elastin deposition, such as via minoxidil use, but there are no good ways of doing this systemically that do not result in untenable side-effects. And so forth. More attention is needed in this part of the field.

The Elastin Receptor Complex: An Emerging Therapeutic Target Against Age-Related Vascular Diseases

Aging is accompanied by changes in vascular structure and function, especially in the large arteries. Due to their elasticity and resilience capacities, the concentric elastic lamellae of the aorta play a pivotal role in reducing the high systolic pressure at the outlet the heart. In other words, elastic lamellae stretch during cardiac ejection phases allowing the radius of the aorta to increase and to convert the pulsatile flow leaving the heart into a continuous flow in arteries. With age, these elastic lamellae exhibit wear characterized by zones of rupture. This leads to loss of elasticity and progressive hardening of the aorta and release of elastin-derived peptides (EDPs) in the circulating blood.

Elastic fibers fragmentation and release of elastin degradation products, also known as elastin-derived peptides (EDPs), are typical hallmarks of aged conduit arteries. Along with the direct consequences of elastin fragmentation on the mechanical properties of arteries, the release of EDPs has been shown to modulate the development and/or progression of diverse vascular and metabolic diseases including atherosclerosis, thrombosis, type 2 diabetes, and nonalcoholic steatohepatitis.

Most of the biological effects mediated by these bioactive peptides are due to a peculiar membrane receptor called elastin receptor complex (ERC). This heterotrimeric receptor contains a peripheral protein called elastin-binding protein, the protective protein/cathepsin A, and a transmembrane sialidase, the neuraminidase-1 (NEU1). In this review, after an introductive part on the consequences of aging on the vasculature and the release of EDPs, we describe the composition of the ERC, the signaling pathways triggered by this receptor, and the current pharmacological strategies targeting ERC activation.

Researchers are expanding their explorations of cellular reprogramming applied to living animals, delivering Yamanaka factors as a gene therapy. There are in principle ways to balance this sort of approach in order to minimize the conversion of somatic cells into induced pluripotent stem cells, and thus the risk of cancer, while maximizing the epigenetic rejuvenation and restoration of mitochondrial function that occurs as an early part of the reprogramming process.

Forcing cells in aged tissues to act as though they are present in youthful tissues is expected to produce meaningful benefits to health, and indeed has done so in some animal studies. It cannot fix issues related to metabolic waste that cannot be cleared effectively by even a young physiology, or issues related to stochastic DNA damage, but the hope is that the issues of aging that reprogramming can effectively address will make this a useful approach to the treatment of aging as a medical condition.

In 2016, researchers reported for the first time that they could use the Yamanaka factors to counter the signs of aging and increase life span in mice with a premature aging disease. More recently, the team found that, even in young mice, the Yamanaka factors can accelerate muscle regeneration. Following these initial observations, other scientists have used the same approach to improve the function of other tissues like the heart, brain, and optic nerve, which is involved in vision.

In the new study, researchers tested variations of the cellular rejuvenation approach in healthy animals as they aged. One group of mice received regular doses of the Yamanaka factors from the time they were 15 months old until 22 months, approximately equivalent to age 50 through 70 in humans. Another group was treated from 12 through 22 months, approximately age 35 to 70 in humans. And a third group was treated for just one month at age 25 months, similar to age 80 in humans. "What we really wanted to establish was that using this approach for a longer time span is safe. Indeed, we did not see any negative effects on the health, behavior, or body weight of these animals."

When the researchers looked at normal signs of aging in the animals that had undergone the treatment, they found that the mice, in many ways, resembled younger animals. In both the kidneys and skin, the epigenetics of treated animals more closely resembled epigenetic patterns seen in younger animals. When injured, the skin cells of treated animals had a greater ability to proliferate and were less likely to form permanent scars - older animals usually show less skin cell proliferation and more scarring. Moreover, metabolic molecules in the blood of treated animals did not show normal age-related changes.

This youthfulness was observed in the animals treated for seven or 10 months with the Yamanaka factors, but not the animals treated for just one month. What's more, when the treated animals were analyzed midway through their treatment, the effects were not yet as evident. This suggests that the treatment is not simply pausing aging, but actively turning it backwards - although more research is needed to differentiate between the two.

Link: https://www.salk.edu/news-release/cellular-rejuvenation-therapy-safely-reverses-signs-of-aging-in-mice/

Therapies capable of reducing systemic inflammation are at present quite blunt, largely interfering in signaling that is needed for necessary short-term inflammation as well as that involved in excessive, unresolved inflammation. This has negative effects on immune function, leading to vulnerability to pathogens, for example. There is the hope that targeting the function of inflammasomes, protein complexes involved in the mechanisms of the immune response, will prove to be somewhat more selective for unwanted inflammation. This is likely not the final destination for the desired goal of only eliminating excess inflammation, however.

Aging is a significant risk factor for the development of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Inflammation also plays a role in the development of neurodegenerative diseases. Inflammaging, a low level of chronic inflammation that occurs due to old age, is a normal part of the aging process. It has been shown that the inflammasome contributes to age-related inflammation and development of neurodegenerative diseases. Thus, the inflammasome is a potential therapeutic target to ameliorate inflammaging and to prevent and/or treat neurodegenerative diseases.

In this study, we show the anti-inflammatory effects of anti-ASC, a monoclonal antibody against ASC, in the cortex of aged mice. We found that protein levels of IL-1β, ASC, caspase-1, and NLRP1 were significantly elevated in the cortex of aged mice and that anti-ASC treatment inhibits the protein levels of these inflammasome signaling proteins. ASC speck formation was examined and protein levels of ASC specks were increased in old age and anti-ASC inhibits the formation of ASC specks. Moreover, we investigated the protein levels of the non-canonical inflammasome proteins caspase-8 and caspase-11. We found that caspase-8 was also elevated in the cortex of aged mice and that anti-ASC decreased the protein levels of this protein. However, we did not see any significant differences between young and aged mice in the protein levels of caspase-11.

Together, these results indicate that a novel NLRP1-caspase-8 non-canonical inflammasome is present in the cortex of mice and that anti-ASC is a potential therapeutic to decrease inflammasome-mediated inflammaging in the central nervous system.

Link: https://doi.org/10.3389/fnmol.2022.774014

The cryonics industry, and cryopreservation as a technological capability, are important. Very important. The absence of a truly large scale cryonics industry means that more than a billion lives are lost permanently every two decades; intelligent, thinking, feeling minds vanishing into the abyss of non-existence in vast numbers. The world is that way, but it doesn't have to be. Given a better, more rational history of technological progress and patient advocacy, we could now be living in a world in which the funds presently spent on funerary arrangements and monuments would instead go towards the cryopreservation of the recently dead, allowing them a chance at renewed life in a future era.

At some point in the future, relentless technological progress will lead to the means to revive vitrified individuals, and provide them with restored bodies, for costs that are trivial compared to the vast wealth possessed by a society that has mastered those and countless other abilities. The mind is an arrangement of atoms. The body also. Increasingly fine control over arrangement of atoms is well understood to be the long-term future of human technology. In addition to all of the other dreams realized by mature molecular nanotechnology, it will allow for restoration of vitrified minds to life and the construction of new bodies, biological or otherwise, from feedstock. Storage at liquid nitrogen temperatures, with the structure of the mind intact, allows clinically dead individuals to wait indefinitely for that time.

Unfortunately, cryonics has remained a persistently fringe industry since its inception in the 1960s, supported by a few philanthropists and a small community of activists, researchers, and advocates. Across a span of decades in which more than two billion people have died, only a few hundred have both had the opportunity and made the choice to be cryopreserved. An admirable amount of progress has been made in improving the quality of cryopreservation procedures and storage facilities by the primary organizations, given the little funding available, but it is still far too little, achieved far too slowly.

Like the cryonics industry, the rejuvenation industry was once a small, fringe concern. Yet it has now become an accepted young industry, passing the point at which it rapidly achieved acceptance and interest, growing to billions of dollars in high profile funding over the last decade. What could bring cryonics to the same sort of growth and expansion enjoyed by the rejuvenation industry? I would argue that this sort of progress is derived entirely from proof of technological capabilities. That the growth in rejuvenation derives initially from single gene alterations that extend life in short-lived laboratory species, but to a much greater degree from the widespread demonstrations of rejuvenation in mice produced by senolytic drugs.

In my view of the world, technology determines society. Technological capabilities are the greatest of the influences that shape the world we live in, our lives. More importantly, there will be only limited support at best for any field for which there are few or no established proofs of concept. The best that any of us could do to accelerate the growth of the cryonics industry, and support for cryonics as a field of human endeavor, with the goal of saving as many lives as possible, as soon as possible, is thus to produce proof of concept studies, technology demonstrations, technological capabilities. The rest will follow. Not out of the blue, and not without a great deal of work on the part of the community and particularly the staff at the cryonics provider organizations, but it will inevitably happen after that point is reached.

At the top of the list and probably the capability that will do the most to advance cryonics is reversible vitrification of organs. The broader research community is close to achieving this goal in a practical fashion, which would mean making at least one of the various approaches reliable enough to build a company, and then introducing this technology into the organ transplant industry. The logistics of organ transplantation would become much less challenging given the ability to indefinitely store tissues in a state of vitrification, with minimal resulting harm. Those same benefits will apply to xenotransplantation and engineering of universal or patient-matched organs to order. It is exactly the fact that there is such a large, obvious market for this capability that puts it at the top of the list. When it is evident that a heart can be vitrified, thawed, and transplanted, then it becomes that much less of a leap to consider the merits of the vitrification of people at the end of life.

Another set of capabilities revolve around (a) quality of cryopreservation, and (b) determining the quality of a cryopreservation via scanning technologies rather than dissection and inspection. The quality of cryopreservation is in turn a field of research that, beyond mechanical questions of perfusion and fraction, operates at the cutting edge of neuroscience: where is the mind stored; how do we best determine whether those nanoscale structures are preserved; and is that even possible without physical access to the brain? This is an area of research of great interest to cryonics organizations, but is one of those in which they are most resource constrained. It isn't cheap to work with large mammals and imaging. Given a potential improvement to cryopreservation protocols, one can in principle run large mammal studies, say in pigs, and dissect the brain to determine quality of preservation. But that is less convincing than being able to show that a cryopreserved patient is in optimal condition.

The one technological capability that many feel is required for cryonics to ever become close to mainstream, where mainstream means, let's say, 1% of the population is signed up, is of course the revival of a vitrified individual. I feel that even setting aside the question of repair of aging or replacement of tissues, for the sake of argument let us say we're talking about a healthy young individual, then this ability still lies far in the future. It is a tough challenge, and cryonics will have to prosper without that demonstration. Which is why it is important to go through the list of other incremental steps towards that goal, those that could in principle be achieved with a reasonable level of funding and support.

It is well known that gene expression becomes disarrayed in cells in old tissues. Mechanisms controlling the structure of nuclear DNA become dysfunctional, and that can unleash all sorts of errant protein production by allowing the machinery of gene expression to reach sections of the genome that are normally folded away and inaccessible. Recent work suggests that cycles of DNA double strand break repair may be close to the root of the cause of this, but it is undoubtedly far from simple as a process. Impaired gene expression control likely results in a feedback loop causing further impairment in gene expression control. Increased activity of transposons is one consequence of a failure to repress expression across the genome. There will be countless others.

The interesting question is the degree to which this matters in comparison to other mechanisms of aging. That is a hard question to answer. It is easier to identify and explore a specific mechanisms than it is to correct it in isolation of all other aspects of cellular biochemistry, and thus gain some insight into how much damage it causes. Very few mechanisms of aging can be corrected in that way, and specific portions of the age-related disarray of gene expression are not yet in that list. Still, researchers here make a good effort to connect disarray in gene expression with the mechanisms of cellular senescence and inflammatory signaling in aging, where the research community does have a better grasp on the likely relative importance to aging.

Cellular aging is characterized by disruption of the nuclear lamina and its associated heterochromatin. How these structural changes within the nucleus contribute to age-related degeneration of the organism is unclear. Genes lacking CpG islands (CGI- genes) generally associate with heterochromatin when they are inactive. Here, we show that the expression of these genes is globally activated in aged cells and tissues.

We show that in humans and mouse models, global up-regulation of CGI- gene expression is a hallmark of normal and pathological aging. CGI- gene misexpression plays a central role in age-associated degenerative changes by penetrating and interconnecting previously established hallmarks of aging: disruption of nuclear architecture and epigenetic alterations in aged or senescent cells are tightly associated with CGI- gene up-regulation, which, in turn, disturbs intercellular communication. Moreover, CGI- gene misexpression provides insights into the underlying molecular mechanisms of various phenomena observed in aged cells, including global loss of functional identity and increased transcriptional noise.

In particular, a large fraction of the misexpressed CGI- genes encode secreted proteins, many of which are associated with the senescence-associated secretory phenotype (SASP); aged kidneys and hearts from diversity outbred mice, mouse models with disrupted nuclear architectures, and progeria and senescent cells express proinflammatory secretory CGI- genes, and most proteins whose levels increase in aged plasma are encoded by CGI- genes. Together, our findings suggest that disorganization of the nuclear periphery in aged cells results in misexpression of CGI- genes that are a direct source of systemic inflammatory mediators associated with aging.

Link: https://doi.org/10.1126/sciadv.abj9111

Researchers here report on their identification of a novel form of protein aggregate in the aging human brain, involving altered TMEM106B, associated with multiple types of neurodegenerative condition. It is far too early to talk about how greatly this dysfunction contributes to specific conditions, versus other, better characterized mechanisms. Determining whether it is important or a curiosity will be the work of years yet. The pace at which novel mechanisms such as this are discovered might give us some insight into how much more there is to be discovered in the biochemistry of the aging brain. TDP-43, another protein capable of aggregating, is also discussed in this paper, and it is worth noting that the relevance of TDP-43 to neurodegeneration is also a comparatively recent discovery.

Neurodegenerative proteinopathies are characterized by the deposition of filamentous protein aggregates in neurons and/or glia. The transactive response DNA-binding protein-43 (TDP-43), the microtubule-associated phosphoprotein tau, and α-synuclein protein can each misfold and accrue intracellularly into tangled filamentous inclusions manifesting in neurodegenerative diseases known collectively as TDP-43 proteinopathies, tauopathies, and synucleinopathies, respectively. The structures of TDP-43 and tau filaments in frontotemporal lobar degeneration (FTLD) and α-synuclein fibrils in multiple system atrophy (MSA) have recently been reported. What has emerged from these studies is that each disease has a homotypic molecular fold, or conformer, characteristic of the underlying neuropathology. The evidence for the "one conformer per disease" paradigm is growing, with the presence of unknown buried cofactors mediating the structural diversity of fibrillar polymorphs.

Here, using a combination of cryoelectron microscopy (cryo-EM) and mass spectrometry (MS), we show that a previously unsolved amyloid fibril found in cases representing a variety of neurodegenerative conditions is composed of a 135 amino acid C-terminal fragment of TMEM106B, a known risk gene for FTLD-TDP and aging. The fibrillization of TMEM106B into identical fibrillar structures in a wide range of sporadic or genetic TDP-43 proteinopathies (FTLD-TDP), a tauopathy (progressive supranuclear palsy), and a synucleinopathy (dementia with Lewy bodies) points toward a commonality between these diverse neurodegenerative diseases. This suggests that the formation of amyloid fibrils composed of TMEM106B, a lysosomal/endosomal protein, may contribute to pathogenicity via a loss or gain of function.

Link: https://doi.org/10.1016/j.cell.2022.02.026

Today's open access review discusses the growing burden of cellular senescence with age in the context of brain tissue and neurodegenerative disease. Cells become senescent constantly throughout life, largely the result of ordinary somatic cells hitting the Hayflick limit on replication, but also, and increasingly with age, due to a stressful, damaging, inflammatory environment. Senescent cells serve a useful purpose when present for the short term, in the context of wound healing or cancer suppression for example, by rousing the immune system into action and changing the behavior of nearby cells. But the signaling of senescent cells becomes very harmful to tissue function when sustained for the long term.

Unfortunately, this long term inflammatory signaling by senescent cells is exactly what happens in later life. The pace of creation picks up and the pace of clearance of senescent cells, via programmed cell death or via immune system activities, declines. The result is a growing imbalance and increased burden of senescent cells in tissues throughout the body. In recent years ever more evidence points to a meaningful role for senescent cells in the brain, particularly microglia and astrocytes. Chronic inflammation in brain tissue is strongly implicated in the progression of neurodegenerative conditions, and it is becoming clear that senescent cells are likely a major contributing cause of that inflammation.

Clearance of senescent cells using first generation senolytic therapies, at least those capable of passing the blood-brain barrier to enter the brain, has shown promising results in animal models of Alzheimer's disease, and a clinical trial of the same therapeutics in Alzheimer's patients is getting underway. It will be some years before we know in certainty that senolytic treatments are a good approach to Alzheimer's disease, but it seems plausible.

Aging, Cellular Senescence, and Alzheimer's Disease

Alzheimer's disease (AD) is an aging-related neurodegenerative disease and a major cause of dementia in the elderly. It is estimated that the incidence of AD doubles every 5 years after age 65, and 50% of the population aged 85 or older suffer from AD. Therefore, aging is considered the greatest risk factor for AD, although the mechanism underlying the aging-related susceptibility to AD is unknown. Evidence from both human and animal studies indicates that cellular senescence plays a critical role in the development of many aging-related diseases, including AD.

Senile plaques, which are extracellular deposits of β-amyloid (Aβ) peptides, and neurofibrillary tangles (NFTs), which are intracellular accumulation/deposition of hyperphosphorylated tau proteins, are two neuropathological features of AD. Although it is still debatable whether and how Aβ and hyperphosphorylated tau lead to neurodegeneration, a foundation of memory loss in AD, accumulating evidence indicates that both Aβ and tau pathologies are potent inducers of cellular senescence.

Senescent cells have been detected in the brain of AD patients and AD model mice that overexpress Aβ or tau protein. Removal of senescent cells pharmacologically and genetically reduced brain Aβ load and tauopathy and improved memory in these AD model mice. These data strongly suggest that cell senescence mediates Aβ- and tauopathy-induced neuropathophysiology in AD. These data also suggest that cell senescence promotes Aβ and tau pathologies. Elucidation of the mechanisms underlying brain cell senescence during aging and in AD, as well as the mechanism by which senescent cells contribute to neurodegeneration in AD, will be key to the development of strategies for the prevention and treatment of this devastating disease.

There is a growing interest in the role of transposable elements, or transposons, in degenerative aging. Transposons are sequences in the genome capable of abusing genomic machinery in order to replicate themselves, thought to be the remnants of ancient viral activity. Their activity is repressed in youth, but those repression mechanisms are degraded by aging, as is true for near all systems in our cells. Rising transposon activity may contribute to dysfunction in all of the ways we might expect for genomic disruption, altering gene expression in cells throughout the body. Thus ways to prevent transposon activity are presently under investigation.

Transposable elements, also called transposons, are genetic parasites found in all animal genomes. Normally, transposons are compacted away in silent chromatin in young animals. But, as animals age and transposon-silencing defense mechanisms break down, transposon RNAs accumulate to significant levels in old animals like fruit flies. An open question is whether the increased levels of transposon RNAs in older animals also correspond to increased genomic copies of transposons.

This study approached this question by sequencing the whole genomes of young and old wild-type and mutant flies lacking a functional RNA interference (RNAi) pathway, which naturally silences transposon RNAs. Although the wild-type flies with intact RNAi activity had little new accumulation of transposon copies, the sequencing approach was able to detect several transposon accumulation occurrences in some RNAi mutants. In addition, we found that some fly transposon families can also accumulate as extra-chromosomal circular DNA copies.

Lastly, we showed that genetically augmenting the expression of RNAi factors can counteract the rising transposon RNA levels in aging and promote longevity. We show that knocking down PAF1, a conserved transcription elongation factor that antagonizes RNAi pathways, may bolster suppression of TEs during aging and extend lifespan. Our study suggests that in addition to a possible influence by different genetic backgrounds, small RNA and RNAi mechanisms may mitigate genomic transposon expansion despite the increase in transposon RNA transcripts during aging.

Link: https://doi.org/10.1371/journal.pgen.1010024

The most commonly used animal models in aging research are nematode worms, flies, and mice. The ubiquitous use of animal models for discovery of mechanisms of aging and assessment of therapies to potentially slow or reverse aging is a matter of economics. It is more cost effective to carry out studies in lower animals with short life spans, even given the sizable fraction of discoveries that turn out to be inapplicable to longer-lived mammals, or even outright misleading. A fair amount of effort goes towards improving the cost-effectiveness of short-lived model organisms in this regard. A number of groups explore the use species that fall outside the usual set, such as daphnia, a class of small aquatic crustaceans.

There is a vast body of literature where people claim that certain drugs, diets, or regimens extend the lives of model organisms such as ants, worms, flies, fish, or mice. People perform an intervention, measure how long the animals live, get an extension of median life of 10, 15, or 20 percent, and publish a paper. There are several problems with this approach. One problem is that papers - even those on the same species - often use different controls, making it impossible to compare results. We're lacking nice, standardized data about life span across laboratories and across organisms.

My colleagues and I realized that we need a standardized, scalable system we can use to test how drugs, diets, and other interventions affect behavior, reaction to stimuli, and additional measures of health span. We started developing a system using Daphnia magna, a species of water flea that has been used in toxicology and environmental research for decades, but hasn't been used to study aging.

What's so great about Daphnia? The species has a life span of one month, and even though it's an invertebrate, it is a complex organism. It is beautifully transparent, with a beating, two-chambered heart, an innate immune system, eyes, a brain, and muscle tissue. In fact, when we use electron microscopy to zoom in on the cells of Daphnia, we see that the neurons and muscle cells look very similar to human neurons and muscle cells. Daphnia is also extremely sensitive to small concentrations of drugs.

Our recent paper is establishing the baseline for Daphnia as a new model organism for studying aging. We describe the system in detail, including how we set up the tank, fed the animals, removed new offspring, and set the light cycles and temperature. These appear to be boring details, but the whole point is getting the boring details right. We are developing a set of routines that are needed to raise Daphnia in a standardized way that is also scalable.

Link: https://hms.harvard.edu/news/age-old-problem

One of the important areas of cancer research and development that appears to receive a great deal of attention and funding, but in practice seems slow to make it from the laboratory to the clinic, is the targeting of therapeutics to cancerous cells. Reductio ad absurdum, near any of dozens of existing chemotherapeutics would do the job of completely clearing tumors, with minimal to no side-effects, if one could only find a way to delivery tiny amounts of the therapeutic to every cancer cell while avoiding every healthy cell. The inability to target treatments this effectively is exactly why cancer remains such a problem. Killing cells is easy. Killing only the desired cells is hard.

Today's research materials provide an example of this principle. Tumors compromise the immune system, and many of the more recent cancer therapies involve delivery of signals to rouse otherwise suppressed immune cells to unfettered aggression. This is a double-edged sword: an aggressive immune system is capable not only of attacking the cancer, but also of causing a great deal of harm to the patient in the worse cases. Still, this balance of benefit and harm is largely a better one for patients than is the case for chemotherapy. Why not make this delivery of immune-modulating signals much more targeted, however? As it turns out, this greatly improves the therapy.

'Drug factory' implants eliminate ovarian, colorectal cancer in mice

The researchers used implantable "drug factories" the size of a pinhead to deliver continuous, high doses of interleukin-2, a natural compound that activates white blood cells to fight cancer. The drug-producing beads can be implanted with minimally invasive surgery. Each contains cells engineered to produce interleukin-2 that are encased in a protective shell.

Interleukin-2 is a cytokine, a protein the immune system uses to recognize and fight disease. It is an FDA-approved cancer treatment, but the drug factories provoke a stronger immune response than existing interleukin-2 treatment regimens because the beads deliver higher concentrations of the protein directly to tumors. "Once we determined the correct dose - how many factories we needed - we were able to eradicate tumors in 100% of animals with ovarian cancer and in seven of eight animals with colorectal cancer. If you gave the same concentration of the protein through an IV pump, it would be extremely toxic. With the drug factories, the concentration we see elsewhere in the body, away from the tumor site, is actually lower than what patients have to tolerate with IV treatments. The high concentration is only at the tumor site."

Clinically translatable cytokine delivery platform for eradication of intraperitoneal tumors

Proinflammatory cytokines have been approved by the Food and Drug Administration for the treatment of metastatic melanoma and renal carcinoma. However, effective cytokine therapy requires high-dose infusions that can result in antidrug antibodies and/or systemic side effects that limit long-term benefits. To overcome these limitations, we developed a clinically translatable cytokine delivery platform composed of polymer-encapsulated human ARPE-19 (RPE) cells that produce natural cytokines.

Tumor-adjacent administration of these capsules demonstrated predictable dose modulation with spatial and temporal control and enabled peritoneal cancer immunotherapy without systemic toxicities. Interleukin-2 (IL2)-producing cytokine factory treatment eradicated peritoneal tumors in ovarian and colorectal mouse models. Furthermore, computational pharmacokinetic modeling predicts clinical translatability to humans. Notably, this platform elicited T cell responses in non-human primates, consistent with reported biomarkers of treatment efficacy without toxicity. Combined, our findings demonstrate the safety and efficacy of IL2 cytokine factories in preclinical animal models and provide rationale for future clinical testing in humans.

Researchers here report on the effects of low dose chloroquine on aged tissues in rats. It is not all positive, but the balance of benefits and harms still leads to modest extension of life span. The effects may include suppression of cellular senescence to some degree, but it isn't clear that this is the major driver of benefits. In the wake of deaths during the period in which chloroquine was discussed as a potential treatment for COVID-19, it is worth noting that this is not a safe drug and is to be avoided at higher doses. Chloroquine has a narrow therapeutic window for its originally intended uses, and going over that range will have unpleasant and potentially fatal consequences.

To examine the systemic effects of chloroquine (CQ) in vivo, we treated 24-month-old Sprague Dawley (SD) male rats with CQ twice a week for 5 months at a low dose of 0.1 mg/kg orally by water to avoid potential side effects. Low-dose CQ administration extended the lifespan of rats by approximately 6% in terms of median longevity and by about 13% in terms of maximum longevity. CQ-treated rats also tended to have decreased serum TNF-α levels and reduced the numbers of circulating white blood cells (WBC) and neutrophils (NEU) in old rats, suggestive of attenuated chronic inflammation.

In this study, we found that low concentrations of CQ alleviated stem cell senescence, repressed tissue fibrosis, and extended lifespan. Multi-tissue transcriptomic inspection demonstrated that CQ may have both beneficial and detrimental effects on aged animals in a tissue-specific manner. By surveying the transcriptomic landscape of CQ-treated tissues, we found that low-dose CQ treatment attenuated age-associated gene expression across tissues. The strongest effect was observed in the kidney where we found decreased levels of interferon-stimulated responsive element (ISRE)-containing genes and increased expression of transporter encoding genes. However, CQ also augmented pro-aging transcriptional signatures, which may elicit potential cardiac toxicity without detectable functional impairment during the duration of the experiment.

The role of CQ in counteracting aging may be linked to its ability to inhibit chronic inflammation systematically and alleviate fibrosis. Consistent with our observations, CQ reduces inflammation and effectively decreases the salivary and serum levels of IL-6, a key component of the senescence-associated secretory phenotype (SASP). In summary, our results demonstrate a geroprotective role of low-dose CQ on physiologically aged rats.

Link: https://doi.org/10.1007/s13238-021-00903-1

Age-related mitochondrial dysfunction is particularly relevant to the progression of neurodegenerative conditions, as the brain is an energy-hungry organ. Mitochondria provide the chemical energy store molecules needed to power cellular operations, but their function declines with age throughout the body. Cells change their behavior for the worse as a consequence. Some part of this involves characteristic age-related changes in the expression of proteins necessary for mitochondrial function, another part is damage to mitochondrial DNA, such as via oxidative reactions that become more common in aged tissues, leading to loss of production of necessary proteins and detrimental alterations to mitochondrial behavior. Approaches, such as mitochondrial transplantation, that might at least temporarily restore mitochondrial function in old people should be a high priority for the longevity industry.

Many neurodegenerative disorders, including Alzheimer's disease (AD), are strongly associated with the accumulation of oxidative damage. Transgenic animal models are commonly used to elucidate the pathogenic mechanism of AD. Beta amyloid (Aβ) and tau hyperphosphorylation are very famous hallmarks of AD and well-studied, but the relationship between mitochondrial dysfunction and the onset and progression of AD requires further elucidation.

In this study we used transgenic mice (the strain name is 5xFAD) at three different ages (3, 6, and 20 months old) as an AD model. Cognitive impairment in AD mice occurred in an age-dependent manner. Aβ1-40 expression significantly increased in an age-dependent manner in all brain regions with or without AD, and Aβ1-42 expression in the hippocampus increased at a young age. In a Western blot analysis using isolated mitochondria from three brain regions (cerebral cortex, cerebellum, and hippocampus), NMNAT-3 expression in the hippocampi of aged AD mice was significantly lower than that of young AD mice. SOD-2 expression in the hippocampi of AD mice was lower than for the age-matched controls. However, 3-NT expression in the hippocampi of AD mice was higher than for the age-matched controls. NQO-1 expression in the cerebral cortex of AD mice was higher than for the age-matched controls at every age that we examined. However, hippocampal NQO-1 expression in 6-month-old AD mice was significantly lower than in 3-month-old AD mice.

These results indicate that oxidative stress in the hippocampi of AD mice is high compared to other brain regions and may induce mitochondrial dysfunction via oxidative damage. Protection of mitochondria from oxidative damage may be important to maintain cognitive function.

Link: https://doi.org/10.3390/biomedicines10020281

Chronic inflammation is a potent mechanism in aging, disruptive of tissue function throughout the body. The focus in today's open access paper is on the effects of inflammatory signaling in blood vessel walls, particularly on the endothelial cells that play a role in maintaining the ability of blood vessels to contract and dilate. Dysfunction in blood vessels throughout the body causes harms ranging from hypertension to blood-brain barrier leakage to reduced blood flow that impacts the function of muscle and brain tissue.

Approaches to suppressing inflammatory signaling developed and brought to the clinic have to date taken the form of blunt blockades of important signaling molecules, such as TGF-α, or core processes in immune cell function, such as antigen presentation. Unfortunately, this causes as many problems over the long-term as it brings benefits in cases of inflammatory disease. Short-term inflammation is critical to the function of the immune system in its roles in defending against pathogens, tissue maintenance, and regeneration from injury. But therapies do not well distinguish between good inflammation and bad inflammation, suppressing both.

There is the hope that approaches targeting the NLRP3 inflammasome and related biochemistry will prove to be at least incrementally more selective, as discussed here, but it is likely that realization of the goal of effective, minimally harmful inhibitors of chronic inflammation lies still further in the future.

Pharmacological Blockade of NLRP3 Inflammasome/IL-1β-Positive Loop Mitigates Endothelial Cell Senescence and Dysfunction

Vascular aging is a multifaceted and complex process that ultimately renders the vessels prone to profound functional and structural disturbances that favor cardiovascular disease. One of the main mechanisms contributing to vascular aging is endothelial cell senescence. Senescent cells undergo functional and morphological changes that ultimately lead to growth arrest while remaining metabolically active. Importantly, these cells acquire a senescence-associated secretory phenotype (SASP), which results in the over-production and release of a wide array of cytokines and chemokines. The SASP favors leukocyte recruitment and is considered a main driver of sterile age-related inflammation or "inflammaging". Functionally, endothelial cell senescence is tightly associated with endothelial dysfunction and defective vasodilatation, considered as early markers of vascular disease and atherosclerosis.

In the present study, we have evaluated whether a positive feedback of IL-1β in the NLRP3 inflammasome via NF-κB could promote human endothelial senescence in vitro and murine endothelial dysfunction in vivo. Our results indicate that the NLRP3 inflammasome is pivotal in mediating the detrimental effects of IL-1β, showing that auto-activation is a crucial feature boosting endothelial cell senescence in vitro, which is paralleled by vascular dysfunction in vivo. Hence, the inhibitor of NLRP3 inflammasome assembly, MCC 950, was able to disrupt the aforementioned positive loop, thus alleviating inflammation, cell senescence and vascular dysfunction.

Besides, we explored alternative NLRP3 inflammasome inhibitory agents such as the RAS heptapeptide Ang-(1-7) and the anti-aging protein klotho, both of which demonstrated protective effects in vitro and in vivo. Altogether, our results highlight a fundamental role for the hereby described NLRP3 inflammasome/IL-1β positive feedback loop in stress-induced inflammaging and the associated vascular dysfunction, additionally providing evidence of a potential therapeutic use of MCC 950, Ang-(1-7) and recombinant klotho to block this loop and its deleterious effects.

Past studies have demonstrated reduced mortality as a result of strength training in older individuals. Muscle tissue is metabolically active, involved in a range of processes in the body, such as insulin metabolism and control of inflammation. Here this review paper, researchers note the correlation between activities that strengthen muscle and lower mortality in epidemiological data. It is worth thinking about for those of us tempted to let the exercise schedule lapse as life moves on.

Physical inactivity is a global public health problem. Regular engagement in muscle-strengthening activities (eg, resistance training) increases or preserves skeletal muscle strength, which has been shown to be inversely associated with mortality and the risk of non-communicable diseases (NCDs) such as cardiovascular disease (CVD) and cancer. Therefore, promoting muscle-strengthening activities may help in reducing the risk of premature death and NCDs.

Compared with aerobic activities, muscle-strengthening activities have been less frequently investigated in terms of their influence on the prevention of premature death and NCDs. Although these findings suggested a favourable influence of muscle-strengthening activities on the risk of NCDs and mortality, the dose-response association was not quantified. We therefore conducted a systematic review and meta-analysis of prospective cohort studies on muscle-strengthening activities and the risk of mortality and NCDs among adults aged ≥18 years. In addition to examining the health benefits of engaging in muscle-strengthening activities compared with the absence of muscle-strengthening activities independent of aerobic activities, we quantified the dose-response association between muscle-strengthening activities and health outcomes.

Sixteen studies met the eligibility criteria. Muscle-strengthening activities were associated with a 10-17% lower risk of all-cause mortality, cardiovascular disease (CVD), total cancer, diabetes, and lung cancer. No association was found between muscle-strengthening activities and the risk of some site-specific cancers (colon, kidney, bladder, and pancreatic cancers). J-shaped associations with the maximum risk reduction (approximately 10-20%) at approximately 30-60 min/week of muscle-strengthening activities were found for all-cause mortality, CVD, and total cancer, whereas an L-shaped association showing a large risk reduction at up to 60 min/week of muscle-strengthening activities was observed for diabetes. Combined muscle-strengthening and aerobic activities (versus none) were associated with a lower risk of all-cause, CVD, and total cancer mortality.

Link: https://doi.org/10.1136/bjsports-2021-105061

Nicotinamide adenine dinucleotide (NAD) is a component of mitochondrial function in cells, and its decline with age is thought to be involved in loss of mitochondrial function. Researchers here note results from an animal study of injected nicotinamide riboside, a vitamin B3 derivative. It increased NAD+ levels, as one would expect, but does not improve measures of function related to muscle tissue. In the broader context, trials of ways to upregulate NAD+ have had mixed results, while the various vitamin B3 based approaches to increase NAD+ levels in aged tissues do not generally do as well at producing this outcome as structured exercise programs.

We designed this study to determine whether stably elevated NAD+ levels in skeletal muscle would affect insulin sensitivity or mitochondrial function in mice fed a Western diet and whether pterostilbene (PT) would interact with nicotinamide riboside (NR) on these readouts. To accomplish this, mice received daily NR injections intravenously to bypass intestinal degradation and first-pass metabolism in the liver and make NR directly available to peripheral tissues such as skeletal muscle. PT was given through the diet, owing to its insolubility in water. We successfully increased NAD+ levels not only in skeletal muscle but also inguinal white adipose tissue (iWAT). This was not simply an acute effect around the time of the injection, but rather a sustained increase throughout the intervention period. In contrast, NAD+ levels in liver were unchanged by NR at this timepoint, which could be a result of the higher NAD+ turnover in this tissue.

In clinical trials, oral supplementation with nicotinamide riboside (NR) fails to increase muscle mitochondrial respiratory capacity and insulin sensitivity but also does not increase muscle NAD+ levels. This study tests the feasibility of chronically elevating skeletal muscle NAD+ in mice and investigates the putative effects on mitochondrial respiratory capacity, insulin sensitivity, and gene expression. The metabolic effects of NR and PT treatment were modest. We conclude that the chronic elevation of skeletal muscle NAD+ by the intravenous injection of NR is possible but does not affect muscle respiratory capacity or insulin sensitivity in either sedentary or physically active mice. Our data have implications for NAD+ precursor supplementation regimens.

Link: https://doi.org/10.1016/j.isci.2022.103863

There is plenty of evidence for particulate air pollution to have a negative effect on long-term health, particularly those derived from Asian populations that are exposed to more coal and wood smoke than tends to be the case in the US and Western Europe. While the relative importance of the various mechanisms involved are up for debate, the most plausible are those involving raised inflammation as a result of interactions between particles and lung tissue. The chronic inflammation of aging drives near all age-related conditions, and more inflammation means more dysfunction.

As researchers note here, not all particulate air pollution is equal. It is reasonable to expect some types of particle to be worse than others, and that is what is found by mining data on health and pollution in a region of the US. This is focused on the Northeast, and one might consider comparing this with another interesting analysis of long-term US data on health and air pollution, that one covering the Puget Sound region. Both studies focused on the link to age-related neurodegeneration, a set of conditions strongly correlated with inflammation.

Long-term effects of PM2.5 components on incident dementia in the northeastern United States

Fine particulate matter (PM2.5) is an important air pollutant worldwide. Exposure to PM2.5 has been associated with adverse health effects, including cardiovascular disease, respiratory disease, lung cancer, and premature mortality. Several studies also suggest that long-term PM2.5 exposure is a risk factor for neurodegenerative diseases. Studies suggest that PM2.5 has the potential to induce dementia through biological mechanisms such as systemic inflammation, oxidative stress, and neuroinflammation. In addition, some evidence indicates that PM2.5 can exacerbate or accelerate existing diseases via these biological pathways.

A growing body of epidemiological evidence suggests that particulate air pollution contributes to dementia, including several longitudinal studies conducted in the United States and around the world. The majority of these studies found positive associations between PM2.5 and dementia. A systematic review and meta-analysis also concluded that exposure to PM2.5 is associated with a 16% higher risk of dementia per 10 μg/m3 increase in PM2.5 concentration.

However, previous studies have almost exclusively focused on the effects of PM2.5 mass concentrations. As a complex mixture, the toxic effects of PM2.5 may be determined primarily by its chemical components. PM2.5 components, such as organic matter (OM), inorganic nitrate (NO3-), inorganic sulfate (SO42-), black carbon (BC), soil particles (SOILs), and sea salt (SS), emitted from specific sources, have different physicochemical and toxicological characteristics, resulting in various health effects. To fill these knowledge gaps, we conducted a population-based cohort study of the Medicare dataset and a well-validated high-resolution (1 km × 1 km) PM2.5 components dataset from 2000-2017. The latter includes data on OM, NO3-, SO42-, BC, SOILs, and SS in the northeastern United States, where better exposure estimates exist.

We identified dementia diagnoses from patients' hospital and medical insurance records and carried out Cox proportional hazards regression to investigate their association with PM2.5 components. Among ∼2 million participants, 15.1% developed dementia. From the single-pollutant models, hazard ratios per interquartile range increase were 1.10 for black carbon, 1.08 for inorganic nitrate, 1.03 for organic matter, 1.13 for sulfate, 1.07 for soil particles, and 1.04 for sea salt. Increase in exposure to black carbon and sulfate per interquartile range had the strongest associations with dementia incidence.

Physical fitness, and the exercise needed to produce that state, has a sizable influence on later life health. Along with calorie restriction, effect sizes on disease risk and mortality are larger for the average person than near any medical technology for which equivalent data exists. We might hope that senolytics, clearance of senescent cells, may prove to better, but that remains to be seen. Exercise and fitness affect the pace of neurodegeneration through numerous mechanisms, such as upregulation of neurogenesis, increased blood flow to the brain, slowing vascular aging, and so forth. The epidemiological data here adds to a sizeable existing set of studies showing the effects of fitness of late life health.

People who are more physically fit are less likely to develop Alzheimer's disease than people who are less physically fit, according to a preliminary study. The study involved 649,605 military veterans in the Veterans Health Administration database with an average age of 61 who were followed for an average of nine years. They did not have Alzheimer's disease at the start of the study. Researchers determined participants' cardiorespiratory fitness. Cardiorespiratory fitness is a measure of how well your body transports oxygen to your muscles, and how well your muscles are able to absorb oxygen during exercise.

The participants were divided into five groups, from least fit to most fit. Fitness levels were determined by how well participants did on a treadmill test. This test measures exercise capacity, the highest amount of physical exertion a person can sustain. For people who are middle-aged and older, the highest level of fitness can be achieved by walking briskly most days of the week, for two and a half hours or more per week.

The group with the lowest level of fitness developed Alzheimer's at a rate of 9.5 cases per 1,000 person-years, compared to 6.4 cases per 1,000 person-years for the most fit group. When researchers adjusted for other factors that could affect risk of Alzheimer's disease, they found that the people in the most fit group were 33% less likely to develop Alzheimer's disease than those in the least fit group.

Link: https://www.eurekalert.org/news-releases/944452

The blood-brain barrier is a layer of specialized cells that tightly control passage of cells and molecules from the vasculature to the central nervous system. When the blood-brain barrier becomes dysfunctional and leaky with age, this contributes to chronic inflammation in brain tissue. The paper here provides an interesting discussion of the degree to which blood-brain barrier dysfunction in aging is secondary to reduced blood flow to the brain. A combination of factors lead to reduced circulation in the brain: loss of capillary density; small vessel disease in which the vessels narrow and weaken; heart failure; loss of physical fitness and reduced level of exercise; and so forth.

Vascular cognitive impairment (VCI) covers an entire spectrum of vascular pathologies that contribute to cognitive impairment, from pre-clinical subjective states to the manifestation of a severe state of cognitive decline such as vascular dementia (VaD). Even without the presence of risk factors, vascular aging leads to chronic cerebral hypoperfusion (CCH) that induces phenotypical changes in the brain and therefore makes the brain more vulnerable to disease. This emphasizes the importance of cerebral blood flow (CBF) regulation under physiological and pathological conditions. Cerebral blood vessels are responsible for the delivery of many important substances to the brain such as nutrients and oxygen, which is necessary for neuronal oxidative metabolism of energy substrates. Neurons have limited capacity for anaerobic metabolism, thus adequate CBF is critically important for function and viability of neurons.

CCH was reported to be a common feature in all subtypes of VCI. In fact, CCH was reported to begin at early stages of VCI and continue till the late demented state of VaD. Furthermore, in a severe state of VaD, global CBF reduction in patients was reported to be more extensive than age-matched controls and Alzheimer's disease patients. VaD patient cohorts reportedly showed decreased CBF to all parts of the brain. A study reported a 31% decrease in CBF at the frontal cortex and a 39% decrease in CBF at the parietal cortex.

It is postulated that CCH is a major cause of VCI. CCH activates a molecular and cellular injury cascade that leads to breakdown of the blood brain barrier (BBB) and neurodegeneration. The BBB tightly regulates the movement of substances between the blood and the brain, thereby regulating the microenvironment within the brain parenchyma. Here we illustrate how BBB damage is causal in the pathogenesis of VCI through the increased activation of pathways related to excitotoxicity, oxidative stress, inflammation, and matrix metalloproteinases that lead to downstream perivascular damage, leukocyte infiltration, and white matter changes in the brain. Thus, CCH-induced BBB damage may initiate and contribute to a vicious cycle, resulting in progressive neuropathological changes of VCI in the brain.

Link: https://doi.org/10.7150/thno.68304

The rate of living view of aging is one of the discarded historical hypotheses that occurred along the way to the modern competing ideas about why aging occurs, and why there are differences in longevity between species. Roughly, the rate of living hypothesis says that a faster metabolism means a shorter life, that underlying processes (such as accumulation of molecular damage) depend strongly on metabolic rate. This doesn't appear to be the case, however; setting aside more detailed considerations, there are enough exceptions to the rule, species with high metabolism and exceptional longevity, to sink the argument. It isn't just metabolic rate that determines species longevity.

In today's single author paper, rate of living sidles back into the picture via a more complicated relationship between energy metabolism, body mass, temperature, heart rate, and respiratory rate. Species across a wide range of sizes and metabolic rates all come decently close to conforming. So perhaps this scientist is on to something, and one will find that these aspect of physiology correlate quite well to the pace of creation of important forms of molecular damage in aging, or, alternatively, exceptions will be found and this will go the way of the original rate of living theory. Either way, the data is the data, and it is an interesting read.

Universal relation for life-span energy consumption in living organisms: Insights for the origin of aging

It is natural to try to associate the process of aging with metabolism, since all living organisms obtain the energy required to stay alive from such a process. In 1908 researchers compared the energy metabolisms and lifespans of five domestic animals (guinea pig, cat, dog, cow and horse) and humans and found that the lifespan (total) energy expenditure per gram for the five species is approximately constant, suggesting that the total metabolic energy consumption per lifespan is fixed, which later became known as the 'rate of living' theory.

Decades later, a mechanism was found by which the idea behind a fixed energy consumption per lifespan might operate, the 'free-radical damage' hypothesis of aging, in which the macromolecular components of the cell are under perpetual attack from toxic byproducts of metabolism, such as free radicals and oxidants. However, the 'free-radical' theory has lost support in recent years, with evidence that a reduction in free radicals by antioxidant supplementation in the diets of laboratory animals does not significantly increase their life expectancy.

The rate of living relation was partially confirmed for approximately one hundred mammals and was extended to birds, ectotherms, and even unicellular organisms such as protozoa and bacteria, totaling almost three hundred different species in a range of 20 orders of magnitude in body mass. Although the total metabolic energy exhausted per lifespan per body mass of a given species appears to be a relatively constant parameter - approximately a million Joules per gram of body weight for mammals - variations of more than an order of magnitude have been found among different animal classes; this result is considered the most persuasive evidence against the 'rate of living' theory.

Here, we present a universal relation that relates lifespan energy consumption to several physiological variables, such as body mass, temperature, and the ratio of heart rate to respiratory rate, which have been shown to be valid for ∼300 species representing different classes of living organisms, from unicellular organisms to the largest mammals. This relation has an average scattered pattern restricted to factors of 2, with 95% of the organisms having departures of less than a factor of π from the relation, despite the difference of ∼20 orders of magnitude in body mass.

This result can be interpreted as supporting evidence for the existence of an approximately constant total number (10^8) of respiration cycles per lifetime for all organisms studied, effectively predetermining the extension of life through the basic energetics of respiration. This is an incentive to conduct future studies on the relation of such a constant number of cycles per lifetime due to the production rates of free radicals and oxidants, or alternative mechanisms, which may yield definite constraints on the origin of aging.

One of the impressions received from the literature on electromagnetic stimulation of the brain is that results likely depend strongly on the fine details of the protocol. Current, frequency, duration, and any of the score of other parameters that can be adjusted via a different experimental setup. The use of direct current may have better results to date simply because there are fewer parameters to adjust. Nonetheless, "better results to date" is not a glowing recommendation. The bar as very low, and as pointed out here, the state of clinical trials seen as a whole isn't all that convincing. You might compare this with a similar review from last year.

Alzheimer's disease (AD) and Parkinson's disease (PD) are neurodegenerative disorders characterized by cognitive impairment and functional decline increasing with disease progression. Within non-pharmacological interventions, transcranial direct current stimulation (tDCS) might represent a cost-effective rehabilitation strategy to implement cognitive abilities with positive implications for functional autonomy and quality-of-life of patients. Our systematic review aimed at evaluating the effects of tDCS upon cognition in people suffering from AD and PD. We searched for randomized controlled trials (RCTs). Three review authors extracted data of interest, with neuropsychological tests or experimental cognitive tasks scores as outcome measures.

A total of 17 RCTs (10 trials for AD and 7 trials for PD) were included. Compared with sham stimulation, tDCS may improve global cognition and recognition memory in patients with AD and also some executive functions (i.e., divided attention, verbal fluency, and reduction of sensitivity to interference) in patients with PD. Criticism remains about benefits for the other investigated cognitive domains. Despite preliminary emerging evidences, larger RCTs with common neuropsychological measures and long-term follow-ups establishing longevity of the observed effects are necessary for future research in applied psychology field, alongside improved clinical guidelines on the neurodegenerative disorders pertaining electrodes montage, sessions number, duration and intensity of the stimulation, and cognitive battery to be used.

Link: https://doi.org/10.3389/fneur.2021.798191

Researchers have in recent years identified CYTOR as a regulator of muscle growth, a line of work that is progressing towards the development of therapies to combat sarcopenia, the age-related loss of muscle mass and strength. This is a compensatory approach, forcing cells to override their natural response to the aged environment rather than trying to address the environment itself. Since evidence suggests that aged muscle stem cells are competent, capable of function, but made quiescent in response to the altered signaling environment in old tissues, restoring stem cell function (and thus muscle maintenance and growth) in this way may be at the more effective end of what is possible to achieve in the treatment of aging without targeting the deeper causes of dysfunction.

Your average 80-year-old has lost over 30 per cent of the muscle mass they had as a young adult. Without exercising to counteract the loss of muscle mass, humans already start to lose muscle around age 30. The body has two basic types of muscle fibres: the slow-twitch (type I) muscle fibres needed for endurance activities, and the fast-twitch (type II) muscle fibres used for short bursts of strength. As we age, we primarily lose type II muscle mass. "Our experiments show that CYTOR contributes to increased development of precisely the type II muscle fibres."

The next step for the researchers was to take a closer look at what happens when gene therapy is used to increase CYTOR levels. Using the CRISPR-Cas9 method, the researchers increased CYTOR production in live animals and in precursors to muscle cells from older humans. The results are very promising. "In human cells, CYTOR production increased as a result of gene therapy. We also observed that the therapy stimulated the cells to promote the development of fast-twitch type II muscle."

Experiments with mice confirmed that gene therapy not only provides a theoretical effect at the cellular level, but can actually provide improved muscle function. Gene therapy, which increased CYTOR production in the calf muscles of ageing mice, gave the mice increased muscle mass, better grip strength in their hind legs and greater running capacity. When the researchers reduced CYTOR production in young mice, however, the mice developed weaker muscles and more inflammation and cell death in the muscles. "The CYTOR gene seems to be absolutely crucial in order to maintain normal muscle function."

Link: https://norwegianscitechnews.com/2022/02/could-gene-therapy-soon-curb-muscle-loss-in-the-elderly/

The small, long-standing cryonics community and industry is focused on saving lives by offering the possibility of low-temperature storage at death, using cryoprotectants to induce a state of vitrification rather than straight freezing, a shot at preserving the structure and data of the mind for a future society capable of revival from this state. This has been an ongoing project for quite some time now, since the 1960s or so, albeit with a small budget and few research programs.

I was recently in New York to attend the 50th anniversary gathering for the Alcor Life Extension Foundation, among the oldest of cryonics organizations. It was an occasion also marking the launch of a new book by Robert Freitas, a specialist in molecular nanotechnology and nanomedicine. The book, Cryostasis Revival, is essentially a 700 page scientific paper that outlines, in detail, what we know of the research and development that would be required to revive a vitrified individual. This starts as a matter of neuroscience, based our knowledge of the brain and its tissues and function, but encompasses a great deal more as well.

People interested in progress in cryonics tend to be interested in progress towards the development of rejuvenation therapies, though there is too little overlap in the other direction. Both were once more fringe than they are now, but work on rejuvenation has expanded and found far more support than is the case for cryonics. There is an old debate, often held between those with a foot in both camps: given that most of us in the later half of life expect the likely pace of progress in rejuvenation therapies to result in a sizeable improvement in old age, but not prevent us from dying from the effects of aging, why are we not fully focused instead on enabling cryonics to become a robust, large, dynamic industry? Isn't the primary object to avoid death, to avoid ceasing to exist? Why not then work on the better solution to that specific goal, rather than a path that can only improve health and thereby longevity in the time we have left?

I was asked this again at the Alcor event by Emil Kendziorra, co-founder of Tomorrow Biostasis, a comparatively new European cryonics venture that may well be pushing some of the older organizations to modernize more than they would otherwise have done, in his role as provocateur. He makes a habit of this, it is a part of his advocacy for the cause.

While I can't talk to the decisions of others, I can shed some light on why I am presently working on rejuvenation, and only plan to focus more of my time on cryonics later in life. Pre-pandemic, I said - to Emil Kendziorra, even - that ten years from now I would be spending more time on cryonics. It may still be ten years at this point post-pandemic, if early access to reprogramming or a combination of other plausible technologies pans out over the next five years and proves influential on health. My timing to switch to work on cryonics is in one sense driven by my projected health trajectory. At what point in the future do I predict that I only have 20 years left before there is a real risk of serious, debilitating age-related disease that drastically limits my ability to contribute? At that point I should put a great deal more effort into making those 20 years a productive time for the cryonics industry.

In the more general sense, considering health and other factors, I will put more work into cryonics when the balance shifts to the point at which improvement in the state of cryonics will be more of a benefit to me than improvements in the state of rejuvenation. "Balance" is a loose word. Guesstimation and gut feel goes into (a) what I think can be achieved for many people over the next few decades via improvements in rejuvenation therapies, (b) what I think can be achieved for myself 20-30 years from now in rejuvenation by helping now, (c) what I can do for the cryonics industry now versus later, and (d) the likelihood that my present efforts in the biotech sector will produce significant personal capital to devote to cryonics research, development, and industry growth.

That last point is an important one. Improvement in the practical implementation of low-temperature cryopreservation proceeds at a very slow pace, with minimal funding. This is a consequence of it being a small field. Yet we can argue quite strongly that the lack of demonstrated capabilities, such as, let us say, reversible vitrification of organs used in the tissue engineering and organ donation fields, is the biggest impediment to convincing the world that cryonics is real. Many people feel that cryonics won't become even a minority concern in a meaningful way until the first person is brought back successfully - but that is a long way in the future, and so we must find incremental steps along the way that will help make a convincing argument to laypeople that this is possible in principle.

At this point, it would probably cost $10 million to $20 million to push reversible vitrification of organs past the point at which more funding will arise organically and industry will inevitably form. Either philanthropy focused on academic-style programs or a deep-pocketed venture backed company might achieve the same result. But money doesn't grow on trees, and so far even the more visionary philanthropists have committed only a fraction of this amount to this sort of cryonics research. Turning up to put my shoulder to the wheel with the intent to find this funding is one thing. Turning up with those funds in hand is quite another. The odds of either path working out, and when they will work out, are worth considering when running the calculus of when to become more involved.

In any case, I am sympathetic to the argument that one should be working to speed up the growth and development of a future cryonics industry. One day I will do more than talking about it. Just not today.

Increased generation of new neurons in the brain, upregulation of the process of neurogenesis, is an important goal for the field of regenerative medicine. It would likely improve brain function at all ages, but since neurogenesis declines with age as stem cell populations become less active, it would be of particular relevance to the aging brain. Thus researchers are looking for ways to influence the regulatory systems controlling quiescence versus activity in neural stem cells and progenitor cells, in order to override the natural response to the aged tissue environment and put them back to work.

In most mammals, neurogenesis in the dentate gyrus (DG) and subventricular zone (SVZ) continues during adulthood. In rodents and non-human primates, new neurons generated in the SVZ migrate to the olfactory bulb. In humans, on the other hand, the addition of new neurons to the olfactory bulb is likely negligible and new neurons produced in the SVZ migrate to the neighboring striatum. Growing evidence suggests that the decline in neurogenesis observed during aging in mammals is due to increased quiescence of neural stem cells (NSCs) and progenitors (hereafter progenitors refers to both NSCs and progenitors).

Studies in rodents have shown that adult NSCs arise from a population of quiescent radial glial cells that accumulate embryonically. Rather than being a static non-proliferating pool of cells, studies in rodents have demonstrated that they are a very dynamic population of cells that transit between proliferative and quiescent states. With aging progenitors become less plastic and remain mainly quiescent, which prevents depletion of the progenitor pool. The mechanisms that regulate quiescence of progenitors are just beginning to be unraveled.

We have previously identified CD271 as a marker expressed by progenitors of the aged human SVZ. The present study assesses the molecular identity of CD271-positive progenitors from the SVZ of the aged human brain at single-cell level and investigates a mechanism through which human progenitors could be maintained in a quiescent state. We identify the secreted frizzled-related protein-1 (SFRP1), an inhibitor of the Wnt signaling pathway, to be among genes whose expression changes over time. We demonstrate that inhibition of SFRP1 with a small molecule stimulates proliferation in vitro, in human iPSC-derived NSCs, and in vivo in early postnatal mice. Altogether, our work proposes a mechanism that maintains quiescence of progenitors of the human SVZ, which opens up future possibilities to stimulate NSCs of the human brain to promote repair.

Link: https://doi.org/10.1038/s41467-022-28626-9

Muscle stem cells, or satellite cells, are one of the better studied stem cell populations in the body, particularly in the context of aging and loss of stem cell function. The balance of evidence to date indicates that these stem cells remain largely intact and capable in an old individual, but quiescent. Thus there may be comparatively simple ways to active these cells in order to improve maintenance of aged muscle tissue, given a better idea of the regulation of quiescence versus activity. Thus the existence of research programs akin to the one noted here, in which researchers are in search of ways to provoke aged muscle stem cells into greater activity.

Skeletal muscle stem cells, or satellite cells (SCs), are indispensable for repairing damaged muscle and are key targets for treating muscle diseases. In healthy uninjured muscle, these reserve stem cells lie in quiescence, a dormant state, to maintain the resident stem cell pool for future muscle repair. When muscle damage occurs, these quiescent muscle stem cells will quickly "wake up", generating enough muscle progenitor cells to build new muscle. Despite being a critical step in muscle regeneration, the muscle stem cell quiescence-to-activation transition remains an elusive process.

Recently, using a whole mouse perfusion technique to obtain the true quiescent SCs for low-input mass spectrometry analysis, a team of scientists revealed that a regulating protein called CPEB1 is instrumental in reprogramming the translational landscape in SCs, hence driving the cells into activation and proliferation. "Our analysis shows that levels of CPEB1 protein are low in quiescent SCs, but upregulated in activated SCs, with loss of CPEB1 delaying SC activation."

In their subsequent RNA immunoprecipitation sequencing analysis and CPEB1-knockdown proteomic analysis, the researchers found that CPEB1 phosphorylation regulates the expression of the crucial myogenic factor MyoD - a protein involving in skeletal muscle development - by targeting some of the sequences found within the three prime untranslated region (3'UTR) of the target RNA transcript to drive SC activation. "It means that the manipulation of CPEB1 levels or phosphorylation can increase SC proliferation to generate enough myogenic progenitor cells for muscle repair, which could be a potential therapeutic target for muscle repair in the elderly."

Link: https://www.eurekalert.org/news-releases/944595

First generation stem cell therapies, such as forms of mesenchymal stem cell therapy, have underperformed in comparison to the original hopes for the scope of benefits to patients. Treatments fairly reliably reduce chronic inflammation in aged or lastingly injured individuals, but boosted regenerative capacity and functional improvement are uncommon, unreliable, and unpredictable. Effects vary widely from individual to individual and clinic to clinic.

One view on why this is the case is that not enough has been done to make the injected cells optimally effective. Even minor differences in protocol when culturing stem cells can produce widely divergent outcomes, such as quite different degrees of cellular senescence, or other cell behaviors. Thus therapies might be meaningfully improved by, for example, using senolytic strategies to clear senescent cells from stem cell cultures. Further, it is possible work towards triggering specific beneficial cell behaviors prior to injection via the use of signal molecules. Not enough work has yet taken place to truly judge whether or not this view is correct, but it seems plausible that there is scope for improvement.

Enhancement strategies for mesenchymal stem cells and related therapies

It is almost impossible to catalogue all of the therapeutic investigations conducted and ongoing using mesenchymal stem cells (MSCs). However, the excitement in this burgeoning field has been somewhat dampened by some less than stellar clinical trial results and persistent variability of effect due to production practicalities and correlative, rather than causative, potency assays.

During these studies an immense amount of data has been generated regarding stem cell biology and possible mechanism of action in diseases, including the physiological niche where various stem cells are sourced, cell-cell contact-dependent mechanisms and a rich secretome containing small molecules, proteins, organelles and even full membrane bound bodies. Indeed, much of this data has been accumulated regardless of whether the overall subsequent clinical trials themselves were successful. These have prompted a multitude of strategies that could putatively be included in the cell manufacturing process to improve outcomes in patients.

In this review we will look at current and future strategies that might overcome limitations in efficacy. Many of these take their inspiration from stem cell niche and the mechanism of MSC action in response to the injury microenvironment, or from previous gene therapy work which can now benefit from the added longevity and targeting ability of a live cell vector. We will also explore the nascent field of extracellular vesicle therapy and how we are already seeing enhancement protocols for this exciting new drug. These enhanced MSCs will lead the way in more difficult to treat diseases and restore potency where donors or manufacturing practicalities lead to diminished MSC effect.

As a general rule, methods that produce 10-20% life extension in mice are unlikely to prove all that interesting in humans. But it depends on what is going on under the hood. In most cases interventions act on life span by upregulating cellular stress response mechanisms, and there is more than enough evidence to suggest that this category of approaches is far more effective at extending life in short-lived species than is the case in long-lived species such as our own. In this case, the mechanism of interest may be anti-inflammatory, a reduction of age-related chronic inflammation. There is not yet a body of evidence to tell us whether or not this is less interesting in long-lived species such as our own, at the same time as there is a great deal of evidence telling us that chronic inflammation drives many age-related diseases in humans.

The cystine/glutamate antiporter system xc- has been identified as the major source of extracellular glutamate in several brain regions as well as a modulator of neuroinflammation, and genetic deletion of its specific subunit xCT (xCT-/-) is protective in mouse models for age-related neurological disorders. However, the previously observed oxidative shift in the plasma cystine/cysteine ratio of adult xCT-/- mice led to the hypothesis that system xc- deletion would negatively affect life- and healthspan. Still, till now the role of system xc- in physiological aging remains unexplored.

We therefore studied the effect of xCT deletion on the aging process of mice, with a particular focus on the immune system, hippocampal function, and cognitive aging. We observed that male xCT-/- mice have an extended lifespan, despite an even more increased plasma cystine/cysteine ratio in aged compared to adult mice. This oxidative shift does not negatively impact the general health status of the mice. On the contrary, the age-related priming of the innate immune system, that manifested as increased LPS-induced cytokine levels and hypothermia in xCT+/+ mice, was attenuated in xCT-/- mice.

While this was associated with only a very moderate shift towards a more anti-inflammatory state of the aged hippocampus, we observed changes in the hippocampal metabolome that were associated with a preserved hippocampal function and the retention of hippocampus-dependent memory in male aged xCT-/- mice. Targeting system xc- is thus not only a promising strategy to prevent cognitive decline, but also to promote healthy aging.

Link: https://doi.org/10.1038/s41380-022-01470-5

The state of the art for detecting Alzheimer's disease in earlier stages has advanced considerably in the last decade. As noted here, methods are presently good enough to worth using. What should one do if given an early diagnosis of Alzheimer's disease? Based on what is known of the relevant mechanisms, and their plausibility as a direct contribution, an adventurous person might: (a) start taking antiviral drugs, given the possibility that persistent viral infection drives progression of the condition; (b) work to reduce chronic inflammation by all available means, from exercise to senolytics, as inflammation is clearly important in neurodegeneration; (c) clear the worst microglia from the brain, either via senolytics that can cross the blood-brain barrier (e.g. the dasatinib and quercetin combintion) or some form of CSF1R inhibitor. There are probably other reasonable strategies, given a sensible consideration of plausible cost and plausible benefit, even in the absence of clinical proof.

A blood test has proven highly accurate in detecting early signs of Alzheimer's disease in a study involving nearly 500 patients from across three continents, providing further evidence that the test should be considered for routine screening and diagnosis. The blood test assesses whether amyloid plaques have begun accumulating in the brain based on the ratio of the levels of the amyloid beta proteins Aβ42 and Aβ40 in the blood.

Researchers have long pursued a low-cost, easily accessible blood test for Alzheimer's as an alternative to the expensive brain scans and invasive spinal taps now used to assess the presence and progression of the disease within the brain. Evaluating the disease using PET brain scans - still the gold standard - requires an average cost of $5,000 to $8,000 per scan. Another common test, which analyzes levels of amyloid-beta and tau protein in cerebrospinal fluid, costs about $1,000 but requires a spinal tap process that some patients may be unwilling to endure.

This study estimates that prescreening with a $500 blood test could reduce by half both the cost and the time it takes to enroll patients in clinical trials that use PET scans. Screening with blood tests alone could be completed in less than six months and cut costs by tenfold or more, the study finds. Known as Precivity AD, the commercial version of the test is marketed by C2N Diagnostics. The current study shows that the blood test remains highly accurate, even when performed in different labs following different protocols, and in different cohorts across three continents.

Link: https://medicine.wustl.edu/news/blood-test-for-alzheimers-highly-accurate-in-large-international-study/

Parkinson's disease is associated with the spread of α-synuclein aggregates, misfolded proteins that can pass from cell to cell and encourage other α-synuclein molecules to misfold in the same way. These aggregates are surrounded by a halo of toxic biochemistry, altering cell behavior for the worse, and killing cells. The primary victims are dopaminergenic neurons necessary to motor control, leading to the characteristic symptoms of Parkinson's disease. In later stages neurons throughout the brain die, causing neurological pathologies of other sorts and eventual death.

Maintenance processes in the cell, responsible for removing damaged proteins and components, have long been an important area of research in the Parkinson's field. Mutations in genes relating to mitophagy, the process of clearing dysfunctional mitochondria, raise Parkinson's risk by making dopaminergenic neurons more vulnerable. Autophagy in general is one of the processes responsible for clearing aggregates and misfolded proteins. In today's research materials, scientists report on findings in the dysfunction of autophagy noted in Parkinson's disease, and how that might contribute to the pathological spread of α-synuclein in the brain.

Discovery points to possible driver of Parkinson's disease

Parkinson's disease may be driven in part by cell stress-related biochemical events that disrupt a key cellular cleanup system, leading to the spread of harmful protein aggregates in the brain, according to a new study. Parkinson's entails the deaths of neurons in a characteristic sequence through key brain regions. The killing of one small set of dopamine-producing neurons in the midbrain leads to the classic Parkinsonian tremor and other movement impairments. Harm to other brain regions results in various other disease signs including dementia in late stages of Parkinson's.

Affected neurons contain abnormal protein aggregations, known as Lewy bodies, whose predominant ingredient is a protein called alpha-synuclein. In the new study, researchers demonstrated that a type of nitrogen-molecule reaction called S-nitrosylation can affect an important cellular protein called p62, triggering the buildup and spread of alpha-synuclein aggregates. The p62 protein normally assists in autophagy, a waste-management system that helps cells get rid of potentially harmful protein aggregates. The researchers found evidence that in cell and animal models of Parkinson's, p62 is S-nitrosylated at abnormally high levels in affected neurons. This alteration of p62 inhibits autophagy, causing a buildup of alpha-synuclein aggregates.

S-Nitrosylation of p62 Inhibits Autophagic Flux to Promote α-Synuclein Secretion and Spread in Parkinson's Disease and Lewy Body Dementia

Dysregulation of autophagic pathways leads to accumulation of abnormal proteins and damaged organelles in many neurodegenerative disorders, including Parkinson's disease (PD) and Lewy body dementia (LBD). Autophagy-related dysfunction may also trigger secretion and spread of misfolded proteins such as α-synuclein (α-syn), the major misfolded protein found in PD/LBD. However, the mechanism underlying these phenomena remains largely unknown.

Here, we used cell-based models, including human induced pluripotent stem cell (hiPSC)-derived neurons, CRISPR/Cas9 technology, and male transgenic PD/LBD mice, plus vetting in human postmortem brains (both male and female). We provide mechanistic insight into this pathological pathway. We find that aberrant S-nitrosylation of the autophagic adaptor protein p62 causes inhibition of autophagic flux and intracellular build-up of misfolded proteins, with consequent secretion resulting in cell-to-cell spread.

Thus, our data show that pathological protein S-nitrosylation of p62 represents a critical factor not only for autophagic inhibition and demise of individual neurons, but also for α-syn release and spread of disease throughout the nervous system.

First generation stem cell therapies are highly variable. While they fairly reliably suppress chronic inflammation for a time, other benefits vary widely from clinic to clinic and approach to approach. In part this may be because cells are hard to manage. Small differences in protocol, even unintentional differences, can produce large differences in outcome. Of late, researchers have started to ask whether variations in cell therapy outcomes may be in part mediated by a large variability in the degree to which cells become senescent in culture during the preparation for injection. Only a tiny proportion of cells need to be senescent in order to produce detrimental effects on the others. Thus researchers are now investigating the use of senolytics and other means as a way to improve the quality of this class of cell therapy.

Mesenchymal stem cells (MSCs) are recognized as potential treatments for multiple degenerative and inflammatory disorders as a number of animal and human studies have indicated their therapeutic effects. There are also several clinically approved medicinal products that are manufactured using these cells. For such large-scale manufacturing requirements, the in vitro expansion of harvested MSCs is essential. Multiple subculturing of MSCs, however, provokes cellular senescence processes which is known to deteriorate the therapeutic efficacy of the cells. Strategies to rejuvenate or selectively remove senescent MSCs are therefore highly desirable for fostering future clinical applications of these cells.

In this present study, we investigated gene expression changes related to cellular senescence of MSCs derived from umbilical cord blood and found that CD26, also known as DPP4, is significantly upregulated upon cellular aging. We further observed that the inhibition of CD26 by genetic or pharmacologic means delayed the cellular aging of MSCs with their multiple passaging in culture. Moreover, the sorting and exclusion of CD26-positive MSCs from heterogenous cell population enhanced in vitro cell attachment and reduced senescence-associated cytokine secretion. CD26-negative MSCs also showed superior therapeutic efficacy in a mouse model of lung emphysema. Our present results collectively suggest CD26 is a potential novel target for the rejuvenation of senescent MSCs for their use in manufacturing MSC-based applications.

Link: https://doi.org/10.3389/fcell.2021.803645

mTORC1 inhibition slows aging modestly, albeit to a greater degree in short-lived species. It is an open question as to whether the benefits in humans are large enough to be worth chasing versus other programs of research and development. Early trials of mTORC1 inhibitor drugs have produced results that were interesting but mixed. mTORC1 inhibition is, considered at the high level, a form of calorie restriction mimetic approach, thought to act on life span primarily through upregulation of stress response mechanisms such as autophagy. Researchers here follow the trail of connections to investigate the role of ATF-4 in the signaling changes produced by mTORC1 inhibition, linking this research to other lines of inquiry related to the role of hydrogen sulfide in metabolism relevant to aging.

Inhibition of the master growth regulator mTORC1 slows ageing across phyla, in part by reducing protein synthesis. Various stresses globally suppress protein synthesis through the integrated stress response (ISR), resulting in preferential translation of the transcription factor ATF-4. Here we show in C. elegans that inhibition of translation or mTORC1 increases ATF-4 expression, and that ATF-4 mediates longevity under these conditions independently of ISR signalling.

ATF-4 promotes longevity by activating canonical anti-ageing mechanisms, but also by elevating expression of the transsulfuration enzyme CTH-2 to increase hydrogen sulfide (H2S) production. This H2S boost increases protein persulfidation, a protective modification of redox-reactive cysteines. The ATF-4/CTH-2/H2S pathway also mediates longevity and increased stress resistance from mTORC1 suppression. Increasing H2S levels, or enhancing mechanisms that H2S influences through persulfidation, may represent promising strategies for mobilising therapeutic benefits of the ISR, translation suppression, or mTORC1 inhibition.

Link: https://doi.org/10.1038/s41467-022-28599-9