Abstract
Androgens are crucial for normal folliculogenesis and female fertility as evidenced in androgen receptor-null and granulosa cell conditional knockout mice. It is thought, however, that the multiple effects of androgens in the ovary are mainly complementary to the actions of gonadotropins. Using primary rat granulosa cells, we demonstrated that in the absence of gonadotropins, testosterone (T) increases aromatase (Cyp19) and P450 side-change cleavage expression, two enzymes crucial for normal ovarian function. T can be converted into estradiol, a classical estrogen, by Cyp19 and into 5α-dihydrotestosterone, a pure androgen, by 5α-reductase. However, inhibition of Cyp19 and/or 5α-reductase did not prevent the stimulatory effects of T. In contrast, the effect of this steroid was potentiated by blocking 5α-reductase. Additionally, T, not 5α-dihydrotestosterone, stimulates liver receptor homolog-1 (LRH-1) expression, whereas the expression of steroidogenic factor-1 (SF-1) was not affected by either steroid. LRH-1 and SF-1 are transcription factors known to be involved in the regulation of Cyp19. Accordingly, small interference RNA against LRH-1 prevented Cyp19 and P450 side-change cleavage up-regulation whereas anti-SF-1 small interference RNA had no effects. Chromatin immunoprecipitation demonstrated that T stimulation of LRH-1 leads to the recruitment of LRH-1 to the native Cyp19 promoter, which was not affected by cotreatment with 5α-reductase and Cyp19 inhibitors. Finally, gel shift and supershift analysis demonstrated that the androgen receptor binds to an androgen response element located within the LRH-1 promoter. These results provide novel evidence that T has a direct effect on the expression of genes involved in granulosa cell differentiation.