MicroRNAs in human skin ageing.

The skin protects humans from the surrounding environment. Tissues undergo continuous renewal throughout an individual's lifetime; however, there is a decline in the regenerative potential of tissue with age. The accumulation of senescent cells over time probably reduces tissue regenerative capacity and contributes to the physiological ageing of the tissue itself. The mechanisms that govern ageing remain unclear and are under intense investigation, and insight could be gained by studying the mechanisms involved in cellular senescence. In vitro, keratinocytes and dermal fibroblasts undergo senescence in response to multiple cellular stresses, including the overproduction of reactive oxygen species and the shortening of telomeres, or simply by reaching the end of their replicative potential (i.e., reaching replicative senescence). Recent findings demonstrate that microRNAs play key roles in regulating the balance between a cell's proliferative capacity and replicative senescence. Here, we will focus on the molecular mechanisms regulated by senescence-associated microRNAs and their validated targets in both keratinocytes and dermal fibroblasts.