Mechanism of Action of Androgen in Hair Follicles

The study investigated the effects of testosterone (T) on human hair follicles by examining its metabolism and the localization of androgen receptors in outer root sheath cells (ORSC) and dermal papilla cells (DPC) from various body sites. It was found that T was primarily metabolized to androstenedione in both beard ORSC and epidermal keratinocytes, with beard DPC showing significantly higher 5α-reductase activity compared to occipital scalp and axillary DPC. Androgen receptors were present in beard and axillary DPC but not in occipital scalp DPC. Testosterone did not stimulate proliferation in ORSC or DPC when cultured alone but did so in ORSC co-cultured with beard or axillary DPC, suggesting that beard and axillary DPC produce androgen-dependent growth factors that stimulate follicular epithelial cells.