Balding hair follicle dermal papilla cells contain higher levels of androgen receptors than those from non-balding scalp

Androgens can gradually transform large scalp hair follicles to smaller vellus ones, causing balding. The mechanisms involved are unclear, although androgens are believed to act on the epithelial hair follicle via the mesenchyme-derived dermal papilla. This study investigates whether the levels and type of androgen receptors in primary lines of cultured dermal papilla cells derived from balding scalp hair follicles differ from those of follicles from non-balding scalp. Androgen receptor content was measured by saturation analysis using the non-metabolisable androgen, [3H]mibolerone (0.05-10 nM) in a 9-10 point assay. Pubic dermal fibroblasts and Shionogi cells were examined as positive controls. Repetitive assays of Shionogi cells showed good precision in the levels of androgen receptor content (coefficient of variation = 3.7%). Specific, high affinity, low capacity androgen receptors were detected in dermal papilla cells from both balding and non-balding follicles. Balding cells contained significantly (P < 0.01) greater levels of androgen receptors (Bmax = 0.06 +/- 0.01 fmol/10(4) cells (mean +/- S.E.M.)) than those from non-balding scalp (0.04 +/- 0.001). Competition studies with a range of steroids showed no differences in receptor binding specificity in the two cell types. The higher levels of androgen receptors in cells from balding scalp hair follicles with similar properties to those from non-balding scalp concur with the expectations from their in vivo responses to androgens. This supports the hypothesis that androgens act via the dermal papilla and suggests that cultured dermal papilla cells may offer a model system for studying androgen action in androgenetic alopecia.