Salomon Alexander K, Leon Kathleen, Campbell Melissa M, Young Kelly A
Department of Biological Sciences, California State University Long Beach, Long Beach, CA 90840, United States.
Department of Biological Sciences, California State University Long Beach, Long Beach, CA 90840, United States.
Gen Comp Endocrinol. 2018 May 1;260:90-99. doi: 10.1016/j.ygcen.2018.01.003. Epub 2018 Jan 6.
The early stages of ovarian folliculogenesis generally progress independent of gonadotropins, whereas later stages require signaling initiated by FSH. In Siberian hamsters, cycles of folliculogenesis are mediated by changes in photoperiod which depress the hypothalamic pituitary gonadal axis. Reduced gonadotropins lead to decreases in mature follicle development and ovulation; however, early stages of folliculogenesis have not been explored in regressed ovaries. We hypothesized that intraovarian factors that contribute predominantly to later stages of folliculogenesis would react to changes in photoperiod, whereas factors contributing to earlier stages would not change. To probe if the early stages of folliculogenesis continue in the photoinhibited ovary while late stages decline, we measured the mRNA abundance of factors that interact with FSH signaling (Fshr, Igf1, Cox2) and factors that can function independently of FSH (c-Kit, Kitl, Foxo3, Figla, Nobox, Sohlh1, Lhx8). While plasma FSH, antral follicles, and corpora lutea numbers declined with exposure to inhibitory photoperiod, the numbers of primordial, primary, and secondary follicles did not change. Expression of factors that interact with FSH signaling changed with changes in photoperiod; however, expression of factors that do not interact with FSH were not significantly altered. These results suggest that the photoinhibited ovary is not completely quiescent, as factors important for follicle selection and early follicle growth are still expressed in regressed ovaries. Instead, the lack of gonadotropin support that characterizes the non-breeding season appears to inhibit only final stages of folliculogenesis in Siberian hamsters.
卵巢卵泡发生的早期阶段通常独立于促性腺激素进行，而后期阶段则需要由促卵泡激素（FSH）启动信号传导。在西伯利亚仓鼠中，卵泡发生的周期由光周期变化介导，光周期变化会抑制下丘脑 - 垂体 - 性腺轴。促性腺激素减少会导致成熟卵泡发育和排卵减少；然而，卵泡发生的早期阶段在退化卵巢中尚未得到研究。我们假设，主要促成卵泡发生后期阶段的卵巢内因子会对光周期变化做出反应，而促成早期阶段的因子则不会改变。为了探究在光抑制的卵巢中卵泡发生的早期阶段是否持续，而后期阶段衰退，我们测量了与FSH信号相互作用的因子（Fshr、Igf1、Cox2）以及可独立于FSH发挥作用的因子（c-Kit、Kitl、Foxo3、Figla、Nobox、Sohlh1、Lhx8）的mRNA丰度。虽然随着暴露于抑制性光周期，血浆FSH、窦状卵泡和黄体数量减少，但原始卵泡、初级卵泡和次级卵泡的数量没有变化。与FSH信号相互作用的因子的表达随光周期变化而改变；然而，不与FSH相互作用的因子的表达没有显著改变。这些结果表明，光抑制的卵巢并非完全静止，因为对卵泡选择和早期卵泡生长重要的因子在退化卵巢中仍有表达。相反，非繁殖季节特有的促性腺激素支持的缺乏似乎仅抑制西伯利亚仓鼠卵泡发生的最后阶段。
