Fig. 9
Mechanism of the permanent loss of regeneration. In transient loss condition, human HFs recover their regenerative segment based on intact HFSCs in the permanent segment through dystrophic anagen pathway or dystrophic catagen pathway13,45. However, in permanent loss condition, priming mobilization of HFSCs by initial Bu treatment makes quiescent HFSCs vulnerable to DNA damage-induced cell death by subsequent Cy treatment, resulting in loss of the stem cell reserve for regeneration. Bu busulfan, Cy cyclophosphamide, Bu/Cy busulfan followed by cyclophosphamide, HFSC hair follicle stem cell, ORS outer root sheath
