Immunolocalization of 5 alpha-reductase isozymes in acne lesions and normal skin

Background: Dihydrotestosterone mediates androgen-dependent diseases, such as acne, hirsutism, and androgenetic alopecia. This hormone is produced fro m testosterone by the 5 alpha-reductase enzyme. There are 2 isozymes of 5 a lpha-reductase (types 1 and 2) that differ in their localization within the body and even within the skin. Activity of the type 1 isozyme predominates in sebaceous glands, where it may be involved in regulation of sebum produ ction. Since specific inhibition of 5 alpha-reductase type 1 may represent a novel therapeutic approach to acne, it is important to define the localiz ation of these isozymes in normal sebaceous follicles and acne lesions. Observations: Skin biopsy specimens were obtained from the backs of 11 subj ects: 8 with acne and 3 without acne. Sections of normal follicles, open co medones, closed comedones, and inflammatory lesions were incubated with ant ibodies to types 1 and 2 5 alpha-reductase. In all samples, type 1 antibody localized specifically to sebaceous glands, and the type 2 antibody locali zed to the companion layer of the hair follicle (the innermost layer of the outer root sheath) and granular layer of the epidermis. Localization of th e type 2 isozyme was also noted within the walls of open and closed comedon es and in endothelial cells from sections of inflammatory lesions. Conclusions: The immunolocalization of 5 alpha-reductase isozymes in normal sebaceous follicles and acne follicles is similar to the pattern described in terminal hair follicles and corresponds with the findings of biochemica l studies that have demonstrated predominance of type 1 activity in sebaceo us glands. The function of type 2 5 alpha-reductase in comedones or endothe lial cells in inflammatory lesions is unknown.