ABSTRACTGenomic instability is a hallmark of aging and cancer. A key contributor to genomic instability includes alternative DNA structures, such as cruciform‐forming inverted repeats (IRs). Short IRs (< 100 bps) are abundant in the human genome, mutagenic, and enriched at mutation hotspots in human cancer genomes. Using an innovative mutation‐reporter mouse model, we showed that short IRs are mutagenic in vivo. Further, we found that aging exacerbates IR‐induced genomic instability, as evidenced by increased mutation frequencies and altered spectra in the spleen and brain of mice harboring either a short IR or control B‐DNA sequence at 2 and 24 months of age. These findings establish a link between aging and enhanced mutagenesis at short IRs, providing a unique in vivo platform to investigate age‐related mechanisms of DNA structure‐mediated genomic instability.

ABSTRACTMitochondrial calcium (Ca2+) homeostasis plays a critical role in aging and cellular fitness. In the search for novel antiaging approaches, we explored how genetic and pharmacological inhibition of mitochondrial Ca2+ uptake influences the lifespan and health of Caenorhabditis elegans. Using live‐cell imaging, we demonstrate that RNA interference‐mediated knockdown of mcu‐1, the nematode ortholog of the mitochondrial Ca2+ uniporter (MCU), reduces mitochondrial Ca2+ levels, thereby extending lifespan and preserving motility during aging, while compromising early‐life survival. This longevity benefit requires intervention before day 14 and coincides with a transient increase in reactive oxygen species (ROS), which activates pathways involving pmk‐1, daf‐16, and skn‐1, orthologs of human p38 mitogen‐activated protein kinase (p38 MAPK), forkhead box O (FOXO), and nuclear factor erythroid 2–related factor 2 (NRF2), respectively. This pathway promotes antioxidant defense mechanisms and preserves mitochondrial structure and function during aging, maintaining larger, more interconnected mitochondria and restoring the oxidized/reduced nicotinamide adenine dinucleotide (NAD+/NADH) ratio and oxygen consumption rates to youthful levels. Pharmacological inhibition of mitochondrial Ca2+ uptake using the MCU inhibitor mitoxantrone mirrors the effects of mcu‐1 knockdown, extending lifespan and improving fitness in aged nematodes. In human foreskin fibroblasts, short‐term mitoxantrone treatment also transiently elevates ROS production and induces enhanced expression and activity of antioxidant defense enzymes, underscoring the translational relevance of findings from nematodes to human cells. Our findings suggest that modulation of mitochondrial Ca2+ uptake induces mitohormesis through ROS‐mediated signaling, promoting improved longevity and healthspan in nematodes, with possible implications for healthy aging in humans.

ABSTRACTCellular senescence is an irreversible form of cell‐cycle arrest caused by excessive stress or damage. While various biomarkers of cellular senescence have been proposed, there are currently no universal, stand‐alone indicators of this condition. The field largely relies on the combined detection of multiple biomarkers to differentiate senescent cells from non‐senescent cells. Here we introduce a new approach: unbiased cell culture selections to identify senescent cell‐specific folded DNA aptamers from vast libraries of trillions of random 80‐mer DNAs. Senescent mouse adult fibroblasts and their non‐senescent counterparts were employed for selection. We demonstrate aptamer specificity for senescent mouse cells in culture, identify a form of fibronectin as the molecular target of two selected aptamers, show increased aptamer staining in naturally aged mouse tissues, and demonstrate decreased aptamer staining when p16 expressing cells are removed in a transgenic INK‐ATTAC mouse model. This work demonstrates the value of unbiased cell‐based selections to identify new senescence‐specific DNA reagents.

ABSTRACTMetabolomics has been associated with cognitive decline and dementia, but the relationship between metabolites and brain aging remains unclear. We aimed to investigate the associations of metabolomics with brain age assessed by neuroimaging and to explore whether these relationships vary according to apolipoprotein E (APOE) ε4. This study included 17,770 chronic brain disorder‐free participants aged 40–69 years from UK Biobank who underwent neuroimaging scans an average of 9 years after baseline. A total of 249 plasma metabolites were measured using nuclear magnetic resonance spectroscopy at baseline. Brain age was estimated using LASSO regression and 1079 brain MRI phenotypes and brain age gap (BAG; i.e., brain age minus chronological age) was calculated. Data were analyzed using linear regression. We identified 64 and 77 metabolites associated with brain age and BAG, respectively, of which 55 overlapped. Lipids (including cholesterol, cholesteryl esters, free cholesterol, phospholipids, and total lipids) in S/M‐HDL, as well as phospholipids and triglycerides as a percentage of total lipids in different‐density lipoproteins, were associated with larger BAG. The percentages of cholesterol, cholesteryl esters, and free cholesterol to total lipids in VLDL, LDL, and HDL of different particle sizes were associated with smaller BAG. The associations of LA/FA, omega‐6/FA, SFA/FA, and phospholipids to total lipids in L‐HDL with brain age were consistent across APOE ε4 carriers and non‐carriers (all p for interaction > 0.05). Plasma metabolites show remarkably widespread associations with brain aging regardless of APOE ε4 genetic risk. Metabolic profiles could serve as an early indicator of accelerated brain aging.

ABSTRACTEvidence connecting skin aging to functional decline and systemic aging biomarkers is lacking. This study investigated how skin‐aging biomechanics were associated with changes in intrinsic capacity (IC), a marker of healthy aging. We also explored their links with biological aging clocks (epigenetic and inflammatory clocks) and potential moderating effects on the skin‐IC relationship. Baseline skin elasticity and viscoelasticity were measured in 441 INSPIRE‐T participants aged 20 to 93 (59.9% women) using Cutometer parameters. IC was evaluated over 3 years as a five‐domain score covering cognition, locomotion, psychology, vitality, and sensory (a higher score indicated better). Biological aging was measured at baseline using six epigenetic clocks (Horvath pan‐tissue, Horvath skin & blood, Hannum, PhenoAge, GrimAge, and DunedinPACE) and inflammatory clock (iAge). Poor skin elasticity and viscoelasticity in older adults were associated with lower baseline IC after controlling for demographic, medical, and lifestyle factors. Longitudinally, older men with a higher viscoelastic ratio (R6) experienced a faster decline in IC (a standardized coefficient [95% CI] ranged from −0.37 [−0.72, −0.03] at age 62 to −1.32 [−1.91, −0.73] at age 93). Accelerated iAge was associated with reduced skin elasticity (R2, R5, R7). Moreover, the association between parameters related to elastic recovery (R5, R7) and baseline IC became more pronounced as accelerated iAge increased. This is the first study demonstrating the association between skin‐aging biomechanics and IC. Poor skin elasticity was associated with higher systemic inflammation. Therefore, skin biomechanical properties may reflect overall functional aging, with inflammation serving as a common underlying factor.

ABSTRACTOlder adults are the primary population for cell‐based therapies for age‐related diseases, but the efficacy of administering autologous mesenchymal stem cells (MSCs) is impaired due to biological aging. In the present study, we cultured aging adipose (AD)‐derived MSCs from > 65‐year‐old donors on extracellular matrix (ECM) synthesized by human amniotic fluid‐derived pluripotent stem cells (ECM Plus) versus tissue culture plastic (TCP) and hypothesized that ECM Plus provided an ideal “young” microenvironment for reactivating and preserving early‐stage progenitor cells within aging AD‐MSCs. To test our hypothesis, we serially sub‐cultured aging AD‐MSCs on ECM Plus or TCP and characterized the cells both phenotypically and functionally, and then analyzed the cells at the single‐cell transcriptomic level for the mechanisms that control cell fate. The results showed that the maintenance of aging AD‐MSCs on ECM Plus significantly restored their quantity and quality. The mechanisms responsible for these effects were associated with a remarkable up‐regulation of intracellular CD74 when cells were maintained on ECM Plus compared to TCP, which triggered activation of the phosphoinositide‐3‐kinase (PI3K) pathway as a key modulator of cell survival (anti‐apoptosis) and suppression of cellular senescence. Moreover, AD‐MSCs maintained on ECM Plus increased their expression of HLA‐DR and stimulated T cell activity. These findings challenge the “immune privilege” of allogeneic MSCs as a universal source for MSC‐based therapies. The present study leads to a new paradigm for treating age‐related diseases: serial administration of rejuvenated autologous MSCs, which may not only replace aged MSCs but also gradually reverse the aged microenvironment.

ABSTRACTStrategies to slow the aging process or mitigate its consequences on health rely on the validation of minimally‐invasive biomarkers of aging that can be used to track aging and test the effectiveness of antiaging interventions. Study of aging in a nonhuman primate species offers a robust translational approach to achieving these aims, avoiding wide differences in genetics and environmental exposures that confound human aging studies. As epigenetic age appears to predict biological aging, biomarkers linked to epigenetic aging should be especially valuable in identifying individual differences in aging progression and documenting the impact of antiaging strategies. Proteins are the final effectors in most signaling pathways, indicating that alteration in levels of circulating proteins potentially offers an informative and valuable quantitative index of aging. Accordingly, a proteomic analysis was conducted on matching CSF and plasma samples collected from a large group of African green monkeys, with epigenetic ages ranging from young to old as determined by differential methylation of blood DNA. In addition to analyzing the data with linear statistical models, a gradient boosting machine learning technique was employed to identify not only individual CSF and plasma proteins that correlated with aging progression but also groups of proteins that could be used as predictors of global aging and of specialized aspects of aging such as inflammation. Overall, this study identified new CSF and plasma protein targets for understanding aging biology, together with identifying biomarkers to track changes in the rate of biological aging in a translationally relevant nonhuman primate model.

ABSTRACTAn increasing number of physically active adults are taking the mTOR inhibitor rapamycin off label with the goal of extending healthspan. However, frequent rapamycin dosing disrupts metabolic health during sedentary conditions and abates the anabolic response to exercise. Intermittent once‐weekly rapamycin dosing minimizes many negative metabolic side effects of frequent rapamycin in sedentary mice. However, it remains unknown how different rapamycin dosing schedules impact metabolic, physical, and skeletal muscle adaptations to voluntary exercise training. Therefore, we tested the hypothesis that intermittent rapamycin (2 mg/kg; 1×/week) would avoid detrimental effects on adaptations to 8 weeks of progressive weighted wheel running (PoWeR) in adult female mice (5‐month‐old) by evading the sustained inhibitory effects on mTOR signaling by more frequent dosing schedules (2 mg/kg; 3×/week). PoWeR improved maximal exercise capacity, absolute grip strength, and myofiber hypertrophy with no differences between vehicle or rapamycin‐treated mice despite greater voluntary running volume with intermittent rapamycin treatment. Conversely, frequent and intermittent rapamycin‐treated mice had impaired glucose tolerance and insulin sensitivity compared to vehicle‐treated mice after PoWeR; however, intermittent rapamycin reduced the impact on glucose intolerance versus frequent rapamycin. Collectively, these data in adult female mice suggest that (1) rapamycin is largely compatible with the physical and skeletal muscle benefits of PoWeR and (2) the detrimental effects of rapamycin on glucose metabolism in the context of voluntary exercise may be reduced by intermittent dosing.

ABSTRACTThis study investigates the role and mechanism of Coactivator Associated Arginine Methyltransferase 1 (CARM1) in osteoarthritis (OA). OA is a prevalent joint disease characterized by cartilage degradation, subchondral bone remodeling, and inflammation. Our research revealed that CARM1 expression is significantly increased in the cartilage tissues of OA patients and OA model mice. Experimental results showed that inhibiting CARM1 reduces cartilage matrix degradation and chondrocyte apoptosis, while overexpression of CARM1 exacerbates these conditions. Mechanistically, CARM1 regulates OA progression through the phosphorylation of the ERK1/2 signaling pathway. Inhibition of CARM1 suppresses ERK1/2 activation, thereby reducing extracellular matrix degradation and chondrocyte apoptosis. These findings suggest that the CARM1‐ERK1/2 axis is crucial in modulating cartilage matrix metabolism and chondrocyte apoptosis in OA, highlighting CARM1 as a potential therapeutic target for OA treatment.

ABSTRACTLens epithelial cell (LEC) senescence is one of the key pathological processes of age‐related cataract (ARC) and is associated with oxidative stress, mitochondrial dysfunction, and protein aggregation. This study aimed to elucidate the pathogenesis of LEC senescence in ARC. The protein expression level of silencing regulatory protein 1 (SIRT1) and aptamer protein (p66Shc) was quantified. Reactive oxygen species (ROS) and mitochondrial superoxide levels were measured to evaluate cellular oxidative stress. Senescence‐associated protein expression (p21 and p53) and SA‐β‐galactosidase staining were employed to assess the aging status of LEC. Targeted metabolic analysis was conducted to explore energy changes during LEC senescence, and mitochondrial morphology and function were assessed in the cell models. The aging and damage conditions of the lens in ARC rats were evaluated through histological staining, transmission electron microscopy, expression of senescence‐related proteins, and oxidative stress markers. We comprehensively investigated the downregulation of SIRT1 expression and the upregulation of p66Shc expression in human cataract samples, UVB‐induced rat cataract models, and UVB‐treated LEC. SIRT1 could alleviate UVB‐induced oxidative stress, as well as mitochondrial dysfunction, inhibiting p66Shc expression in LEC. Nicotinamide mononucleotide (NMN) effectively alleviated the abnormal expression of aging‐related proteins and inhibited mitochondrial morphological and functional disorders by activating SIRT1. In conclusion, NMN activated SIRT1, inhibiting mitochondrial dysfunction, oxidative stress, and senescence in LEC, delaying lens opacity. This mechanism could be associated with the onset and progression of ARC, providing a new strategy for its prevention and treatment.