Xue Kai, Liu Jia-yin, Murphy Bruce D, Tsang Benjamin K
State Key Laboratory in Reproductive Medicine, Centre for Clinical Reproductive Medicine, Nanjing Medical University, Nanjing 210029, Jiangsu Province, China.
Mol Endocrinol. 2012 Dec;26(12):2004-15. doi: 10.1210/me.2012-1200. Epub 2012 Oct 1.
Nuclear receptor subfamily 4 group A member1 (NR4A1), an orphan nuclear receptor, is involved in the transcriptional regulation of thecal cell androgen biosynthesis and paracrine factor insulin-like 3 (INSL3) expression. Androgens are known to play an important regulatory role in ovarian follicle growth. Using a chronically androgenized rat model, a preantral follicle culture model and virus-mediated gene delivery, we examined the role and regulation of NR4A1 in the androgenic control of preantral follicular growth. In the present study, Ki67 staining was increased in preantral follicles on ovarian sections from 5α-dihydrotestosterone (DHT)-treated rats. Preantral follicles from DHT-treated rats cultured for 4 d exhibited increased growth and up-regulation of mRNA abundance of G(1)/S-specific cyclin-D2 (Ccnd2) and FSH receptor (Fshr). Similarly, DHT (1 μm) increased preantral follicular growth and Ccnd2 and Fshr mRNA abundance in vitro. The NR4A1 expression was high in theca cells and was down-regulated by DHT in vivo and in vitro. Forced expression of NR4A1 augmented preantral follicular growth, androstenedione production, and Insl3 expression in vitro. Inhibiting the action of androgen (with androgen receptor antagonist flutamide) or INSL3 (with INSL3 receptor antagonist INSL3 B-chain) reduced NR4A1-induced preantral follicular growth. Furthermore, NR4A1 overexpression enhanced DHT-induced preantral follicular growth, a response attenuated by inhibiting INSL3. In conclusion, DHT promotes preantral follicular growth and attenuates thecal NR4A1 expression in vivo and in vitro. Our findings are consistent with the notion that NR4A1 serves as an important point of negative feedback to minimize the excessive preantral follicle growth in hyperandrogenism.
核受体亚家族4 A组成员1（NR4A1）是一种孤儿核受体，参与卵泡膜细胞雄激素生物合成和旁分泌因子胰岛素样3（INSL3）表达的转录调控。已知雄激素在卵巢卵泡生长中起重要调节作用。我们使用慢性雄激素化大鼠模型、窦前卵泡培养模型和病毒介导的基因传递，研究了NR4A1在雄激素对窦前卵泡生长控制中的作用和调控。在本研究中，5α-双氢睾酮（DHT）处理大鼠的卵巢切片上，窦前卵泡中的Ki67染色增加。培养4天的DHT处理大鼠的窦前卵泡生长增加，G(1)/S特异性细胞周期蛋白D2（Ccnd2）和促卵泡激素受体（Fshr）的mRNA丰度上调。同样，DHT（1μm）在体外增加了窦前卵泡的生长以及Ccnd2和Fshr的mRNA丰度。NR4A1在卵泡膜细胞中表达较高，在体内和体外均被DHT下调。在体外，强制表达NR4A1可增强窦前卵泡的生长、雄烯二酮的产生和Insl3的表达。抑制雄激素的作用（使用雄激素受体拮抗剂氟他胺）或INSL3的作用（使用INSL3受体拮抗剂INSL3 B链）可降低NR4A1诱导的窦前卵泡生长。此外，NR4A1过表达增强了DHT诱导的窦前卵泡生长，这种反应可通过抑制INSL3而减弱。总之，DHT在体内和体外均可促进窦前卵泡生长并减弱卵泡膜细胞中NR4A1的表达。我们的研究结果与以下观点一致，即NR4A1作为负反馈的重要节点，可使高雄激素血症中过度的窦前卵泡生长最小化。
