Effects of Immunosuppressive Peptidyl-Prolyl Cis-Trans Isomerase (PPIase) Inhibitors, Cyclosporin A, FK506, Ascomycin, and Rapamycin, on Hair Growth Initiation in Mice: Immunosuppression Is Not Required for New Hair Growth

The study investigated the effects of immunosuppressive peptidyl-prolyl cis-trans isomerase (PPIase) inhibitors on hair growth initiation in mice. It was found that single topical applications of cyclosporin A and FK506 induced new hair growth within 12 days, while ascomycin and rapamycin did not, even at higher doses. Ascomycin did not inhibit hair induction by cyclosporin A but did inhibit FK506-induced hair growth, whereas rapamycin inhibited hair growth induced by both cyclosporin A and FK506. The results suggested that PPIase inhibition was not necessary for initiating a new hair cycle, and the hair growth effects of cyclosporin A and FK506 were not due to immunosuppression.