Author Response: Coordinated Hedgehog Signaling Induces New Hair Follicles in Adult Skin

Sun et al. demonstrated that localized Hedgehog (Hh) signaling could induce the formation of new hair follicles in adult mouse skin, specifically at the touch dome, while diffuse activation did not. The newly formed follicles had necessary structures and could produce hair, but activation in both epithelial and dermal cells also led to basal cell carcinoma (BCC), with immature follicles as part of the tumor. The study highlighted the potential of Hh signaling for hair follicle formation in humans, though it posed a cancer risk. In Gli1creERT2/R26Tom/Ptch1fl/fl mice, about 2% of hair follicles formed de novo in the isthmus area, cycling through growth phases and persisting despite treatment with the Smo inhibitor vismodegib. The research suggested that high Hh signaling levels could induce new follicles, mimicking embryonic development, with implications for hair loss treatment if cancer risks could be managed.