A Profile of Buck Institute Startup Company Gerostate Alpha

A sizable fraction of the startup biotech companies in the small but growing longevity industry are essentially screening programs, in that they are developing various improvements on the standard approaches to screening small molecule databases in search of drugs that affect mechanisms relevant to aging. Some of them intend to take the best results from their screens into clinical development, while others intend to provide infrastructure drug development services, such as better, faster, or cheaper compound discovery and early validation, to the broader biotech industry. Examples among the first generation of longevity industry biotech startups include In Silico Medicine, BioAge, and Gero, among others.

Today's articles profile Gerostate Alpha, a more recently formed company that is incubated at the Buck Institute for Research on Aging, benefiting from the science and infrastructure there. The founders are most interested in entirely unbiased screening for compounds that slow aging and extend healthy life span, and less interested in a focus on any specific theory of aging or set of mechanisms. In the bigger picture, this is a useful exercise with a small chance of turning up interesting mechanisms involved in the progression of aging that have been overlooked.

That said, based on the results from other screening efforts, it is reasonable to believe that the vast majority of the output of the Gerostate Alpha screening process, meaning compounds that slow aging in short-lived species, will be those that upregulate stress response mechanisms, akin to those triggered by calorie restriction, and will thus have much smaller and less reliable effects in long-lived species. Whether there are specks of gold to be found amidst that low value dross is a question that can only be answered by a lot more unbiased screening than has so far taken place.

This low ratio of useful to entirely mediocre mechanisms and modulators of aging is the reason why I'm less in favor of unbiased screening than in the entirely biased approach of repairing the forms of cell and tissue damage known to be at the root of aging. That entirely biased strategy gave us senolytics, treatments that robustly produce rejuvenation in animal models by clearing senescent cells. There are a wide range of other forms of damage to be repaired, and an expectation that every one of them could turn out to be as good a field as senolytics. Aging is caused by damage. The best way forward is deliberate, targeted, periodic repair of that damage.

Gerostate Alpha: "The major modulators of aging remain to be discovered"

While many companies in Longevity are focused on addressing one or more of the hallmarks, or pillars, of aging, the founders of Gerostate Alpha always saw things a little differently. "People take the hallmarks of aging as a launching off point, thinking that if they can forestall a particular pillar, let's say inflammation, then they'll get beneficial outcomes - but this is a biased approach. We've always been interested in looking at aging mechanisms in an unbiased way, whether through genetic interventions, or pharmacological interventions, we're not beholden to a particular mechanism, per se."

"Having been involved in the basic biology of aging and trying to understand the degenerative changes of aging from a mechanistic perspective for many years, that resonated with us. And so we put together a proposal focused around some of the ideas, particularly with regard to an unbiased way to identify molecules which might retard the aging process. We pitched it to Y Combinator, they really liked us and gave us a million dollars to start the company. It was certainly the fastest million we ever made in our careers!"

"You often hear people say they 'target aging' but you have to ask what does that mean - does it mean targeting a pillar of aging: senescence, inflammation, mitochondrial dysfunction? That's not targeting aging - that's targeting something other people have said is linked to aging processes. Everyone is very familiar now with using those terms, but it roots you in the idea that we understand what aging is, and we don't think we do. We believe that these pillars of aging are just one of many, and we think that the major modulators of aging remain to be discovered."

Gerostate Alpha: "Our phenotype is lifespan"

At the platform's "front end", the high throughput screen is predominantly based on lifespan extension data from a variety of strains and species of Caenorhabditis nematodes - simple, short-lived organisms, which allow manipulations of lifespan to be studied more easily. "At the back end, we phenotype the successful interventions that target different aspects of aging, in mice. And we're looking at multiple indications simultaneously, whether muscle dysfunction, lung function, bone function, cardiac function, the central nervous system to some extent. All of these things are screened for simultaneously. And I would argue this is something we can do better than anyone else."

The founders' confidence is largely because of the infrastructure that has been built up at the Buck Institute over many decades, and which would cost tens of millions of dollars if a start-up were to attempt to replicate it. "Our initial strategy was to screen small molecule libraries, so we did that on around 60,000 compounds, and we identified over 30 hits that have been validated. We're now prepping those and derivatives of those into lead candidates to move into our preclinical mouse models. But in parallel to that, we screened some libraries of off-patent compounds, and we've moved those through into preclinical mouse models already. We've had some really interesting hits and we're now doing our follow up experiments on the pathways involved in those and the efficacy of those compounds, in those specific tissues."

EP2 Knockdown in Macrophages Reduces Inflammation and Restores Cognitive Function in an Alzheimer's Mouse Model

Chronic inflammation is clearly very important in the progression of numerous neurodegenerative conditions, Alzheimer's disease included. Inflammatory signaling, when unrelenting, disrupts cell and tissue function in many tissue types. In recent years, the elimination of lingering senescent cells has been shown in animal studies to reduce inflammation and reverse many of the issues it causes in the aged body. Researchers here take a different approach to suppressing chronic inflammation, sabotaging the ability of macrophage cells to contribute to the inflammatory environment. This has the effect of reversing some of the cognitive decline observed in a mouse model of Alzheimer's disease.

Overexpression of cyclooxygenase-2 (COX-2), a major mediator of inflammation, in the brain produces Alzheimer's disease-like symptoms in mice: age-dependent inflammation and cognitive loss. COX-2 activation is the first step in the production of a lipid called prostaglandin E2 (PGE2), which can bind to one of its receptors, EP2, on immune cells and promote inflammation. To plug up the pathway, researchers have shown that deleting the EP2 receptor in mouse macrophages and brain-specific microglia - the cells normally responsible for detecting and destroying immune invaders and cellular debris - reduces inflammation and increases neuronal survival in response to both a bacterial toxin and a neurotoxin.

In the current study, the researchers wanted to understand how eliminating PGE2 signaling in macrophages could have these effects. They started by comparing macrophages from human blood donors either younger than 35 or older than 65. The cells from older donors made much more PGE2 and had higher abundance of the EP2 receptor than did macrophages from younger donors. When the researchers exposed human macrophages to PGE2, the cells altered their metabolism. Rather than using glucose to make energy, the cells converted it to glycogen and stored it, locking it up where the mitochondria couldn't access it for ATP production. "The result of that is that the cells are basically energy-depleted. They're just fatigued, and they don't work well. They don't phagocytose. They don't clear debris, including misfolded proteins associated with neurodegeneration."

When the scientists treated human macrophages from donors with an average age of about 48 with one of two EP2 receptor inhibitors, glycogen storage decreased, energy production increased, and cells shifted to express anti-inflammatory markers. As in human cells, aged mice also have higher levels of PGE2 in the blood and brain and EP2 receptor levels in macrophages, compared to younger mice. When the researchers knocked down the receptor in macrophages throughout the body in a mouse model of Alzheimer's disease or treated animals with either of two drugs to suppress EP2 function, cells had improved metabolism. The mice's age-associated inflammation also reversed and, with it, age-associated cognitive decline. Treating animals with an EP2 antagonist that couldn't get in the brain and thus only targeted the receptor in peripheral macrophages also led to cognitive improvement in older mice.

Link: https://www.the-scientist.com/news-opinion/a-tweak-to-immune-cells-reverses-aging-in-mice-68371

More Evidence for Senescent Cell Clearance as a Treatment for Neurodegenerative Conditions

Senescent cells accumulate in the brain with age, and these cells generate chronic inflammation in brain tissue. Neurodegenerative conditions such as Alzheimer's disease are known to prominently involve inflammation in the progression of pathology. At least one senolytic treatment, the combination of dasatinib and quercetin, can pass the blood-brain barrier to destroy senescent cells in the brain, and has been shown to reduce inflammation and reverse tau pathology in mouse models of Alzheimer's disease. Researchers here add more data to this subject, clearing senescent cells from the brains of aged mice, and finding that this reverses a sizable fraction of the age-related loss of cognitive function that normally takes place. At least one human trial has started up to test the use of dasatinib and quercetin to treat Alzheimer's disease; this is a very promising area of study.

Cellular senescence is characterized by an irreversible cell cycle arrest and a pro-inflammatory senescence-associated secretory phenotype (SASP), which is a major contributor to aging and age-related diseases. Clearance of senescent cells has been shown to improve brain function in mouse models of neurodegenerative diseases. However, it is still unknown whether senescent cell clearance alleviates cognitive dysfunction during the aging process.

To investigate this, we first conducted single-nuclei and single-cell RNA-seq in the hippocampus from young and aged mice. We observed an age-dependent increase in p16Ink4a senescent cells, which was more pronounced in microglia and oligodendrocyte progenitor cells and characterized by a SASP. We then aged INK-ATTAC mice, in which p16Ink4a-positive senescent cells can be genetically eliminated upon treatment with the drug AP20187 and treated them either with AP20187 or with the senolytic cocktail Dasatinib and Quercetin. We observed that both strategies resulted in a decrease in p16Ink4a exclusively in the microglial population, resulting in reduced microglial activation and reduced expression of SASP factors.

Importantly, both approaches significantly improved cognitive function in aged mice. Our data provide proof-of-concept for senolytic interventions' being a potential therapeutic avenue for alleviating age-associated cognitive impairment.

Link: https://doi.org/10.1111/acel.13296

An Interview with Ronjon Nag, Investor in the Longevity Industry

Ronjon Nag is an academic turned inventor turned entrepreneur turned investor in the communications and software industries, and now of late the longevity industry, a career path shared with a growing number of his peers in the Bay Area investment community. Alongside his principals Anastasiya Giarletta and Artem Trotsyuk, Ronjon Nag runs R42, a fund that grew out of his angel investing experience and successes. As is the case for near all of those who arrived comparatively early to the advent of this new industry, the R42 Group principals have a strong personal interest in health and longevity.

The longevity industry started up in earnest over the past five years or so, as early successes in aging research moved out of the labs and into biotech companies. In parallel, a growing number of technology investors have developed an interest in this field, expanding their portfolios to include biotechnology startups focused on aging. This is the next step in an ongoing process of support and interest: the application of the life sciences to the slowing and reversal of aging has long been an attraction to the successful and the influential of the Bay Area. It isn't an accident that the SENS Research Foundation was located there, for example, and nor is it an accident that much of the charitable funding that has supported rejuvenation research programs over the past decade or more was provided by technology industry philanthropists.

Your history is that of a technology entrepreneur turned technology investor; what drew your interests to biotech and the longevity industry?

I like really tough problems - I've done a lot of work in artificial intelligence and 30 years ago speech recognition was really tough yet we now see these technologies being used everywhere. Just as speech recognition predominately started out in university labs, it was commercialization that really got it into people's hands. I'm a big believer in the entrepreneurial process to speed things along, and I think in biotech and longevity the entrepreneurial process is going to accelerate the field. I'm still view myself as an entrepreneur as well as an investor - I really get involved with the companies I invest in - I have about 60 positions and I think the entrepreneurs appreciate working with someone who has been where they are currently. The empathy is important to have enhanced communication to help solve problems.

You have many fellow travelers in the technology investor and AI community, folk with an interest in aging. Why do you think there is such an overlap between software, technology, AI, longevity?

Today there is currently an inflection point where the tools of mathematics and computer science are accelerating the developments in biotech. We now live in a world where no one person has all the skills individually to solve problems and so I feel I can contribute mathematically, scientifically and commercially. Like artificial intelligence before, which is still quite difficult, biotech is also difficult - unlike physics, laws of biology are difficult to come by. Biology is beginning to turn into an engineering subject and I think we are seeing that subject can be accelerated and deployed at lower cost than previously. Biotech is notoriously expensive, and also takes a long time. We now have the vision that solutions can simply be "calculated"; we still have to do clinical trials which take actual time, but even there we can use Bayesian tests to efficiently implement trials.

Over at R42, we have a very wide definition of longevity from curing age related diseases in biotech, searching for solutions to the root cause of aging, but also technologies to assist people as they age, robots and the like.

My end of the longevity community is much more interested in biotech than in infrastructure technologies such as AI for drug discovery. What is on your investment radar in pure biotech for longevity?

Well, I would say that AI for drug discovery could actually find new drugs to solve aging, and quite optimistic on that, making several bets in that area, and a fundamental thesis is that computation can spit many more candidates for longevity that anyone can do manually. On the radar for pure biotech really looking at mechanisms that start to crumble as we get older. One is the thymus which helps us build out our immune system but goes away in our late teens. There are a few efforts looking at regrowing the thymus when we need it again when we are 80. We have an investment in Repair Biotechnologies, your company! Another area we are looking at is mitochondrial mechanisms. Mitochondria provide 90% of the energy of our cells, and as we age, they don't work the same. Looking at how we can correct them or replace them with fresh ones is an area to look at.

None of us are getting any younger yet, at least not meaningfully so. What is your take on what we should be doing to speed up progress towards human rejuvenation?

We do need more focused funds like R42 to able to sort the wheat from the chaff and be triage systems for larger funds to follow with more money in the best ideas. These early funds need to surround these early stage ideas with resources - people, connections, partners to make sure they flourish. Since aging is a significant source of mortality, matching government funds would be able to accelerate more efforts given the risk in the field. I think once we have a poster child of a successful aging company going public there will be an acceleration of investment.

You are big on education, formally and informally; what do you hope to be the outcome of your efforts to raise the profile of work on longevity?

Yes, education is important. I teach courses on AI and Longevity both at the R42 Institute and at Stanford University. The main thing here is to provide people from many disciplines the tolls to be able to contribute in their own way. If people can contribute then people will participate. There is a natural interest in living healthy and having a long life. There are many disciplines - physicists, psychologists, chemists, engineers, even ethicists, economists and lawyers who can bring their perspectives and with more people talking about from different fields it will naturally raise the profile of longevity science.

Reviewing the Epigenetics of Aging

Epigenetic mechanisms regulate the pace of production of specific proteins in a cell. Feedback loops link the activities of proteins produced, input from the surrounding cell environment, and epigenetic alterations that change further production of proteins. Epigenetic control of protein production shifts constantly in response to circumstances, but many changes are characteristic of aging and the aged tissue environment. These are largely thought to be reactions to (or side effects of) underlying molecular damage such as DNA double strand breaks, or environmental change such as increased inflammatory signaling, but a minority of researchers think epigenetic change to be a significant independent cause of aging. Partial reprogramming of cells can reverse many of the epigenetic changes that are characteristic of aged cells, so tests of the hypotheses regarding the role of epigenetic change in aging will be forthcoming in the years ahead.

Epigenetic changes directly contributing to aging and aging-related diseases include the accumulation of histone variants, loss of histones and heterochromatin, and deregulated expression/activity of miRNAs. In addition, histones show aberrant post-translational modifications leading to the imbalance of activating and repressing modifications. Moreover, remodeling complexes modulate chromatin accessibility and there is an aberrant expression/activity of miRNAs. Together, these epigenetic deregulations contribute to aging-associated changes in gene transcription and, as a consequence, translation as well as the stabilization or degradation of molecular factors.

While mechanisms underlying aging-related pathologies remain to be elucidated in detail, various studies demonstrate an epigenetic component. In fact, the aforementioned epigenetic modifications were shown to play essential roles in diseases including inflammation, cancer, osteoporosis, neurodegenerative diseases, and diabetes. While the precise mechanisms and connections between several epigenetic changes and human pathologies are still poorly understood, state-of-the-art next generation sequencing methods will allow researchers to address remaining questions.

An improved understanding of epigenetic mechanisms affecting longevity will be deciding crucial step towards the identification of new potential therapeutic targets. In fact, epigenetic drugs are of particular interest to the clinic due to their reversible and transient effect. A limitation of epigenetic studies, however, are the variations among single cells (both on an individual and tissue level), which occur with an even higher frequency in aged organisms. This biologically relevant heterogeneity might be further investigated, understood and potentially deconstructed with the help of new technological approaches like single-cell genomics. Together, characterizing molecular changes in different species during aging using state-of-the-art techniques will provide key insights into the relevance of epigenetics of aging and aging-associated diseases.

Link: https://doi.org/10.3390/ijms22010401

Visual Decline Correlates with Severity of Parkinson's Disease

Researchers here note that in many people visual decline precedes the more evident worsening of Parkinson's disease as it progresses. Similar mechanisms of neurodegeneration contribute to both manifestations of aging. Neurodegenerative conditions are the result of many interacting processes that collectively harm function in the brain, from the structural issues resulting from vascular aging, to failing mitochondrial function, to the formation of protein aggregates. These processes give rise to numerous distinct forms of loss of function, and thus people who exhibit any one of those losses are more likely to develop the others.

A new study adds to evidence that vision changes precede the cognitive decline that occurs in many, but not all, people with Parkinson's. A second new study found that structural and functional connections of brain regions become decoupled throughout the entire brain in people with Parkinson's disease, particularly among people with vision problems. The two studies together show how losses and changes to the brain's wiring underlie the cognitive impairment experienced by many people with Parkinson's disease.

In the first study, researchers studied 77 people with Parkinson's disease and found that simple vision tests predicted who would go on to get dementia after a year and a half. Dementia is a common, debilitating aspect of Parkinson's disease, estimated to affect roughly 50% of people within 10 years of a Parkinson's diagnosis. These longitudinal findings add weight to previous studies that were done at one time point, which had suggested that performance in vision tests was linked to the risk of cognitive decline. Those who went on to develop Parkinson's dementia had white matter damage to some of the long-distance wiring connecting the front and back of the brain, which helps the brain to function as a cohesive whole network.

The second study involved 88 people with Parkinson's disease (33 of whom had visual dysfunction and were thus judged to have a high risk of dementia) and 30 healthy adults as a control group, whose brains were imaged using MRI scans. In the healthy brain, there is a correlation between how strong the structural (physical) connections between two regions are, and how much those two regions are connected functionally. That coupling is not uniform across the brain, as there is some degree of decoupling in the healthy brain, particularly in areas involved in higher-order processing, which might provide the flexibility to enable abstract reasoning. Too much decoupling appears to be linked to poor outcomes.

The researchers found that people with Parkinson's disease exhibited a higher degree of decoupling across the whole brain. Areas at the back of the brain, and less specialised areas, had the most decoupling in Parkinson's patients. Parkinson's patients with visual dysfunction had more decoupling in some, but not all brain regions, particularly in memory-related regions in the temporal lobe.

Link: https://www.ucl.ac.uk/news/2021/jan/eye-tests-predict-parkinsons-linked-cognitive-decline-18-months-ahead

Senescent Microglia are Present in Greater Numbers in the Brains of Patients with Neurodegenerative Conditions

Accumulation of lingering senescent cells is an important mechanism of aging, as these errant cells secrete a potent mix of molecules that spurs chronic inflammation and degrades nearby tissue structure and function. Evidence has emerged for the presence of senescent supporting cells in the brain, such as microglia and astrocytes, to contribute to many different neurodegenerative diseases. Animal studies in which first generation senolytic drugs are used to clear senescent cells from the brain have show that such treatments are capable of reversing some forms of neurodegenerative pathology, such as the neuroinflammation and tau aggregation characteristic of tauopathies.

In today's open access paper, the authors report on an assessment of the numbers of what they term dystrophic microglia in human brains, cells that are most likely senescent but not conclusively determined to be so. They find that the numbers of these dystrophic cells are elevated in neurodegenerative conditions when compared to similarly aged controls without clear neurodegenerative disease. Aging progresses at a somewhat different pace from individual to individual, and differences in the burden of senescent cells - perhaps due to exposure to pathogens in the case of microglia and other immune cells - may be an important determinant of differences in the rate of aging and risk of age-related disease.

Dystrophic microglia are associated with neurodegenerative disease and not healthy aging in the human brain

Inflammation and cellular senescence are hallmarks of aging. Almost two decades ago, dystrophic microglia were described with beading and fragmentation of the branches of the microglia. In contrast to the hypertrophic microglia often seen following central nervous system injury, the dystrophic microglia were proposed to be a form of microglia senescence. While there is no single specific marker of cellular senescence, a handful of markers, such as p16INK4a, have some affinity for identifying senescent cells. Using a p16INK4a approach to target the removal of senescent cells in a mouse model of tauopathy resulted in reduced tau pathology, neuronal degeneration, and cognitive deficits. Given the necessary cellular stressors, microglia can become senescent/dystrophic.

Throughout the body, cellular senescence is associated with the secretion of inflammatory mediators, defined as the senescence-associated secretory phenotype. Even a small number of senescent cells in any organ can contribute to disease and by the spread of the senescence phenotype to neighboring healthy cells. The hypothesis that dystrophic microglia is an age-associated microglia morphology has not been experimentally tested. While cellular senescence generally increases with age, it can occur at any stage of life in response to stressors. This led our first question: are dystrophic microglia associated with chronological age in people? We hypothesized that with increasing years, there would be an increasing proportion of dystrophic microglia. Previous work, including our own, has found dystrophic microglia in aged humans without neurodegenerative pathology.

In contrast to the view that dystrophic microglia are purely an age-related change in microglial morphology, there is compelling evidence that dystrophic microglia are more closely associated with neurodegenerative disease. Previous studies identified dystrophic microglia in people with age-related neurodegenerative disease, including Alzheimer's disease (AD). These findings lead to our second question: is increased dystrophic microglia a disease associated phenomenon? We hypothesized that the absolute numbers, and/or percentage of dystrophic microglia, would be greater in people with neurodegenerative disease than age-matched controls.

To address these questions, we studied brains from the University of Kentucky Department of Pathology and the UK-ADRC biobank, covering the adult lifespan from 10-90+ years of age. Stereological counts of the total number of microglia, number of hypertrophic microglia, and the number of dystrophic microglia were conducted in 3 brain regions: hippocampal CA1, frontal cortex, gray matter, and white matter. We found that in the absence of neurodegenerative disease, there was only a modest increase in dystrophic microglia with age. However, with neurodegenerative pathology, the percentage of microglia observed to be dystrophic was much greater than aged-matched controls.

Reduced Capillary Density in the Retina Indicative of the Progression of Neurodegeneration

Capillary networks are very dense, hundreds of capillaries passing through any given square millimeter of tissue. This network of microvessels is necessary to supply tissues with oxygen and nutrients. Unfortunately it declines in density with age, for reasons that are not well understood in detail. This likely contributes meaningfully to age-related loss of function, particularly in energy-hungry tissues such as muscles and the brain. Researchers here illustrate that loss of capillary density as observed in the retina - the eyes being a convenient window into that outpost of the central nervous system - correlates with the progression of neurodegeneration in the brain. Some thought should go towards finding the means to encourage greater maintenance and formation of capillary networks throughout the body.

The retina and brain share many neuronal and vasculature characteristics, and potential biomarkers may be present in the retina. Previous studies have analyzed digital fundus photographs and reported a range of retinal vessel alterations in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). However, images obtained from this technique can only provide information of retinal arterioles and venules measuring 60-300 μm in diameter. Optical coherence tomography angiography (OCTA) is a recent innovation that allows for further quantification of the retinal microvasculature and visualization of capillaries measuring 5-15 μm in diameter, which may be more representative of the entire microvascular network. Thus, the OCTA may be a potential non-invasive optical imaging tool to determine the presence and role of microvascular dysfunction in AD and cognitive impairment.

While there are a few OCTA studies investigating AD, there have been mixed conclusions. Some researchers reported finding significant reduction in the vessel density (VD) only in the superficial plexus, which complements histology findings and OCT studies since the superficial plexus mainly supplies the inner retinal layer. However, others reported finding changes only in the deep plexus. Studies have also used OCTA to examine participants with MCI, who are at higher risk for dementia and AD, but have drawn conflicting results as well.

To address these gaps, the purpose of the current study is to compare the retinal microvasculature metrics using OCTA, accounting for potential measurement bias and projection artifacts in participants with AD, MCI, and controls. We hypothesize that alterations in OCTA metrics as characterized by sparser vessel density and loss of vessel complexity will occur predominately within the superficial capillary plexus, in AD and to a lesser extent in MCI compared to controls.

24 AD participants, 37 MCI participants, and 29 controls were diagnosed according to internationally accepted criteria. OCTA images of the superficial and deep capillary plexus (SCP, DCP) of the retinal microvasculature were obtained using a commercial OCTA system. The main outcome measures were vessel density (VD) and fractal dimension (FD) in the SCP and DCP within a 2.5-mm ring around the fovea which were compared between groups.

Compared with controls, AD participants showed significantly sparser VD in both plexuses whereas MCI participants only showed reduction at the superficial plexus. In terms of FD, AD and MCI participants exhibited a loss of vessel complexity of the SCP when compared with controls. Our study adds further to the concept that there are possible progressive differences in retinal microvascular alterations between AD and MCI. Taken together with increasing evidence from other research, our current study demonstrates that differences in retinal microvascular changes using OCTA may potentially be used to identify and screen for AD and earlier cognitive phenotypes (i.e., MCI).

Link: https://doi.org/10.1186/s13195-020-00724-0

Aging is Contagious within the Body

In the midst of a discussion regarding the limitations of life span studies, in that the use of death as an endpoint fails to capture all of the variances in health due to aging, the authors of this paper offer up the thought that aging is contagious within the body. Declines in one cell spread to another, directly or indirectly. Consider that the secretions of senescent cells can make nearby cells senescent. Declines in one tissue can spread to another, directly or indirectly. Consider that the progressive failure of kidney function produces cardiovascular and cognitive dysfunction as a result, because the vascular system and the brain are so very dependent on the environment that the kidney is primarily responsible for maintaining. What might we take from this line of thinking? Perhaps that every form of repair therapy can be helpful, and equally that any one form of repair might not be enough, and the details matter in every case.

Given the complex heterogeneities of cell and tissue aging in any single individual and the notion of the most rapidly aging tissues being the driver of the aging of that organism, do those more rapidly aging tissues accelerate the aging of other tissues in the body? Does the aging of one cell affect the age of another cell? Is aging contagious? The notion of the aging process spreading from one cell to another is highlighted by the field of cellular senescence. The secretome of senescent cells has been shown to induce senescence of neighboring cells. In that sense, there can be cellular leaders that accelerate the aging of other cells in the tissue.

The notion of cell-to-cell spreading of cellular dysfunction is of course not limited to the biology of senescence. This is becoming an increasingly recognized phenomenon in the pathogenesis of neurodegenerative diseases. In many diseases, including Alzheimer's disease, Huntington's disease and Parkinson's disease, a cardinal feature of the pathology is intracellular aggregation of proteins. While seemingly a cell-intrinsic phenomenon, one of the curious features of the pathology of these diseases is the apparent spread of the cellular abnormalities to anatomically connected brain regions.

The general concept of this kind of spreading proteinopathy from one cell to another, locally, arises from the biology of prions and prion diseases. Of course, some prions are truly contagious, in the sense of being transmissible between individuals or across species, but the spread within the central nervous system of an individual suggests cell-to-cell spread. As with senescence, this phenomenon could represent the conversion of cells from one state (free from aggregates) to another (aggregate-laden) since protein aggregation can be self-propagating. As protein aggregation is one of the key features of cellular aging, it is intriguing to consider the possibility of aged cells achieving a sufficiently dysfunctional state as a result of protein aggregation, then conferring an aging signal to nearby cells through non-cell autonomous regulation of proteostasis.

If aging is indeed contagious, is the spread restricted to neighboring cells or might it spread to distant tissues via the systemic circulation? Based on early work from our laboratories that ushered in a new era of the use of the technique of parabiosis in aging research, it is clear that systemic factors originating from distant tissues in the body are able to either promote or reverse cell and tissue aging phenotypes. These findings, as well as many follow-up studies, including the demonstration that plasma infusions alone are sufficient to exert these effects, have unequivocally demonstrated that factors in the blood are able to communicate information from one or more source tissues to other tissues throughout the body. These could potentially accelerate, delay, or even reverse the rate of aging of other tissues in the body. Indeed, studies of brain endothelial cell aging showed that infusion of aged plasma can accelerate while young plasma can reverse aging as determined by analysis of the transcriptome. These studies highlight the fact that cellular aging does not occur independent of influences that are both local and systemic.

Link: https://doi.org/10.1038/s43587-020-00015-1

Request for Startups in the Rejuvenation Biotechnology Space, 2021 Edition

For a few years now, I've suggested areas of opportunity in rejuvenation biotechnology in which either (a) it seems quite viable to start a company, given what I've seen going on in industry and academia, or (b) it would be very helpful should someone step up with an approach that works, given the need for a solution. The longevity industry is still young, still small, and countless valuable programs in the aging research field remain waiting to be championed and carried forward to the clinic. The low-hanging fruit is still near all there to be claimed: what is possible is a far greater space than what is presently being attempted.

A Gene Therapy Platform that Just Works

The primary challenges in gene therapy are easily stated: express genes for (a) a controllable length of time, (b) to a useful degree in specific tissues without overloading other tissues, (c) with a high degree of coverage of cells in the tissues of interest. It would be nice to also have (d) at a reasonable cost, but cost will come down given a platform that can be used for most gene therapies and hits points (a) through (c). That there isn't a good off-the-shelf approach that can be directly and easily applied to an arbitrary gene therapy in an arbitrary tissue is hindering development.

At present plasmid delivery via more recent varieties of lipid nanoparticle, with expression made selective to cell type by use of appropriate promoters, looks like it may be able to achieve the goal of a general gene therapy platform useful for most therapies, given further advances in the technical capabilities of existing platforms. That said, near all gene therapy delivery technologies have the issue that when delivered systemically via intravenous injection, 80% or more of the injected vector will end up in the liver. Thus there must be a way to make that excess a non-event while still getting a useful amount of vector into the tissue of interest. Perhaps this could be solved by more sophisticated and much safer means of direct injection of internal organs, or more sophisticated carriers that can be steered to specific locations in the body before releasing their gene therapy cargo. Regardless, it seems plausible that there is some combination of the many approaches demonstrated in the laboratory or presently in clinical development that could result in a Gene Therapy Platform that Just Works for a majority of treatments.

Repurpose Fecal Microbiota Transplantation for the Treatment of Frailty

Repurposing an existing therapy is considerably easier than building a new one. Fecal microbiota transplantation is used to treat conditions in which the gut has been overtaken by pathological bacteria, and works quite well. The gut microbiome deteriorates with age, becoming more inflammatory, alongside a reduced production of the beneficial metabolites needed by the body. It has been demonstrated that transplanting gut microbes from young animals to old animals restores a more youthful microbiome, and as a consequence improves health and extends life span. Bringing that same approach to humans will require only modest refinement of the existing protocols, with perhaps more of an emphasis on screening out potentially harmful microbial species that a young immune system is better equipped to handle. Treating frailty by rejuvenating the gut microbiome might be a good option for a new development program, given that chronic inflammation is an important contributing cause of the condition.

Hematopoietic Cell Mobilization for Revascularization

The density of capillary networks throughout the body declines with age. This is likely quite important in loss of tissue function, particularly in muscle and brain, as these organs have a high need for nutrients and energy. The process of generating new blood vessels, particularly in response to injury, involves hematopoietic cells leaving their bone marrow niche and migrating to the area of injury. In connection with hematopoietic stem cell transplantation, a range of drugs are presently employed to provoke this exit of hematopoietic cells from the bone marrow into the circulatory system, where they can be easily harvested via drawing blood. These compounds target proteins such as CXCL12, CXCR4, CDC42, or their receptors, all involved in regulating the mechanisms that determine whether hematopoietic cells leave their niches. Can these mechanisms, and the state of the art in this part of the field, be used to increase capillary and other vessel density in uninjured individuals?

Regrow the Thymus to a Greater Degree than the Intervene Immune Approach

COVID-19 has hopefully made more people aware of the importance of age-related immunosenescence to declining health and resilience in later life. A sizable part of the decline of the immune system is the result of the atrophy of the thymus. Intervene Immune demonstrated that thymic rejuvenation is practical, and that it can measurably improve immune system function in aging humans, even when the degree of regrowth is only modest. Now we need more companies - beyond Lygenesis and Repair Biotechnologies - hard at work on better approaches that are capable of (a) producing much larger degrees of thymic regrowth, and (b) being made safe and cost-effective enough to be delivered to the entire adult population. There are many strategies that could in principle achieve the first goal, but the second is a tall order.

Make Worthwhile Treatments for Aging Accessible to the Masses

A number of possible approaches to the treatment of aging appear to pass the cost-benefit calculation, are therapies that exist today, and can be used by the medical community as off-label treatments. Examples include the first generation senolytic drugs that have undergone human trials, such as the dasatinib and quercetin combination. We might also consider periodic plasma dilution to reduce damaging signaling in the aging body. And so forth. The adoption of these approaches by physicians and clinics will be slow and patchy, and there is an opportunity here for companies that can accelerate this approach. Consider a venture like AgelessRx, for example, but with a much higher bar on the quality of treatments offered. Or physician network providers, or a chain of clinics, or a coordinated effort to make medical tourism work for senolytic therapies, wherein every older person in the US is a potential customer. There are many possibilities here in the ecosystem of medical services.

Platforms for the Destruction of Metabolic Waste

A very wide variety of metabolic waste is involved in aging. Misfolded proteins, some of which form amyloids, advanced glycation end-products, altered cholesterols, all sorts of garbage molecules that end up in the lysosome, and so on. Each of these categories contains many different molecular species, found in different places inside and outside the cell, requiring different classes of approach to find and break down. One universal platform for all unwanted molecules in the body isn't a feasible prospect, but there must still be a more efficient approach to break down or sequester or otherwise deal with the many different molecules in each specific location. Platforms are needed, approaches that can be cost-effectively customized to attack many molecules with very different characteristics. The catalytic antibody platform of Covalent Bioscience is one illustrative example. Another might be a company that uses recently developed techniques for culturing arbitrary bacterial species in order to efficiently mine soil and ocean bacteria for the tools they use to break down specific problem molecules, and which can serve as the basis for enzyme therapies.

Restore Youthful Hematopoietic Function

A complex hierarchy of hematopoietic cells in bone marrow is responsible for generating all immune cells, but this system runs awry with age. It begins to generate too many myeloid cells, and the hematopoietic cells themselves become inherently damaged, as well as dysfunctional in response to signaling changes, such as those that accompany chronic inflammation. Next to regrowth of the thymus, rejuvenation of hematopoiesis is the other important component needed to restore an aged immune system to more youthful function. The most direct of potential approaches is the transplantation of new hematopoietic stem cells. The older the patient, the more damaged the existing population, and the more likely it is that this will be necessary. But there are other approaches that might be taken earlier, such as adjusting signaling, protecting existing hematopoietic cells, changing the behavior of supporting stem cell niche cells, and so forth. This is a field which has for some years seemed on the verge of generating a viable approach to a rejuvenation therapy, and many lines of research are at the point at which they could in principle transition to clinical development. Champions are needed.

Suppression of Tyrosine Degradation Modestly Extends Life Span in Flies

There are a great many ways to influence cellular metabolism to modestly slow the pace of aging, but few of them are of lll that much interest from a practical point of view, as a basis for therapies that might meaningfully extend human life spans. If an approach involves improvements in mitochondrial function and less than a 10% increase in life span in a short-lived species such as flies, as is the case here, then it is only of academic interest to scientists who closely study the intersection between metabolism and degenerative aging. Improvements in life span in short-lived species achieved in this manner, via changes in mitochondrial function, scale down dramatically when the same approach is tried in longer-lived species. Thus this method of slowing aging is unlikely to be any better for human health than the well-described outcomes of eating somewhat less or exercising somewhat more.

One approach to identify new traits responsible for aging is to compare how these traits change with age in control and long-lived animals of the same species. For example, centenarians have a distinctive epigenetic profile compared to an age-matched control population. Similarly, we previously showed that flies with increased longevity have dramatic differences in many metabolites associated with methionine metabolism even at 1 week of age when 100% of both control- and long-lived flies are still alive.

To identify novel metabolic pathways that correlate with lifespan and that can be responsible for aging, we compared the metabolome of 1-week- and 4-week-old wild-type and long-lived flies to identify changes in metabolites that correlate with lifespan and identified tyrosine as an age-dependent metabolite. We demonstrate that Drosophila has a single tyrosine aminotransferase (TAT). Whole-body or neuronal-specific downregulation of TAT as well as other downstream enzymes in the tyrosine degradation pathway significantly extend Drosophila lifespan, cause alterations of multiple metabolites associated with increased lifespan, and lead to an increase in tyrosine and tyrosine-derived neuromediators (dopamine, octopamine, and tyramine). We further demonstrate that mitochondrial dysfunction may serve as an age-dependent stimulus that redirects tyrosine from neuromediator production into mitochondrial metabolism.

In conclusion, our studies highlight the important role of the tyrosine degradation pathway and position TAT as a link between neuromediator production, dysfunctional mitochondria, and aging.

Link: https://doi.org/10.7554/eLife.58053

Supporting Evidence for the Hypothesis that NAD+ Upregulation Increases Cancer Risk

NAD+ levels in the mitochondria decline with age, and this is a proximate cause of reduced mitochondrial function. Approaches to increasing levels of NAD+ in aging cells have been shown to improve metabolism and mitochondrial function in mice, but the evidence is mixed in humans for there to be any meaningful effect on age-related conditions. The common approaches to NAD+ upregulation, meaning supplementation with derivatives of vitamin B3, such as nicotinamide riboside, are about as effective as structured exercise programs in increasing NAD+ levels.

There is the suspicion that taking this shortcut - without adding all of the other metabolic effects of exercise - could increase the harms done by problem cells in the aging body, such as senescent cells and cancerous cells, by allowing them greater activity. The evidence is sparse for this to be the case, but it is a concern amongst researchers. The research noted here adds a little more weight to the concern side of the scales.

In the 1920s, German chemist Otto Warburg discovered that cancer cells don't metabolize sugar the same way that healthy cells usually do. Since then, scientists have tried to figure out why cancer cells use this alternative pathway, which is much less efficient. Researchers have now found a possible answer to this longstanding question. They showed that this metabolic pathway, known as fermentation, helps cells to regenerate large quantities of a molecule called NAD+, which they need to synthesize DNA and other important molecules. Their findings also account for why other types of rapidly proliferating cells, such as immune cells, switch over to fermentation.

Fermentation is one way that cells can convert the energy found in sugar to ATP, a chemical that cells use to store energy for all of their needs. However, mammalian cells usually break down sugar using a process called aerobic respiration, which yields much more ATP. Cells typically switch over to fermentation only when they don't have enough oxygen available to perform aerobic respiration. Warburg originally proposed that cancer cells' mitochondria, where aerobic respiration occurs, might be damaged, but this turned out not to be the case. Other explanations have focused on the possible benefits of producing ATP in a different way, but none of these theories have gained widespread support.

Researchers treated cancer cells with a drug that forces them to divert a molecule called pyruvate from the fermentation pathway into the aerobic respiration pathway. They saw that blocking fermentation slows down cancer cells' growth. Then, they tried to figure out how to restore the cells' ability to proliferate, while still blocking fermentation. One approach was to stimulate the cells to produce NAD+, a molecule that helps cells to dispose of the extra electrons that are stripped out when cells make molecules such as DNA and proteins. When the researchers treated the cells with a drug that stimulates NAD+ production, they found that the cells started rapidly proliferating again, even though they still couldn't perform fermentation.

This led the researchers to theorize that when cells are growing rapidly, they need NAD+ more than they need ATP. During aerobic respiration, cells produce a great deal of ATP and some NAD+. If cells accumulate more ATP than they can use, respiration slows and production of NAD+ also slows. Therefore, switching to a less efficient method of producing ATP, which allows the cells to generate more NAD+, actually helps them to grow faster. "Not all proliferating cells have to do this. It's really only cells that are growing very fast. If cells are growing so fast that their demand to make stuff outstrips how much ATP they're burning, that's when they flip over into this type of metabolism. So, it solves, in my mind, many of the paradoxes that have existed."

Link: https://news.mit.edu/2021/cancer-cells-waste-energy-0115

A Conceptual Shift to (Finally) Seeing Aging as the Cause of Age-Related Disease

The mainstream of the scientific community has for decade after decade followed an entirely incorrect strategy in the matter of aging, and it was only comparatively recently that this state of affairs was changed for the better by the advocacy of groups like the SENS Research Foundation, Methuselah Foundation, and their allies, alongside advances in the science of slowing and reversing aging that couldn't be easily dismissed, much of that funded by philanthropy rather than established institutions. Given a poor strategy, in which age-related diseases were studied separately from aging, and in their end stages, and without considering their root causes, it isn't all that surprising to find that treating age-related disease progressed poorly and incrementally. The only way to effectively treat age-related conditions is to address their deeper causes, which is to say the mechanisms of damage that lie at the root of aging, such as accumulation of senescent cells.

The commentary I'll point out today has its origin in the National Institute on Aging hierarchy. While reading, it is worth bearing in mind that there is often a great deal of hindsight and positioning in any one individual's explanations for why aging was largely ignored as a cause of disease, and why efforts to treat aging as a medical condition were actively discouraged for decades. The existence of the anti-aging marketplace - a noisy pit of fraud, lies, and false hope - had as much to do with the reluctance of the academic community to engage meaningfully with the treatment of aging as any ivory tower miscategorizations that placed aging and age-related disease in different buckets. Regardless of cause, it is a tragedy that so much time was lost and wasted in the matter of aging, with a cost in tens of millions of lives for every year of delay in the arrival of meaningfully effective rejuvenation therapies.

Reflections on aging research from within the National Institute on Aging

Sixty years ago, Nathan Shock created the Baltimore Longitudinal Study of Aging, and his idea was that we needed to dissociate aging from disease, because only at that point would we know what disease is and how to treat patients. There was an interest in trying to understand aging so that we could ignore it, because there was nothing that we could do about it. And then, as researchers started to look at aging and began searching for the point of dissociation between aging and disease, they found that it was much more difficult than expected. As our technologies became more developed and sophisticated, the boundaries between aging and diseases continued to blur.

The risk factor paradigm started with cardiovascular and cancer epidemiology; the basic idea is that if you wait a certain amount of time, risk factors will trigger a disease. People initially thought that there was some specificity between risk factors and diseases, but over time we have discovered that this specificity was not really there. Exercise and physical activity can reduce the risk of developing cardiovascular diseases, cancers, pulmonary diseases, sarcopenia, and so on. Smoking increases the risk of developing these diseases, too. You can say the same thing for many different risk factors that are being considered. Cancer and cardiovascular disease, the two major causes of mortality, share many of the same risk factors. Think about obesity: it's associated with most chronic diseases that you can think of. And so there has been a shift in how we have considered aging, from something that we needed to account for and eliminate by statistical adjustment to a causal factor in disease. And I think that it makes a lot of sense.

This explains why aging is a much stronger risk factor for dementia than carrying an APOE4 allele. This shift in thinking is important because it places aging at the forefront of medicine. Now, if this is true, understanding aging provides the strongest chance to prevent chronic diseases and expand healthspan. This shift creates incredible opportunities, and even private companies have started to become interested in studying aging.

Mitochondrial Aging as a Contributing Cause of Sarcopenia

Mitochondria are the power plants of the cell, producing adenosine triphosphate (ATP) to power cellular processes. When mitochondrial function declines all cell functions are negatively affected as a consequence. Many age-related conditions clearly involve mitochondrial dysfunction, particularly in the most energy-hungry tissues, the muscles and the brain.

In addition to damage to the fragile mitochondrial DNA, some forms of which cause a small number of cells to become pathologically broken in ways that actively harms surrounding tissues, all mitochondria throughout the body become more worn and dysfunctional with age. Their dynamics change, the organelles becoming larger and more resistant to the quality control process of mitophagy. The deeper roots of this sweeping decline, and all of the gene expression changes that accompany it, are unclear, but many proximate contributing causes have been identified. Loss of NAD+, reduced expression of mitochondrial fission genes, dysfunction in specific portions of the mitophagy machinery, and so forth.

Efficient skeletal muscle bioenergetics hinge on mitochondria, and mitochondrial dysfunction is recognized as a major hallmark of aging. Indeed, protecting mitochondria is a determinant to preserve proteostasis in skeletal muscle. To date, a growing body of evidence on mitochondrial impairment in sarcopenia has been provided by both animal and human studies. Dysfunctional mitochondria are associated with both ATP depletion and ROS/RNS excess, with the consequent activation of harmful cellular pathways. A decrease in mitochondrial mass, activity of tricarboxylic acid cycle enzymes, as well as O2 consumption and ATP synthesis occurs in aged skeletal muscle tissue. Changes in function, dynamics, and biogenesis/mitophagy could explain in part alteration in oxidative capacity and content of skeletal muscle mitochondria. Furthermore, mitochondrial dysfunction induces the activation of apoptosis, potentially impairing skeletal muscle quality.

Several mitochondrial functions are impaired in old in comparison to young skeletal muscle, including the activity of metabolic enzymes and oxidative phosphorylation (OXPHOS) complexes (i.e., citrate synthase and cytochrome c oxidase), respiration, protein synthesis, and ATP production rate. The reduced mitochondrial content in aged skeletal muscle may be also related to lower PGC-1α gene and protein expression. However, the molecular mechanisms that underpin this reduction are worth further investigation. Apart from PGC-1α, different studies show divergent results in the levels of its downstream transcription factor Tfam in old skeletal muscle.

Changes related to mitochondrial content and function in old skeletal muscle may also be related to a reduced amount, increased mutations, deletions, and rearrangements of mitochondrial DNA (mtDNA). A greater prevalence of mtDNA deletion mutations is described in skeletal muscle fibers, which were more subjected to oxidative damage. An age-dependent increase in skeletal muscle fibers presenting with alterations of mitochondrial enzymes due to mtDNA deletion mutations is reported both in rhesus monkeys presenting with early-stage sarcopenia and in humans.

Morphological studies in aged skeletal muscle show giant mitochondria with disrupted cristae. Altered morphology in old skeletal muscle mitochondria may be the consequence of impaired mitochondrial dynamics, with a disbalance in favor of fission rather than fusion. Mutations in mtDNA may lead to dysregulation of mitochondrial dynamics in sarcopenia, as suggested by results from old mice expressing a defective mtDNA polymerase gamma, which showed higher mitochondrial fission in skeletal muscle. A shift toward mitochondrial fusion rather than fission was also reported in skeletal muscle of very old hip-fractured patients.

The reduced capacity of skeletal muscle cells to remove damaged organelles could be another cause of mitochondrial alteration in aging. Studies performed on rodent models describe controversial results on mitophagy modulators in aged skeletal muscle. A further investigation reported data indicative of increased mitophagy but lysosomal dysfunction in skeletal muscle from old mice, suggesting that lysosomal dysfunction may cause accumulation of disrupted mitochondria. Nevertheless, further investigation on the role of mitophagy in old skeletal muscle is needed in humans.

Link: https://doi.org/10.3390/biology10010031

A Review of Research into Intermittent Fasting and its Effects on Longevity

Intermittent fasting (such as alternate day fasting) is not as effective as calorie restriction (consistent reduction in calories every day) in extending life span in animal models such as mice, but it does have many of the same effects on health and longevity. Even when total calorie intake is held consistent between intermittent fasting animals and controls, there are still benefits that accrue to the fasting animals. One might conclude that time spent in a state of hunger, with all of the signaling and changes in cell behavior that comes with it, is a meaningful component of the benefits derived from calorie restriction.

In contrast to the short and very frequent fasting periods of intermittent fasting (IF), periodic fasting (PF) or a fasting mimicking diet (FMD) last in most cases between 2 and 7 days (2-3 days in mice and 4-7 days in humans) and are followed by a high-nourishment refeeding period of at least 1 week. Another major difference from IF is that PF can be periodic and does not have to be carried out at a specific interval, but can be applied for one or several cycles either as a preventive measure or to treat a specific disease or condition. FMDs were developed to promote the effects of fasting while standardizing dietary composition, providing nourishment and minimizing the burden and side effects associated with water-only fasting. These steps are necessary for PF and possibly IF to move toward approval from the US Food and Drug Administration and standard-of-care applications.

Sixteen-month-old female C57BL/6 mice placed on a periodic 4-day FMD twice per month, alternating with a normal diet, display an 11% increase in their median lifespan, in addition to significant weight and visceral-fat loss, without loss of muscle mass. Moreover, FMD cycles reduce tumor incidence by 45% and delay tumor development. Notably, the FMD cycles also promote changes leading to an immune-system profile in 20.5-month-old mice more similar to that of younger mice (4 months old), in agreement with the effect of PF on hematopoietic stem cell (HSC)-dependent regeneration of immune cells.

In summary, similarly to the well-established effects of calorie restriction, FMD cycles delay the onset and reduce the incidence of age-related diseases, but achieve this with minimal or no long-term reduction in calorie intake and with positive effects on immunity and a targeted reduction in visceral fat. Thus, PF/FMD but potentially also certain dietary restrictions, including IF, may achieve many beneficial effects by mechanisms that are independent of reduced calorie intake.

Link: https://doi.org/10.1038/s43587-020-00013-3