Initiation Phase Cellular Reprogramming Rejuvenates DNA Damage Repair Defect In The Ercc1 Accelerated Aging Mouse Model

Unlike aging somatic cells, which exhibit a decline in molecular fidelity and eventually reach a state of replicative senescence, pluripotent stem cells can indefinitely replenish themselves while retaining full homeostatic capacity. The conferment of beneficial -pluripotency related traits via in vivo partial cellular reprogramming (IVPR) significantly extends lifespan and restores aging phenotypes in mouse models. Although the phases of cellular reprogramming are well characterized, details of the rejuvenation processes are poorly defined. Here we created the first reprogrammable accelerated aging mouse model with a DNA damage repair defect to better understand the effects of reprogramming on a key driver of aging. Using enhanced partial reprogramming by combining small molecules with the Yamanaka factors, we observed potent reversion of DNA damage, significant upregulation of multiple DNA damage repair processes, and restoration of the epigenetic clock is observed. In addition, we present evidence that TGFb inhibition of the ALK5 or ALK2 receptor is able to phenocopy some benefits including epigenetic clock restoration suggesting a role in the mechanism of rejuvenation during partial reprogramming. Overall design: Fibroblasts from WT, ERCC1 d/-, OSKM, Oct4-GFP mice and crosses were isolated from the tail tip or skin and cultured. For reprogramming experiments, doxycycline was added to the medium for 2 or 4 days. For TGFB inhibition experiments, small molecule TGBF inhibitors were added to the medium.