Objective: Androgens have paradoxically different effects on hair follicles depending on body site, stimulating beard growth while inducing regression in some areas of the scalp. The mesenchyme derived dermal papilla at the base of the hair follicle regulates many aspects of the growth of follicular epithelium, and is probably the site of androgen action. Since 5 alpha-dihydrotestosterone is considered to be the active intracellular androgen in many target tissues and is required for some androgen-mediated hair growth, such androgen-sensitive cells should contain 5 alpha-reductase. This study was designed to investigate whether cultured human dermal papilla cells contain 5 alpha-reductase and whether the metabolic capacity varies with the body site of the follicle in line with the clinical picture.
Design: Testosterone metabolism in cultured dermal papilla cells from androgen sensitive beard follicles was compared with less androgen dependent non-balding scalp follicles. Primary cell cultures were established from follicles of 11 patients with normal hair growth. The cells were grown to confluence in 10-cm Petri dishes and incubated with 5 nM 3H-testosterone in serum-free medium for 2 hours. The cells and the culture medium were collected separately for individual analysis.
Measurements: Unlabelled carrier and 14C-marker steroids were added to both the cell and medium extracts before separation by thin-layer chromatography. The individual steroid identities were confirmed by recrystallizing up to five times to a constant 3H/14C ratio.
Results: Testosterone was taken up by both cell types; significant amounts of 5 alpha-dihydrotestosterone were recovered inside beard cells, but not in scalp cells, whereas androstenedione was identified in both. An unidentified compound was present intracellularly in both cell types, but was not present in the culture medium. 5 alpha-Dihydrotestosterone was present only in the culture medium of beard cells but androstenedione was present in a similar amount in the medium from both cell types. The presence of other steroids could not be confirmed in either the cell extracts or the culture medium.
Conclusions: The production of 5 alpha-dihydrotestosterone by beard cells concurs with the poor beard growth in men with 5 alpha-reductase deficiency, supporting our hypothesis that androgens mediate their effects on the hair follicle via the mesenchyme-derived dermal papilla.