Fight Aging! Newsletter, July 3rd 2023

Aging is characterized by increased concentrations of many pro-inflammatory factors in the circulation. In addition, chronic low-grade inflammation has been identified as a key process involved in aging. Chronic low-grade inflammation is influenced by changes in different tissues (muscle, adipose tissue), organs (brain, liver), systems (immune system), and ecosystems (gut flora). It can indirectly trigger diseases in other organs (e.g., metabolic diseases, neuroinflammatory diseases, cardiovascular diseases, etc.). Chronic low-grade inflammation is one of the main contributing factors to various age-related diseases in the elderly.

Furthermore, chronic low-grade inflammation is closely related to the dysregulation of gut flora. Many immune cells and microbiota in the digestive tract interact with each other to maintain immune homeostasis. Intestinal microbiota plays a role in maintaining healthy levels of inflammation by integrating gastrointestinal, immune, and neurological information. Data obtained from animal models have demonstrated that age-related microbial ecological disorders can lead to intestinal permeability, systemic inflammation, and premature death. Altering the gut microbiota of older adults with wholesome bacteria exerts positive effects on the maintenance of optimal immune responses, which decline with age. Such effects include delaying the aging of T lymphocytes and increasing the number of immune cells that respond to acute antigen exposure.

Probiotics can effectively assist in maintaining the balance in the composition of gut microbial flora, thereby protecting the gut barrier and regulating gut immunity. Increasing scientific evidence has shown that probiotics exert a positive effect on chronic low-grade inflammation and play a key role in healthy aging and improving age-related diseases. Probiotics might be an important therapeutic strategy for the prevention, delay, or even reversal of low-grade inflammation in old age. However, robust controlled clinical trials are warranted to further validate this hypothesis.

Transposable element (TE) activity and accumulation can have manifold effects on genomes and biological phenotypes. Multiple studies have linked TEs to ageing and the development of several diseases including cancer. Here, we have studied the relationship between TEs and two different aspects of mammal life: longevity and cancer incidence. In rodents, the short lifespan is associated with the presence of cancer. On the other hand, bats are considered cancer-resistant species. The bats and rodents considered in this study are known to have different lifespans while sharing similar, small, body sizes (under 2 kg). H. glaber is the rodent with the longest lifespan known (31 years) and resistant to cancer while the other rodents show shorter lifespans of 12 (C. porcellus), 4 (M. musculus) and 3.8 (R. norvegicus) years.

By analysing the TE annotations, we found that the main difference between short- and long-lived species of rodents is represented by a drop in non-LTR retrotransposon accumulation at recent times. Similarly, the long-lived species of bats showed a drop in non-LTR retrotransposon accumulation at recent times while presenting an overall accumulation of class II transposons (DNA transposons and Helitrons). Previous studies hypothesised that bats have a higher tolerance for the activity of transposable elements with alternative ways to dampen potential health issues due to this activity. Given our observation on the shared drop of non-LTR retrotransposons accumulation in bats and in H. glaber, we add to the aforementioned hypothesis, that the specific repression of non-LTR retrotransposon activity may enhance cancer resistance. In fact, the non-LTR retrotransposons are the most prevalent types of TEs in rodents and the most extensively investigated by biomedical research given that they are the only active TEs in the human genome.

As expected, cancer-prone species present a higher load of recently inserted non-LTR retroelements than cancer-resistant species. While lifespan of rodents showed a strong relation with the recent activity of non-LTR retrotransposons, the same type of relation for bats is less clear. However, based on a comparison of density of insertion (DI) of retrotransposons, we noticed that the long-lived bats show a DI similar to the sole long-lived cancer-resistant rodent (H. glaber), while the sole short-lived bat (M. molossus) shows a DI value more similar to short-lived rodents. Given the pattern of DI observed in rodents, we speculate that the recent accumulation of non-LTRs may be related to the lifespan of these species.

The increased transcription of non-LTR retrotransposons in humans may contribute to so-called "sterile inflammation", a phenomenon for which a chronic state of inflammation is triggered without the presence of any obvious pathogen and that is exacerbated with age ("inflammaging"). The density of recently inserted non-LTR elements in short-lived bat M. molossus is 8269 per Gb, which is comparable to the value in the short-lived rodent Cavia porcellus (9,163 insertions per Gb). In contrast, the long-lived rodent Heterocephalus glaber has a DI of only 4,550 insertions per Gb, while the long-lived bat Myotis lucifugus has 4,531 insertions per Gb. Therefore, we speculate that the marked accumulation of non-LTR retrotransposons in M. molossus might trigger phenomena similar to the sterile inflammation and inflammaging that can cause a shortening of its lifespan. For these reasons M. molossus, together with the well-known H. glaber, may be an exceptional model for biogerontology.

Extending lifespan or delaying aging has been shown to protect against degenerative diseases, and interventions that slow down the normal aging process can ameliorate multiple age-related pathologies and increase lifespan. For this reason, age-related diseases may be viewed as organ-specific conditions of accelerated aging. Therefore, slowing down the aging process is vital to prevent age-associated diseases.

Transcription factor EB (TFEB) is a key transcriptional regulator of autophagy and lysosomal biogenesis. Laboratory experiments in model organisms demonstrated that TFEB overexpression promoted longevity and reduced the burden of diseases. In rodents, healthy lifestyle interventions, such as caloric restriction and physical activity, were found to activate TFEB and upregulate autophagy, leading to a lower disease burden and extended lifespan. Pharmacological activators of TFEB, such as metformin and trehalose, also promoted autophagy and therapeutic benefits similar to caloric restriction and physical exercise. In humans, the dysregulation of TFEB is implicated in aging and diseases. Clinical trials are underway to test the safety and efficacy of caloric restriction mimetics known for their potent activation of TFEB and autophagy, such as metformin, trehalose, resveratrol, and spermidine.

Understanding the functional role of TFEB in the aging process and disease could help in the development of new therapeutic interventions for treating age-related diseases, which can extend lifespan. In this review, we provide up-to-date information on the contributions of TFEB activation in the modulation of the various hallmarks of aging and discuss the specific impact these may have on different tissues in the context of aging and age-related diseases. Furthermore, we argue that TFEB activation is a vital effector mechanism by which healthy lifestyle behaviors including caloric restriction, intermittent fasting, and exercise prevent diseases and extend lifespan.

Mesenchymal stem cells (MSCs) therapies are emerging as a promising approach to therapeutic regeneration. Therapeutic persistence and reduced functional stem cells following cell delivery remain critical hurdles for clinical investigation due to the senescence of freshly isolated cells and extensive in-vitro passage. In this study, cultured adipose-derived stem cells (ASCs) were derived from subcutaneous white adipose tissue isolated from mice fed a normal diet. We performed senescence-associated-β-galactosidase (SA-β-gal) staining, real-time PCR, and Western blot to evaluate the levels related to cellular senescence markers.

The mRNA expression levels of senescence markers were significantly increased in the later passages of ASCs. We show that light activation reduced the expression of senescent genes, and SA-β-Gal in all cells at passages. Moreover, the light-activated ASCs-derived exosomes decrease the expression of senescence, and SA-β-Gal in the later passage cells. We further investigated the photoreceptive effect of Opsin3 (Opn3) in light-activated ASCs. Deletion of Opn3 abolished the differences of light activation in reduced expression of senescent genes, increased Ca2+ influx, and cAMP levels.

We explored the effects of photomodulation on exosome secretion. The concentration of light-treated ASC exosomes represented approximately a fivefold increase compared with non-light-treated ASCs. Light-activated ASC-derived exosomes could represent a new protective paradigm for cellular senescence resulting from in-vitro passaging.

Myocardial infarction is a leading cause of morbidity and mortality. While reperfusion is now standard therapy, pathological remodelling leading to heart failure remains a clinical problem. Cellular senescence has been shown to contribute to disease pathophysiology and treatment with the senolytic navitoclax attenuates inflammation, reduces adverse myocardial remodelling and results in improved functional recovery. However, it remains unclear which senescent cell populations contribute to these processes.

To identify whether senescent cardiomyocytes contribute to disease pathophysiology post-myocardial infarction, we established a transgenic mouse model in which p16 (CDKN2A) expression was specifically knocked-out in the cardiomyocyte population. Following myocardial infarction, mice lacking cardiomyocyte p16 expression demonstrated no difference in cardiomyocyte hypertrophy but exhibited improved cardiac function and significantly reduced scar size in comparison to control animals. This data demonstrates that senescent cardiomyocytes participate in pathological myocardial remodelling.

Importantly, inhibition of cardiomyocyte senescence led to reduced senescence-associated inflammation and decreased senescence-associated markers within other myocardial lineages, consistent with the hypothesis that cardiomyocytes promote pathological remodelling by spreading senescence to other cell-types. Collectively this study presents the demonstration that senescent cardiomyocytes are major contributors to myocardial remodelling and dysfunction following a myocardial infarction. Therefore, to maximise the potential for clinical translation, it is important to further understand the mechanisms underlying cardiomyocyte senescence and how to optimise senolytic strategies to target this cell lineage.

Cellular senescence is generally driven by aging and is strongly associated with age-related disorders. It promotes the common age-associated phenotypes of reduced number of functional cells and size of tissues/organs, increased fibrosis, inflammation, and accumulation of cells with genetic defects. However, other disorders such as type 2 diabetes (T2D), obesity, and NAFLD/NASH are also characterized by increased cellular senescence in metabolic cells.

Aged tissues are characterized by dysfunctional cells and increased inflammation, and both progenitor cells and mature, fully differentiated and nonproliferating cells are afflicted. Recent studies have shown that hyperinsulinemia and associated insulin resistance promote cellular senescence in both human adipose and liver cells. Similarly, increased cellular senescence can promote cellular insulin resistance, showing their interdependence. Furthermore, the increased adipose cellular senescence in T2D is independent of age, BMI, and degree of hyperinsulinemia, suggesting premature aging. These results suggest that senomorphic or senolytic therapy may become important for treating these common metabolic disorders.

Chronic wounds are characterized by a persistent, hyper-inflammatory environment that prevents progression to regenerative wound closure. Such chronic wounds are especially common in diabetic patients, often requiring distal limb amputation, but occur in non-diabetic, elderly patients as well. Induced expression of HoxA3, a member of the Homeobox family of body patterning and master regulatory transcription factors, has been shown to accelerate wound closure in diabetic mice when applied topically as a plasmid encased in a hydrogel.

The mechanisms underlying the wound healing ability of HOXA3 has been preliminarily investigated. Macrophages transduced with HOXA3 promoted M2 polarization compared to controls. Furthermore, HOXA3 treatment mobilized and recruited endothelial progenitor cells while attenuating inflammatory pathways when compared to control mice and HOXA3 promotes the differentiation of hematopoietic progenitor cells into proangiogenic myeloid cells that stimulate neovascularization.

We now provide independent replication of those foundational in vivo diabetic wound closure studies, observing 16% faster healing (3.3 mm wounds vs 3.9 mm wounds at Day 9 post original injury of 6 mm diameter) under treatment with observable microscopic benefits. We then expand upon these findings with minimal dose threshold estimation of 1 μg HoxA3 plasmid delivered topically at a weekly interval. Furthermore, we observed similarities in natural wound healing rates between aged non-diabetic mice and young diabetic mice, which provided motivation to test topical HoxA3 plasmid in aged non-diabetic mice. We observed that HoxA3 treatment achieved complete wound closure (0 mm diameter) at 2 weeks whereas untreated wounds were only 50% closed (3 mm wound diameter). We did not observe any gross adverse effects macroscopically or via histology in these short studies. Whether as a plasmid or future alternative modality, topical HoxA3 is an attractive translational candidate for chronic wounds.

The young African turquoise killifish has a high regenerative capacity, but loses it with advancing age, adopting several aspects of the limited form of mammalian regeneration. We deployed a proteomic strategy to identify pathways that underpin the loss of regenerative power caused by aging. Cellular senescence stood out as a potential brake on successful neurorepair.

We applied the senolytic cocktail Dasatinib and Quercetin (D + Q) to test clearance of chronic senescent cells from the aged killifish central nervous system (CNS) as well as rebooting the neurogenic output. Our results show that the entire aged killifish telencephalon holds a very high senescent cell burden, including the parenchyma and the neurogenic niches, which could be diminished by a short-term, late-onset D + Q treatment. Reactive proliferation of non-glial progenitors increased substantially and lead to restorative neurogenesis after traumatic brain injury.

Our results provide a cellular mechanism for age-related regeneration resilience and a proof-of-concept of a potential therapy to revive the neurogenic potential in an already aged or diseased CNS.

Researchers have evaluated a new therapeutic class of molecules that can be used to treat a leaky blood-brain barrier. The researchers started by looking at WNT signaling, a communication pathway used by cells to promote tissue regeneration and wound healing. WNT signaling helps maintain the blood-brain barrier by promoting cell-to-cell communication that lines brain blood vessels. Scientists have been focusing on frizzled, a protein receptor that initiates the WNT pathway, for blood-brain barrier therapies since mouse mutations in the frizzled gene cause blood-brain barrier abnormalities.

Many different molecules bind to frizzled protein receptors, such as the frizzled receptor FZD4, so to narrow their search for a potential therapeutic molecule, the researchers selected only those that specifically target cells that line the brain's blood vessels. Researchers created L6-F4-2, a FZD4 binding molecule that activates WNT signaling 100 times more efficiently than other FZD4 binders.

Researchers then studied models of ischemic stroke, in which blood vessels and the blood-brain barrier are damaged, and fluid, blood and inflammatory proteins involved in cellular communication can leak into the brain. They found that L6-F4-2 reduced the severity of stroke and improved survival of mice compared with mice that had untreated strokes. Importantly, L6-F4-2 reversed the leakiness of brain blood vessels after stroke. Mice treated with L6-F4-2 had increased stroke survival, compared to those that were not treated. The finding shows that, in mice, the blood-brain barrier could be restored by drugs that activate FZD receptors and the WNT signaling pathway.

Frailty has been recognized as a growing issue in older adults, with recent evidence showing that this condition heralds several health-related problems, including cognitive decline. The objective of this work is to determine if frailty is associated with cognitive decline among older adults from different countries. We analyzed the baseline the Study on Global Ageing and Adult Health (SAGE), that includes six countries. A cross-sectional analysis was used to assess how frailty was related with the Clinical Frailty Scale (CFS) decision tree, while cognitive decline was evaluated using standardized scores of tests used in SAGE.

A total of 30,674 participants aged 50 years or older were included. To the best of our knowledge this is the first study to assess the association between cognitive performance tests and frailty measured using the CFS decision tree. Moreover, this adds to the current knowledge on how frailty relates to cognitive status in older adults, the higher the burden of frailty the lower the cognitive test scores.

Previous evidence shows that frailty could precede dementia and other neurocognitive disorders, and even be related to neuropathological findings. On the other hand, there have been some interventions - mainly based in physical activity - that have shown to improve the overall health status of an older adult with frailty, and this has the potential to stop the progression of both cognitive and physical decline. However, this relationship is still not fully understood, and merits further research.

The modification of diet for longevity has long been of interest, research generally having been conducted in animal experiments. Caloric restriction (CR) is known to contribute to a prolongation of lifespan, even in higher animals. Recently, caloric restriction, fasting, and fasting intervals, and the time of eating with consideration to species-appropriate circadian alignment has been investigated. While caloric restriction itself has been found in numerous species to result in a significant prolongation of lifespan, it has also been shown that fasting regimens can independently promote longevity as well as improve deteriorated metabolic functions.

Researchers have reported that circadian alignment in addition to fasting promotes longevity independently of caloric restriction in male mice. The study compares the contribution of adjusted feeding times in addition to fasting in five caloric restriction groups on behavioral, metabolic, and molecular outcomes using automated feeders. Diet energy was restricted by 30% in all caloric restriction groups of mice fed under five caloric restriction protocols: two of the groups were fed during the active (night) or non-active (day) period for 2 hours; two groups were fed regularly every 90 minutes during half (12 hours) of the active or non-active period; and one group was fed every 160 minutes throughout the 24 hour day.

The results are intriguing. Caloric restriction itself extended the lifespan by 10%; when the fasting time was added, the lifespan was increased to 20%; and when the feeding time was aligned to the active period, the lifespan was further extended to 35%, demonstrating that when food intake is restricted to an appropriate time of the day there is an additional benefit to caloric restriction and fasting on lifespan.

For many decades after their discovery, astrocytes, the abundant glial cells of the brain, were believed to work as a glue, supporting the structure and metabolic functions of neurons. A revolution that started over 30 years ago revealed many additional functions of these cells, including neurogenesis, gliosecretion, glutamate homeostasis, assembly and function of synapses, neuronal metabolism with energy production, and others. These properties have been confirmed, limited however, to proliferating astrocytes.

During their aging or following severe brain stress lesions, proliferating astrocytes are converted into their no-longer-proliferating, senescent forms, similar in their morphology but profoundly modified in their functions. The changed specificity of senescent astrocytes is largely due to their altered gene expression. The ensuing effects include downregulation of many properties typical of proliferating astrocytes, and upregulation of many others, concerned with neuroinflammation, release of pro-inflammatory cytokines, dysfunction of synapses, etc., specific to their senescence program. The ensuing decrease in neuronal support and protection by astrocytes induces the development, in vulnerable brain regions, of neuronal toxicity together with cognitive decline. Similar changes, ultimately reinforced by astrocyte aging, are also induced by traumatic events and molecules involved in dynamic processes.

Senescent astrocytes play critical roles in the development of many severe brain diseases. The first demonstration, obtained for Alzheimer's disease less than 10 years ago, contributed to the elimination of the previously predominant neuro-centric amyloid hypothesis. The initial astrocyte effects, operating a considerable time before the appearance of known Alzheimer's symptoms evolve with the severity of the disease up to their proliferation during the final outcome. Involvement of astrocytes in other neurodegenerative diseases is now intensely investigated.

For decades bringing organs back from a deep freeze without injury and with full function has remained a frustrating problem for the field. Researchers have already vitrified and revived human, mouse, and pig pancreas islet cells, and vitrified and rewarmed rat hearts and livers. When vitrifying, scientists first infuse the organ or tissue with magnetic nanoparticles and safeguarding chemicals called cryoprotective agents that serve as a kind of antifreeze. Afterward, they cool it quickly - 24 degrees Celsius per minute - to bypass the formation of cell-shredding ice crystals and directly enter a glass-like state.

Researchers have spent years developing technology that can rewarm vitrified materials fast enough to avoid ice-crystal formation in the physical transition back from glass. This rewarming, critically, also must be uniform, to avoid an organ cracking and splitting from its outside surfaces being too different a temperature from its core - like an ice cube in a glass of room-temperature water. Their solution is a technique called nanowarming, which utilizes a radio-frequency copper coil to create a magnetic field that excites iron nanoparticles throughout the organ all at once, similar to a microwave oven, but more uniform.

The experimental thawed rat kidneys produced urine within 45 minutes of transplantation into young rats, compared to a few minutes for their fresh counterparts. And for the first days after surgery, they were slower to clear out creatinine, a chemical waste product that kidneys remove from the body. "The biggest issue is that the kidneys were, in fact, badly damaged. The function of those kidneys was cut in about half. These were kidneys in the peak of life, in perfect health - and they barely made it." On the other hand, the degree to which the kidneys did heal and recover was "remarkable and encouraging." The researchers also noted that because they ended the study 30 days post-transplant, they weren't able to assess longer-term survival.

Researchers said they plan to spend the next six months attempting to scale their cryopreservation method up to pig organs - a size change, kidney-wise, from a large grape (in rats) to about a pear (in pigs). As they go, they will continue to study whether rewarmed animal organs recover their original physiological, chemical, and electrical properties. Down the line, if all goes well, the future might hold living banks where organs, skin, nerves, blood vessels, cartilage, and stem cells are preserved in liquid nitrogen for years until they're matched with the right patients.

Niche signals maintain stem cells in a prolonged quiescence or transiently activate them for proper regeneration. Altering niche signalling can lead to regenerative disorders. Melanocytic skin nevi in human often display excessive hair growth, suggesting hair stem cell hyperactivity. Here, using genetic mouse models of nevi, we show that dermal clusters of senescent melanocytes drive epithelial hair stem cells to exit quiescence and change their transcriptome and composition, potently enhancing hair renewal.

Nevus melanocytes activate a distinct secretome, enriched for signalling factors. Osteopontin, the leading nevus signalling factor, is both necessary and sufficient to induce hair growth. Injection of osteopontin or its genetic overexpression is sufficient to induce robust hair growth in mice, whereas germline and conditional deletions of either osteopontin or CD44, its cognate receptor on epithelial hair cells, rescue enhanced hair growth induced by dermal nevus melanocytes. Osteopontin is overexpressed in human hairy nevi, and it stimulates new growth of human hair follicles.

Although broad accumulation of senescent cells, such as upon ageing or genotoxic stress, is detrimental for the regenerative capacity of tissue, we show that signalling by senescent cell clusters can potently enhance the activity of adjacent intact stem cells and stimulate tissue renewal. This finding identifies senescent cells and their secretome as an attractive therapeutic target in regenerative disorders.