C型钠肽在腔前卵泡成腔启动中的关键作用研究

Conventional superovulation just induce growth and development of antral follicles, however, the greatly abundant preantral follicles in ovaries are unresponsive to gonadotropin. Therefore, the antrum formation is of prime importance for the usage of ovarian follicles. However, the mechanism underlying the antrum formation of preantral follicels is a scientific puzzle that has never been determined. The results of our previous work showed that C-type natriuretic peptide (CNP) can facilitate the growth and proliferation of in vitro cultured preantral follicles and its granulosa cells, which is independent on FSH. In addition, the expression of CNP and its receptor NPR2 increased dramatically during the preantral to early antral transition. These results, together with previously reported evidences, suggest that CNP appears to be the key factor responsible for initiating antrum formation of preantral follicels. The present study, using mouse and bovine as models, are aimed to testing the role of CNP in initiating antrum formation, and determining the fate of preantral follicles. Moreover, we want to explore the involvement of ovarian hormones and growth factors in regulating CNP-NPR2 signaling, as well as the mechanism of CNP-induced antrum formation. Next, based on the potential of CNP in inducing antrum formation, we want to establish a novel strategy for improving efficiency of superovulation in bovines.

常规超数排卵技术只能促进有腔卵泡的生长发育，但卵巢上极其丰富的腔前卵泡却无法响应。如何促进腔前卵泡成腔启动，形成大量的有腔卵泡，是提高卵泡资源利用效率的关键。然而，腔前卵泡成腔启动机制一直是配子发育领域悬而未决的科学问题。本实验室的前期数据显示，C型钠肽（CNP）可不依赖于FSH促进小鼠腔前卵泡及其颗粒细胞的体外发育和增殖，并且CNP及其受体NPR2表达在卵泡成腔转化过程中显著增加。结合此前报道的重要线索，提示CNP极有可能是腔前卵泡成腔启动的关键控制因子。本项目拟针对腔前卵泡成腔启动这一重要命题，利用小鼠和牛作为模型，探索CNP启动卵泡成腔，决定卵泡发育命运的作用。进一步，揭示卵泡中激素及生长因子对CNP-NPR2信号的调控作用，以及CNP-NPR2下游实现卵泡成腔启动的作用路径。在此基础上，利用CNP的成腔启动能力，探索建立超数排卵的新方法，从根本上提高牛的卵泡资源利用效率。

项目针对家畜卵泡资源利用率低的问题，从腔前卵泡发育机制入手，以小鼠和牛为模型，探讨了C型钠肽（C-type natriuretic peptide，CNP）在腔前卵泡成腔转变中的作用，以及卵泡发育过程中牛卵母细胞减数分裂调节的独特机制。明确了CNP通过刺激颗粒细胞增殖，在腔前卵泡生长中发挥的重要作用。在基础上，揭示了卵泡发育过程中，牛卵泡壁层颗粒细胞来源的CNP可以同时通过卵丘细胞和卵母细胞上的NPR2受体，参与卵母细胞减数分裂调节的独特机制。基于上述机制研究，项目还发明了提基于CNP预处理的“三步法”卵母细胞体外成熟新方法，大幅提高了牛卵母细胞体外成熟的效率和质量，获得美国专利。目前该技术已经纳入国内龙头种业企业牛羊体外胚胎生产技术标准，应用于体外胚胎工厂化生产，实现良种快速扩繁。此外，研究成果作为核心技术发明，获得教育部技术发明一等奖（2019年）和大北农科技奖一等奖（2019年）。

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