Synergistic interplay between UV and urban particulate matter exposure induces melanocyte senescence and contributes to human skin aging.

Extrinsic skin aging is driven by environmental factors, including ultraviolet (UV) radiation and air pollution. While melanocytes serve as key protectors against UV-induced damage, their role in aging, particularly through the process of senescence, remains underexplored. Here, we exposed human neonatal melanocytes and ex vivo skin explants to UV (UVA + UVB), urban particulate matter (UPM), and their combination (UV + UPM) to assess the effects on melanocyte function and skin aging. We demonstrate that combined UV + UPM exposure triggers oxidative stress, mitochondrial and DNA damage, senescence, apoptosis, and modulation of melanogenesis in human neonatal melanocytes. In addition, skin explants subjected to the same treatments showed hallmark features of aging, including epidermal thinning, barrier disruption, fibrosis, and altered pigmentation. These findings highlight that melanocytes respond to environmental stress through multiple interconnected mechanisms, potentially affecting both cell survival and pigmentary function. Our model offers a useful platform to study how environmental stressors affect melanocyte function and skin biology, potentially supporting the development of future strategies targeting pigmentation disorders and environmentally driven skin aging.