Fight Aging!

The hundreds of mitochondria found in every cell are in effect power plants, their primary task being to manufacture the chemical energy store molecule adenosine triphosphate (ATP), which is used to power cellular processes. Mitochondria become damaged like every cellular component, and are recycled frequently. With age, however, changes in expression of mitochondrial and other proteins lead to dysfunctional recycling and dysfunctional mitochondria. ATP production suffers, side-effects of ATP production such as the generation of free radical molecules grow to become problematic, and cell function is impacted. This happens throughout the body, and is thought to be an important contributing cause of degenerative aging.

At least two companies are working earnestly on developing mitochondrial transplantation therapies as a way to treat aging, Mitrix Bio and Cellvie Scientific. Cells will readily take up mitochondria from the surrounding environment. Studies in animals suggest that supplying fully functional mitochondria, harvested from cell cultures, to tissues in which mitochondria are dysfunction can fix the problem for long enough to be interesting as a basis for therapy. The primary challenges are (a) to understand whether mitochondrial haplotypes must match between donor and recipient, (b) cost-effective and reliable manufacture of large enough amounts of undamaged, function mitochondria, and (c) delivery to the harder-to-reach parts of the body. The companies are primarily engaged in the logistics of large-scale manufacture.

Today's open access paper is a compelling demonstration from researchers associated with Cellvie Scientific, demonstrating sizable gains in mitochondrial function, muscle function, and endurance in old mice resulting from direct injection of mitochondria into hindlimb muscles. The amount of mitochondria harvested and injected is reasonable from a manufacturing point of view if scaling up to human use. I expect these companies to initially target frailty, sarcopenia, and related conditions. I also expect the medical tourism community to begin to offer mitochondrial transplantation therapies on much the same timescale. Clinical businesses already have a great deal of experience in managing cell cultures and cell harvesting, and moving from there to harvesting mitochondria is an achievable goal. They have already achieved a similar shift in moving to the use of extracellular vesicles in therapy.

Mitochondrial Transplantation's Role in Rodent Skeletal Muscle Bioenergetics: Recharging the Engine of Aging

Cardiorespiratory fitness is a health indicator of all-cause mortality. One critical component of cardiorespiratory fitness is the function of mitochondria within the skeletal muscle which generates energy to perform exercise or activities of daily living. There is clear evidence that aging results in a reduction in mitochondrial function. Initially proposed as the mitochondrial theory of aging in the 1950s, age-related decreases in mitochondrial function have since been shown to play a major role in skeletal muscle decline. Not surprisingly, in regard to aging-related decline of skeletal muscle, mitochondrial oxidative capacity has been implicated in sarcopenia. Research suggests that the skeletal muscle of elderly individuals exhibits a rise in nonoperational mitochondria, an increase in mutated and deleted mitochondrial DNA with an associated decrease in mitochondrial density.

Non-exercise alternatives such as nutraceuticals or pharmacological agents to improve skeletal muscle bioenergetics act systemically and have resulted in moderate success. Nevertheless, these natural and pharmacological compounds have limitations, particularly in the duration of time (i.e., weeks or months) to induce beneficial molecular and cellular changes in skeletal muscle. Thus, the question arises: "Is there a faster, tissue targeted, and more effective approach to enhance skeletal muscle bioenergetics?"

Mitochondrial transplantation represents a novel therapy designed to enhance energy production of tissues impacted by defective mitochondria. This innovative approach involves transferring isolated mitochondria from either a donor to a host or from the host to itself. Initially used to attenuate the effects of ischemia-reperfusion injury in cardiac tissue transplanted mitochondria, which are rapidly purified and remain viable and capable of respiration, are directly injected into the target tissue. In skeletal muscle, mitochondrial transplantation has proven effective in enhancing hindlimb bioenergetics in various rodent models. Mitochondrial transplantation circumvents the limitations of both exercise and non-exercise interventions by directly delivering isolated mitochondria into the target tissue.

To date, no studies have used mitochondrial transplantation as an intervention to attenuate aging-induced skeletal muscle mitochondrial dysfunction. In this study 15 female mice (24 months old) were randomized into two groups (placebo or mitochondrial transplantation). Isolated mitochondria from a donor mouse of the same sex and age were transplanted into the hindlimb muscles of recipient mice. The results indicated significant increases (ranging between ~36% and ~65%) in basal cytochrome c oxidase and citrate synthase activity as well as ATP levels in mice receiving mitochondrial transplantation relative to the placebo. Moreover, there were significant increases (approximately two-fold) in protein expression of mitochondrial markers in both glycolytic and oxidative muscles. These enhancements in the muscle translated to significant improvements in exercise tolerance.

The practice of calorie restriction, intermittent fasting, and related strategies such the fasting mimicking diet are thought to produce benefits largely through increased or more efficient operation of the cellular maintenance process of autophagy. The various forms of autophagy work to remove damaged molecules and structures in the cell, and better cell function maintained over time throughout the body is expected to result in slowed aging. Certainly a great many of the approaches shown to slow aging in short-lived species are characterized by improved autophagy, and influence the same regulatory systems that are triggered by a low calorie intake and consequent hunger.

Autophagy is a prosurvival mechanism for the clearance of accumulated abnormal proteins, damaged organelles, and excessive lipids within mammalian cells. A growing body of data indicates that autophagy is reduced in aging cells. This reduction leads to various diseases, such as myocardial hypertrophy, infarction, and atherosclerosis. Recent studies in animal models of an aging heart showed that fasting-induced autophagy improved cardiac function and longevity. This improvement is related to autophagic clearance of damaged cellular components via either bulk or selective autophagy (such as mitophagy).

Short-term caloric restriction (CR) for 10 weeks in mice rejuvenated symptoms of the aging heart, such as significant improvement in diastolic function and regression of age-dependent cardiac hypertrophy. Moreover, CR reversed age-dependent cardiac proteome remodeling and mitigated oxidative damage and ubiquitination in these mice. In aged animals, hypertrophy, and fibrosis, as well as systolic and diastolic dysfunctions, improved after CR. The beneficial effects of CR observed in cardiomyocytes include enhanced mitochondrial fitness and reduced oxidative stress, apoptotic cell death, inflammation, and importantly, senescence.

In vasculature, CR helps improve endothelial cell function and attenuates collagen deposition, elastin remodeling, and oxidative stress; as a result, CR reduces arterial stiffness. Another study revealed improvements in numerous markers of cardiovascular health in humans after short-term periodic fasting, which is also a pro-autophagic dietary regimen.

In conclusion, fasting-induced autophagy is beneficial for ensuring cardiac function, preventing disease, and improving longevity. However, additional studies in vivo in animal models of cardiac aging are needed to determine the specific molecular mechanisms involved in normalizing autophagy by fasting. In addition, large-scale studies on humans are needed. Importantly, further in vitro research should be directed toward human cardiac tissues to better understand the molecular mechanisms of fasting-induced autophagy and its beneficial effects on longevity pathways and prevention of cardiovascular disease.

Link: https://doi.org/10.4330/wjc.v16.i3.109

Researchers here explore age-related changes that take place in the innate immune cells known as macrophages, as well as the precursor circulating cell type known as monocytes. Macrophages undertake a wide range of tasks, not just responsible for chasing down infectious pathogens, but also clearing molecular waste and cell debris, destroying problematic cells, and helping to coordinate regenerative processes following injury. Altered macrophage behavior is implicated in a range of age-related diseases, and this is also the case for changes that take place in the analogous cell population of microglia resident in the central nervous system. A better understanding of these alterations may lead to ways to restore a more youthful pattern of behavior in these cells.

Macrophages are central innate immune cells whose function declines with age. The molecular mechanisms underlying age-related changes remain poorly understood, particularly in human macrophages. We report a substantial reduction in phagocytosis, migration, and chemotaxis in human monocyte-derived macrophages (MDMs) from older (more than 50 years old) compared with younger (18-30 years old) donors, alongside downregulation of transcription factors MYC and USF1.

In MDMs from young donors, knockdown of MYC or USF1 decreases phagocytosis and chemotaxis and alters the expression of associated genes, alongside adhesion and extracellular matrix remodeling. A concordant dysregulation of MYC and USF1 target genes is also seen in MDMs from older donors. Furthermore, older age and loss of either MYC or USF1 in MDMs leads to an increased cell size, altered morphology, and reduced actin content. Together, these results define MYC and USF1 as key drivers of MDM age-related functional decline and identify downstream targets to improve macrophage function in aging.

Link: https://doi.org/10.1016/j.celrep.2024.114073

This messy popular science article is an essay length expression of futility on the part of a journalist who accepts that he is not equipped to understand the field of aging research and the longevity industry that has arisen in the past decade. One can talk to the talking heads, but they will all say something different. One can look for proof of efficacy for specific approaches, and find only contradictory data, or only compelling animal data, or only small effect sizes, and a lack of the sort of certainty that arises from large human trials. Those trials are still in the future for near every approach to the treatment of aging that might work.

Like most tours of the field written by journalists, the article lumps together terrible approaches, promising approaches, approaches with good supporting data, approaches with mixed to bad supporting data, and makes little attempt to distinguish between them. The journalist cannot distinguish between them, he doesn't have the several years of learning the science that would be needed to even start to have a useful opinion on approach A versus approach B. For the layman it is just a list, and those most willing to talk about the list are those with a vested interest in profiting from companies working on one item or another item, or are scientist with career prospects that require them to be overly cautious in their public pronouncements. Objectivity is hard to find.

The Wild Science of Growing Younger

There are a lot of hyperbolic and crazy-sounding theories and assertions in the vast movement to counteract the inexorable march from the quick to the dead. Xprize founder Dr. Peter Diamandis thinks we may one day upload our consciousness to the cloud. As such, the 62-year-old is doing everything he can to keep his body healthy in the meantime and maybe reach "longevity escape velocity" - continuing to extend his life long enough to take advantage of ever-more life-extending methods. His business partner - motivational speaker and entrepreneur Tony Robbins - says that stem cell injections he received in Panama (because it's illegal in the U.S.) not only repaired a torn rotator cuff but rejuvenated his entire body. Half-billionaire Bryan Johnson reportedly spends about two million dollars a year on testing, taking more than 100 drugs and supplements, and - for a time - infusing his teenage son's blood plasma. And they are not alone. Jeff Bezos, Yuri Milner, and other tech titans are reported to have together poured about $3 billion into Altos Labs, a startup promising to reprogram human cells to their youthful state.

Rejuvenation efforts also promise to brighten the twilight years by allowing people to live longer and be healthier and more vigorous. Picture 80-year-olds with the body of a 60-year-old. Proponents talk about not only extending lifespan but also what they call healthspan. "It's this biology of aging that makes us get Alzheimer's or cancer or heart disease or diabetes," says Dr. Nir Barzilai. "Aging is the mother of those diseases ... You deal with the mother, and you don't have those kids." After speaking with a dozen experts or advocates, reading four books, parsing over 30 research papers, and absorbing popular press coverage, I know two things about the possibility of slowing or reversing aging. First, anyone can do a few cheap, simple things (like exercise) to improve their longevity prospects. Second, several new tactics, technologies, and tools might someday work.

If you'd hoped for a conclusive destination at the end of this journey, I'm sorry. But in place of answers, we have a framework for evaluating the many questions that emerge. Science has a good sense of what healthy aging should look like. And objective research can begin to explore if any far-fetched ideas mimic that, without bad side effects. Some medications might slow down some aspects of aging. Or perhaps the side effects of these meds just substitute new health problems for the ones proponents aim to fix. You might wait for more info on that before you swallow. Can we inject foreign cells to repair our bodies or inject chemicals that reinvigorate our own cells? This seems to work in mice, worms, or petri dishes. But people without vested interests say we need much more evidence. That's going to take a long time. For so much of anti-aging or reverse-aging science, the old academic refrain applies: "further research is needed."

The evidence for transfusion of young plasma to produce benefits in old animals and human patients is mixed. Despite compelling demonstrations for the dilution of blood to produce benefits in older individuals, there remain many research groups who consider that the primary goal should be the identification of factors within young blood that can produce improvements to health. Inconveniently for those who argue for the primacy of dilution in producing the benefits of plasma transfusion, there are studies such as this one in which factors derived from young plasma do in fact improve health significantly in old mice.

Recent investigations into heterochronic parabiosis have unveiled robust rejuvenating effects of young blood on aged tissues. However, the specific rejuvenating mechanisms remain incompletely elucidated. Here we demonstrate that small extracellular vesicles (sEVs) from the plasma of young mice counteract pre-existing aging at molecular, mitochondrial, cellular and physiological levels. Intravenous injection of young sEVs into aged mice extends their lifespan, mitigates senescent phenotypes, and ameliorates age-associated functional declines in multiple tissues.

Quantitative proteomic analyses identified substantial alterations in the proteomes of aged tissues after young sEV treatment, and these changes are closely associated with metabolic processes. Mechanistic investigations reveal that young sEVs stimulate PGC-1α expression in vitro and in vivo through their microRNA cargoes, thereby improving mitochondrial functions and mitigating mitochondrial deficits in aged tissues. Overall, this study demonstrates that young sEVs reverse degenerative changes and age-related dysfunction, at least in part, by stimulating PGC-1α expression and enhancing mitochondrial energy metabolism.

Link: https://doi.org/10.1038/s43587-024-00612-4

You might compare the LEV Foundation's Rodent Aging Interventions Database with the DrugAge database, both emerging from the efforts of researchers who found themselves frequently reviewing the existing literature on age-slowing interventions in animal models. One of the things to bear in mind about the existing literature is that rodent studies that show an apparent modest slowing of aging frequently fail to replicate when later investors take a more rigorous approach, with larger numbers of mice. The history of the NIA Interventions Testing Program is largely a repeated demonstration of this point.

The Rodent Aging Interventions Database (RAID) project arose as a result of work conducted during late 2022 in preparation for the first study in LEV Foundation's Robust Mouse Rejuvenation (RMR) program: specifically, a comprehensive survey conducted by LEVF of publications documenting successful lifespan extension in strains of rodents (mice and rats) with normal baseline lifespans. That survey played an important role in informing the selection of interventions for the RMR program.

Recognising that this compilation of data may be of interest to other researchers in the field of longevity/aging research, we decided to make it publicly available. To enable convenient exploration of the results, we have also developed a visualization tool which depicts the increases in lifespan achieved in different studies as a single bar chart.

The dataset queried by this tool is intended to cover all published studies that meet the inclusion criteria: (a) in mice (Mus musculus) or rats (Rattus norvegicus), (b) a genetic background consistent with normal aging rates (e.g. no progeria, PolG mitochondrial DNA mutator, Alzheimer's models such as APP/PS1, etc.), and (c) the study reports an intervention with some statistically significant effect on average or maximum lifespan. It is our intention to update the dataset periodically, but some newer (or recently identified) publications may not yet be indexed.

Link: https://www.levf.org/projects/raid

A variety of approaches show some promise in improving the function of stem cells in aged tissues. Stem cell populations support their tissue by providing a supply of daughter somatic cells to replace losses. This supply diminishes over time as stem cells reduce their activity for reasons that descend from the known root causes of aging, but which are not fully understood in detail. To the degree that reduced stem cell function is a response to the aged environment rather than a consequence of damage inherent to these cells, then it is useful to find ways to force stem cells to be more active. Whether this is the case may differ for different cell types, but there is ample evidence for interventions that can at least modestly enhance stem cell activity.

Perhaps the most interesting of these interventions are partial reprogramming and CDC42 inhibition via CASIN. The latter is much more feasible than the former when considering the prospects for near-term human use, but both offer the prospect of one-time treatments that produce a lasting reversal of stem cell aging and consequent improvement in tissue function. It is most likely a long road ahead to the first partial reprogramming therapies, but CASIN only awaits initial human testing to establish that safety is similar to that observed in mice.

Rejuvenating aged stem cells: therapeutic strategies to extend health and lifespan

Aging is associated with a global decline in stem cell function. To date, several strategies have been proposed to rejuvenate aged stem cells: most of these result in functional improvement of the tissue where the stem cells reside, but the impact on the lifespan of the whole organism has been less clearly established. Here, we review some of the most recent work dealing with interventions that improve the regenerative capacity of aged somatic stem cells in mammals and that might have important translational possibilities.

The beneficial effect of exercise on health has been known for a long time. It has been shown that moderate intensity running for 30 minutes per day for 8 weeks increases the number of skeletal muscle stem cells in aged mice. The brain is another organ that is affected by exercise. Neurogenesis increases in mice transplanted with plasma from exercised aged mice. Some other aged stem cells also benefit from exercise, such as tendon stem cells.

Calorie restriction (CR) and fasting are two other strategies that have been largely studied for their rejuvenating capacities. Intestinal stem cells increase in number and replicate more after CR and fasting-mimicking diet (FMD), and their capacity to form organoids is improved after fasting. In the skeletal muscle, muscle stem cells seem to enter a deep quiescent state after fasting, which is not recovered by re-feeding. This slows muscle regeneration but improves the survival of these stem cells.

An exciting strategy that has been proposed for cell rejuvenation is reprogramming cells to a more undifferentiated state by inducing expression of the Yamanaka factors. A cyclic induction of OSKM was able to increase the numbers of muscle stem cells and hair follicle stem cells in adult mice with progeria and to improve regeneration of the skeletal muscle. Further studies will be needed to better understand the effect of reprogramming on stem cells and lifespan, and to define an optimal treatment strategy to achieve rejuvenation without the risk of cancer induction.

Cellular senescence is characterized by a stable cell-cycle arrest of dysfunctional cells which also present with a senescence-associated secretory phenotype (SASP). Clearance of senescent cells with senolytics was shown to exert promising results on hematopoietic stem cells and muscle stem cells. Senescent cells form an inflamed niche that mirrors the inflammation associated with aging by arresting stem cell proliferation and regenerative potential. In young and aged mice, the reduction of senescent cells or of the inflammation associated with senescent cells accelerates tissue regeneration.

Cell polarization, defined as the uneven distribution of RNAs, proteins, organelles, and cytoplasm, occurs in many forms and the most widely known is the apical-basal polarity of epithelial cells. The capacity of establishing cell polarity, associated with the activity or the expression of specific polarity proteins, appears to be linked to aging of asymmetrically dividing cells such as stem cells. In the context of somatic stem cell rejuvenation, targeting cell polarity represents a potential strategy to improve tissue and organ regeneration. For example, Cdc42 is involved in the establishment of cell polarity in many cell types and its activity level increases over time, driving loss of polarity and aging in stem cells. Cdc42 activity can be efficiently targeted by using a specific small molecule inhibitor named CASIN (Cdc42 activity-specific inhibitor). CASIN treatment has been shown to rejuvenate different somatic stem cell types.

In recent years, researchers have been putting more effect into analyses of the CALERIE 2 study of human calorie restriction. The study took place some years ago, but new results continue to be published. Here, researchers show that effects on telomere length and a related aging clock are inconclusive. Telomere length measured in the white blood cells of a blood sample is not a great measure of aging. It is highly variable between individuals, is influenced day to day changes in immune status, and it takes a fairly large study group for age-related trends to show up. It has rightfully been eclipsed by the development of aging clocks derived from omics data.

Caloric restriction (CR) modifies lifespan and aging biology in animal models. The Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE) 2 trial tested translation of these findings to humans. CALERIE randomized healthy, nonobese men and premenopausal women (age 21-50 years; BMI 22.0-27.9 kg/m2), to 25% CR or ad-libitum (AL) control (2:1) for 2 years. Prior analyses of CALERIE participants' blood chemistries, immunology, and epigenetic data suggest the 2-year CR intervention slowed biological aging. Here, we extend these analyses to test effects of CR on telomere length (TL) attrition.

TL was quantified in blood samples collected at baseline, 12-, and 24-months by quantitative PCR (absolute TL; aTL) and a published DNA-methylation algorithm, DNA methylation estimated telomere length (DNAmTL). Intent-to-treat analysis found no significant differences in TL attrition across the first year, although there were trends toward increased attrition in the CR group for both aTL and DNAmTL measurements. When accounting for adherence heterogeneity with an Effect-of-Treatment-on-the-Treated analysis, greater CR dose was associated with increased DNAmTL attrition during the baseline to 12-month weight-loss period. By contrast, both CR group status and increased CR were associated with reduced aTL attrition over the month 12 to month 24 weight maintenance period.

No differences were observed when considering TL change across the study duration from baseline to 24-months, leaving it unclear whether CR-related effects reflect long-term detriments to telomere fidelity, a hormesis-like adaptation to decreased energy availability, or measurement error and insufficient statistical power. Unraveling these trends will be a focus of future CALERIE analyses and trials.

Link: https://doi.org/10.1111/acel.14149

Researchers here report on the results of transfusion of young rat plasma into old rats, starting every other week in later life. The study is small, and is one more data point to add to a mixed set of results. Plasma transfusion from young individual to old individual doesn't look that impressive, all told, either in animals or in human patients. That doesn't appear to be discouraging the community of researchers and developers who continue to work on approaches to transfusion that they believe may move the needle. The example here is a straightforward approach to transfusion, the procedure conducted every other week, and is one of the studies in which the intervention appears to work well enough to be interesting.

There is converging evidence that young blood conveys cells, vesicles, and molecules able to revitalize function and restore organ integrity in old individuals. We assessed the effects of young plasma on the lifespan, epigenetic age, and healthspan of old female rats. Beginning at 25.6 months of age, a group of 9 rats (group T) was intraperitoneally injected with plasma from young rats until their natural death. A group of 8 control rats of the same age received no treatment (group C). Blood samples were collected every other week. Survival curves showed that from age 26 to 30 months, none of the group T animals died, whereas the survival curve of group C rats began to decline at age 26 months.

Blood DNA methylation (DNAm) age versus chronological age showed that DNAm age in young animals increased faster than chronological age, then slowed down, entering a plateau after 27 months. The DNAm age of the treated rats fell below the DNAm age of controls and, in numerical terms, remained consistently lower until natural death. When rats were grouped according to the similarities in their differential blood DNA methylation profile, samples from the treated and control rats clustered in separate groups. Analysis of promoter differential methylation in genes involved in systemic regulatory activities revealed specific gene ontology term enrichment related to the insulin-like factors pathways as well as to cytokines and chemokines associated with immune and homeostatic functions.

We conclude that young plasma therapy may constitute a natural, noninvasive intervention for epigenetic rejuvenation and health enhancement.

Link: https://doi.org/10.1093/gerona/glae071

The research community has come to see chronic inflammation and other age-related immune system dysfunctions as an important aspect of neurodegenerative conditions. Inflammation in the short term is necessary for defense against pathogens and regeneration following injury. Unresolved, constant inflammation is harmful to tissue structure and function, however, changing cell behavior for the worse. In brain tissue, the effects of inflammatory signaling on the behavior of innate immune cells called microglia appears particularly important. Neurogenerative conditions are characterized by activated microglia. These microglia are less able to perform maintenance activities, while also contributing to loss of synapses and other pathological changes in the brain.

The authors of today's open access review paper take a broad view of the impact of immune system aging on the brain, and its potential roles in the development of neurodegenerative conditions. All such conditions exhibit changes in cellular biochemistry that can be linked to changed immune activity. Further, an inflammatory state appears correlated with onset and progression of these conditions. There is ample evidence for immunomodulatory, anti-inflammatory approaches to be a sensible way forward in the treatment of neurodegeneration, but adjusting the immune system is not straightforward. The fine details of the inflammatory mechanisms involved in pathology matter when it comes to building a better therapy.

Immunological aspects of central neurodegeneration

The etiology of various neurodegenerative disorders (NDs) that mainly affect the central nervous system including (but not limited to) Alzheimer's disease, Parkinson's disease, and Huntington's disease has classically been attributed to neuronal defects that culminate with the loss of specific neuronal populations. However, accumulating evidence suggests that numerous immune effector cells and the products thereof (including cytokines and other soluble mediators) have a major impact on the pathogenesis and/or severity of these and other neurodegenerative syndromes. These observations not only add to our understanding of neurodegenerative conditions but also imply that (at least in some cases) therapeutic strategies targeting immune cells or their products may mediate clinically relevant neuroprotective effects. Here, we critically discuss immunological mechanisms of central neurodegeneration and propose potential strategies to correct neurodegeneration-associated immunological dysfunction with therapeutic purposes.

While most central NDs appear to originate from genetic or environmental alterations of cellular homeostasis in the brain parenchyma, it is now clear that such perturbations are accompanied by the activation of innate and (at least in some cases) adaptive immune effector mechanisms that contribute to disease pathogenesis. Multiple NDs are associated with mutations in genes encoding components of the innate or adaptive immune system, such as TREM2 or HLA-DRB1. Moreover, hitherto unrecognized connections are emerging between central ND susceptibility genes, such as SNCA, and core immunological functions, such as the development of normal innate and adaptive immune reactions to bacterial challenges. Finally, patients affected by numerous NDs including Alzheimer's disease, Parkinson's disease, Huntington's disease, Lewy body dementia, and frontotemporal dementia exhibit shifts in the circulating levels of pro-inflammatory cytokines or peripheral immune populations, further supporting a pathogenic role for altered immune responses in the central nervous system in the progression of NDs.

With a few exceptions including the robust implication of CD4+ in disease pathogenesis in mouse models of Lewy body dementia, most of the current links between immunological mechanisms and ND pathogenesis rely on observational and correlative rather than mechanistic experimental setups. While at least partially this reflects the limited number of rodent models that recapitulate the emergence and progression of NDs in humans, it will be important to harness currently available models to implement antibody-mediated depletion, pharmacological inhibition, or genetic deletion/downregulation experiments to mechanistically link altered immune functions to ND pathogenesis and potentially identify novel targets for therapeutic interventions. While additional work is required to elucidate the actual therapeutic potential of immunotherapy for patients with central NDs, both innate and immune dysfunctions have been documented in the progression of NDs. It will be important to obtain further mechanistic insights into the immunological aspects of human degeneration in existing and newly developed rodent ND models to develop disease-modifying treatment options for these patient populations.

Mitrix Bio is one of the companies developing the means to produce large amounts of mitochondria for transplantation. Cells will take up new mitochondria from the surrounding environment, and mitochondria can be harvested from cell cultures. Mitochondrial function declines with age, the result of (a) gene expression changes in the cell nucleus that alter mitochondrial dynamics and the quality control process of mitophagy, and (b) damage to mitochondrial DNA. Evidence from animal studies suggests that replacing mitochondria in aged tissues produces benefits to health and organ function that last for long enough to be interesting as a basis for therapy. From a regulatory perspective in the US, harvested mitochondria are in the same class of treatment as harvested stem cells, so it is somewhat easier to progress to initial human trials than is the case for new drugs. It will be interesting to see the results.

We are proud to announce "The 130-Year-Old-Lifespan Trials". Our volunteers - mostly in their 70s and 80s - aim to be the first people in history to break past the current "Lifespan Barrier" for the human species, which stands at 122. We aim to give them average lifespans of 130 with the health, strength, and appearance of 50. This trial will be conducted in our new division - Biotech Explorers. Because there will be very limited space to treat people in the early years, this treatment will be provided initially to current and former astronauts, and children with certain premature aging diseases.

We've known for the past year, from animal trials, that bioreactor-grown mitochondria transplantation had the potential to dramatically speed healing, fight infection, and extend lifespan. We could see in animal tests in the brain, muscles, immune system, and skin, that the effect was real. Other types of mitochondrial transplantation have already been safely used for in human patients for rare diseases. The 130-year-old lifespan treatment will be based on Bioreactor-Grown Mitochondrial Transplantation - a technique that our parent firm Mitrix Bio has been developing for several years. We are now making animals in the lab younger routinely.

Now the job in front of us, is to make the leap with careful, rigorous human trials targeting a 130-year-old lifespan. There is so much work to be done, but our team of top scientists from major universities and other research groups are ready to take on this challenge.

Link: https://www.linkedin.com/posts/activity-7181774280462938112-oLbY

Researchers here look at cellular dysfunction that may form the earliest stages of Alzheimer's disease, prior to the accumulation of misfolded amyloid-β and cognitive decline. In general, intervening early in the progression of a disease will always be easier, given the right target. The challenge lies in identifying and understanding the causative mechanisms, in an environment in which (a) there is little access to brain tissue in the earliest stages of Alzheimer's disease, and (b) the animal models are highly artificial, as mice do not normally develop anything resembling Alzheimer's disease, and thus may not accurately reflect important aspects of the human condition.

Amyloid precursor protein (APP) is found in the cell membranes of brain cells. The brain constantly produces new APP molecules while breaking down and removing old ones. This process involves enzymatic scissors, with gamma-secretase being the final one that generates the well-known and well-studied amyloid-β (Aβ) peptides in Alzheimer's disease (AD). For a long time, it was thought that blocking gamma-secretase would be the logical step to prevent the production of toxic Aβ fragments. However, this leads to the accumulation of their precursor, the APP-C-Terminal Fragments, or APP-CTFs. Now, researchers have discovered that these fragments are also toxic to neurons. They appear to accumulate between the endoplasmic reticulum (ER), the compartment that is crucial for lipid synthesis and calcium storage, and the lysosomes, the so-called 'waste bins' of neurons, which are critical for degrading the cell's waste products.

By doing so, APP-CTFs disrupt the delicate balance of calcium within lysosomes. This disruption triggers a cascade of events. The ER can no longer effectively refill lysosomes with calcium, leading to a buildup of cholesterol and a decline in their ability to break down cellular waste. This results in the collapse of the entire endolysosomal system, a crucial pathway for maintaining healthy neurons. The new study further supports that the APP-CTFs resulting from suppressing gamma-secretase might actually be the culprit behind endolysosomal dysfunction, as observed in the very early stages of AD.

This research significantly advances our comprehension of the potential causes of disease in the early stages of AD. A remarkable outcome of this study is that these early stages could be caused by another fragment of the same APP molecule rather than Aβ. This has significant implications for the current therapeutic approaches that aim to clear the AD brain from amyloid plaques, as they tend to ignore the toxic effects of other fragments. Other attempts focus on tau proteins or neuroinflammation, which are other hallmarks of AD progression that target later events. However, early intervention is likely the key to stopping or even preventing AD.

Link: https://press.vib.be/new-mechanism-uncovered-in-early-stages-of-alzheimers-disease

Like the accumulation of senescent cells, loss of stem cell function is a problematic feature of aging. Also like the accumulation of senescent cells, loss of stem cell function is likely downstream of a combination of forms of molecular damage and consequent changes in cell behavior and cell signaling that are presently incompletely understood in detail and harder to address. Senescent cells can be cleared more readily than prevented, and stem cells may be more readily coerced into activity or replaced entirely than is the case for prevention of their age-related functional decline.

Stemness is a property of stem cells. Tautologically it is what distinguishes stem cells from somatic cells, primarily meaning (a) continual self-renewal of the population and (b) the ability to differentiate into multiple other cell types. Stem cell activity declines with age, but that doesn't necessarily mean that stemness is in decline. In muscle stem cells, for example, there is evidence for aged muscle stem cells to perform just as well as young muscle stem cells once removed from the aged tissue environment, even given a presumably greater burden of many forms of age-related damage inherent to the cells themselves. One can argue that many types of stem cell are restrained by damage to their niches, or by changes in the aged signaling environment, not by any inherent damage that reduces the potential for stemness.

In today's open access paper, researchers generate a stemness score based on transcriptomic data, and see how it changes with age in many tissues in the human body. This may be a blurred measure of capacity for stemness coupled with the impact of the aged microenvironment in which cells find themselves. Another interesting addition to this data would be to take cell samples and put them in a youthful environment, then test again and see how their stemness score changes.

Evidence of a pan-tissue decline in stemness during human aging

Although the aging process is the leading cause of human mortality and morbidity, being associated with several diseases, scientists still debate its causes and mechanisms. Among the biological pathways associated with aging, we can highlight stem cell exhaustion, which argues that during normal aging, the decrease in the number or activity of these cells contributes to physiological dysfunction in aged tissues. This concept is supported by the observation that aging is associated with reduced tissue renewal and repair at advanced ages. Moreover, longevity manipulations in mice often affect growth and cell division, which has been hypothesized to relate to stem cells.

Despite their importance, in vivo detection and quantification of stem cells are challenging, which makes it difficult to study their association with aging, especially in humans. In this context, detecting stemness-associated expression signatures is a promising strategy for studying stem cell biology. Stemness refers to a distinctive attribute marked by a series of molecular processes that delineate the essential properties of stem cells, enabling the generation of daughter cells and self-renewal. While widely employed in oncology, the exploration of this concept in gerontology has been comparatively limited.

In this study, we applied a machine learning method to detect stemness signatures from transcriptome data of healthy human tissues. The methodology, developed by Malta et al., was trained on stem cell classes and their differentiated progenitors and went through rigorous validation steps including tests in several datasets from tumor and non-tumor samples. Although initially used to study oncogenic dedifferentiation, this approach has also been employed to study normal and pathological (non-tumorous) samples. Therefore, we first downloaded expression data of 17,382 samples, divided into 30 tissues aged between 20 and 79 years, from GTEx in transcripts per million (TPM). After that, we followed assigned a stemness score to all GTEx samples.

We found that ~60% of the studied tissues exhibit a significant negative correlation between the subject's age and stemness score. The only significant exception was the uterus, where we observed an increased stemness with age. Moreover, we observed that stemness is positively correlated with cell proliferation and negatively correlated with cellular senescence. Finally, we also observed a trend that hematopoietic stem cells derived from older individuals might have higher stemness scores. In conclusion, we assigned stemness scores to human samples and show evidence of a pan-tissue loss of stemness during human aging, which adds weight to the idea that stem cell deterioration may contribute to human aging.

Exercise is well known to correlate with reduced risk of cardiovascular disease in human epidemiological studies. In animal studies, it is possible to demonstrate that increased physical activity does in fact cause a lower incidence of cardiovascular disease. Here researchers argue that stress has a significant effect on cardiovascular outcomes, as demonstrated by the fact that patients with greater degrees of stress, such as those with major depressive disorder, exhibit a larger beneficial correlation of reduced cardiovascular disease with exercise. It is interesting to ask which mechanisms are causing this association; exercise produces sweeping beneficial effects on body and brain, so picking apart specific contributions to an observed correlation is challenging. Yes, exercise reduces the consequences of stress, but depression tends to lead to reduced activity, and those depressed patients who are exercising were probably better off than their peers to start with. And so forth. For every proposition, there is a counterargument.

To assess the mechanisms underlying the psychological and cardiovascular disease benefits of physical activity, researchers analyzed medical records and other information of 50,359 participants from the Mass General Brigham Biobank who completed a physical activity survey. A subset of 774 participants also underwent brain imaging tests and measurements of stress-related brain activity. Over a median follow-up of 10 years, 12.9% of participants developed cardiovascular disease. Participants who met physical activity recommendations had a 23% lower risk of developing cardiovascular disease compared with those not meeting these recommendations.

Individuals with higher levels of physical activity also tended to have lower stress-related brain activity. Notably, reductions in stress-associated brain activity were driven by gains in function in the prefrontal cortex, a part of the brain involved in executive function (i.e., decision making, impulse control) and is known to restrain stress centers of the brain. Analyses accounted for other lifestyle variables and risk factors for coronary disease.

Moreover, reductions in stress-related brain signaling partially accounted for physical activity's cardiovascular benefit. As an extension of this finding, the researchers found in a cohort of 50,359 participants that the cardiovascular benefit of exercise was substantially greater among participants who would be expected to have higher stress-related brain activity, such as those with pre-existing depression. "Physical activity was roughly twice as effective in lowering cardiovascular disease risk among those with depression. Effects on the brain's stress-related activity may explain this novel observation."

Link: https://www.eurekalert.org/news-releases/1040861

Researchers here discuss some of the results achieved in building the Human Skeletal Muscle Aging Atlas. Focusing on stem cells in muscle tissue, they find numerous changes in gene expression relating to inflammation and reduced activity. The chronic inflammation characteristic of aging, provoked by senescent cells and innate immune reactions to molecular damage, is known to be involved in many of the dysfunctions of aging. Loss of stem cell activity, and thus a reduced supply of daughter somatic cells to replace losses and repair damage, is one of those dysfunctions.

Skeletal muscle aging is a key contributor to age-related frailty and sarcopenia with substantial implications for global health. Here we profiled 90,902 single cells and 92,259 single nuclei from 17 donors to map the aging process in the adult human intercostal muscle, identifying cellular changes in each muscle compartment.

From our in-depth analysis, we identified aging mechanisms acting in parallel across different cell compartments. In the muscle stem cell (MuSC) compartment, we found downregulation of ribosome assembly resulting in decreased MuSC activation as well as upregulation of pro-inflammatory pathways, such as NF-κB, and increased expression of cytokines, such as CCL2. In the MF microenvironment, we found several cell types that expressed pro-inflammatory chemokines, such as CCL2, CCL3, and CCL4. These cytokines may mediate the recruitment of lymphoid cells into muscle and the pro-inflammatory environment of aged muscle. Moreover, our cross-species and cross-muscle integrated aging atlas highlights an overall downregulation in gene expression, an increase in inflammation and a decrease in pro-growth, repair, and innervation pathways. Pan-microenvironment upregulation of CCL2 with age was not recapitulated in mice, suggesting an interesting human-mouse distinction in orchestration of inflammation.

Our atlas also highlights an expansion of nuclei associated with the neuromuscular junction, which may reflect re-innervation, and outlines how the loss of fast-twitch myofibers is mitigated through regeneration and upregulation of fast-type markers in slow-twitch myofibers with age. Furthermore, we document the function of aging muscle microenvironment in immune cell attraction.

Link: https://doi.org/10.1038/s43587-024-00613-3