Hair Growth on Nude Mice Due to Cyclosporin A

The study investigated the effects of cyclosporin A (CsA) on hair growth in nude mice, which are T-cell-deficient and congenitally athymic. Researchers administered CsA to young BALB/c female nude mice through topical, oral, and subcutaneous methods over 3 to 4 weeks. Hair growth was observed as early as 7 days after treatment, with a dose-dependent increase becoming evident after 3 weeks. The hair growth was not limited to the application site and followed the natural hair growth pattern of the mice. Control mice, which received only olive oil, showed no hair growth. Histological analysis indicated no structural differences in skin and hair between treated and control mice, and the number of hair follicles did not significantly increase. Hair growth ceased after stopping CsA treatment and returned to control levels within 14 days, but resumed with retreatment. However, older mice (9 months old) did not exhibit hair growth after a 4-week CsA treatment.