The effects of gamma rays on the regeneration of hair follicles are carried over to later hair cycles

Purpose: The purpose of this study was to determine whether the effects of gamma rays on the regeneration of hair follicles are carried over to later hair cycles.Materials and methods: The whole bodies of C57BL/10JHir mice in the 1st telogen phase were irradiated with Co-60 -rays. Mice were examined for the effects on hair follicles, including their number, morphology and pigmentation in the 3rd anagen phase. Effects of -rays on hair follicle stem cells were investigated by the indirect immunolabeling of keratin 15 (K15).Results: Decreased hair follicle density and induction of curved hair follicles were observed in the dermis of irradiated skin. In addition, white hair and hypopigmented hair bulbs were found. The number of K15-positive hair follicle stem cells in the hair bulge region of irradiated skin appeared to decrease slightly but not significantly.Conclusions: These results suggest that the effects of -rays are carried over to a later hair cycle to affect the number, structure and pigmentation of hair follicles in the 3rd anagen phase when stem cells and committed progenitors for keratinocytes and melanocytes are irradiated in the 1st telogen phase.