Topical application of cyclosporin A induces rapid-remodeling of damaged ain cyclophosphamide anagen hair follicles produced administered mice

Adult C3H mice which had either anagen IV or anagen VI hair follicles were given the anti-tumor drug cyclophosphamide, and cyclosporin A or minoxidil were topically applied to the mice daily from the 4th day after cyclophosph amide administration. In the mice that had anagen IV-hair follicles, 0.5% c yclosporin A induced very thick and long hairs after 21 days of cyclophosph amide administration, while vehicle and 1% minoxidil induced sparsely visib le, short hairs. In the mice which received cyclosporin A. the injured hair follicles seemed to remodel themselves into intact anagen hair follicles a nd restart the production of hairs, instead of shifting to telogen. In the mice that had anagen VI-hair follicles at the time of cyclophosphamide admi nistration, complete alopecia occurred within the first 7 days in all group s. After 14 days of cyclophosphamide administration, hair regrowth was obse rved in both the 0.5% cyclosporin A-group and the 1% minoxidil-group with t he predominant effect over the vehicle. This study shows that anagen hair f ollicles respond to cyclophosphamide in different ways depending on their s tages (IV and VI), and that the damaged anagen IV hair follicles have the p otential of remodeling themselves. which is promoted by topical cyclosporin A administration. (C) 2001 Elsevier Science Ireland Ltd. All rights reserv ed.