超促排卵中孕激素抑制LH峰机理研究

Elevated oestradiol concentrations during the follicular phase encourage a secretion in gonadotropin-releasing hormone (GnRH)，stimulating a surge in luteinising hormone (LH) concentration, which leads to ovulation. The key of in vitro fertilization technology lies in the grasp of LH surge. Traditional ovarian stimulation protocols, by down-regulating the pituitary pulsatile secretion, have an unnatural hormone background for follicle generation, and result in low efficiency in ovarian stimulation, also causing an increasing rate of side effect such as Ovarian Hyper Stimulation Syndrome (OHSS). By introducing progesterone as a suppression of LH surge in ovarian stimulation protocol, it is proved to have a satisfying embryology and clinical pregnancy results in our clinic, which probably due to maintain of pulsatile secretion of gonadotropin and more nature hormone background. Previous researches have shown that progesterone can block LH surge by feedback function on the hypothalamus level. However, the mechanism is still largely unknown, causing the bottleneck in study on LH surge induction. We presumed that progesterone might block the LH by feedback effect mediated by GnRH neuron or other middle neuron in hypothalamus under the condition of ovarian hyperstimulation. By adopting the optogenetics strategy to control GnRH neuron pulse, GnRH pulsatile secretion mode under which LH surge is blocked by progesterone can be detected. Then, it is necessary to indirectly prove previous result by monitoring LH pulse by serial blood sampling test and exploring sections of brain tissues in immunohistochemistry. This study will overcome disadvantages of previous research, fill out the blank of GnRH research under ovarian stimulation background and look into hypothalamic GnRH secretion mode under high progesterone condition from indirect and direct perspective. At the same time, the study will help to explain the relationship between LH surge and GnRH pulsatile secretion, as well as the mechanism of high progesterone blocking LH surge by feedback effect in hypothalamus level, also, to find possible novel position in hypothalamus for drug manufacture and provide new perspective for safer, more efficient and optimal ovarian hyperstimulation.

当雌激素到达阈值，通过正反馈机制刺激下丘脑分泌促性腺激素释放激素（GnRH），控制垂体出现黄体生成素（LH）峰值，诱发自发性排卵。对LH峰和提早排卵的控制是试管婴儿超促排卵的关键。传统方案通过垂体“降调节”抑制LH峰，存在反自然、效率低及并发症多等固有弊端。本中心将孕激素（P）作为促排卵中抑制LH峰新方法，临床上证明更加自然、安全和高效。P通过性腺轴反馈作用，从下丘脑水平抑制LH峰同时不阻断垂体功能，此过程机理尚未明确，为LH峰研究及P在促排卵中应用造成瓶颈。本项目假设:在促排卵中，P可反馈性调控下丘脑GnRH分泌模式及中间神经元兴奋性实现LH峰抑制。项目拟采用大鼠模型光遗传学方法直接控制GnRH脉冲观察LH峰发生，通过猕猴内分泌监测及免疫组化方法，实现直接和间接证明孕激素背景下GnRH分泌模式与LH峰关系及明确P在下丘脑作用位点，层层阐明P抑制LH峰机制，为优化促排卵中关键步骤提供新策略

临床发现高孕激素促排卵方案可有效抑制排卵前LH峰的发生。为了确认该现象并探索其神经生物学机制，我们首先在非人灵长类上建立高孕激素促排卵模型，研究发现MPA可明显抑制雌激素诱发的LH峰，并且减缓了LH pulse的发生；接着通过光/化学遗传学在体操控小鼠下丘脑GnRH神经元活性，发现GnRH神经元精确调控着排卵相关的LH surge和pulse的发生，进一步证明雌激素诱发的LH surge与pulse密切相关；最终我们在大鼠高孕激素促排卵研究模型上，实验表明高孕激素通过作用于AVPV脑区介导GnRH神经元活性，抑制了雌激素诱发的LH峰，而通过作用于ARC脑区最终介导GnRH神经元活性抑制了LH pulse的发生。以上研究结果为高孕激素促排卵方案在临床进一步改进，优化和推广提供了坚实的理论依据和指导。