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，我们检测了培养的人毛囊细胞中雄激素受体、5 α-还原酶和的表达。雄激素受体mRNA在腋毛和胡须毛中强表达，而I型5 α-还原酶基因在毛中普遍表达，II型5 α-还原酶基因仅在胡须和额部毛中表达，女性腋毛强表达III型17 β-羟类固醇脱氢酶。相反，滤泡上皮细胞不具有靶细胞的特征。虽然雄激素本身没有任何类型的细胞单独培养时的增殖作用，雄激素显着刺激毛囊上皮细胞与胡须或腋窝毛乳头细胞共培养的增殖。胰岛素样生长因子-I（IGF-I）是DPC中的一种雄激素依赖性旁分泌生长因子，IGF-I中和抗体可拮抗雄激素对与胡须毛乳头细胞共培养的外根鞘细胞生长的刺激作用。雄激素刺激胡须和腋窝DPC中IGF-I的表达。这些发现表明IGF-I是雄激素诱导的毛发生长因子的候选者。近年来，我们发现在小鼠乳腺Sjionogi癌细胞系（SC-3）中，自分泌的雄激素依赖性生长因子FGF 8的表达也受到雄激素的上调，FGF 8是雄激素依赖性毛发生长因子的另一个候选者。

In order to study the mechanism of action of androgen in human hair follicles, we examined the expressions of androgen receptor, 5alpha-reductase and in cultured human hair follicle cells. Androgen receptor mRNA was strongly expressed in axillary and beard DPC.While the expression of type I 5alpha-reductase is ubiquitous property of DPC,type II 5alpha-reductase gene expression is limited to beard and frontal scalp DPC.Female axillary DPC strongly expressed type III 17beta-hydroxysteroid dehydrogenase. In contrast, follicular epithelial cells do not have characteristics of the target cells. Although androgen itself did not have a proliferative effect on either type of cells when cultured alone, androgen significantly stimulated the proliferation of follicular epithelial cells which were cocultured with beard or axillary dermal papilla cells. We found that insulin-like growth factor-I (IGF-I) is one of the androgen dependent paracrine growth factors in DPC.Neutralizing antibody against IGF-I antagonized the stimulatory effect of androgen on the growth of outer root sheath cells cocultured with beard dermal papilla cells. The expression of IGF-I in beard and axillary DPC was stimulated by androgen. These findings suggest that IGF-I is a candidate for androgen induced hair growth factors. Recently we found that the expression of FGF8 which is an autocrine androgen-dependent growth factor in mouse mammary Sjionogi carcinoma cell line (SC-3) is also upregulated by androgen in beard DPC.FGF8 is another candidate for androgen dependent hair growth factor.