Aging Cell

Mesenchymal stem cells (MSCs) can differentiate into osteoblasts and adipocytes, play a critical role for maintaining bone homeostasis. Although, aging impairs MSC function and contributes to several complications, the effects of aging on subcellular structure and related gene expression need further investigation. Here we established an in vitro system to study MSCs isolated from bones of 5, 12, and 24 months old mice which showed significantly decreased bone volume and exercise performance with age. RNA sequencing revealed downregulation of genes related to cell-matrix interactions, cell metabolism, and division. Functionally MSCs extracted from 24mo showed significantly increased adipogenesis and reduced osteogenesis compared to 5mo, which was accompanied by reduced levels of cell proliferative marker Ki67 and increased expression of senescence protein p16. Data-driven segmentation of F-actin architecture revealed no cell-wide or nuclei-associated alteration, while 24mo MSCs showed decreased nuclear volume and increased spreading and higher nuclear stiffness compared to 5mo. Mitochondria from 12mo and 24mo showed increased length and volume of fibers when compared to 5mo, which was accompanied by gene expression changes associated with mitochondrial inflammation and oxidative phosphorylation. To test the functional consequences, MSCs were subjected to mechanical stress for 72 hours using 90Hz, 07g low-intensity vibration (LIV). While 5mo MSCs showed a robust fusing of individual mitochondrial fibers, LIV response of 12mo and 24mo MSCs were progressively less, indicating an already stressed mitochondria compromised to mechanical challenge. In summary, this study has established an in vitro assay system, revealing age-associated impairments in differentiation, mitochondrial function, and mechanotransduction capacity.

Aging is accompanied by a decline in physiological function and increased vulnerability to disease, with mitochondrial dysfunction and epigenetic alterations recognized as key hallmarks. Nicotinamide riboside (NR), a vitamin B3 precursor to NAD, and high-intensity interval training (HIIT) have both been proposed to ameliorate aging-related mitochondrial decline, but their effects on skeletal muscle epigenetic aging are not fully elucidated. Here, we assessed the impact of 5-month NR supplementation and 4-6 weeks HIIT on epigenetic age acceleration (EAA, via seven epigenetic clocks) in human skeletal muscle across three independent studies. NR supplementation was associated with reduced muscle EAA, particularly when measured with the PCHannum, MEAT, and DunedinPACE clocks, while HIIT produced opposite effects in some clocks, notably increasing pace of aging by DunedinPACE. Correlation analyses revealed that changes in skeletal muscle mitochondrial content correlated with changes in MEAT-derived EAA after NR and 6-weeks of HIIT. Together, these findings indicate that skeletal muscle epigenetic aging can be modulated by NR and HIIT interventions but in opposing directions, highlighting a potential link between mitochondria abundance and epigenetic clocks. Further studies are warranted to clarify how NR and exercise regulate epigenetic aging. These results offer new insights into development of strategies for promoting epigenetic outcomes and healthy aging.

DNA methylation-based age estimators (DNAm aging clocks) are currently one of the most promising biomarkers for predicting biological age. However, the relationships between objectively measured physical fitness, including cardiorespiratory fitness, and DNAm aging clocks are largely unknown. We investigated the relationships between physical fitness and the age-adjusted value from the residuals of the regression of DNAm aging clock to chronological age (DNAmAgeAcceleration: DNAmAgeAccel) and attempted to determine the relative contribution of physical fitness variables to DNAmAgeAccel in the presence of other lifestyle factors. DNA samples from 144 Japanese men aged 65-72 years were used to calculate first- (i.e., DNAmHorvath and DNAmHannum) and second- (i.e., DNAmPhenoAge, DNAmGrimAge and DNAmFitAge) generation DNAm aging clocks. Various surveys and measurements were conducted, including physical fitness, body composition, blood biochemical parameters, nutrients intake, smoking, alcohol consumption, disease status, sleep status, and chronotype. The peak oxygen uptake (VO2peak) per kg body weight had a significant negative correlation with GrimAgeAccel (r = -0.222, p = 0.008). A comparison of the tertile groups showed that the GrimAgeAccel of the highest VO2peak group was decelerated by 1.6 years compared to the lowest group (p = 0.035). Multiple regression analysis suggested that rather than physical fitness, serum triglycerides, carbohydrate intake, and smoking status, were significantly associated with DNAmAgeAccel. In conclusion, the contribution of cardiorespiratory fitness to DNAmAgeAccel was relatively low compared to lifestyle factors such as smoking. However, this study reveals a negative relationship between cardiorespiratory fitness and DNAmAgeAccel in older men.

Semaglutide is a once-weekly GLP-1 receptor agonist that has been proposed as a gerotherapeutic, yet no data exist on its effects on epigenetic aging. We therefore conducted a post-hoc epigenetic analysis of a 32-week, double-blind, placebo-controlled phase 2b trial in adults with HIV-associated lipohypertrophy (semaglutide n = 45; placebo n = 39). Paired peripheral-blood methylomes were profiled to evaluate semaglutides impact across multiple generations of DNA-methylation clocks. After adjustment for sex, BMI, hsCRP, and sCD163, semaglutide significantly decreased epigenetic aging: PCGrimAge (-3.1 years, P = 0.007), GrimAge V1 (-1.4 years, P = 0.02), GrimAge V2 (-2.3 years, P = 0.009), PhenoAge (-4.9 years, P = 0.004), and DunedinPACE (-0.09 units, {approx}9 % slower pace, P = 0.01). Semaglutide also lowered the multi-omic OMICmAge clock (-2.2 years, P = 0.009) and the transposable element-focused RetroAge clock (-2.2 years, P = 0.030). Eleven organ-system clocks showed concordant decreased with semaglutide, most prominently inflammation, brain and heart, whereas an Intrinsic Capacity epigenetic clock was unchanged (P = 0.31). These findings provide, to our knowledge, the first clinical-trial evidence that semaglutide modulates validated epigenetic biomarkers of aging, justifying further evaluation of GLP-1 receptor agonists for health-span extension.

Age-related skeletal muscle decline (sarcopenia) is a major contributor to frailty and mortality during aging, yet the extent to which sex shapes muscle aging and its response to dietary interventions remains poorly understood. Here, we use the short-lived vertebrate Nothobranchius furzeri (African turquoise killifish; ATK) to investigate how sex and intermittent fasting (IF) interact to regulate lifespan and skeletal-muscle aging. We establish and optimize an IF regimen that significantly extends lifespan in both male and female killifish, albeit with classical trade-offs including reduced growth and reproductive output. Despite these costs, IF markedly improves swimming performance in aged animals of both sexes. Structural analyses of killifish on a normal diet reveal pronounced sexual dimorphism in muscle aging. Males exhibit age-associated myofiber hyperplasia, whereas females maintain fiber number but undergo hypertrophic remodeling. IF partially reverses both phenotypes, restoring a more youthful fiber size distribution in both males and females. Single-nucleus RNA sequencing uncovers sex-specific remodeling of muscle-fiber composition in killifish on a normal diet, with females displaying an age-associated shift toward oxidative slow-twitch fibers that is reversed by IF, while males show relatively stable fiber-type proportions under normal and IF feeding regimens. Cell-cell communication analyses further reveal a global decline in intercellular signaling with age, alongside sex-specific restoration of distinct pathways under IF, including axon guidance and IGF signaling in females and metabolic ANGPTL signaling in males. Finally, bulk transcriptomic profiling demonstrates that aging follows largely sexually dimorphic molecular trajectories, whereas IF induces both sex-specific and shared responses. Notably, under IF, both sexes exhibit upregulation of ribosome biogenesis and genes supporting myofibrillar organization and contraction, likely underlying preserved muscle function. Together, these findings demonstrate that IF promotes longevity and muscle health through conserved anabolic mechanisms alongside sex-specific cellular and molecular rejuvenation strategies. Our work highlights the importance of incorporating sex as a biological variable when designing dietary interventions to promote healthy aging.

Nucleos(t)ide reverse transcriptase inhibitors (NRTIs) used for HIV treatment and pre-exposure prophylaxis have been proposed as gerotherapeutics based on their capacity to suppress age-associated retrotransposon activity. However, evidence in humans is currently lacking. Here we evaluated DNA methylation-based measures of biological aging in healthy people without HIV (aged 18-50) using samples from two separate randomized, directly observed dosing pharmacokinetic studies of FDA-approved NRTI regimens containing emtricitabine-tenofovir-alafenamide (FTC/TAF;200 mg/25 mg) or FTC-tenofovir-disoproxil fumarate (FTC/TDF; 200 mg/300 mg) for 12 weeks. In the FTC/TAF study (N=36), epigenetic aging measures based on DNA methylation (DNAm) profiling decreased over follow-up, including DunedinPACE (-0.061, p=0.019) and PhenoAge (-6.33, p=0.008), with concordant reductions (p<0.05) across additional systems-specific epigenetic clocks including those estimating brain aging. DNAm-based proxies of inflammatory biomarkers also declined, with significant reductions in epigenetic IL-6 (-0.058, p=0.029) and a trend toward reduced C-reactive protein (-0.231, p=0.059). In contrast, the FTC/TDF study (N=43) showed no significant changes across epigenetic clocks and proxies. These findings are consistent with TAFs more favorable cellular pharmacology compared with TDF and support gerotherapeutic effects of FTC/TAF. Prospective placebo-controlled studies are warranted that integrate clinical pharmacology, direct transposable element readouts, and prespecified geroscience and DNA methylation-based aging endpoints.

We aim to improve anti-ageing drug discovery, currently achieved through laborious and lengthy longevity analysis. Recent studies demonstrated that the most accurate molecular method to measure human age is based on CpG methylation profiles, as exemplified by several epigenetics clocks that can accurately predict an individuals age. Here, we developed CellAgeClock, a new epigenetic clock that measures subtle ageing changes in primary human cells in vitro. As such, it provides a unique tool to measure effects of relatively short pharmacological treatments on ageing. We validated the CellAgeClock against known longevity drugs such as rapamycin and trametinib. Moreover, we uncovered novel anti-ageing drugs, torin2 and Dactolisib (BEZ-235), demonstrating the value of our approach as a screening and discovery platform for anti-ageing strategies. The CellAgeClock outperforms other epigenetic clocks in measuring subtle ageing changes in primary human cells in culture. The tested drug treatments reduced senescence and other ageing markers, further consolidating our approach as a screening platform. Finally, we show that the novel anti-ageing drugs we uncovered in vitro, indeed increased longevity in vivo. Our method expands the scope of CpG methylation profiling from measuring human chronological and biological age from human samples in years, to accurately and rapidly detecting anti-ageing potential of drugs using human cells in vitro, providing a novel accelerated discovery platform to test sought after geroprotectors.

Progressive telomere shortening during lifespan is associated with increased genome instability, block to cell proliferation and aging. Apoptosis and senescence are the two main cellular outcomes upon irreversible cell damage. In this study, we show a transition between apoptosis to senescence in cells of two independent tissues in telomerase zebrafish mutants. In young mutants, proliferative tissues exhibit defects in cell proliferation and p53-dependent apoptosis, but no senescence. Progressively, these tissues display signs of tissue dysfunction, loss of cellularity and increased senescence. These alterations are accompanied by an activation of pro-proliferative stimulus mediated by AKT. Consequently, FoxO1 and FoxO4 transcriptional factors are inactivated, reducing SOD2 levels, causing an increase in ROS. These alterations elicit the activation of the zebrafish p16/15 and senescence. Thus, upon telomere shortening in aging, early apoptosis induces compensatory proliferation. However, progressive decline in cell proliferation results in tissue damage and proliferative signals, promoting a switch to senescence.

Senescent cells are characterized by the expression of the cell cycle inhibitor and biomarker of aging, p16INK4A, and the capacity to modify the microenvironment through the senescence-associated secretory phenotype (SASP). Senescent cells accumulate in physiological and pathological conditions, including aging. In spite of this, fibroblasts ectopically expressing p16INK4A do not release a SASP nor communicate with the microenvironment. Here, we find that human primary fibroblasts expressing p16INK4A release more small extracellular vesicles (sEV) as part of the SASP than proliferating cells. In addition, we show that sEV isolated from p16INK4A cells are able to mediate paracrine senescence by inducing a growth arrest and DNA damage response in proliferating cells albeit not stimulating the expression of IL-8. Furthermore, we show the transmission of paracrine senescence via sEV is conserved in two cellular models of ageing: expression of progerin, mimicking an accelerated form of ageing, and inducing telomere shortening using a dominant negative mutant. Importantly, sEV isolated from fibroblasts derived from old donors also induce paracrine senescence in fibroblasts derived from young donors. In conclusion, our data indicate that sEV released by senescent and aging cells are an important mechanism of intercellular communication and could potentially explain tissue dysfunction in aging.

Proteome integrity is vital for survival and failure to maintain it results in uncontrolled protein abundances, misfolding and aggregation which cause proteotoxicity. In multicellular organisms, proteotoxic stress is communicated among tissues to maintain proteome integrity for organismal stress resistance and survival. However, nature of these signalling molecules and their regulation in extracellular space is largely unknown. Secreted proteins are induced in response to various stresses and aging, indicating their roles in the inter tissue communication. To study fates of age-regulated proteins with potential localization to extracellular, we analysed publicly available age-related proteome data of C. elegans. We found that abundance of proteins with signal peptides (SP) increases with age and result in their aggregation. Intriguingly, these changes are differentially regulated in the lifespan mutants. A subset of these SP proteins is also found in the cargo of extracellular vesicles. Many of these proteins are novel and functionally uncharacterized. Reducing levels of a few extracellular proteins result in increasing lifespan. This suggest that uncontrolled levels of extracellular proteins might disturb proteostasis and limit the lifespan. Overall, our findings suggest that the age induced secreted proteins might be the potential candidates to be considered as biomarkers or for mitigating age-related pathological conditions.

The identification of genetic factors influencing cardiac senescence in natural populations is central to our understanding of cardiac aging and to identify the etiology of associated cardiac disorders in human populations. However, the genetic underpinning of complex traits in human is almost impossible, due to the infeasibility to control genetic background and gene-environment interactions. Drosophila has striking similarities in cardiac aging with humans, highlighting the conserved nature of cardiac aging for organisms with a heart. Leveraging on a large collection of inbred lines from the Drosophila Genetic Reference Panel (DGRP), we provide an accurate analysis of cardiac senescence in a natural population of flies. This permitted the discovery of an unprecedented number of variants and associated genes significantly associated to the natural variation of cardiac aging. We focused on the function of the PAR-domain bZIP transcription factor Pdp1 for which several variants were found associated with natural variation of the aging of multiple cardiac functional traits. We demonstrated that Pdp1 cell autonomously plays a central role in cardiac senescence and might do so by regulating mitochondria homeostasis. Overall, our work provides a unique resource regarding the genetics of cardiac aging in a natural population.

BackgroundAdvanced ageing has been associated with an increased risk of serious disease endpoints in people with HIV (PWH). We conducted a longitudinal analysis to assess advanced proteomic ageing during untreated HIV infection and the effect of antiretroviral therapy (ART) on it by comparing the plasma proteome before and after ART initiation. Methods416 protein abundance estimates were used to train a linear regression model predicting chronological age on 727 samples from Swiss HIV Cohort Study (SHCS) participants on long-term suppressive ART (median ART duration, 11.7 years). Advanced ageing was defined as age predicted by the proteomic ageing clock (PAC) minus chronological age. We evaluated the effect of successful ART on advanced proteomic ageing in an independent set of 80 PWH who had 4 longitudinal samples available, that is 2 samples during untreated HIV infection (>3 years apart, median interval between samples, 8{middle dot}08 years (IQR 4{middle dot}83-11{middle dot}09)) and 2 samples during suppressive ART (>3 years apart, median interval between samples, 9{middle dot}81 years (7{middle dot}16-11{middle dot}01)). FindingsIn the longitudinal test cohort, participants showed significantly higher proteomic age during untreated HIV infection than during suppressive ART, with a mean difference of 5.99 years (95% CI 4.25, 7.72), p = 0.0001. Thus, ART was associated with a marked reduction in proteomic advanced ageing. Although proteomic age remained higher than chronological age at all time points, linear interpolation of per-participant advanced ageing showed progressive normalisation towards chronological age during long-term suppressive ART. We validated these findings with our previously published epigenetic ageing study in the same cohort and extended those observations to the functional proteome, showing that proteomic data can capture acute immune signatures. Further, mediation analysis suggests that reversal of advanced ageing under ART is not driven by CD4+ or CD8+ T cell counts, indicating that the proteome captures ageing signals beyond immune reconstitution. InterpretationsIn a longitudinal study spanning more than 17 years, the advanced proteomic ageing observed during untreated HIV infection showed immediate and persistent deceleration under suppressive ART, demonstrating the importance of minimising the duration of untreated HIV infection. FundingSwiss HIV Cohort Study Research in contextO_ST_ABSEvidence before this studyC_ST_ABSCurrent guidelines recommend prompt antiretroviral therapy (ART) initiation after HIV diagnosis, making it now difficult to quantify the potential effects of untreated HIV on advanced ageing. Biological ageing clocks serve as proxies for individual-level disease impact and are associated with serious disease endpoints in people with HIV (PWH). We searched PubMed for English-language reports from database inception to February 24, 2026, using combinations of the terms "HIV infection," "antiretroviral therapy," "proteomic ageing," "proteomic clocks," "proteomic advanced ageing," and "age advancement." We identified one study reporting that virally suppressed HIV infection is associated with a significant increase in proteomic ageing. We have previously shown in the well established longitudinal SHCS cohort with blood samples spanning >17 years and available both pre-ART and post-ART, that telomere length attrition and epigenetic ageing is accelerated during untreated HIV infection and that initiation of successful ART is associated with a significant reduction in accelerated ageing. Added value of this studyTo our knowledge, this is the first study to examine the impact of untreated HIV on the proteome using a proteomic ageing clock. Our results demonstrate that proteomic age is elevated before ART initiation and decreases significantly following successful viral suppression on ART. This reduction was not mediated by standard immunological markers (CD4+ and CD8+ T-cell counts,CD4:8 ratio). Compared with our previous epigenetics study, the proteome appears more responsive: advanced ageing increases more sharply during untreated HIV infection and is faster to decrease after ART initiation. Implications of all the available evidenceOur findings demonstrate the importance of prompt ART initiation for PWH and reveal HIV-related ageing signals in the proteome that extend beyond immune reconstitution. Further, given the established association between advanced ageing and serious disease endpoints, this evidence motivates future studies into persistent advanced ageing to enable identification and stratification of high-risk PWH.

The rapid increase in the proportion of older adults worldwide poses a huge challenge for healthcare systems. Currently, age-related chronic diseases account for over 90% of annual healthcare expenditures (more than $4.1 trillion) in the US alone. Thus, new therapies to improve healthspan and reduce the burden of chronic disease are needed. Herein, we conducted a phase 3 controlled clinical trial to evaluate the biological age (BA) effects of different therapeutic plasma exchange (TPE) modalities in ambulatory individuals. We longitudinally profiled the subjects to measure changes in the epigenome, proteome, metabolome, glycome, and shifts in immune cell composition (cytomics). We demonstrate that administering TPE supplemented with intravenous immunoglobulin (IVIG) (TPE-IVIG) on a biweekly regime (two sessions in the first week, followed by a three-week break) is a robust therapy for BA rejuvenation. This intervention induced coordinated cellular and molecular omics responses, reversed age-related immune decline, and modulated key cellular senescence-associated proteins. Integrative analysis revealed baseline biomarkers associated with successful responses, indicating that TPE-IVIG treatment benefits those with a poorer baseline health status. In summary, this is the first multi-omics study to examine the effectiveness of various TPE modalities, which demonstrate biological age rejuvenation and the molecular features associated with this rejuvenation.

Genome-wide association studies of physical activity traits have mapped numerous loci, yet the molecular mechanisms through which exercise influences human biology remain poorly defined. Mechanistic progress has been limited by heritability-dominated signals, siloed single-omic analyses, and the lack of integrative models that connect genetic associations to causal, system-level pathways. We introduce the first deep learning, multi-omic framework for exercise genomics, unifying causal inference, molecular topology, protein structure, and functional context within a supervised Graph Neural Network (GNN) with experimental validation. Using linkage disequilibrium-aware Mendelian randomisation with accelerometer-derived vigorous physical activity as the exposure, we integrated four omic layers--plasma proteomics, blood CpG methylation, blood single-cell transcriptomics, and plasma glycomics. The GNN prioritised a coherent, multi-omic network of exercise-responsive genes spanning glycosylation and immunity, apoptosis/stress signalling, growth and transcription factors, proteostasis/autophagy, metabolism, oxidative stress/redox, mitochondrial/oxidative phosphorylation, chromatin/epigenetic, translation/ribosome, RNA splicing/processing, DNA damage and repair, cell cycle, and cytoskeleton/ECM functions. Pathway annotation and alignment with ageing biology using differentially methylated regions and principal component features from five biological ageing clocks (Horvath, Hannum, DunedinPACE, PhenoAge, Proteomic Clock), used as contextual markers of ageing-related regulation, mapped to: 1) autophagy (Fas signalling); 2) stress and DNA damage response pathways (Hypoxia-Inducible Factor, apoptosis, p53, p38, PI3K, Ras, oxidative stress, DNA replication, purine/pyrimidine metabolism and biosynthesis, pentose phosphate, Rho GTPase, G protein, ubiquitin proteasome, Epidermal Growth Factor Receptor); 3) immune and inflammatory pathways (cytokine and interleukin signalling, T and B cell activation, Toll-like receptor signalling); 4) physiological adaptation (VEGF, Wnt, GnRH, Fibroblast Growth Factor, Platelet-Derived Growth Factor, Thyrotropin-Releasing Hormone, glutamate receptor, plasminogen, endothelin, heme biosynthesis, cholecystokinin, Corticotropin-Releasing Hormone signalling); 5) neuroendocrine and neurotransmitter pathways (acetylcholine, dopamine, oxytocin, opioid, {beta}-adrenergic signalling); 6) neurodegeneration pathways (Alzheimers, Parkinsons, Huntingtons disease); 7) protein metabolism (leucine, isoleucine, valine biosynthesis); and exercise-responsive epigenetic regulatory pathways (S-adenosylmethionine, thiamine, vitamin D biosynthesis, bZIP transcription, and circadian rhythm). Finally, we partially validated GNN predictions in humans, demonstrating acute exercise-induced shifts in plasma glycomic markers consistent with GNN-predicted glycomic remodelling. This work establishes a deep learning, multi-omic map of exercise-responsive pathways in humans and identifies actionable regulators that couple habitual vigorous physical activity to stress-resilient immunometabolic regulation and healthy ageing trajectories.

Ageing is considered as a process were molecular, cellular and tissular function is impaired. One classic cellular phenotype that increases during ageing is cellular senescence. Upon senescence, the cells stop proliferating and release a variety of cytokines, chemokines and extracellular vesicles. However, the implication of biomolecules derived from lipids such as resolvins are not well characterised in senescence and ageing. Here, we find that the resolvin E and D biosynthesis pathway is activated as observed by an increase in their corresponding receptors and enzymes implicated. Furthermore, knockdown of the resolvins E and D receptors impairs the induction of senescence. This pathway is conserved not only during senescence but also in fibroblasts derived from aged human individuals, aged mice and during other inflammatory responses. A metabolomics analyses shows an increase in different precursors of resolvins in senescence. In accordance with prior data, we find that small extracellular vesicles (sEV) isolated from young human donors ameliorate inflammation and the biogenesis of resolvins both in different cell models and in aged mice. In summary, here we present data showing that the resolvins biogenesis pathway is induced in ageing and cellular senescence.

Biological brain ageing is a major risk factor for neurodegenerative diseases, which are characterized by selective degeneration of particular neuron types. We analyzed the impact of ageing on the transcriptome of neurons in the ventral tegmental area (VTA), substantia nigra pars compacta (SNc) and locus coeruleus (LC), that show differential vulnerabilities to Parkinsons disease. Neurons were isolated from human post mortem brain tissues originating from 48 individuals ranging from 17 to 102 years of age and subjected to Smart-seq2 RNA sequencing. We identified 2,764 genes that were correlated with chronological ageing. This gene expression data was used to develop a feature selection-based Time Traversal algorithm, utilizing functionally grouped gene sets, GO terms, with high predictive accuracy of biological brain ageing. We identified 59 GO terms that can predict biological age using a linear regression model, where leave-one-out cross validation demonstrated a strong correlation between chronological age and predicted biological age (Pearson correlation coefficient = 0.946; adjusted R{superscript 2} = 0.771). The algorithm was validated on five independent datasets with high predictive performance, demonstrating shared ageing features across the human brain. Nonetheless, our analysis also highlights brain region and neuron type specificity in particular ageing features. Resilient neurons showed a weaker association with age-related transcriptional changes, indicating that they age slower than their vulnerable counterparts, thus revealing targets that may be used to slow down ageing and prevent disease development.

Skin ageing is defined in part by collagen depletion and fragmentation that leads to a loss of mechanical tension. This is currently believed to reflect, in part, the accumulation of senescent cells. We compared the expression of genes and proteins for components of the extracellular matrix (ECM) as well as their regulators and found that senescent cells produced more matrix metalloproteinases (MMPs) than proliferating cells from adult and neonatal donors. This was consistent with senescent cells contributing to increased matrix degradation with age; however, cells from adult donors proved significantly less capable of producing new collagen than neonatal or senescent cells, and they showed significantly lower myofibroblast activation as determined by the marker -SMA. Functionally, adult cells also showed slower migration than neonatal cells. We concluded that while increased collagen degradation with age might reflect senescent cell accumulation, the reduced collagen production that prevents the skin from maintaining homeostasis must reflect senescence-independent processes.

Aging impairs tissue function and tolerance to cellular stress by reprogramming the behavior of resident cells. With global increases in lifespan, the prevalence of chronic and degenerative musculoskeletal disorders, including tendon degeneration, continues to rise; however, effective interventions to counteract age-related decline remain limited. Here, we investigate how a central age-associated stressor, inflammation, differentially modulates tendon cell behavior derived from young and mature-aged donors. Using super-resolution microscopy to resolve nanoscale chromatin organization in conjunction with epigenomic and transcriptomic profiling, we identify age-dependent regulatory mechanisms that govern inflammatory responsiveness. Mature-aged tendon cells exhibit exaggerated pro-inflammatory and catabolic responses across chromatin, gene expression, and protein signaling levels, characterized by enhanced TNF receptor organization, elevated accessibility at pro-inflammatory regulatory elements, and robust induction of matrix-degrading enzymes. Notably, the AP-1 transcription factor family emerges as a central age-dependent regulator, displaying distinct motif accessibility patterns that bias mature tenocytes toward inflammatory and degenerative transcriptional programs. Taken together, our findings demonstrate that age-dependent epigenetic priming amplifies inflammatory sensitivity and constrains reparative gene regulation in mature tendon cells. This work provides a mechanistic framework linking chromatin remodeling to tendon degeneration and holds potential to identify epigenetic and transcriptional pathways as potential targets for rejuvenation strategies in aging musculoskeletal tissues.

The lifelong maintenance of cognitive abilities in an increasingly aging human society is one of the major challenges of future research and medical services. For this, a better understanding of the cellular aging processes in the mammalian brain is a fundamental requirement. In particular, the functioning of postmitotic neurons, which require special strategies for lifelong functionality, is still elusive in many details. Among many other hallmarks of neuronal aging, the impairment of autophagy as an essential element of cellular homeostasis is of particular importance. However, the mechanisms for regulating these processes have not yet been fully elucidated. Establishing an in vitro model from primary cortical cells of the mouse brain, which shows the characteristic features of cellular senescence that are also observed in the total brain, we found the accumulation of dsDNA in the cytosol of neurons. Since dsDNA is a trigger for the activation of the cGAS-STING signaling and its primordial function is a non-canonical activation of autophagy, we analyzed its impact on aging neurons. We were able to demonstrate that the age-dependent downregulation of cGAS- STING signaling in neurons leads to an inhibition of autophagy at different levels. In contrast, activation of STING led to a complete rescue of autophagy in old neurons. Additionally, we found no evidence for age dependent cGAS-STING mediated IFN-I production. Hence, we propose that the primary function of cGAS-STING signaling in neurons is to maintain autophagy rather than contribute to age-related inflammation, and thus represents a target for therapeutic intervention.

Aging is the major risk factor for most human diseases and represents a major socio-economical challenge for modern societies. Despite its importance, the process of aging remains poorly understood. Epigenetic dysregulation has been proposed as a key driver of the aging process. Modifications in transcriptional networks and chromatin structure might be central to age-related functional decline. A prevalent feature described during aging is the overall reduction in heterochromatin, specifically marked by the loss of repressive histone modification, Histone 3 lysine 9 trimethylation (H3K9me3). However, the role of H3K9me3 in aging, especially in mammals, remains unclear. Here we show using a novel mouse strain, (TKOc), carrying a triple knockout of three methyltransferases responsible for H3K9me3 deposition, that the inducible loss of H3K9me3 in adulthood results in premature aging. TKOc mice exhibit reduced lifespan, lower body weight, increased frailty index, multi-organ degeneration, transcriptional changes with significant upregulation of transposable elements, and accelerated epigenetic age. Our data strongly supports the concept that the loss of epigenetic information directly drives the aging process. These findings reveal the importance of epigenetic regulation in aging and suggest that interventions targeting epigenetic modifications could potentially slow down or reverse age-related decline. Understanding the molecular mechanisms underlying the process of aging will be crucial for developing novel therapeutic strategies that can delay the onset of age-associated diseases and preserve human health at old age specially in rapidly aging societies.