Co-regulatory mechanisms of skin and hair aging.

As a cutaneous appendage, the hair follicle is tightly associated with the skin during growth, pigmentation, and aging. These two interconnected tissues share evolutionarily conserved regulatory mechanisms-including stem cell niche signaling, inflammatory cascades, and oxidative stress-and collectively function as hallmarks of systemic organismal aging. Hair abnormalities are well-established concomitant manifestations of aged skin. The crosstalk between skin aging and hair aging is particularly pronounced in several hereditary progeroid disorders, which are typified by concurrent premature aging in both tissues. Notably, multiple intervention strategies have shown promising therapeutic efficacy against both aging processes. To date, numerous molecular cascades have been implicated in skin aging, including DNA damage accumulation, telomere attrition, oxidative stress, chronic low-grade inflammation, and stem cell exhaustion. Given the intricate interplay among these pathways, this review systematically dissects the contributions of each mechanism to hair follicle aging and further clarifies the mechanistic links underlying skin and hair aging.