Osteoarthritis as an Inflammatory Condition

This open access paper discusses current views on the degree to which osteoarthritis is driven by inflammation, as is the case for many other age-related diseases. With aging the immune system declines into a malfunctioning state of chronic inflammation, ever more active while also ever less effective at the tasks of destroying pathogens and errant cells. In young people, inflammation in short bursts is a necessary part of the immune response, but in the old it becomes a consistent destructive process, gnawing away at the proper function of organs and systems in the body and brain. Addressing this in some way, perhaps through an adaptation of the immune destruction and recreation approach taken for some autoimmune diseases, should be broadly beneficial.

Affecting approximately 3.8% of the global population, osteoarthritis (OA) is regarded as a prevalent cause of morbidity and disability worldwide. OA shows many disease characteristics, such as cartilage degradation, moderate synovial inflammation, pain, alteration of bony structure, and impaired mobility. However, despite the severity of the disease, relatively little is known about its exact etiology. Recent compelling investigations have attributed the onset of OA to various person-level factors such as age, sex, obesity, and diet and joint-level factors such as injury, malalignment, and abnormal joint loading. Although more and more researchers have recently presented hypotheses concerning the involvement of these factors in OA, especially for person-level factors, few of their hypotheses have been demonstrated experimentally, and some have even been challenged by the latest observational studies and clinical trials.

Of the several factors potentially involved in the pathogenesis of OA, T cell-mediated immune responses and their influence on the biology of OA are the focus of this review. The scientific community once understood OA to be induced by mechanical stress in the form of cartilage destruction, with minimal if any involvement of immune responses. Thus, OA was regarded as a non-inflammatory disease, in contrast with rheumatoid arthritis (RA), an inflammatory disease. However, recent studies suggest that at least in certain patients, OA is an inflammatory disease; patients have frequently been found to exhibit inflammatory infiltration of synovial membranes. Most recent studies have shown that the number of inflammatory cells in the synovial tissue is lower in patients with OA than in patients with RA, but higher than that in healthy subjects. Indeed, little difference has been found in the percentages of T cells, B cells, and natural killer cells in the peripheral blood between patients with OA and RA. The similarity of the immune cell profiles of RA and OA and suggested that abnormalities in T cells may also contribute to the pathogenesis of OA.

Further experiments indicated that inflammation in OA is anatomically restricted and varies in intensity. The synovial membranes in regions rimming the cartilage of OA patients, which contain T cells bordered by B lymphocytes and plasma cells, showed a pronounced inflammatory response. In contrast, only a few infiltrating lymphocytes were observed in the synovial membranes taken from macroscopically non-inflamed areas in OA patients. This may explain the suggestion made by some researchers that immune responses are not involved in the pathogenesis of OA. When synovial samples from patients with knee OA were analyzed, the synovial lining cells showed strong immunoreactivity and phagocytic potential with cluster of differentiation (CD) 68 antibodies. These findings suggested that macrophages may be associated with the pathogenesis of knee OA. Of 20 osteoarthritic synovial membranes, 5 showed lymphoid follicles containing T cells, B cells, and macrophages, and 10 (including the latter five) displayed a diffuse cellular infiltrate containing T and B cells, macrophages, and granulocytes. These results suggested that B cells and granulocytes may also be involved in the pathogenesis of knee OA.

Link: https://dx.doi.org/10.3389/fimmu.2017.00356

Evidence for Fat-Triggered Immune Dysfunction in the Liver to Contribute to the Symptoms of Type 2 Diabetes

In this research, scientists explore a link between the presence of excess fat and the dysfunctional blood sugar regulation that is characteristic of type 2 diabetes. The vast majority of type 2 diabetes patients suffer the condition because they are overweight, and could turn back its progression even in late stages through sustained low-calorie diets and losing that weight. Type 2 diabetes is a prevalent age-related disease because we live in an age of cheap calories and little exercise, older people have more time and opportunity to gain the necessary excess fat tissue to trigger the condition, and other mechanisms cause a decline in the aging pancreas and its beta cells, making it more likely that a given gain in weight will push metabolic syndrome over the line into full blown diabetes.

Using cells from mice and human livers, researchers demonstrated for the first time how under specific conditions, such as obesity, liver CD8+ T cells, white blood cells which play an important role in the control of viral infections, become highly activated and inflammatory, reprogramming themselves into disease-driving cells. Scientists have been trying for many years to discover why the liver continues to pump out too much glucose in people with diabetes. This paper sheds light on the markers of activation and inflammation in CD8+ T cells and the Interferon-1 pathway which helps stimulate their function. In fact, the normal function of the immune cells becomes misdirected. The pathways they would typically use to fight infection create inflammation, unleashing a chemical cascade which impacts insulin and glucose metabolism.

In the study, researchers fed mice a high-fat diet, 60 per cent of which was saturated fat, for 16 weeks. Compared with normal chow diet-fed mice, the high-fat diet mice showed worsened blood sugar, increased triglycerides, a type of fat (lipid) in the blood, and a substantial increase in the numbers of CD8+ T cells in the liver. Instead of responding to viruses or other foreign invaders in the body, the activated CD8+ T cells launch an inflammatory response to fat, and to bacterial components that migrate to the liver from the gut through the blood. The activated T-cells divide rapidly, pumping out increased numbers of cytokines, proteins that assist them in an active and excessive immune response. This pro-inflammatory response in turn interferes with normal metabolism in the liver, specifically jamming up or blocking insulin signaling to the liver cells.

Since the liver stores and manufactures glucose or sugar depending upon the body's need, the hormone insulin signals whether the liver should store or release glucose. This system keeps circulating blood sugar levels in check. If that signal is disrupted or blocked, the liver continues to make more sugar, pouring it into the bloodstream. If the liver is over-producing glucose, it becomes difficult to regulate blood sugar. "We're moving from studying diabetes as a metabolic syndrome - a combination of nutritional and hormonal imbalances - to include the role of the immune system and inflammation. That's the developing link. Inflammation is emerging to be a major mediator of insulin resistance."

The researchers found that in genetically-modified mice lacking Interferon-1, who were also fed a high-fat diet, the CD8+ T cells did not produce an inflammatory response, and the mice had near normal blood sugar levels. In further investigations of human liver cells from nearly 50 donor tissues of humans with varying degrees of body mass index (BMI) and liver fat, higher levels of CD8+ T cells were linked with higher levels of blood sugar or more advanced fatty liver disease.

Link: http://www.uhn.ca/corporate/News/PressReleases/Pages/when_liver_immune_cells_turn_bad.aspx

If Much Older than 30, Save More Aggressively Over the Next Decade or Two

Five years from now, it will be possible to fly to an overseas clinic and undergo a treatment that will clear out between a quarter and half of the senescent cells in your body. That will to some degree damp down fibrosis, restore tissue elasticity, reduce inflammation, reduce calcification of blood vessels, and in addition improve many other measures of health that are impacted by the normal progression of aging. In short you will walk away a little rejuvenated, literally: one of the root causes of aging will be turned back for some years, perhaps decades, however long it takes for the removed senescent cells to emerge once again. Given the present cost of senolytic drug candidates, varying from a few dozen to a few thousand dollars per dose depending on whether or not they are at present mass manufactured, I think that the likely initial cost of treatment five years from now will be somewhere in the $5,000 to $25,000 range. Higher would seem unlikely, given that this is a competitive area of development already, and lower will probably have to wait for bigger players to enter the game in regulated markets. That cost will then fall as availability spreads.

Senolytics are just the start. Five years to a decade after the first candidate therapy for breaking glucosepane cross-links in humans, that treatment will also be available to anyone with the necessary funds put aside. It will also turn back the clock, removing some portion of one of the root causes of aging. Tissue elasticity will be restored, hypertension controlled as arteries become more flexible, and scores of other consequences of cross-linking reduced in their impact. That first therapy could emerge in the laboratories this year or at any time thereafter; a number of groups are working on it. There are a range of other rejuvenation treatments and compensatory therapies at similar points, on the verge in one way or another. Gene therapies to boost muscle generation, or dramatically reduce blood cholesterol. Approaches to clear harmful amyloids from old tissue. The next twenty years will bring numerous opportunities to benefit for anyone willing organize their own treatments via medical tourism, and who happens to know enough about the field to pick out the metal from the dross.

Therapies are not free, however. Funds are needed. Thus anyone much over the age of 30 who has an interest in this field should be saving more aggressively than he or she is at present. Live more frugally. Put more aside. On one chart is the ascending curve of savings and safe investments, on another chart the descending curve of cost of therapies. The objective for most of us is to make those lines cross sooner rather than later. If you dent your savings in a way that pushes out the achievement of traditional retirement goals by a few years in order to undergo an effective rejuvenation therapy, I think that puts you ahead of the game. Besides, traditional retirement isn't going to look very traditional any more by the time most of the younger folk in the audience get there. The aging of the population ensures that more people will simply remain working because there will be more work to accomplish than young people available to accomplish it. The advent of rejuvenation therapies will mean that older people can in fact continue working. And not just working: living a life that is worth it; interesting and active. Rejuvenation means additional health and vigor, not just extra years.

The rest of this century will be a grand adventure. The course of a human life is no longer planned and plotted and set in stone as it was for your grandparents. Medical technology, the development of rejuvenation therapies, will break us from tradition and the limits that aging places on the human condition. The traditional ways and means, the passing of generations, the declining trajectory of old age, are on the way out, fast or slow, sooner or later. We'll all be making it up as we go, exploring entirely new territory when it comes to the manners and organization of society. In the early days, however, only the prepared will find it easy to hitch a ride. So don't be unprepared. Everyone in the younger half of life has years ahead in which to save funds while keeping a weather eye on the state of research and medical tourism. Having a nest egg put aside will make all the difference when it comes time to strike out, repair the damage that aging has inflicted upon your health, and stride forth into a far better future than was offered to our ancestors.

How Does Tau Cause Neurodegeneration?

As research progresses, it is becoming clear that the situation for amyloid-β and tau in the aging brain is quite similar at the high level. As amounts increase with advancing age, perhaps due to the progressive failure of clearance mechanisms, both produce distinct solid aggregates, neurofibrillary tangles in the case of tau, but the aggregrates themselves do not appear to be the primary harmful mechanism that damages neural function and kills cells. This open access paper takes a look at what is known of tau and its involvement in age-related neurodegeneration:

Aging has long been considered as the main risk factor for several neurodegenerative disorders including a large group of diseases known as tauopathies. Even though neurofibrillary tangles (NFTs) have been examined as the main histopathological hallmark, they do not seem to play a role as the toxic entities leading to disease. Recent studies suggest that an intermediate form of tau, prior to NFT formation, the tau oligomer, is the true toxic species. However, the mechanisms by which tau oligomers trigger neurodegeneration remain unknown.

NFTs do not appear to be the main toxic entities leading to disease. In Alzheimer's disease, tau pathology and neuronal cell loss coincide in the same brain regions, and as brain dysfunction progresses, NFTs are found in greater anatomical distributions. However, the role of NFTs in the progression of the disease is poorly understood. Compared to non-demented controls, Alzheimer's brains exhibit up to 50% of neuronal loss in the cortex, exceeding the number of NFTs. In addition, neurons containing NFTs are functionally intact in vivo and have been found in brains of cognitively normal individuals. Further, intra-neuronal NFTs do not affect post-synaptic function and signaling cascades responsible for long-term synaptic plasticity, suggesting that synaptic deficits cannot be attributed to NFTs.

While evidence indicates that these deposits are not toxic, many studies suggest that the tau oligomer, an intermediate entity, is likely responsible for disease onset. Hyper-phosphorylated tau assembles into small aggregates known as tau oligomers in route of NFT formation. As hyper-phosphorylated tau dislodges from microtubules, its affinity for other tau monomers leads individual tau to bind each other, forming oligomeric tau, an aggregate. These tau oligomers potentiate neuronal damage, leading to neurodegeneration and traumatic brain injury. As these granular tau oligomers fuse together, they form tau fibrils, which ultimately form NFTs. These steps hint that tau oligomers may be involved in neuronal dysfunction prior to NFT formation.

When tau oligomers, rather than tau monomers or fibrils, are injected into the brain of wild-type mice, cognitive, synaptic, and mitochondrial abnormalities follow. Additionally, studies have discovered that aggregated tau inhibits fast axonal transport in the anterograde direction at all physiological tau levels, whereas tau monomers have had no effect in either direction. This suggests that monomers are not the toxic entity either. Most noteworthy, tau oligomers induce endogenous tau to misfold and propagate from affected to unaffected brain regions in mice, whereas fibrils do not. This indicates that tauopathies progress via a prion-like mechanism dependent upon tau oligomers. With this concept, tau may be able to translocate between neurons and augment toxic tau components; in fact, evidence suggests probability of tau oligomer propagation between synaptically connected neurons. If true, then pathology begins in a small area and becomes symptomatic as it spreads to other areas of the brain.

Discovering the pathological role of tau oligomers within the brain along with related mechanisms of cellular tau oligomer secretion, propagation, and uptake will allow for a better understanding of tauopathies. Further, mitochondrial dysfunction caused by internalized tau oligomers may play an important role in pathogenesis. Admittedly, little is known regarding cellular tau oligomer release. Yet with greater knowledge regarding disease pathogenesis, better therapeutic approaches can be generated. We hypothesize that preventing tau oligomers from cellular release and uptake will relieve some toxic effects induced by tau oligomers in tauopathies.

Link: https://doi.org/10.3389/fnagi.2017.00083

Increased Cardiac Troponin T Associated with Neuromuscular Junction Aging

Decline in the neuromuscular junctions that connect nerve tissue to muscle tissue is one of the ways in which muscles age and lose strength. Researchers here examine changing levels of proteins in neuromuscular junctions, and identify increased amounts of cardiac troponin T as one of the proximate causes of decline. Reducing the amount of this protein improves the function of aged neuromuscular junctions in mice:

Ageing skeletal muscle undergoes chronic denervation, and the neuromuscular junction (NMJ), the key structure that connects motor neuron nerves with muscle cells, shows increased defects with ageing. Previous studies in various species have shown that with ageing, type II fast-twitch skeletal muscle fibres show more atrophy and NMJ deterioration than type I slow-twitch fibres. However, how this process is regulated is largely unknown. A better understanding of the mechanisms regulating skeletal muscle fibre-type specific denervation at the NMJ could be critical to identifying novel treatments for sarcopenia. Cardiac troponin T (cTnT), the heart muscle-specific isoform of TnT, is a key component of the mechanisms of muscle contraction. It is expressed in skeletal muscle during early development, after acute sciatic nerve denervation, in various neuromuscular diseases and possibly in ageing muscle. Yet the subcellular localization and function of cTnT in skeletal muscle is largely unknown.

Studies were carried out on isolated skeletal muscles from mice, vervet monkeys, and humans. Immunoblotting, immunoprecipitation, and mass spectrometry were used to analyse protein expression, real-time reverse transcription polymerase chain reaction was used to measure gene expression, immunofluorescence staining was performed for subcellular distribution assay of proteins, and electromyographic recording was used to analyse neurotransmission at the NMJ.

Levels of cTnT expression in skeletal muscle increased with ageing in mice. In addition, cTnT was highly enriched at the NMJ region - but mainly in the fast-twitch, not the slow-twitch, muscle of old mice. We further found that the protein kinase A (PKA) RIα subunit was largely removed from, while PKA RIIα and RIIβ are enriched at, the NMJ - again, preferentially in fast-twitch but not slow-twitch muscle in old mice. Knocking down cTnT in fast skeletal muscle of old mice: (i) increased PKA RIα and reduced PKA RIIα at the NMJ; (ii) decreased the levels of gene expression of muscle denervation markers; and (iii) enhanced neurotransmission efficiency at NMJ. This knowledge could inform useful targets for prevention and therapy of age-related decline in muscle function.

Link: http://onlinelibrary.wiley.com/doi/10.1002/jcsm.12204/full

Calorie Restriction Slows Progression of the Earliest Stages of Cancer

The practice of calorie restriction has been shown to extend both healthy and overall life span in near every species tested to date - though of course the human life span data is still too sparse to do more than make educated guesses. Calorie restriction also provides considerable short term benefits to measures of heath, larger than anything that medical science can presently provide for basically healthy individuals, and the short term human data matches that obtained from other mammals. Eating less while maintaining optimal levels of micronutrients is a healthy practice, with a weight of evidence backing that claim, even if there is considerable uncertainty over the degree to which it will lengthen human life. It certainly doesn't produce the same 40% extension of life observed in mice, as that outcome would have been noted centuries past. As a general rule the life spans of short-lived species are far more plastic in response to circumstances than those of long-lived species. The consensus in the research community is that calorie restriction, while being very good for your health, and significantly reducing incidence of age-related disease, probably doesn't add more than five years of life at the outside.

Almost every measure of aging is slowed and almost every aspect of cellular metabolism is altered in calorie restricted individuals. Nutrient sensing mechanisms touch on all of the low-level, important cellular behaviors, such as replication and maintenance processes, and this has made it very difficult to understand how exactly the calorie restriction response works. Understanding calorie restriction cannot easily be separated from the vast undertaking of building a complete understanding of cellular biochemistry and the way in which it changes over the course of aging - and why. Some major areas of interest in cellular biology have been blocked out by the aging research community, such as insulin signaling, sirtuins, mTOR, and so forth. Over the past twenty years a great deal of time and funding has gone towards mapping more of these mechanisms, in search of ways to reproduce calorie restriction without the dieting, but for all that effort there are few signs that an end is in sight. Human biochemistry is enormously complex.

The paper here is an example of one of the many ways in which calorie restriction slows the progression of aging. The researchers provide evidence to show that the earliest stages of cancer advance more slowly and are in general suppressed in calorie restricted animals. Cancer is a manifestation of aging in the sense that it is a numbers game: firstly, the more damage to DNA that an individual suffers, the more likely that a cancerous cell arises. Secondly the mechanisms responsible for assassinating cancerous cells falter with age due to their own burden of damage and dysfunction. Lastly the inflamed environment of old tissues makes it easier for cancers to thrive once they get underway. Calorie restriction has a positive impact on all of these points, and hence calorie restricted individuals have a lower incidence of cancer. Understanding exactly why this is the case at a deep enough level to produce therapies that replicate its effects is whole different story, of course, and something than may not happen for decades yet.

Caloric restriction delays early phases of carcinogenesis via effects on the tissue microenvironment

Neoplastic disease is inextricably associated with aging. Five out of six cancer-related deaths occur in patients aged 60 years and older. However, the intimate nature of this association is yet to be fully clarified. An important concept emerging from the literature is that aging and cancer do not merely represent two chronologically parallel processes, but they share relevant pathogenetic mechanisms. Along these lines, in a recent study we have provided evidence to indicate that aging promotes the growth of pre-neoplastic cells through alterations imposed on the tissue microenvironment, i.e. by generating an age-associated, neoplastic-prone tissue landscape. Similarly, it has been reported that aging-associated inflammation promotes selection for adaptive oncogenic events in B cell progenitors; it was proposed that cell competition may in fact drive the emergence of oncogenically altered cells in a background of age-induced decline in tissue fitness, in a process that has been referred to as "adaptive oncogenesis".

The notion that age-associated tissue changes may play a direct role in the origin of neoplasia has far-reaching implications. It suggests that strategies aimed at modulating the rate of aging may have a direct impact on early and/or late steps of neoplastic disease, i.e. the quest for a longer lifespan may coincide, at least in part, with the goal to defer the occurrence of cancer.

A most effective and consistent means to delay aging is by reducing caloric intake compared to ad libitum (AL) feeding. Caloric restriction (CR) is the most studied and reproducible non-genetic intervention known to extend lifespan in organisms ranging from unicellular yeast to mammals, including non-human primates, although the latter observation is disputed. On the other hand, it is also well documented that CR exerts a beneficial effect on the incidence of chronic diseases related to old age, including cancer, consistent with the notion that changes occurring during the aging process may bear direct relevance to the pathogenesis of neoplasia. However, the precise mechanisms responsible for the CR-induced delay on carcinogenic process are yet to be identified.

Based on the above, in the present studies we tested the hypothesis that the modulatory effect of CR on age-associated neoplastic disease might be related, at least in part, to a CR-induced delay in the emergence of age-related tissue alterations promoting the growth of pre-neoplastic cells. Using a well characterized cell transplantation system in the rat, we report that when pre-neoplastic hepatocytes were infused in aged animals exposed to either AL or CR diet, their growth was significantly reduced in the latter group. Analysis of donor-derived cell clusters performed at 10 weeks post-transplant revealed a significant shift towards smaller class sizes in the group receiving CR diet. Clusters comprising more than 50 cells, including large hepatic nodules, were thrice more frequent in AL vs. CR animals. Incidence of spontaneous endogenous nodules was also decreased by CR. These results are interpreted to indicate that CR delays the emergence of age-associated neoplastic disease through effects exerted, at least in part, on the tissue microenvironment.

Show Your Appreciation for the Fundraising Work of Lifespan.io

The Lifespan.io and Life Extension Advocacy Foundation (LEAF) volunteers have over the past few years put together and maintained a crowdfunding infrastructure used to successfully raise hundreds of thousands of dollars for rejuvenation research projects. They have carried the message that aging can be effectively treated as a medical condition out to new audiences, expanded our community of supporters, and helped to connect researchers and entrepreneurs to new patrons. The LEAF volunteers are presently running a small fundraiser in search of monthly donors to help expand their present advocacy for the cause of rejuvenation research. If you have been following their efforts for the past few years, I encourage you show your appreciation for all they have done by signing up for a modest monthly donation.

Here at Lifespan.io we are funding research to help extend healthy human lifespan, and thanks to our community here we've done amazing work already: raising over $200,000 for companies and nonprofits working to overcome age-related disease, decrease the period of ill-health during life, and address key societal issues being faced by our aging population. All we've done thus far has been primarily volunteer effort, and we believe we can go so much further with even a modest budget of our own. So we're turning to you, and asking you to stand with us, to #BeTheLifespan, and help us overcome age-related diseases for good. What this means is that we're asking you to be a Lifespan Hero by supporting us with monthly contributions, which will allow us to not only fund more research but also offer amazing community rewards.

In addition to improving our features on this site, we'll create a private networking group for patrons and researches. We'll also begin running a live-streamed journal review, led by our own Dr. Oliver Medvedik, where we'll go through the latest papers with researchers and you, so we all learn together. We'll be able to make awesome collaboration videos with popular creators on services like YouTube to engage the world. This has the power to inform millions of people about the feasibility and desirability of longevity research, and can be a game changer in terms of raising societal awareness. If we can get to $10,000 a month, we'll even start running an annual full-scale longevity conference in New York City, to help make this research truly mainstream. In addition to driving the field forward with increased sharing of information, a stronger presence in NYC will attract private capital, and help build a thriving longevity biotech industry.

Every day over 100,000 people die of age related diseases: Alzheimer's, heart disease, cancer. Together we can fight this; together we can be Heroes.

Link: https://www.lifespan.io/campaigns/join-us-become-a-lifespan-hero/

A Perspective on Clinical Translation of Senolytic Drugs

Researchers here discuss the path to the clinic for the first batch of senolytic drugs, compounds that nudge senescent cells into self-destruction. Senescent cells accumulate with age, and secrete signals that disrupt tissue function and produce chronic inflammation. Their growing presence is one of the root causes of aging, and their effects on surrounding cells contribute to many age-related diseases. Researchers have demonstrated extended life and reversal of measures of aging in rodents through the targeted removal of senescent cells; the sooner this class of treatment makes it to the clinic the better.

Cellular senescence entails essentially irreversible replicative arrest, apoptosis resistance, and frequently acquisition of a pro-inflammatory, tissue-destructive senescence-associated secretory phenotype (SASP). Senescent cells accumulate in various tissues with aging and at sites of pathogenesis in many chronic diseases and conditions. The SASP can contribute to senescence-related inflammation, metabolic dysregulation, stem cell dysfunction, aging phenotypes, chronic diseases, geriatric syndromes, and loss of resilience. Delaying senescent cell accumulation or reducing senescent cell burden is associated with delay, prevention, or alleviation of multiple senescence-associated conditions.

The first senolytic drugs, compounds that selectively eliminate senescent cells by causing apoptosis, were discovered using a hypothesis-driven approach. This approach was based on the observation that senescent cells are resistant to apoptosis, suggesting senescent cells have up-regulated pro-survival pathways that protect them from their own pro-apoptotic SASP. Up-regulation of these Senescent Cell Anti-apoptotic Pathways (SCAPs) might be related to senescence-associated mitochondrial dysfunction (SAMD). An essential part of SAMD appears to be a decrease in mitochondrial membrane potential related to mitochondrial membrane permeabilization. SAMD could explain why senescent cells depend on upregulated pro-survival pathways and why they are more sensitive to drugs that interfere with these SCAP pathways than non-senescent cells.

The first SCAPs were identified through expression profiling of senescent vs. non-senescent human cells and confirmed in RNA interference studies. Drugs that target these SCAPs were tested for senolytic activity. The tyrosine kinase inhibitor, dasatinib (D) and the flavonoid, quercetin (Q), were shown to induce apoptosis in senescent cells. Ten months later, two groups simultaneously reported that navitoclax (N; ABT-263), which targets components of the Bcl 2 pathway, is senolytic. Recently, the specific BCL-XL inhibitors A1331852 and A1155463, were found to be senolytic. Fisetin, related to Q, was discovered to be senolytic. Fisetin is an especially promising candidate because of its favorable side-effect profile. Piperlongumine, which is also related to Q, was noted to be senolytic in vitro in some senescent cell types. None of the individual agents reported so far selectively induces apoptosis of all senescent cell types. N, A1155463, and possibly A1331852 appear to be more toxic than D, Q, piperlongumine, or fisetin. A number of additional senolytic drugs are currently being developed. Some of the most promising senolytic agents are already being moved through preclinical studies towards clinical application.

To conduct clinical trials with senolytics, it will be important to have ways to track changes in senescent cell burden. It might be feasible to do so using biopsies, blood assays, other body fluids, and imaging, but more research on developing and optimizing assays needs to be done and reported. Complicating matters, the definition of cellular senescence is somewhat vague, particularly since several potentially pro-inflammatory cell types, such as macrophages or osteoclasts as well as pre-cancerous or cancer cells share many characteristics of senescent cells and could arguably be the same as what are currently regarded as being senescent cells. Few tissue assays are very sensitive or specific for senescent cells. Work needs to be done to establish, optimize, and validate these assays. Novel assays, such as of the microvesicles shed into blood or urine by senescent cells, need to be developed and optimized for use in clinical trials of senolytic drugs.

Healthspan, lifespan, or other very long-term potential endpoints for clinical trials of interventions that target basic aging processes, including SASP-inhibitors or senolytics, would be difficult or next to impossible to study for reasons that are obvious, as would endpoints occurring in old age as a consequence of beginning to administer a drug in adulthood or middle-age. Initial trials of senolytics or other agents that target fundamental aging processes will need to test effects on endpoints that can be measured weeks to a couple of years after initiating treatment. Furthermore, because the risk:benefit ratio must favor benefits for the ethical conduct of clinical trials, new interventions would have to be tested in situations in which side-effects would be considered to be acceptable. In diseases for which no effective treatment is available, some side effects may be acceptable in individuals who are already symptomatic or who are almost certain to become symptomatic within a short time. If any consequential side effects are anticipated, the treatment would also need to address a problem that would cause serious harm if left untreated.

There is a possibility that senolytics and SASP inhibitors could be transformative, substantially benefiting the large numbers on patients with chronic diseases and enhancing healthspan. That said, as this is a very new treatment paradigm, there are many obstacles to overcome. Treatments that appear to be highly promising in mice frequently fail once clinical trials start, with lack of effectiveness in humans compared to mice related to the unique aspects of human biology, unforeseen side-effects, and a host of other issues. At least one reassuring advantage of targeting cellular senescence is the conservation of fundamental aging mechanisms such as senescence across mammalian species. In diseases like Alzheimer's dementia, atherosclerosis, or non-injury-related osteoarthritis, which do not occur naturally in mice, translation from genetically- or surgically-induced mouse models of these conditions to humans is more likely to fail than conditions that are more evolutionarily conserved, such as aging. Furthermore, unlike the situation for developing drugs to eliminate infectious agents or cancer cells, not every senescent cell needs to be eliminated to have beneficial effects. Unlike microbes or cancer cells, senescent cells do not divide, decreasing risk of developing drug resistance and, possibly, speed of recurrence. With respect to risk of side-effects, single or intermittent doses of senolytics appear to alleviate at least some age- or senescence-related conditions in mice. This suggests that intermittent treatment may eventually be feasible in humans.

Link: http://www.ebiomedicine.com/article/S2352-3964(17)30154-8/fulltext

Transfusion of Young Blood Associates TIMP2 with Aging and Cognitive Function

A growing collection of studies and projects have emerged from parabiosis experiments in which the circulatory systems of a young and an old individual are joined. The old individual experiences a modest reduction in the impact of aging, in measures such as regeneration, stem cell activity, and more. This has prompted researchers to search for proteins in young blood that might act as signals to improve function when delivered to old tissues, though the field is young enough and complex enough that there is considerable uncertainty over whether or not youthful signals are in fact the mechanism of interest. There is good evidence for the effects to result from a dilution of harmful factors in old blood instead, for example, which might explain past failures to obtain benefits from transfusion of young blood - though human trials are still ongoing on that front. The paper noted below stands somewhat in opposition to this position, in that the researchers involved have identified another candidate factor in young blood that appears to improve health in old animals. Young fields of research are usually characterized by this sort of apparently incompatible evidence.

Considering the bigger picture, the teams involved in this area of research are essentially engaged in a process of cataloging the differences in types and amounts of proteins found in young blood versus old blood. They are carrying out transfusion experiments and building other interventions to try to pin down which of these proteins are involved in age-related decline or in maintaining youthful function - a matter of needles in haystacks. It is plausible that in the years ahead this might be an alternative road to capturing some of the benefits of present stem cell therapies, those that largely work though signals produced by the transplanted cells, and a way to adjust the behavior of native cell populations. It would override cellular reactions to the rising damage of aging, and push cells into a more youthful pattern of behavior. This carries risk, as damaged cells working harder raises the possibility of cancer. That stem cell therapies can be made to work with a minimal cancer risk should give us hope on that front, however.

As the research results below suggest, there are other possibilities beyond that of enhancing regeneration. Improvements in faltering neurogenesis and synaptic plasticity in the brain are a possibility, for example, with the potential to provide greater resilience to cognitive decline in old age. All of these things will likely operate within the same bounds of the possible and the plausible as are observed for stem cell therapies: it is a road to improvements, not to a reversal of aging. Forcing youthful behavior doesn't remove the underlying damage that has caused age-related changes in cellular behavior, and that damage will still win if not repaired. Methods of enhanced regeneration and neural plasticity may still be beneficial enough to spend time on, however. We shall see.

Young human blood makes old mice smarter

For decades, researchers have studied the effects of young blood on ageing in mice through a technique called parabiosis, in which an old mouse is sewn together with a younger one so that they share a circulatory system. Until now, the rejuvenating properties of young blood had only been demonstrated in mouse-to-mouse transfers. Nevertheless, the work has inspired ongoing clinical trials by at least two companies in which elderly people are infused with blood from younger adult donors and then tested for physical improvements. In one of the clinical trials researchers have started testing plasma collected from the umbilical cords of newborn babies. Their goal is to find out how very young human blood might affect the symptoms of ageing.

Infusing this human plasma into the veins of elderly mice, they found, improved the animals' ability to navigate mazes and to learn to avoid areas of their cages that deliver painful electrical shocks. When the researchers dissected the animals' brains, they found that cells in the hippocampus - the region associated with learning and memory - expressed genes that caused neurons to form more connections in the brain. This didn't happen in mice treated with blood from older human donors.

The researchers then compared a slate of 66 proteins found in umbilical cord plasma to the proteins in plasma from older people, and to proteins identified in the mouse parabiosis experiments. They found several potential candidates, and injected them, one at a time, into the veins of old mice. The team then ran the animals through the memory experiments. Only one of these proteins, TIMP2, improved the animals' performance. It did not, however, result in regeneration of brain cells that are lost during normal ageing. Injections of human umbilical cord plasma lacking TIMP2 had no effect on memory. The researchers don't yet know how TIMP2, which is known to be involved in maintaining cell and tissue structure, exerts its effect on memory. And although it is expressed in the brains of young mice, TIMP2 has never before been linked to learning or memory. Researchers suspect that the protein functions as a 'master regulator' of genes involved in the growth of cells and blood vessels, and that increasing its levels affects many pathways simultaneously.

Human umbilical cord plasma proteins revitalize hippocampal function in aged mice

Ageing drives changes in neuronal and cognitive function, the decline of which is a major feature of many neurological disorders. The hippocampus, a brain region subserving roles of spatial and episodic memory and learning, is sensitive to the detrimental effects of ageing at morphological and molecular levels. With advancing age, synapses in various hippocampal subfields exhibit impaired long-term potentiation, an electrophysiological correlate of learning and memory. At the molecular level, immediate early genes are among the synaptic plasticity genes that are both induced by long-term potentiation and downregulated in the aged brain. In addition to revitalizing other aged tissues, exposure to factors in young blood counteracts age-related changes in these central nervous system parameters, although the identities of specific cognition-promoting factors or whether such activity exists in human plasma remains unknown.

We hypothesized that plasma of an early developmental stage, namely umbilical cord plasma, provides a reservoir of plasticity-promoting proteins. Here we show that human cord plasma treatment revitalizes the hippocampus and improves cognitive function in aged mice. Tissue inhibitor of metalloproteinases 2 (TIMP2), a blood-borne factor enriched in human cord plasma, young mouse plasma, and young mouse hippocampi, appears in the brain after systemic administration and increases synaptic plasticity and hippocampal-dependent cognition in aged mice. Depletion experiments in aged mice revealed TIMP2 to be necessary for the cognitive benefits conferred by cord plasma. We find that systemic pools of TIMP2 are necessary for spatial memory in young mice, while treatment of brain slices with TIMP2 antibody prevents long-term potentiation, arguing for previously unknown roles for TIMP2 in normal hippocampal function. Our findings reveal that human cord plasma contains plasticity-enhancing proteins of high translational value for targeting ageing- or disease-associated hippocampal dysfunction.

An Interview with Alex Zhavoronkov

The Life Extension Advocacy Foundation volunteers here interview Alex Zhavoronkov of Insilico Medicine. This company is focused on analysis of aging and discovery of drugs that might modestly slow aging rather than interventions after the SENS rejuvenation research model. If continuing along much the same road in the future, I predict that that the most important contribution to the field arising from this work will likely be a range of novel biomarkers to help determine the effectiveness of therapies that aim to treat aging. I have never been all that enthused by efforts to produce or repurpose drugs that tinker with the operation of metabolism to slightly slow aging, such as calorie restriction mimetics and the like. The plausible outcomes resulting from such efforts look marginal at best, and these research projects are at least as expensive as initiatives that aim at actual rejuvenation, while that rejuvenation has a far greater predicted outcome on health and longevity. On this topic, Zhavoronkov and I clearly differ in our expectations.

Your work focuses on computational medicine, how would you explain this relatively new field of science to our readers?

Computational biomedicine is a very broad field of research, where computational methods and tools are applied for diagnosis, treatment and research. The field has been around since the invention of electronic analytical equipment, but in recent years it got a major boost due to the availability in Big Data, increases in computing power, breakthroughs in machine learning and convergence of the many fields of science and technology.

You are the CEO of Insilico Medicine. What are the main goals of the company for the next 5 years? Can we expect breakthroughs in personalised medicine?

Our long-term goal is to continuously improve human performance and prevent and cure the age-related diseases. In 5 years we want to build a comprehensive system to model and monitor the human health status and rapidly correct any deviations from the ideal healthy state with lifestyle or therapeutic interventions. Considering what we already have, I hope that we will be able to do it sooner than in 5 years. One reason why we can manage over 170 projects is because we use agile development practices and approach every project as a software development project. We treat aging as a salami, constantly "cutting" thin slices and I think we are halfway through.

In 5 years you can definitely expect breakthroughs in personalized medicine and we are not the only company working in the field, so there will be many breakthroughs on the many fronts. The main breakthroughs I can promise from Insilico are in the area of multi-modal biomarkers of aging, where we take as much data available for an individual from simple pictures and regular blood tests to very expensive molecular and imaging data and turn it into a model, which can be used to make a broad range of predictions, recommendations and treatments. We are entering the era of personalized drug discovery and regenerative medicine.

One of our major contributions to the field was the application of deep neural networks for predicting the age of the person. People are very different and have different diseases. But if you want to find just one feature, which is biologically relevant and can be predicted using many data types - it is the person's date of birth. So we build all kinds of predictors of chronological age and then look at what features and at what levels are most important and can be used to infer causality and be targeted with interventions. I think that this approach is novel and will result in many breakthroughs.

How do you decide what projects to get involved in?

The way we prioritize projects at Insilico Medicine is by looking at the number of quality-adjusted life years (QALY) each project can generate. Most pharmaceutical companies, governments, and philanthropists do not realize that aging research generates the maximum number of QALY per dollar spent. It is the most altruistic cause and the most effective investment. If you add just one year of life to everyone on the planet, you generate over 7 billion QALY. The average reasonable cost per QALY is around $50,000. So it is possible to generate several hundred trillion dollars by extending life of everyone on the planet with a simple intervention.

What is your estimate, when we could expect the first powerful treatment to slow down aging appear on the market?

I think that there are several very powerful treatments that are already available on the market and to get the extra 10-20 years or even more we just need to devise a way to turn these into therapeutic regimens. I think that a comprehensive regimen involving metformin, targeted rapalogs, senolytics, anti-inflamatory agents, aspirin, NAC, ACE inhibitors, beta-blockers, PDE5, PCSK9 inhibitors, NAD+ activators and precursors in combination with the regenerative medicine procedures and also a set of cosmetic and lifestyle interventions could easily add 20 years to our life span. And I am sure that some people are already trying these interventions on themselves. Unfortunately, nobody is tracking this data.

Link: http://www.leafscience.org/a-i-versus-aging/

Some Longevity Mutations Can Extend the Period of Frailty and Decline

The primary goal of longevity science is to extend healthy life span. A secondary, less important goal is to reduce the time spent in ill health and declining function at the end of life. That secondary goal receives more attention for largely political reasons, however; it is what researchers talk about when they want to avoid talking about extension of life span. It is unfortunate that this is still a subject that is avoided by many in the research community. People should be more open when it comes to the fact the goal of treating aging as a medical condition is ultimately to extend healthy life indefinitely, to greatly extend the present all too short human life span. Trying to hide that away just makes everything harder.

The merits of a potential approach to treating aging should be judged primarily by the degree to which it can extend healthy life span. It is quite reasonable to expect some classes of treatment to also extend the period of decline in late life. Aging is caused by an accumulation of metabolic waste and molecular damage. A method that slows the pace of damage accumulation should both extend health and extend frailty. A method that periodically repairs damage should extend health and may or may not extend frailty, depending on the details. A method that improves resistance to damage or some of its consequences might fail to extend health while extending the period of frailty. All of these are possible outcomes, and the research community should aim for the most desirable of them, taking into account the size of the effect. A large extension to health span followed by a large extension to the period of frailty is a good deal better than a small gain in health span that does not extend the period of frailty.

Caenorhabditis elegans has been an invaluable experimental organism for the discovery and characterization of conserved pathways that extend lifespan. In particular, reduced signaling through the stress and nutrient-sensing insulin/insulin-like growth factor 1 (IGF-1) pathway was first shown to double the lifespan of C. elegans and was later found to increase the longevity of other species, including mammals. C. elegans with partial loss-of-function mutations in daf-2, the C. elegans insulin/IGF-1-receptor gene, not only live longer but also maintain more youthful characteristics, such as active movement, neuronal function, and memory, indicating an extension of healthspan as well as lifespan. However, a recent study followed the functional ability of daf-2 mutants and found that the daf-2 healthspan, although chronologically longer than that of the wild-type, did not scale with lifespan, resulting in a disproportionately extended period of age-related decrepitude. This report was disconcerting because such an outcome would be undesirable in a human society, where population aging has already increased healthcare costs substantially. It also brought into question the validity of C. elegans as a model organism to study healthy life extension.

In this study, we set out to accomplish three goals: to undertake a quantitative large-scale analysis to corroborate the reported disproportionately extended end-of-life decrepitude in a daf-2 mutant, to determine whether this phenotype could be due to behavioral particularities of the specific daf-2 allele that was examined, and, if not, to elucidate the cause of this apparently undesirable phenotype. We found that two very different daf-2 mutants both remain active longer and age more slowly than the wild-type, at least through mid-life, but then go on to stay alive but decrepit for a long time. We wanted to understand what might cause this extended decrepitude. Theoretically, eliminating a cause of death that kills relatively young individuals would result in a population's growing older and frailer.

We wondered whether resistance to bacterial toxicity might play a role. We measured bacterial colonization of a daf-2 mutant. Colonization of the upper digestive tract was delayed and never reached the same maximum as in the wild-type. This finding is consistent with the idea that resistance to colonization allows daf-2 mutants to survive into old age. Why bacterial colonization occurs in old C. elegans and how exactly it causes death remains unknown. Decreased immune function with age could contribute to bacterial accumulation and proliferation, and daf-2 mutants have higher expression of some antimicrobial genes that curtail the rate of bacterial proliferation in the intestine. If reduced risk of death due to bacterial colonization allows daf-2 mutants to live long enough to become decrepit, then eliminating bacterial colonization as a cause of "premature" death should allow wild-type worms, too, to live long enough to enter a state of end-of-life decrepitude. To test this hypothesis, we fed wild-type animals bacteria killed by gentamicin from the time of hatching. Using killed bacteria as a food source extended the wild-type lifespan by 40%. Eliminating bacterial colonization as a cause of death in wild-type worms copied the extended period of decrepitude seen in daf-2 mutants.

In summary, we find that the level of bacterial colonization predicts wild-type lifespan. The extent of colonization is significantly greater in the wild-type than in daf-2 mutants, and eliminating colonization in wild-type animals allows them to avoid an early death; instead, they remain alive for a longer time in a decrepit, aged state, just like daf-2 mutants. Therefore, we conclude that a beneficial trait (resistance to bacterial colonization) can explain the extended end-of-life frailty of daf-2 mutants. Surviving the hazard from bacterial colonization allows these mutants to grow biologically older and more decrepit than end-of-life wild-type animals. Together, these findings support the argument that C. elegans daf-2 mutants are valuable for studying healthy lifespan extension. daf-2 mutants live longer because of a two-part mechanism: a slower rate of aging (leading to extension of healthspan) and an increased ability to resist death due to bacterial colonization (leading to extension of decrepitude). More generally, the results presented here show how the healthspan of an organism can be affected in opposite ways at different times of life by an intervention that both decreases the rate of aging and also mitigates a disease that kills old individuals. This is important to keep in mind when seeking to develop interventions that act by different demographic mechanisms to increase human lifespan.

Link: http://www.cell.com/cell-reports/fulltext/S2211-1247(17)30423-0

HGFA Signaling Enhances the Stem Cell Response to Injury

In recent years, researchers interested in the mechanisms of regeneration have explored the changing landscape of signals in the blood, both in the short term following injury and over the long term during the aging process. A number of interesting findings have emerged, especially in the course of parabiosis studies in which the circulatory systems of old and young individuals are joined. The field is still evolving fairly rapidly, and some results from just a few years ago now look more uncertain in the face of later evidence. Nonetheless, new mechanisms and areas of focus continue to emerge, such as that described in the open access paper I'll note today. The researchers involved have identified hepatocyte growth factor activator (HGFA) as a key signal in the regenerative process, and a possible path to enhance regeneration in mammals.

As we all know only too well, regeneration falters with advancing age. Our stem cells, the cell populations responsible for turning out new cells to replace those lost to injury or required to rebuild damaged structures, decline over the course of aging. In older individuals, stem cells are ever less active, spending more time quiescent, or the population size is reduced. This may be in part a fairly direct result of the molecular damage that causes aging, but in the most studied stem cell populations, such as those in muscle tissue, it appears that aged stem cells are still quite capable if give the right signals. In older tissues those signals are not present to the necessary degree, or are overridden by other signals that are a reaction to damage in the surrounding environment.

It is thought that the decline in stem cell activity, and consequent failure and frailty of tissues, is part of an evolved balance between death by cancer and death through lack of tissue maintenance - too much cellular activity by damaged cells will ultimately produce cancerous cells. On the other hand, the progress of the stem cell therapy industry to date suggests that the evolved balance has some room for adjustment in favor of more regeneration in the old. Further, we should expect the cancer research community to continue to make progress of its own: greater regeneration in the old can advance hand in hand with a greater ability to effectively treat cancer. Looking beyond that partnership, true rejuvenation therapies, those that repair the molecular damage that is the root cause of aging, should reactivate stem cells and restore regenerative prowess without any further downside.

Alerting stem cells to hurry up and heal

This recent study builds upon a previous finding that when one part of the body suffers an injury, adult stem cells in uninjured areas throughout the body enter a primed or "alert" state. Alert stem cells have an enhanced potential to repair tissue damage. In this new study, researchers identified a signal that alerts stem cells and showed how it could serve as a therapy to improve healing. Searching for a signal that could alert stem cells, the researchers focused their attention on the blood. They injected blood from an injured mouse into an uninjured mouse. In the uninjured mouse, this caused stem cells to adopt an alert state. The researchers identified the critical signal in blood that alerted stem cells: an enzyme called Hepatocyte Growth Factor Activator (HGFA). In normal conditions, HGFA is abundant in the blood, but inactive. Injury activates HGFA, so HGFA signaling can alert stem cells to be ready to heal.

Leveraging this discovery, the researchers asked the question: What happens if HGFA alerts stem cells before an injury occurs? Does this improve the repair response? They injected active HGFA into mice that received either a muscle or skin injury a couple of days later. The mice healed faster, began running on their wheels sooner and even regrew their fur better than mice that did not receive the HGFA booster. These findings indicate that HGFA can alert many different types of stem cells, rousing them from their normal resting or "quiescent" state, and preparing them to respond quickly and efficiently to injury. "This work shows that there are factors in the blood that control our ability to heal. We are looking at how HGFA might explain declines in healing, and how we can use HGFA to restore normal healing."

HGFA Is an Injury-Regulated Systemic Factor that Induces the Transition of Stem Cells into GAlert

Tissue damage induces the activation of quiescent stem cells, initiating a cascade in which stem cells enter the cell cycle, divide, and proliferate to generate the cells required to repair or regenerate damaged tissue. Stem cell activation is a limiting step in the process of tissue repair. In many stem cell pools, the first cell division following activation is slow and can take many days to complete, whereas subsequent cell divisions are much more rapid. Defects in stem cell activation, such as a lengthening in the time of first cell division or a failure in stem cells to activate, can result in significant impairments in the healing process. Little is known about the biologic regulation of stem cell quiescence and activation. Approaches to accelerate the rate-limiting step of stem cell activation could have broad therapeutic applications in regenerative medicine.

We previously reported an acceleration of the activation properties of quiescent stem cells in response to a prior injury, distant from the tissue in which the stem cells were residing. We described this regulation as a transitioning of stem cells from the G0 to the GAlert state of quiescence, where GAlert stem cells are poised to activate quickly in response to injury and to repair tissue damage more effectively. Because of the enhanced functional properties of GAlert stem cells, there may be clinical applications for factors that induce the GAlert state. However, the endogenous signals that stimulate the G0-to-GAlert transition of stem cells in response to distant injuries have not been previously described. Here, we show that a single systemic factor, hepatocyte growth factor activator (HGFA), is sufficient to induce the transition of multiple pools of stem cells into GAlert and that administration of HGFA to animals, prior to an injury, improves the subsequent kinetics of tissue repair.

Failing Autophagy and Lipofuscin Accumulation in the Aging Brain

It is known that the cellular housekeeping process of autophagy declines with aging, and it is also known that the metabolic waste known as lipofuscin builds up in long-lived cells at the same time. In the SENS view of aging, this lipofuscin accumulation is one of the causes of failing autophagy, as it accumulates in the recycling structures called lysosomes, degrading their function. Definitively proving this direction of causation, versus it being the other way around, is ever a challenge, however. The most effective way to do that is to clear out lipofuscin in old tissues and then observe the results, but at present this can only be achieved for a few of the many constituent compounds that make up this form of waste.

Autophagy is a self-degradative, highly regulated process that involves the non-specific degradation of cytoplasmic macromolecules and organelles via the lysosomal system. There are three different autophagic pathways based on the mechanisms for delivery of cargo to lysosomes: macroautophagy, microautophagy and chaperone-mediated autophagy (CMA). Macroautophagy (herein referred to as autophagy) is the major lysosomal pathway for the turnover of cytoplasmic components. Emerging evidence indicates that autophagy protects cells by removing long-lived proteins, aggregated protein complexes, and excess or damaged organelles. Defects in autophagy, therefore, are associated to various pathological conditions within organisms, including tumorigenesis, defects in developmental programs and the build-up of toxic, protein aggregates involved in neurodegeneration such as Amyloid precursor protein (APP). It has been recently suggested that the progressive age-related decline of autophagic and lysosomal activity may also be responsible for the continuous intraneuronal accumulation of lipofuscin, or "age pigment".

For this study, we aimed to investigate the expression of autophagic markers and the accumulation of pathologic proteins such as APP and lipofuscin in aged bovine brains. Microscopic findings in the brains of our aged bovines are similar to those previously described in old animals of other species as well as in cattle. In this study, the age-dependent intraneuronal accumulation of lipofuscin is one of the most striking features of aged brains. This finding is not actually new, as it has been described for more than 150 years. In the past, lipofuscin was generally thought to be an innocent end product of oxidation which has no significant influence on cellular activities, but in the last decade several authors have investigated about the possible detrimental and pathogenic potential of this material.

The so-called "mitochondrial-lysosomal axis theory of aging" tries to explain the possible relationship between lipofuscin accumulation, decreased autophagy, increased Reactive Oxygen Species (ROS) production, and mitochondrial damage in senescent long-lived postmitotic cells. According to this theory, in senescent cells lysosomal enzymes are directed towards the plentiful lipofuscin-rich lysosomes and, subsequently, they are lost for effective autophagic degradation because lipofuscin remains non-degradable. The consequences are a progressive impairment of autophagy and the gradual accumulation of damaged mitochondria, other organelles and misfolded proteins that lead to neurodegeneration. Unfortunately, our results cannot support a direct association between lipofuscin accumulation and autophagy impairment in aged bovine brains. According to recent scientific literature, we can only hypothesize that progressive and severe lipofuscin accumulation may irreversibly lead to functional decline and death of neurons by diminishing lysosomal degradative capacity and by preventing lysosomal enzymes from targeting to functional autophagosomes.

Further studies are indeed necessary to better understand how lipofuscin accumulation can influence the neuronal autophagic and apoptotic pathways in bovine brains. It would be interesting to perform double-staining techniques in order to show whether lipofuscin is directly related to autophagic and apoptosis markers and/or to pathologic protein deposition. Unfortunately, to our knowledge, a specific antibody for lipofuscin is not available since this complex substance is mainly composed of cross-linked protein and lipid residues. Alternatively, combined histochemical and immunohistochemical staining protocols can be performed to simultaneously localize lipofuscin and the antigen of interest. However, since lipofuscin progressively accumulates throughout the life of neurons, this combined immunohistochemical/histochemical protocol is not perfectly indicated to investigate the mechanism and relative timing of intraneuronal lipofuscin accumulation and the deposition of other proteins. Primary cultured neuronal cells exhibit, in vitro, a variety of features that are frequently observed in physiologically aged neurons in vivo, including lipofuscin accumulation. Thus, long-term aging culture of primary cultured neurons would be a remarkable model to unravel, at least in part, the molecular mechanisms behind lipofuscin accumulation and its pathological effects on neuronal cells.

Link: https://dx.doi.org/10.1186/s12917-017-1028-1

Blocking CD47 Reverses the Progression of Fibrosis

Expression of the cell surface marker CD47 helps to protect cells from destruction by the immune system. It is abused by a variety of cancers, and thus blocking CD47 is the basis for a line of research into cancer therapies that might be broadly effective. Other researchers have found that this same approach might help to reduce the size of atherosclerotic plaques, so it seems that it isn't just cancerous cells in which excess CD47 is preventing beneficial destruction. Here, researchers discover that the cells making up the scar tissue of fibrosis are similarly protecting themselves with CD47, and blocking its activity causes the immune system to remove this scarring. Fibrosis is a damaging process, an age-related malfunction in the the normal progression of regeneration, and the scarring it causes in organs such as the heart and kidney degrade their proper function, contributing to decline and disease in later life. There is no effective treatment for fibrosis at the present time, which makes this research particularly exciting.

Researchers have identified a pathway that, when mutated, drives fibrosis in many organs of the body. The pathway underlies what have been considered somewhat disparate conditions, including scleroderma, idiopathic pulmonary fibrosis, liver cirrhosis, kidney fibrosis and more, the researchers found. These diseases are often incurable and life-threatening. Importantly, the researchers were able to reverse lung fibrosis in mice by administering an antibody called anti-CD47 now being tested as an anti-cancer treatment. "The variety of diseases caused by overproduction of fibroblasts has made finding a common root cause very challenging, in part because there has been no good animal model of these conditions. Now we've shown that activating a single signaling pathway in mice causes fibrosis in nearly all tissues. Blocking the CD-47 signal, which protects cancer cells from the immune system, can also ameliorate these fibrotic diseases even in the most extreme cases."

Fibrosis occurs when the body's normal response to injury goes astray. An overenthusiastic or inappropriately timed proliferation of cells called fibroblasts, which make up the connective tissue surrounding and supporting all of our organs, can lead to many devastating diseases. In a mouse model she developed, researchers found that fibroblasts were producing unusually high levels of an important signaling molecule called c-Jun. C-Jun is a transcription factor that drives the production of many proteins involved in critical cellular processes. It's been implicated in many types of human cancer. In the current study, researchers investigated c-Jun expression levels in 454 biopsied tissue samples from patients with a variety of fibrotic diseases. They found that in every case the fibroblasts from the patients with fibrosis expressed higher levels of c-Jun than did control fibroblasts collected from people with nonfibrotic conditions.

Blocking the expression of c-Jun in laboratory-grown lung fibroblasts collected from people with idiopathic pulmonary fibrosis substantially decreased the proliferation of these cells, but not of lung fibroblasts collected from people without fibrosis. Furthermore, mice genetically engineered to overexpress c-Jun in all their body's tissues developed fibrosis in nearly every organ, including lung, liver, skin and bone marrow. "We found that c-Jun overexpression and over-activation is a unifying mechanism in many types of fibrosis. But an even more exciting part of the story is the fact that we observed that the diseased, c-Jun-expressing fibroblasts are surrounded by immune cells called macrophages. This is reminiscent of what's often seen in human cancers." Over the past eight years, researchers have shown that many human cancers evade the immune system by expressing high levels of a protein called CD47 on their surfaces. Blocking this protein with an anti-CD47 antibody restores the ability of the macrophages to gobble the cancer and has proven to be a promising treatment in animal models of the disease. Anti-CD47 antibody is currently undergoing a phase-1 clinical trial in humans with advanced solid tumors.

When researchers treated mice with c-Jun-induced lung fibrosis with daily injections of anti-CD47 antibody, the animals exhibited significantly better lung function, lived longer than their peers and cleared the fibrosis. The researchers plan to investigate whether any patients in the phase-1 trial of the anti-CD47 antibody also suffered from any fibrotic conditions. If so, they are eager to learn whether they experienced any relief as a result of participating in the trial. "We have hit upon something unique in this study. We identified a highly activated pathway that causes fibrosis in many tissues in mice, and we've showed that treating the animals with an anti-CD47 antibody reverses the fibrosis. We're hopeful that this could be a potential treatment for people with many types of fibrotic conditions."

Link: http://med.stanford.edu/news/all-news/2017/04/fibrosis-reversed-when-dont-eat-me-signal-blocked.html

Assessing the Effects of Running on Human Longevity

Armed with better tools, such as lightweight accelerometers, and given much more data to work with, epidemiologists are nowadays trying to quantify the degree to which specific forms of exercise are better or worse then others. Other teams are trying to put rigorous numbers to the dose-response curve for exercise: where is the optimal point when it comes to health and longevity? It is a given that regular moderate aerobic exercise is good for you, and the evidence for that is overwhelming. Sedentary people suffer shorter lives and a greater burden of age-related disease. But once we start to ask how much exercise is most advantageous, or whether one form of exercise is better than another, then the answers become much less certain. They depend far more upon interpretations of data and the limitations of specific data sets, the details of which can be quite complex - and will thus never appear in the popular press when specific research projects are discussed.

The only useful way to look at this sort of research is in aggregate, summed over many studies. At this point there are simply too few papers comparing different forms of exercise to say more than that it is an interesting topic: I would say that many more years of work are needed to assemble a good consensus for human data, and even then that consensus will be fuzzy around the edges, numbers subject to opinion on various scientific factions and their methodologies. Thus attempting to optimize lifestyle for health and longevity strikes me as a pleasant hobby to maintain, but no matter how much effort you put into it, you'll likely never find out whether you are in fact doing any better than the 80/20 level achieved with far less work.

Given that the future of our health will be increasingly determined by progress in medicine as we age, I would argue that we should direct our extra time and effort towards supporting research into therapies to treat the causes of aging, as opposed to chasing the mirage of a perfectly optimal lifestyle. Good enough is comparatively easy to achieve when it comes to personal health, while significantly more than that is a next to impossible goal. Meanwhile, absent new technologies based on the SENS rejuvenation research programs, even the healthiest of us in mid-life today have but a small chance of making it to 100, and we'll be very frail indeed should we manage to hold out to that point. Technology should be the focus.

An Hour of Running May Add 7 Hours to Your Life

Resarchers found that, compared to nonrunners, runners tended to live about three additional years, even if they run slowly or sporadically and smoke, drink or are overweight. No other form of exercise that researchers looked at showed comparable impacts on life span. The findings come as a follow-up to a study done three years ago, in which a group of distinguished exercise scientists scrutinized data from a large trove of medical and fitness tests. That analysis found that as little as five minutes of daily running was associated with prolonged life spans.

Over all, this new review reinforced the findings of the earlier research, the scientists determined. Cumulatively, the data indicated that running, whatever someone's pace or mileage, dropped a person's risk of premature death by almost 40 percent, a benefit that held true even when the researchers controlled for smoking, drinking and a history of health problems such as hypertension or obesity. Perhaps most interesting, the researchers calculated that, hour for hour, running statistically returns more time to people's lives than it consumes. Figuring two hours per week of training, since that was the average reported by runners in the earlier study, the researchers estimated that a typical runner would spend less than six months actually running over the course of almost 40 years, but could expect an increase in life expectancy of 3.2 years, for a net gain of about 2.8 years. In concrete terms, an hour of running statistically lengthens life expectancy by seven hours, the researchers report.

The gains in life expectancy are capped at around three extra years, however much people run. The good news is that prolonged running does not seem to become counterproductive for longevity, according to the data. Improvements in life expectancy generally plateaued at about four hours of running per week, but they did not decline. Meanwhile, other kinds of exercise also reliably benefited life expectancy, the researchers found, but not to the same degree as running. Walking, cycling and other activities, even if they required the same exertion as running, typically dropped the risk of premature death by about 12 percent. Why running should be so uniquely potent against early mortality remains uncertain, but it raises aerobic fitness, and high aerobic fitness is one of the best-known indicators of an individual's long-term health.

Running as a Key Lifestyle Medicine for Longevity

Running is a popular and convenient leisure-time physical activity (PA) with a significant impact on longevity. In general, runners have a 25-40% reduced risk of premature mortality and live approximately 3 years longer than non-runners. Recently, specific questions have emerged regarding the extent of the health benefits of running versus other types of PA, and perhaps more critically, whether there are diminishing returns on health and mortality outcomes with higher amounts of running. This review details the findings surrounding the impact of running on various health outcomes and premature mortality, highlights plausible underlying mechanisms linking running with chronic disease prevention and longevity, identifies the estimated additional life expectancy among runners and other active individuals, and discusses whether there is adequate evidence to suggest that longevity benefits are attenuated with higher doses of running.

Reviewing the State of Biomarkers of Aging

By way of following up on a brace of papers on biomarkers of aging that arrived over the past few weeks, here is an open access review on the topic. It is an important topic, it has to be said. The development of therapies to treat the causes of aging - and thereby significantly extend healthy life spans - is made expensive and slow by the lack of efficient ways to assess outcomes. It is easy enough to see whether a given therapy achieves what it intended to achieve in the short term, that genes are suppressed or unwanted cells are removed, for example, but at present the only way to then link that to increased long-term health and life span is to wait and see. Waiting to see carries a million dollar price tag and several years of effort for studies in mice, and the equivalent situation in humans is obviously impractical. The research community needs a generally agreed upon, robust, low-cost assessment of biological age, an assay that can run immediately before and immediately after a potential rejuvenation therapy to assess its effect on the state of aging in the patient, and does so in a way that is independent of the mechanism of the therapy itself.

Chronological age is a major risk factor for functional impairments, chronic diseases and mortality. However, there is still great heterogeneity in the health outcomes of older individuals. Some individuals appear frail and require assistance in daily routines already in their 70s whereas others remain independent of assistance and seem to escape major physiological deterioration until very extreme ages. In keeping with the unprecedented growth rate of the world's aging population, there is a clear need for a better understanding of the biological aging process and the determinants of healthy aging. Towards this aim, a quest for (biological) markers that track the state of biophysiological aging and ideally lend insights to the underlying mechanisms has been embarked upon.

During the past decades, extensive effort has been made to identify such aging biomarkers that, according to the stage-setting definition, are "biological parameters of an organism that either alone or in some multivariate composite will, in the absence of disease, better predict functional capability at some late age, than will chronological age". Later on, the American Federation for Aging Research (AFAR) formulated the criteria for aging biomarkers as follows: (1) It must predict the rate of aging. In other words, it would tell exactly where a person is in their total life span. It must be a better predictor of life span than chronological age. (2) It must monitor a basic process that underlies the aging process, not the effects of disease. (3) It must be able to be tested repeatedly without harming the person. For example, a blood test or an imaging technique. (4) It must be something that works in humans and in laboratory animals, such as mice. This is so that it can be tested in lab animals before being validated in humans.

However, to date, no such marker or marker combination has emerged. Moreover, the existence of such markers has been questioned, because the effects of many chronic diseases are inseparable from normal aging. The rate of biological aging can also vary across different tissues, and hence it may not be feasible to assume a measurable overall rate. Recently, however, several new biomarkers for biological aging have come into play. They can be separated into molecular (based on DNA, RNA, etc.) or phenotypic biomarkers of aging (clinical measures such as blood pressure, grip strength, lipids, etc.), although we include both types. The focus of this review is on novel biological age predictors, and we define them as markers that predict chronological age, or at least can separate "young" from "old". They should also be associated with a normal aging phenotype or a non-communicable age-related disease independent of chronological age in humans. Promising developments consider multiple combinations of these various types of predictors, which may shed light on the aging process and provide further understanding of what contributes to healthy aging. Thus far, the most promising new biological age predictor is the epigenetic clock; however its true value as a biomarker of aging requires longitudinal confirmation.

Link: http://dx.doi.org/10.1016/j.ebiom.2017.03.046

Assessing Nematode Versions of Human Aging-Associated Genes

An ortholog is a gene in one species that serves the same purpose as its equivalent in another species, a pairing that usually implies common ancestry. In the case of humans and nematode worms such as Caenorhabditis elegans, that is a very distant common ancestry, but nonetheless even between such widely diverse species many cellular mechanisms are surprisingly similar. The basic pattern for cellular life is very ancient, and came into being in the earliest stages of evolution, long before the existence of complex organisms. Here, researchers make a list of nematode orthologs of a number of human genes that are known to vary in gene expression levels as aging progresses, and find that more than half of them affect nematode life span if their activity is suppressed. All in all it is an interesting approach to narrowing the scope of further research into the way in which specific human genes impact the pace of aging.

This is characteristic of the approach to aging taken by much of the research community, in aiming first to completely understand how exactly aging progresses, at the detail level, with all of the influences mapped. Where intervention is the goal, that intervention takes the form of adjusting the operation of cells in order to modestly slow the progression of aging. It is far from the most effective path forward, being slow, costly, and producing only limited benefits, but it is the one that dovetails best with the culture of science and funding of science, which seeks greater understanding of biological processes. This is unfortunate, as far better approaches exist if the goal is longer, healthier lives as soon as possible. Aging is an accumulation of damage, and aiming to repair that damage is far better and more cost-effective than aiming to understand exactly how the damage then causes further problems.

Understanding which molecular processes contribute to aging is critical to developing interventions capable of extending healthy human lifespan and delaying onset of age-associated diseases. A key step in this process is building a comprehensive model encompassing the range of genetic and environmental factors that influence lifespan and describing the complex interaction between these factors in an aging organism. Directly screening interventions for lifespan phenotypes in mammals is limited by long lifespans. Despite evolutionary distance and orders-of-magnitude differences in lifespan, processes that contribute to aging are sufficiently conserved that mechanistic knowledge gleaned from short-lived invertebrates can be beneficially applied to mammalian systems. Genetic screens in the nematode, Caenorhabditis elegans, have identified hundreds of genes capable of influencing lifespan.

An approach that is tractable in humans is to characterize systemic changes that occur during normal aging. This approach identifies traits that change with age or during age-associated disease and employs targeted studies to determine which play a causative role in aging. Early applications focused on easily measurable physiological traits, such as body weight or circulating molecules, but has now expanded into the '-omics' realm to provide systems-level insight into molecular changes that occur with age. As part of the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium, we published a large meta-analysis of gene expression in human peripheral blood from 14,983 individuals representing ages across the adult lifespan. This study identified 1,497 genes with significantly different expression at different ages. Gene sets with a defined age-associated expression pattern provide information about molecular processes with altered activity during aging and provide a valuable diagnostic tool for determining individual biological rate of aging and predicting risk of age-associated disease, as demonstrated in follow-up analyses. On a gene-by-gene basis, differential expression alone is insufficient to distinguish between genes that play a causative role in aging and genes that merely respond to the altered physiological environment in an aging organism.

In this study, we selected the human genes with the most significant differential expression with age from the CHARGE meta-analysis and used RNAi to screen C. elegans orthologs for lifespan phenotypes. This selection criterion ensured that every gene identified in the lifespan screen was already of interest in the context of human aging. The short lifespan of C. elegans allowed genes capable of directly influencing lifespan to be rapidly identified and characterized. The resulting C. elegans candidate list was substantially enriched in genes for which knockdown extends lifespan. The five genes with the greatest impact on lifespan (more than 20% extension) encode the enzyme kynureninase (kynu-1), a neuronal leucine-rich repeat protein (iglr-1), a tetraspanin (tsp-3), a regulator of calcineurin (rcan-1), and a voltage-gated calcium channel subunit (unc-36). Knockdown of each gene extended healthspan without impairing reproduction. Each gene displayed a distinct pattern of interaction with known aging pathways. In the context of published work, kynu-1, tsp-3, and rcan-1 are of particular interest for immediate follow-up. kynu-1 is an understudied member of the kynurenine metabolic pathway with a mechanistically distinct impact on lifespan. Our data suggest that tsp-3 is a novel modulator of hypoxic signaling and rcan-1 is a context-specific calcineurin regulator.

Link: http://onlinelibrary.wiley.com/doi/10.1111/acel.12595/full

Evidence for Cellular Senescence to Contribute to Osteoporosis

Today I noticed a recent paper in which the researchers tested a senolytic drug in the course of working on mechanisms relevant to the development of osteoporosis. Once they realized that cellular senescence might be involved in the development of osteoporosis, they put the drug to work in order to clear out senescent cells and see if that improved the picture. This is something we'll be seeing a lot more of in future research papers, whether in cell cultures or in animal models, and it certainly makes a great deal of difference to the quality of the evidence produced by a study. When researchers can address a specific cause of aging in a narrowly targeted way, rather than simply observing it, then it becomes a great deal easier to (a) show that the mechanism is in fact causing age-related disease, and (b) map the size of its effect.

The weakening of bone known as osteoporosis affects every older individual. It is, at root, an imbalance between the constantly ongoing activities of bone creation and absorption: too few osteoblasts creating bone and too many osteoclasts removing it. Any therapy that can reliably and safely tilt back the balance of activity towards creation should be helpful, but none of the approaches to date address the root causes. Instead, as is usually the case in modern medicine, researchers focus on proximate causes, trying to force cellular behavior back towards a more youthful pattern of activity without addressing the reasons why that pattern has changed. This is usually going to be hard to do well - as is any attempt to keep a damaged engine running without fixing the damage - which is why most present treatments for most age-related diseases are marginal at best.

Senescent cells accumulate with age, a lingering tiny minority of all such cells, the few that manage to evade destruction via programmed cell death or the immune system. They might be few in number, but those numbers grow over time and they cause great harm. These cells behave badly, generating signals that spur chronic inflammation, destructively remodel the extracellular matrix, and change the behavior of nearby cells for the worse as well. This adds up to produce failing organ function and disruption of vital processes such as tissue regeneration. Researchers have shown that removing senescent cells can fairly rapidly remove their malign influence as well, to some degree restoring tissue function and to some degree turning back the clock on measures of aging. Linking osteoporosis to increased numbers of senescent cells offers the hope of a better class of therapy for this condition, one that will arrive in clinics within the next few years. Numerous research groups and companies are presently involved in producing the means to selectively destroy these unwanted, harmful cells.

DNA damage and senescence in osteoprogenitors expressing Osx1 may cause their decrease with age

Old age is, by far, the most important risk factor for the development of osteoporosis. In bone biopsies from elderly men and women, the age-related loss of both cancellous and cortical bone is associated with decreased mean wall thickness - the histomorphometric hallmark of decreased bone formation. Loss of bone mass in aged rodents is associated with a decline in the number of osteoblasts, the cells responsible for the synthesis and mineralization of the bone matrix. Because osteoblasts are postmitotic cells with a short lifespan, they need to be constantly replaced with new ones. Osteoblasts arise from progenitors of mesenchymal origin, which express the transcription factors Runx2 and Osterix1 (Osx1).

The decline in the regenerative capacity of most tissues with old age has led to the idea that aging is due, at least in part, to increased cell senescence causing the loss of functional adult stem/progenitor cells. Cellular senescence is a process in which cells stop dividing and initiate a gene expression pattern known as the senescence-associated secretory phenotype (SASP). Several stimuli associated with aging promote senescence. Because the number of senescent cells increases in multiple tissues with aging, it has been widely assumed that senescence contributes to aging. Importantly, ablation of senescent cells using genetically modified mice prolongs lifespan and delays age-related pathologies in naturally aged mice or progeria models. We have recently shown that senescent cells induced by normal aging or ionizing radiation (IR) can be eliminated by administration of ABT263, a drug that kills senescent cells selectively; and clearance of senescent cells rejuvenates aged tissue stem and progenitor cells.

In both humans and rodents, the reduced osteoblast number in the aging skeleton has been attributed to changes in bone marrow-derived mesenchymal progenitors, including a decrease in the number of mesenchymal stem cells, defective proliferation/differentiation of progenitor cells, increased apoptosis, or increased senescence. However, it remains unclear whether the number of senescent osteoblast progenitors increases with old age. Moreover, the contribution of the decline in osteoblast progenitor number to the decrease in bone formation with age remains unknown because of the lack of methods to specifically identify and isolate mesenchymal progenitors. Therefore, the molecular mechanisms responsible for the decline in osteoblast number have remained elusive. To overcome these limitations, we generated a mouse model in which osteoblast progenitors are labeled with a red fluorescent protein (TdRFP) to facilitate their isolation by fluorescence-activated cell sorting (FACS) and examination of the effects of aging in freshly isolated cells. We present evidence that the decline in bone formation with age can be accounted for by a decrease in the number of osteoprogenitors due to DNA damage-induced cell senescence.

We report that the number of TdRFP-Osx1 cells, freshly isolated from the bone marrow, declines by more than 50% between 6 and 24 months of age in both female and male mice. Moreover, TdRFP-Osx1 cells from old mice exhibited markers of DNA damage and senescence. Bone marrow stromal cells from old mice also exhibited elevated expression of SASP genes, including several pro-osteoclastogenic cytokines, and increased capacity to support osteoclast formation. These changes were greatly attenuated by the senolytic drug ABT263. Together, these findings suggest that the decline in bone mass with age is the result of intrinsic defects in osteoprogenitor cells, leading to decreased osteoblast numbers and increased support of osteoclast formation.

Similarities Between Alzheimer's Disease and Parkinson's Disease

Many of the better known age-related neurodegenerative conditions involve aggregates of damaged or misfolded proteins, but there are other similarities as well. This is too be expected, given that aging is at root caused by a small variety of forms of molecular damage. This damage spirals out into a much larger set of secondary and later consequences, ultimately leading to the wide variety of age-related diseases. Simple processes acting in a complex system, such as human biochemistry, tend to produce complex outcomes. Thus if starting at the point of any two age-related diseases, dig far enough back into their roots and you will arrive at shared origins. Somewhat in that vein, this open access review paper looks over some of the commonalities in Alzheimer's disease and Parkinson's disease:

Alzheimer's disease and Parkinson's disease are two common neurodegenerative diseases of the elderly people that have devastating effects in terms of morbidity and mortality. The predominant form of the disease in either case is sporadic with uncertain etiology. The clinical features of Parkinson's disease are primarily motor deficits, while the patients of Alzheimer's disease present with dementia and cognitive impairment. Though neuronal death is a common element in both the disorders, the postmortem histopathology of the brain is very characteristic in each case and different from each other. In terms of molecular pathogenesis, however, both the diseases have a significant commonality, and proteinopathy (abnormal accumulation of misfolded proteins), mitochondrial dysfunction and oxidative stress are the cardinal features in either case.

These three damage mechanisms work in concert, reinforcing each other to drive the pathology in the aging brain for both the diseases; very interestingly, the nature of interactions among these three damage mechanisms is very similar in both the diseases. In the case of Alzheimer's disease, the peptide amyloid beta (Aβ) is responsible for the proteinopathy, while α-synuclein plays a similar role in Parkinson's disease. The expression levels of these two proteins and their aggregation processes are modulated by reactive oxygen radicals and transition metal ions in a similar manner. In turn, these proteins - as oligomers or in aggregated forms - cause mitochondrial impairment by apparently following similar mechanisms. Understanding the common nature of these interactions may, therefore, help us to identify putative neuroprotective strategies that would be beneficial in both the clinical conditions.

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5358994/

MicroRNA-210 Stabilizes Atherosclerotic Plaques

Researchers here find a way to stabilize the fatty plaques that form in blood vessels as a part of atherosclerosis. On its own this is a pretty poor treatment option, better than nothing, but worse than any approach that removes plaques or prevents them from forming. It will probably be a useful adjunct to any form of removal or reduction of plaque, however, helping to avoid rupture of larger sections of plaque during that process. It is the disintegration of fragile plaques that makes atherosclerosis lethal, as the fragments can then block critical blood vessels to cause a stroke or heart attack.

The molecule microRNA-210 stabilises deposits in the carotid artery and can prevent them from tearing. Thus, it may prevent dangerous blood clots from forming. The most common cause for the narrowing of the carotid artery is atherosclerosis, where so-called plaques build up on the vessel walls. If a plaque ruptures, blood clots can form that either further occlude the site that is already narrowed, or are carried away by the blood flow, which could lead to vascular occlusion at a different site. If this happens in the carotid artery, it could lead to a stroke. How easily a plaque ruptures depends on how thick the tissue layer surrounding its core is. The thicker this fibrous cap, the more stable and therefore more harmless the vessel deposit.

"New imaging procedures enable us to detect dangerous plaques with increasing precision; but the therapies currently available for removing these unstable plaques and thus preventing a stroke entail a certain amount of risk that the plaques will rupture during the procedure. This is why these therapies are not used on individuals with a narrowed carotid artery who have so far not experienced any symptoms. Traditionally, physicians try to reduce the size of the deposits in the vessels in order to widen the narrowed sites. For narrowed carotid arteries, though, the notion of stabilising the plaques is becoming ever more prevalent. Unlike in the coronary vessels, in the carotid artery plaques rupturing is more dangerous than the narrowing."

Researchers compared material from patients with stable and unstable deposits in the carotid artery. They particularly focused on microRNAs. These molecules are involved in the gene regulation in about 60 percent of mammals' genes. They can prevent gene information that has already been read from being translated into proteins, and have become a focus of biomedical research as active ingredients and starting points for new therapies in recent years. The scientists discovered that microRNA-210 was reduced the most in the blood samples of patients with unstable plaques. These were blood samples that were obtained locally near the vessel deposits. Further examinations showed that microRNA-210 is primarily present in the fibrous caps of plaques and that it inhibits the expression of the APC gene. As a consequence, fewer smooth muscle cells die in the fibrous cap and it becomes more stable. Moreover, the animal model could show that fewer plaques rupture when microRNA-210 is administered.

The scientists are currently researching how microRNA-210 can be applied locally. The risk of adverse events in other organs is much too high if microRNA modulators are administered systemically. The main concern with microRNA-210 is that tumour cells that are possibly already in existence will multiply, because the expression of APC is inhibited. This is because APC is a tumour suppressor gene which inhibits the growth of tumours in the healthy body. In order to avoid such off-target effects, the researchers are currently testing coated stents or balloons that are inserted directly into the carotid artery.

Link: https://www.tum.de/en/about-tum/news/press-releases/detail/article/33846/

Use of the CD9 Cell Surface Receptor to Target Senescent Cells

As ever more researchers turn their attention to cellular senescence as a cause of aging and age-related disease, more potential approaches to selectively targeting these unwanted cells are emerging. In the paper I'll point out here, the cell surface receptor CD9 is used to target nanoparticles carrying a therapeutic payload into senescent cells. The researchers chose to use rapamycin as the drug payload, as for one it doesn't matter too greatly if it gets into other cells, and secondly there is a fairly active line of research involving mTOR and its influence over the behavior of senescent cells. Rapamycin, as you'll recall, inhibits mTOR, but has some unpleasant side-effects that make it a poor option for a therapeutic. Targeting via nanoparticles in this way greatly lowers the provided dose; it is a way to deliver potentially harmful drugs in order to obtain a narrow set of benefits while minimizing the unwanted side-effects.

For my money, the best use of targeting mechanisms in the case of senescent cells is to deliver cell-killing mechanisms rather than the sort of cell-adjusting mechanisms used here, but when killing cells the targeting method has to have a very high degree of discrimination. To my knowledge, no-one has made it all that far down that road yet. The present approaches to destroying senescent cells, those under active development and heading towards the clinic, don't even try to deliver their therapeutic agents selectively to senescent cells. They are applied to all cells and target senescence in the sense of preferentially activating inside senescent cells. Some are more effective in that discrimination than others, but the basic concept certainly works. So it is interesting to see a group working on the more traditional method of steering delivery via cell surface markers, in order to place the therapeutic into the target cell population only, or at least to the greatest degree possible. A few years back, I had predicted that this would be the sort of technology first used to destroy senescent cells, and was completely incorrect on that front.

Progressive slowdown/prevention of cellular senescence by CD9-targeted delivery of rapamycin using lactose-wrapped calcium carbonate nanoparticles

Cellular senescence refers to a state of irreversible growth arrest and altered function of normal somatic cells after a finite number of divisions. Senescent cells are characterized by a flattened shape, senescence-associated β-galactosidase (SA-β-gal) activity, and hypersecretion of cytokines, chemokines, and proteases, the senescence-associated secretory phenotype (SASP). Senescence partly depends on mechanistic target of rapamycin (mTOR) signaling that mainly regulates tumor suppressor pathways p53/p21 and Rb/p16, and leads to disease development/progression through tissue function impairment. In addition, progressive inability of the immune system to destroy senescent cells during aging results in the accumulation of "death-resistant" cells that accelerate aging and disease development by altering neighboring cell behavior, lowering the pool of mitotic-competent cells, degrading the cellular matrix, and stimulating cancer. Diverse age-related diseases result from cellular senescence progression. Therefore, strategies for the prevention, treatment, or removal of senescent cells are of prime interest for clinical applications.

A recently reported proof-of-concept demonstrated the use of capped mesoporous silica nanoparticles for targeted cargo delivery inside senescent cells mediated by β-galactosidase activity. However, it fails to justify cell-specific uptake of these nanosystems to senescent cells following intravenous or subcutaneous delivery. A mechanism driven approach for specific interaction and uptake of nanoparticles by senescent cells has thus become a challenging necessity. Hence, we proposed a proof-of-concept regarding delivery of rapamycin (Rapa) loaded calcium carbonate (CaCO3) nanoparticles with CD9 receptor mediated targeting, in addition to utilization of β-galactosidase activity, in senescent cells.

Rapamycin (Rapa), an mTOR inhibitor, was found to prevent replicative senescence in rat embryonic fibroblasts by affecting the p53/p21 pathway. In addition, several studies have indicated the beneficial effects of Rapa for life span extension in aging models. More importantly, CD9 - a glycoprotein receptor of the tetraspanin family that regulates cellular activity, development, growth, and motility - is overexpressed in senescent cells and thus, can potentially be used in targeted drug delivery. Although contradictory reports on CD9 receptors in different cancer cells suggest either enhancement or inhibition of growth and motility functions, implying cell type-specific activity, senescent cells are closely related to cancer development. Our study is the first report for the utilization of CD9 receptors in targeting drug-loaded nanoparticles to senescent cells and can be a stepping stone for further research in the field of targeted therapy to senescent cells.

In our study, CD9 monoclonal antibody-conjugated lactose-wrapped calcium carbonate nanoparticles loaded with rapamycin (CD9-Lac/CaCO3/Rapa) were prepared for targeted rapamycin delivery to senescent cells. The nanoparticles exhibited an appropriate particle size (~130 nm) with high drug-loading capacity (~20%). In vitro drug release was enhanced in the presence of β-galactosidase suggesting potential cargo drug delivery to the senescent cells. Furthermore, CD9-Lac/CaCO3/Rapa exhibited high uptake and anti-senescence effects (reduced β-galactosidase and p53/p21/CD9/cyclin D1 expression, reduced population doubling time, enhanced cell proliferation and migration, and prevention of cell cycle arrest) in old human dermal fibroblasts. Importantly, CD9-Lac/CaCO3/Rapa significantly improved the proliferation capability of old cells along with significant reductions in senescence-associated secretory phenotypes (IL-6 and IL-1β). Altogether, our findings suggest the potential applicability of CD9-Lac/CaCO3/Rapa in targeted treatment of senescence.