Do Hair Bulb Melanocytes Undergo Apotosis During Hair Follicle Regression (Catagen)?

This study investigated the fate of hair follicle melanocytes during the anagen-catagen transition in C57BL/6 mice, comparing spontaneous and pharmacologically induced catagen. It was found that melanocytes underwent apoptosis in both spontaneous and dexamethasone-induced catagen, with more frequent apoptosis in the latter. Cyclophosphamide-induced catagen, however, showed retention of melanogenic melanocytes despite widespread keratinocyte apoptosis, leading to severe melanocyte incontinence and ectopic melanin distribution. The findings suggested that apoptosis contributed to the loss of melanogenic melanocytes during spontaneous catagen, and highlighted the potential of dexamethasone-induced catagen as a model for hair pigmentation research, while cyclophosphamide-induced catagen could be useful for studying melanocyte response to chemical injury.