Longevity Papers

Aneuploid cells are known to increase with age. Previously, we demonstrated that aneuploid cells increase in fibroblasts from aged mice due to chromosomal instability (CIN), which is caused by oxidative stress. It is unclear whether this phenomenon also occurs in human cells, which are more resistant to oxidative stress than mouse cells. Here, we found that fibroblasts from aged individuals exhibited an increase in aneuploid cells. The frequency of chromosome missegregation and micronuclei increased in these cells, indicating CIN. A DNA fiber assay revealed the presence of replication stress, accompanied by an increase in 53BP1 nuclear bodies and ultrafine bridges. Increased levels of reactive oxygen species derived from mitochondria, along with reduced mitochondrial membrane potential, imply that these cells experienced oxidative stress due to mitochondrial functional decline. Antioxidant treatment reduced the frequency of chromosome missegregation and micronuclei, suggesting that oxidative stress causes CIN. Oxidative stress also causes replication stress, which precedes CIN. Spindle microtubules were stabilized in fibroblasts from aged individuals, which was alleviated by antioxidant treatment. Taken together, these findings suggest that aging-related CIN in human fibroblasts is caused by oxidative stress associated with mitochondrial dysfunction, which induces replication stress that in turn causes CIN through microtubule stabilization. Although human fibroblasts are more resistant to the ambient oxygen environment than mouse fibroblasts, our findings showed that they undergo oxidative stress that causes CIN with age in a manner similar to mouse fibroblasts, revealing a conserved phenomenon in mammalian cells.

Cochlear aging causes substantial hearing impairment in older adults, yet primate-specific mechanisms remain poorly characterized. Our comprehensive analysis combining single-cell and histopathological profiling in aging Macaca fascicularis demonstrates progressive cochlear degeneration featuring accelerated sensory hair cell loss, senescent spiral ganglion neurons with elevated neuroinflammation, and marked stria vascularis atrophy. We discovered that downregulation of transmembrane transport proteins, particularly SLC35F1, serves as a critical biomarker of hair cell aging. Functional validation through Slc35f1 knockdown in adult mice successfully recapitulated key aspects of age-related hearing loss, including hair cell degeneration and auditory function decline. Notably, we showed that long-term metformin administration at clinically relevant doses effectively delays cochlear aging in primates. These findings provide fundamental insights into the cellular and molecular basis of primate cochlear aging while establishing a foundation for developing targeted interventions against age-related hearing loss.

Emerging evidence suggests that senescent microglia play a role in β-amyloid (Aβ) pathology and neuroinflammation in Alzheimer's disease (AD). Targeting senescent cells with naturally derived compounds exhibiting minimal cytotoxicity represents a promising therapeutic strategy.

Influenza A virus (IAV) infection causes acute and long-term lung damage. Here, we used immunostaining, genetic, and pharmacological approaches to determine whether IAV-induced cellular senescence causes prolonged alterations in lungs. Mice infected with a sublethal dose of H1N1p2009 exhibited cellular senescence, as evidenced by increased pulmonary expression of p16, p21, β-galactosidase and the DNA damage marker gamma-H2A.X. Cellular senescence began 4 days post-infection (dpi) in the bronchial epithelium, then spread to the lung parenchyma by 7 and 28 dpi (long after viral clearance), and then declined by 90 dpi. At 28 dpi, the lungs showed severe remodeling with structural bronchial and alveolar lesions, abrasion of the airway epithelium, and pulmonary emphysema and fibrotic lesions that persisted up to 90 dpi. In mice and nonhuman primates, persistence of senescent cells in the bronchial wall on 28 dpi was associated with abrasion of the airway epithelium. In p16-ATTAC mice, depletion of p16-expressing cells with AP20187 reduced pulmonary emphysema and fibrosis and led to complete recovery of the airway epithelium at 28 dpi, indicating a marked acceleration of the epithelial repair process. Treatment with the senolytic drug ABT-263 also accelerated epithelial repair without affecting pulmonary fibrosis or emphysema. These positive effects occurred independently of viral clearance and lung inflammation at 7 dpi. Finally, AP20187 treatment of p16-ATTAC mice at 15 dpi led to complete recovery of the airway epithelium at 28 dpi. Thus, virus-induced senescent cells contribute to the pulmonary sequelae of influenza; targeting senescent cells may represent a new preventive therapeutic option.

Protein aggregation is a normal response to age-related exposures. According to the thermodynamic hypothesis of protein folding, soluble proteins precipitate into amyloids (pathology) under supersaturated conditions through a process similar to crystallization. This soluble-to-insoluble phase transition occurs via nucleation and may be catalyzed by ectopic surfaces such as lipid nanoparticles, microbes, or chemical pollutants. The increasing prevalence of these exposures with age correlates with the rising incidence of pathology over the lifespan. However, the formation of amyloid fibrils does not inherently cause neurodegeneration. Neurodegeneration emerges when the levels of functional monomeric proteins, from which amyloids form, fall below a critical threshold. The preservation of monomeric proteins may explain neurological resilience, regardless of the extent of amyloid deposition. This biophysical framework challenges the traditional clinicopathological view that considers amyloids intrinsically toxic, despite the absence of a known mechanism of toxicity. Instead, it suggests that chronic exposures driving persistent nucleation consume monomeric proteins as they aggregate. In normal aging, replacement matches loss; in accelerated aging, it does not. A biophysical approach to neurodegenerative diseases has important therapeutic implications, refocusing treatment strategies from removing pathology to restoring monomeric protein homeostasis above the threshold needed to sustain normal brain function.

Background: The pineal gland secretes melatonin but paradoxically calcifies more than any other intracranial structure, forming hydroxyapatite "brain-sand" (corpora arenacea) that correlates with reduced melatonin output, sleep disruption and heightened neuro-degenerative risk. Whether this mineralization is a passive dystrophic event or an active, bone-like process remains unclear. Methods: Analyzed RNA-seq datasets from pineal glands of six vertebrate species-calcifiers Homo sapiens, Rattus norvegicus and Capra hircus, versus non-calcifiers Mus musculus, Gallus gallus and Danio rerio. Species-specific transcripts were mapped to human orthologues, merged, and filtered. Phylogenetically informed differential expression testing used Brownian-motion and Pagel's lamda phylogenetic generalized least-squares models, calibrated on a TimeTree divergence phylogeny. Genes significant in both models (|logtwoFC| > 1; FDR < 0.05; lamda < 0.7) were assigned to functional pathways and visualized by PCA, heat-mapping and volcano plots. Results: Calcifying species segregated cleanly from non-calcifiers on the first two principal components, reflecting a shared 103-gene "calcifier module". Top up-regulated transcripts included developmental morphogens (GLI4, IQCE, NOTCH4), epigenetic regulators (SETD1A, ZNF274, ATF7IP), inflammatory mediators (CSF2RB), and quality-control factors (GABARAPL2, RHOT2). Every leading candidate exhibited minimal phylogenetic signal (lamda to 0), indicating that differential expression tracks the calcified phenotype rather than shared ancestry. Conversely, only three genes (RMI2, RASL11B, GPR18) formed a non-calcifier module, suggesting potential protective roles that are down-regulated during mineralization. Conclusions: Pineal calcification is not a passive by-product of aging but a regulated, lineage- restricted program that redeploys Hedgehog, Notch and chromatin-remodeling pathways classically required for skeletal ossification. The ten-gene core signature identified offers a molecular foothold for mechanistic dissection and therapeutic targeting aimed at preserving pineal function and circadian health. Significance This is the first phylogenetically controlled transcriptomic survey to link pineal "brain-sand" formation to specific developmental and inflammatory gene networks, revealing convergent evolution of calcification programs across divergent mammalian lineages.

Cardiac fibrosis, a key pathological feature of cardiac remodeling, is a major contributor to mortality in older patients with heart failure. The underlying mechanisms are complex, involving alterations in intercellular communication and chronic inflammation. This study investigates the role of indole-3-propionic acid (IPA) in aging-related myocardial fibrosis and its regulatory effects on autophagy through palmitoyl-protein thioesterase 1 (PPT1). Here, plasma levels of IPA, a tryptophan-derived metabolite, are found to be reduced in older patients with heart failure, and this reduction is associated with deteriorating cardiac function. Notably, IPA supplementation significantly attenuated aging-related myocardial fibrosis. PPT1, a lysosomal enzyme involved in autophagy, is upregulated in macrophages during aging. IPA reversed aging-induced increase in PPT1 expression. Using PPT1

Cellular senescence has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). The mechanisms of senescence in the bronchial epithelium, however, remain largely unknown. This study aimed to elucidate whether cellular senescence in COPD epithelial cells contributes to the pathogenesis of the disease and investigated the potential molecular mechanisms involved. Single cell RNA sequencing was performed on well differentiated primary bronchial epithelial cells from COPD and healthy subjects. We evaluated the abundance and distribution of senescence markers in key epithelial differentiated subtypes and senescence-associated secretory phenotype involved in airway epithelial dysfunction. The effects of interferon pathway inhibitors on cellular senescence were also investigated. There was increased expression of cellular senescence genes in the COPD cohort, which was predominantly in basal and club cells. Enhanced expression of cellular senescence markers, p16 and p21, was observed in COPD cultures, which was histologically confirmed in the lung tissue of COPD patients. There was also a notable increase in IFN-β and IFN-γ. Senescence associated secretory phenotype productions were increased in COPD and was attenuated by JAK-STAT or cGAS-STING pathway inhibitors (baricitinib or C-176). These inhibitors also effectively suppressed expression of senescence markers. COPD bronchial epithelium displays a senescence driven phenotype which is mediated by type I/II interferons. Inhibition of JAK-STAT or STING-cGAS interferon pathways may represent targets to alleviate cellular senescence and chronic inflammation in COPD.

Background: Individuals with mental and behavioural disorders face increased risk of age-related diseases and premature mortality. Accelerated biological ageing may contribute to this disparity. We investigated differences in metabolomic ageing between individuals with and without mental disorders. Methods: The UK Biobank is a community-based health study of middle-aged and older adults. Mental disorders were identified from hospital inpatient, primary care, death registry and self-reported physician diagnosis data. Plasma metabolites were profiled using the Nightingale Health platform. We examined differences in MileAge delta, the difference between metabolite-predicted and chronological age, across broad ICD-10 diagnostic groups and for 45 individual diagnoses. We further investigated sex-specific associations and tested whether polygenic scores for mental disorders were associated with MileAge delta. Results: Amongst 225,212 participants (54% female; mean age = 56.97 years), 38,524 had at least one mental disorder diagnosis preceding baseline. Substance use, psychotic, affective and neurotic disorders were associated with a metabolite-predicted age exceeding chronological age. In contrast, obsessive-compulsive and eating disorders were associated with a younger MileAge, particularly in females. Associations were generally stronger in males, with several diagnoses showing sex-specific patterns. Higher genetic liability to major depression, autism and ADHD was associated with a MileAge exceeding chronological age, whereas psychosis, tobacco use disorder, obsessive-compulsive disorder and anorexia nervosa polygenic scores were associated with a younger MileAge. Conclusions: Metabolomic ageing varies across mental disorders, with direction and strength of association differing by diagnosis and sex. These findings highlight the heterogeneity of biological ageing across mental disorders and contribute to our understanding of the biological processes linking mental disorders to excess morbidity and premature mortality.

Cellular senescence is an aging-related mechanism characterized by cell cycle arrest, macromolecular alterations, and a senescence-associated secretory phenotype (SASP). Recent preclinical trials established that senolytic drugs, which target survival mechanisms of senescent cells, can effectively intervene in age-related pathologies. In contrast, senomorphic agents inhibiting SASP expression while preserving the survival of senescent cells have received relatively less attention, with potential benefits hitherto underexplored. By revisiting a previously screened natural product library, which enabled the discovery of procyanidin C1 (PCC1), we noticed pyrroloquinoline quinone (PQQ), a redox cofactor that displayed remarkable potential in serving as a senomorphic agent. In vitro data suggested that PQQ downregulated the full spectrum expression of the SASP, a capacity observed in several stromal cell lines. Proteomics data supported that PQQ directly targets the intracellular protein HSPA8, interference with which disturbs downstream signaling and expression of the SASP. PQQ restrains cancer cell malignancy conferred by senescent stromal cells in culture while reducing drug resistance when combined with chemotherapy in anticancer regimens. In preclinical trials, PQQ alleviates pathological symptoms by preventing organ degeneration in naturally aged mice while reserving senescent cells in the tissue microenvironment. Together, our study supports the feasibility of exploiting a redox-active quinone molecule with senomorphic capacity to achieve geroprotective effects by modulating the SASP, thus providing proof-of-concept evidence for future exploration of natural antioxidant agents to delay aging and ameliorate age-related conditions. Prospective efforts are warranted to determine long-term outcomes and the potential of PQQ for the intervention of geriatric syndromes in clinical settings.

T stem cell-like memory cells (TSCM cells) are considered to be essential for the maintenance of immune memory. The TSCM population has been shown to have the key properties of a stem cell population: multipotency, self-renewal and clonal longevity. Here we show that no single population has all these stem cell properties, instead the properties are distributed. We show that the human TSCM population consists of two distinct cell subpopulations which can be distinguished by the level of their CD95 expression (CD95int and CD95hi). Crucially, using long-term in vivo labelling of human volunteers, we establish that these are distinct populations rather than transient states of the same population. These two subpopulations have different functional profiles ex vivo, different transcriptional patterns, and different tissue distributions. They also have significantly different TREC content indicating different division histories and we find that the frequency of CD95hi TSCM increases with age. Most importantly, CD95hi and CD95int TSCM cells also have very different dynamics in vivo with CD95hi cells showing considerably higher proliferation but significantly reduced clonal longevity compared with CD95int TSCM. While both TSCM subpopulations exhibit considerable multipotency, no single population of TSCM cells has both the properties of self-renewal and clonal longevity. Instead, the "stemness" of the TSCM population is generated by the complementary dynamic properties of the two subpopulations: CD95int TSCM which have the property of clonal longevity and CD95hi TSCM which have the properties of expansion and self-renewal. We suggest that together, these two populations function as a stem cell population.

Dietary restriction (DR) robustly increases lifespan across taxa. However, in humans, long-term DR is difficult to maintain, leading to the search for compounds that regulate metabolism and increase lifespan without reducing caloric intake. The magnitude of lifespan extension from two such compounds, rapamycin and metformin, remains inconclusive, particularly in vertebrates. Here, we conducted a meta-analysis comparing lifespan extension conferred by rapamycin and metformin to DR-mediated lifespan extension across vertebrates. We assessed whether these effects were sex- and, when considering DR, treatment-specific. In total, we analysed 911 effect sizes from 167 papers covering eight different vertebrate species. We find that DR robustly extends lifespan across log-response means and medians and, importantly, rapamycin-but not metformin-produced a significant lifespan extension. We also observed no consistent effect of sex across all treatments and log-response measures. Furthermore, we found that the effect of DR was robust to differences in the type of DR methodology used. However, high heterogeneity and significant publication bias influenced results across all treatments. Additionally, results were sensitive to how lifespan was reported, although some consistent patterns still emerged. Overall, this study suggests that rapamycin and DR confer comparable lifespan extension across a broad range of vertebrates.

Traditional biomaterial design often prioritizes empirical knowledge over disease mechanisms and pathological dynamics, resulting in imprecise solutions in complex clinical conditions. Age-related osteoporosis (A-OP) is a disease associated with aging, characterized by a dysfunctional pathological microenvironment that hinders the osseointegration of conventional titanium implants. To develop a targeted titanium implant for A-OP, rat single-cell transcriptomics is integrated with human serum-derived transcriptome data to investigate dynamic changes in skeletal stem cells (SSCs) during aging, which guided the implant design. These findings reveal that hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) within SSCs interact via a feedback loop: HSCs undergo premature senescence, leading to depletion of HSCs and secondary senescence of MSCs. Senescent MSCs exhibit adipogenic bias, perpetuating the pathological cycle of A-OP. Using core genes identified in the transcriptome analyses, resveratrol is selected and utilized it and a GelMA-chitosan hydrogel to decorate titanium implants for localized delivery. In the A-OP microenvironment, the hydrogel enables sustained responsive release of resveratrol, which reverses MSC senescence and redirects differentiation from adipogenic to osteogenic lineages, thereby breaking the pathological cycle. This multi-omics-driven implant design enhances precision and offers a novel methodology for biomaterial development.

Ageing has profound effects on the human brain across the lifespan. Cognitive testing and brain imaging are currently used to monitor healthy and pathological brain ageing. However, peripheral markers of cognitive function, cognitive ageing and neurological disease could provide a valuable, minimally invasive approach to tracking these processes longitudinally. In this Review, we introduce the concept of DNA methylation-based biomarkers and present current evidence of their potential to address the challenge of monitoring brain ageing and stratifying the risk of neurological disease. We focus on epigenetic clocks, which can be applied across multiple tissues and organs to estimate biological ageing, as well as on blood-based epigenetic scores (EpiScores) that can directly track brain-based phenotypes, such as cognitive function, and risk factors for neurological diseases, such as lifestyle behaviours and proteomic markers of inflammation. We discuss the associations between these epigenetic biomarkers and multiple measures of cognitive health, including cognitive test data, brain MRI measures and dementia.

The nervous system is primarily composed of neurons and glia, and the communication between them has profound roles in regulating the development and function of the brain. Neuron-glia signal transduction is known to be mediated by secreted signals through ligand-receptor interactions on the cell membrane. Here we show a new mechanism for neuron-glia signal transduction, wherein neurons transmit proteins to glia through extracellular vesicles, activating glial signaling pathways. We find that in the amphid sensory organ of Caenorhabditis elegans, different sensory neurons exhibit varying aging rates. This discrepancy in aging is governed by the cross-talk between neurons and glia. We demonstrate that early aged neurons can transmit heat shock proteins to glia via extracellular vesicles. These neuronal heat shock proteins activate the glial IRE1-XBP1 pathway, leading to the transcriptional regulation of chondroitin synthases to protect glia-embedded neurons from aging-associated functional decline. Therefore, our studies unveil a new mechanism for neuron-glia communication in the nervous system and provide new insights into our understanding of brain aging.

Cellular quiescence is a state of reversible proliferative arrest that plays essential roles in development, resistance to stress, aging, and longevity of organisms. Here we report that rapid depletion of RNase MRP, a deeply conserved RNA-based enzyme required for rRNA biosynthesis, induces a long-term yet reversible proliferative arrest in human cells. Severely compromised biogenesis of rRNAs along with acute transcriptional reprogramming precede a gradual decline of the critical cellular functions. Unexpectedly, many arresting cells show increased levels of histone mRNAs, which accumulate locally in the cytoplasm, and S-phase DNA amount. The ensuing proliferative arrest is entered from multiple stages of the cell cycle and can last for several weeks with uncompromised cell viability. Strikingly, restoring expression of RNase MRP leads to a complete reversal of the arrested state with resumed cell proliferation at the speed of control cells. We suggest that targeting rRNA biogenesis may provide a general strategy for rapid induction of a reversible proliferative arrest, with implications for understanding and manipulating cellular quiescence.

Aging is a physiological and complex process produced by accumulative age-dependent cellular damage, which significantly impacts brain regions like the hippocampus, an essential region involved in memory and learning. A crucial factor contributing to this decline is the dysfunction of mitochondria, particularly those located at synapses. Synaptic mitochondria are specialized organelles that produce the energy required for synaptic transmission but are also important for calcium homeostasis at these sites. In contrast, non-synaptic mitochondria primarily involve cellular metabolism and long-term energy supply. Both pools of mitochondria differ in their form, proteome, functionality, and cellular role. The proper functioning of synaptic mitochondria depends on processes such as mitochondrial dynamics, transport, and quality control. However, synaptic mitochondria are particularly vulnerable to age-associated damage, characterized by oxidative stress, impaired energy production, and calcium dysregulation. These changes compromise synaptic transmission, reducing synaptic activity and cognitive decline during aging. In the context of neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's, the decline of synaptic mitochondrial function is even more pronounced. These diseases are marked by pathological protein accumulation, disrupted mitochondrial dynamics, and heightened oxidative stress, accelerating synaptic dysfunction and neuronal loss. Due to their specialized role and location, synaptic mitochondria are among the first organelles to exhibit dysfunction, underscoring their critical role in disease progression. This review delves into the main differences at structural and functional levels between synaptic and nonsynaptic mitochondria, emphasizing the vulnerability of synaptic mitochondria to the aging process and neurodegeneration. These approaches highlight the potential of targeting synaptic mitochondria to mitigate age-associated cognitive impairment and synaptic degeneration. This review emphasizes the distinct vulnerabilities of hippocampal synaptic mitochondria, highlighting their essential role in sustaining brain function throughout life and their promise as therapeutic targets for safeguarding the cognitive capacities of people of advanced age.

Older adults with established cardiovascular diseases (CVD) are at elevated risk of heart failure (HF). Frailty, a hallmark of multi-system aging, may contribute to HF development through inflammation. However, population-based evidence remains scarce. Leveraging data from 49,530 CVD patients in the UK Biobank, frailty was measured by five components: weight loss, exhaustion, low physical activity, slow walking speed, and low grip strength. We employed Cox regression models to assess the association between frailty and incident HF, and conducted mediation analyses to evaluate mediating roles of 15 inflammatory markers in this association. Furthermore, we constructed a polygenic risk score (PRS) for HF risk based on the Global Biobank Meta-analysis Initiative (N = 1,020,441), and evaluated the joint association and interaction between frailty and PRS in relation to incident HF. During a median follow-up of 13.3 years, 6293 participants developed HF. Compared to robust individuals, pre-frail (hazard ratio (HR) = 1.31 [95% CI: 1.23-1.40]) or frail (HR = 1.80 [1.64-1.98]) participants had a higher risk of HF, and the potential causality was suggested by Mendelian randomization. Such relationship was partially mediated by inflammatory markers, including interleukin-6, tumor necrosis factor-α, and C-reactive protein. Moreover, individuals with both frailty and high PRS had the greatest risk of HF (HR = 4.35 [3.74-5.06]), with a relative excess risk due to interaction of 1.39, accounting for 32% of total risk. Frailty interacts with PRS to enhance risk stratification of HF. Inflammation may mediate the frailty-HF association, suggesting the potential of anti-inflammatory interventions to mitigate HF risk in frail CVD patients.

Measurement of aging is critical to understanding its causes and developing interventions, but little consensus exists on what components such measurements should include or how they perform in predicting mortality. The aim of this study was to identify factors of aging among a comprehensive set of indicators, and to evaluate their relative performance in predicting mortality. Measurements on 34 clinical, survey, and neuroimaging variables, along with epigenetic age markers, were obtained from two waves (2004-2021) of the Midlife in the United States (MIDUS) study. Mortality data was also available on 11875 participants, including 1908 twins. Factor analyses were used to identify aging factors, and these were used to predict mortality as of 2022. Twin data were used to model predictors of mortality within families. Factor analyses identified 9 major dimensions of aging: frailty, cognition, adiposity, glucose, blood pressure, inflammation, lipids, adaptive functioning, and neurological functioning. The strongest predictors of survival among the aging dimensions were cognition, adaptive functioning, and inflammation, and among the epigenetic markers, the decline-predictive markers (GrimAge and DunedinPACE). When entered in joint prediction models, cognition remained a significant predictor of mortality, but the epigenetic markers did not. Cognition, adaptive functioning, and inflammation remained significant predictors of mortality within twin pairs as well. Aging is a multidimensional construct, with cognition, adaptive functioning, and inflammation being the strongest predictors of survival among the aging dimensions examined. Their association with mortality is observed within families, suggesting that early developmental factors cannot entirely account for their association with survival. Interventions and assessments should prioritize cognition in measures of aging quality, along with adaptive functioning and inflammation.

Mutations in mitochondrial complex I can cause severe metabolic disease. Although no treatments are available for complex I deficiencies, chronic hypoxia improves lifespan and function in a mouse model of the severe mitochondrial disease Leigh syndrome caused by mutation of complex I subunit NDUFS4. To understand the molecular mechanism of NDUFS4 mutant pathophysiology and hypoxia rescue, we investigated the structure of complex I in respiratory supercomplexes isolated from NDUFS4 mutant mice. We identified complex I assembly intermediates bound to complex III2, proving the cooperative assembly model. Further, an accumulated complex I intermediate is structurally consistent with pathological oxygen-dependent reverse electron transfer, revealing unanticipated pathophysiology and hypoxia rescue mechanisms. Thus, the build-up of toxic intermediates and not simply decreases in complex I levels underlie mitochondrial disease.

Epigenetic regulatory mechanisms, which include histone modifications and DNA methylation, play a central role in development and aging. Dimethylation of H3K36, deposited mainly by the histone methyltransferase NSD1, occurs predominantly in intergenic regions and recruits the DNA methyltransferase DNMT3A to facilitate DNA methylation. Haploinsufficiency of NSD1 results in the overgrowth disorder Sotos syndrome in vivo, which is associated with aberrant DNA methylation signatures and an enhanced epigenetic age. To understand the mechanisms by which NSD1 may regulate development, differentiation and diseases, we generated human iPSC lines deficient in functional NSD1 (NSD1-KO). NSD1-KO cells exhibit a substrate-specific decrease in proliferation, reduced H3K36me2 levels and extensive DNA hypomethylation. Notably, the loss of functional NSD1 altered the differentiation potential of iPSCs, with aberrant endodermal and mesodermal lineage commitment. Further analysis revealed that NSD1 might drive endodermal differentiation by regulating the expression of an endodermal lncRNA HIDEN by mechanisms independent of the regulation of DNA methylation. Our NSD1-KO iPSC lines partially recapitulate the DNA methylation defects associated with NSD1-related disorders. Additionally, we uncovered a novel mechanism by which NSD1 may regulate endodermal differentiation of human iPSCs.

Accumulating evidence indicates that biological aging can be accelerated by environmental exposures, collectively called the 'exposome'. The skin, as the largest and most exposed organ, can be viewed as a 'window' for the deep exploration of the exposome and its effects on systemic aging. The complex interplay across hallmarks of aging in the skin and systemic biological aging suggests that physiological processes associated with skin aging influence, and are influenced by, systemic hallmarks of aging. This bidirectional relationship provides potential avenues for the prevention of accelerated biological aging and the identification of therapeutic targets. We provide a review of the interactions between skin exposure, aging hallmarks in the skin and associated systemic changes, and their implications in treatment and disease. We also discuss key questions that need to be addressed to maintain skin and overall health, highlighting the need for the development of precise biomarkers and advanced skin models.

The ability of biomolecular condensates to reversibly dissolve and reform is crucial for maintaining cellular stability and functions. In the context of cell physiology and disease, they can serve as a metastable phase mediating the liquid-to-solid transition of disease proteins or rapidly assemble/disassemble as a mechanism for stress response. However, as metabolic rates decline with aging, the protein-rich condensates persist longer, therefore increasing the propensity of undergoing irreversible liquid-to-solid transitions. Temperature, as a physical stimulus, plays a key role in controlling the condensate formation, dissolution, and material properties. In this study, we explore how the reversibility of short peptide biomolecular condensates (z-FF) can be modulated by a temperature change. Our findings reveal that aged condensates exhibit reduced responsiveness to external temperature stimuli. By using thermal cycling experiments to simulate repeated heat stress, we found that the time taken for irreversible fiber formation could be delayed up to 4.7-fold compared to that of condensates without thermal cycles. We also found that the dissolution rate of condensates progressively slows as they age but remains more stable with thermal cycles. Importantly, our results indicate that continuous cycles of liquid-liquid phase separation and dissolution act as a reset mechanism, preserving the biomolecular condensates from further liquid-to-solid transition. These findings provide valuable insights into how aging impacts condensate behavior and highlight potential strategies to preserve cellular function through controlled phase transitions.