A stress-induced miR-31–CLOCK–ERK pathway is a key driver and therapeutic target for skin aging

Regressive changes in epithelial stem cells underlie mammalian skin aging, but the driving mechanisms are not well understood. Here, we report that mouse skin hair follicle stem cell (HFSC) aging is initiated by their intrinsic upregulation of miR-31, a microRNA that can be induced by physical injury or genotoxic stress and is also strongly upregulated in aged human skin epithelium. Using transgenic and conditional knockout mouse models plus a lineage-tracing technique, we show that miR-31 acts as a key driver of HFSC aging by directly targeting Clock, a core circadian clock gene whose deregulation activates a MAPK/ERK cascade to induce HFSC depletion via transepidermal elimination. Notably, blocking this pathway by either conditional miR-31 ablation or clinically approved MAPK/ERK inhibitors provides safe and effective protection against skin aging, enlightening a promising therapeutic avenue for treating skin aging and other genotoxic stress-induced skin conditions such as radiodermatitis. Changes in hair and skin can be the most obvious and earliest signs of aging. The authors report that skin and hair follicle stem cell (HFSC) aging is driven by stress-induced upregulation of miR-31, which targets Clock to activate MAPK/ERK and deplete HFSCs via transepidermal elimination. Blocking the pathway with MAPK/ERK inhibitors protects against skin aging.