Fig. 1
Permanent loss of HF regeneration after Bu/Cy treatment. a Experimental model of cycling human HFs for the investigation of permanent loss of regeneration after alkylating chemotherapy. Microdissected human HFs were transplanted into severe combined immunodeficiency hairless outbred mice (n = 765 transplanted HFs, 32 mice). After 22 weeks of transplantation, human HFs were regenerated into terminal HFs showing anagen stage 6 morphology. b Schedule for sequential Bu/Cy treatment (Bu 20 mg/kg/day, Cy 100 mg/kg/day) into mice with transplanted human HFs, followed by analysis of human HFs at 0, 4, 7, 10, 13, 16, and 60 days. c Representative images of destructive changes mainly in the bulb after Bu/Cy treatment (n = 397 transplanted HFs, 17 mice, 3 independent experiments). The HF epithelium and the DP structure were lost (green arrowhead) with no hair regrowth on day 60, indicating that the permanent segment of HF was lost completely (H&E). d Representative images of dystrophic melanin clumping (red arrow) around the DP in the bulb after Bu/Cy treatment. The pigment distribution became more disorganized over time (Masson Fontana). e Representative images of ALP activity (blue arrowhead) in the DP after Bu/Cy treatment. The ALP activity completely disappeared after day 7 (scale bar = 100 μm). Bu busulfan, Cy cyclophosphamide, H&E hematoxylin and eosin, HF hair follicle, Mx hair matrix, ORS outer root sheath, DP dermal papilla, ALP alkaline phosphatase
