Longevity Papers

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.

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.

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.

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.

Aging is an inevitable process in living organisms, characterized by significant immunological and physiological alterations that increase susceptibility to diseases. Despite decades of research on the interplay between aging and immunity, identifying precise immunogenetic aging markers from high-dimensional (HD) transcriptomics data remains challenging due to the lack of effective pattern-discovery methods for such complex data. Recognizing the crucial role of gene-gene interactions in biological processes, and that aging is reflected in tissue-specific change in these interaction patterns, we first sought a holistic way to represent the intricate relationships among genes within the cells of each tissue. This is technically achieved by converting the scRNA-seq data of a cell into a semantically meaningful image representation, termed a "genomap", through the spatial encoding of the transcriptomic interactions. We then leverage this representation to unveil changes in interaction patterns associated with aging, rather than focusing solely on variations in gene expression profiles. This approach enables the construction of a highly accurate, tissue-specific inflammatory aging clock. Our clock significantly outperforms traditional aging-prediction methods based on blood tests, miRNA, and proteomics data. We illustrate a potential application of our framework in aging interventions via an in silico study targeting the Map3k1/Map2k4/JNK pathway, which may reverse aging-associated declines in B cell function and antibody production, thus mitigating chronic diseases linked to B cells deterioration. Thus, our strategy and pipeline may have broad implications for aging and developmental biology.

Cellular senescence is a stable form of cell cycle arrest that contributes to aging and age-associated diseases through the secretion of inflammatory factors collectively known as the senescence-associated secretory phenotype (SASP). While senescence is driven by transcriptional and epigenetic changes, the contribution of higher-order genome organization remains poorly defined. Here, we present the highest-resolution Hi-C maps (~3 kb) to date of proliferating, quiescent, and replicative senescent (RS) human fibroblasts, enabling a comprehensive analysis of 3D genome architecture during senescence. Our analyses reveal widespread senescence-associated remodeling of chromatin architecture, including extensive compartment and subcompartment switching toward transcriptionally active states, and a dramatic increase in unique chromatin loops. These structural features correlate with local DNA hypomethylation and are largely independent of canonical CTCF binding. The altered 3D genome landscape supports expression of SASP genes, inflammation-related pathways, and neuronal gene signatures consistent with age-associated epigenetic drift. We further demonstrate that architectural changes at multiple levels, including compartments, subcompartments, and loops, facilitate the derepression of LINE-1 retrotransposons, linking 3D chromatin structure to activation of proinflammatory transposable elements. Interestingly, quiescent cells, commonly used as senescence controls, exhibited substantial overlap in inflammatory gene expression with senescent cells, raising important considerations for experimental design. Structural analysis of cell cycle genes showed distinct chromatin configurations in senescence versus quiescence, despite similar transcriptional repression. Together, our results establish a high-resolution framework for understanding how genome architecture contributes to the senescent state.