Long‐Term Post‐Mitotic Culture of Human Fibroblasts Recapitulates and Accelerates Features of In Vivo Aging and Enables Dynamic Testing of Anti‐Aging Compounds

Biological aging drives cellular dysfunction and human disease, yet studying human-specific aging dynamics remains challenging due to limited experimental platforms. Here we show that long-term post-mitotic culture of human fibroblasts authentically recapitulates and accelerates in-vivo aging signatures. Longitudinal paired transcriptomic-epigenetic analyses revealed that in-vitro aging mirrors in-vivo primary fibroblasts aging, with concordant transcriptional aging pathways and accelerated epigenetic clock aging patterns. Direct neuronal conversion of pre-aged fibroblasts preserved biological age, enabling pseudo-longitudinal modeling of neuronal aging. Single-cell transcriptomics revealed a time-dependent increase in age-heterogeneity, reflecting in-vivo observations and revealing heterogeneity driven by the variable loss of transcriptional programs. Using this accelerated aging platform, we evaluated anti-aging compounds: Metformin broadly halted transcriptomic and epigenetic aging, while Rapamycin showed limited efficacy. These findings align with clinical evidence, demonstrating our platform's capacity to predict therapeutic anti-aging efficacy with molecular resolution. This system advances our understanding of aging mechanisms and facilitates the development of interventions against age-related diseases.