Telogen Phase of Hair Growth Cycle Is Regulated by Cyclic Epithelial FGF18 Signaling

The study demonstrated that fibroblast growth factor (Fgf)18 played a crucial role in regulating the telogen phase of the hair growth cycle. Fgf18 was expressed in the hair stem cell niche throughout telogen, and its signaling was essential for maintaining the non-growth phases of the hair cycle. In experiments with mice, conditional knockout of the Fgf18 gene in keratin 5-positive epithelial cells resulted in a significantly shortened telogen phase, leading to rapid hair cycle succession. Conversely, in wild-type mice, the local delivery of FGF18 protein strongly suppressed hair follicle growth during the anagen phase. These findings highlighted the importance of epithelial FGF18 signaling in maintaining the balance between telogen and anagen phases.