Immunohistochemical distribution of aromatase and 3B-hydroxysteroid dehydrogenase in human hair follicle and sebaceous gland.

Human hair follicles (HF) and sebaceous glands (SG) were assessed for the presence and distribution of the cytochrome P-450-aromatase (AR) and 3B-hydroxysteroid dehydrogenase (3B-HSD) enzymes. Immunohistochemical methods were used to examine both enzymes in male and female human skin specimens at various ages and different body sites. AR was found in the external root sheath of anagen, terminal HF, and in SG, whereas the 3B-HSD was found only in the SG. AR was rarely found in telogen HF. The expression of both enzymes, AR and 3B-HSD, did not vary with body site or sex. Localizing AR in the external root sheath of anagen HF suggests that AR may have a function in the HF cycle. We hypothesize that AR may be one of many enzymes or factors that play a role in the HF cycle by regulating the level of androgens formed locally, whereas 3B-HSD is localized in SG, converting weak androgen precursors to potent androgens, stimulating lipogenesis.