Hair Cycle Resting Phase Is Regulated by Cyclic Epithelial FGF18 Signaling

The study demonstrated that fibroblast growth factor (FGF)18 was crucial in regulating the hair cycle, particularly the resting (telogen) phase. In Fgf18 conditional knockout mice, the telogen phase was significantly shortened, leading to rapid hair cycle succession. FGF18 acted as a strong natural inhibitor of hair follicle stem cells, maintaining the telogen phase. Pharmacological experiments showed that FGF18 inhibited anagen progression but weakly induced earlier anagen onset during telogen. The findings suggested that FGF18, along with BMPs, played a crucial role in controlling the telogen phase, with potential implications for alopecia therapies.