Mechanism of action of androgen in human hair follicles

为了研究雄激素在人毛囊中的作用机制，我们在培养的人毛囊细胞中检测了雄激素受体、I型和II型5α -还原酶的表达。与网状真皮成纤维细胞或枕部头皮真皮乳头细胞相比，胡须状真皮乳头细胞具有更高的5 - α还原酶活性和更多的雄激素受体。此外，在胡须真乳头细胞中发现的酶似乎是25型α -还原酶。相反，根外鞘细胞不具有靶细胞的特征。雄激素显著地刺激了外根鞘细胞的增殖，这些细胞与胡须真皮乳头细胞共培养而没有细胞接触。胰岛素样生长因子i (IGF-I) mRNA表达受雄激素刺激，醋酸环丙孕酮拮抗。无论雄激素存在与否，外根鞘细胞均不表达igf - 1 mRNA。两种细胞均表达igf - 1受体mRNA，且表达不受雄激素的影响。抗igf - 1中和抗体可拮抗雄激素对胡须真皮乳头细胞共培养的外根鞘细胞生长的刺激作用。这些发现表明igf - 1是雄激素诱导的毛发生长因子的候选因子。

In order to study the mechanism of action of androgen in human hair follicles, we examined the expressions of androgen receptor, type I and type II 5alpha-reductase in cultured human hair follicle cells. Beard dermal papilla cells possess a higher 5alpha-reductase activity and a larger amount of androgen receptors than reticular dermal fibroblasts or dermal papilla cells from the occipital scalp. Besides, the enzyme found in beard dermal papilla cell appears to be type 2 5alpha-reductase. In contrast, outer root sheathe cells do not have characteristics of the target cells. Androgen significantly stimulates the proliferation of outer root sheath cells that are cocultured with beard dermal papilla cells without cell contact. The expression of insulin-like growth factorI (IGF-I) mRNA in beard dermal papilla cells was stimulated by androgen and antagonized by cyproterone acetate. Outer root sheath cells did not express mRNA for IGF-I either in the presence or absence of androgen. Both of these two types of cells expressed mRNA for IGF-I receptor and the expression was not affected by androgen. Neutralizing antibody against IGF-I antagonized the stimulatory effect of androgen on the growth of outer root sheath cell cocultured with beard dermal papilla cells. These findings suggest that IGF-I is a candidate for androgen induced hair growth factors.