多重抗药性相关蛋白IV（MRP4）参与上皮钠通道调节胚胎着床相关信号机制研究

Embryo implantation is the most intricate and rate-limiting step for human reproduction. Nearly 75% of pregnancy losses in humans are believed to be due to implantation failure. Despite the advances in IVF and embryo transfer for assisted reproductive technology (ART), the pregnancy rate of ART remains low, which is largely due to implantation failure. Defective implantation can also affect later course of pregnancy resulting in poor outcomes or diseases such as preterm labor. However, the molecular mechanism underlying embryo implantation remains largely unknown. We have previously identified a novel role of epithelial sodium channel (ENaC) in the endometrial epithelial cells in embryo-implantation. In response to embryo-derived signals, ENaC is activated, which triggers a series of signaling transductions leading to prostaglandins E 2 (PGE2) production and release. PGE2, in turn, acts on stromal cells and promotes stromal decidualization, which is essential to implantation. Multidrug Resistance protein 4 (MRP4) is a membrane protein that functions in prostaglandins (PGs) transport. Given the importance of PGs in embryo-implantation, a potential role of MRP4 is suggested. We thus hypothesize that ENaC activation upon the embryo-derived signals might lead to upregulation of MRP4, which on the one hand may promote epithelial PGE2 transport to stromal cells and on the other hand, may regulate PGE2 synthesis pathway in a postive-feedback way. Thus, MRP4 may facilitate the process of decidualization for embryo implantation. We propose to use in vivo mouse implantation models and in vitro human endometrial epithelial and stromal cell cultures to test the hypothesis. The results from the proposed study will provide new insights into the molecular mechanisms underlying embryo implantation and also possible treatment targets for embryo-implantation derived diseases.

胚胎着床是人类生殖过程中最为复杂且极其关键的步骤。辅助生殖受孕成功率低（<30%）的主要原因是胚胎着床障碍。胚胎着床不良还可能导致一些妊娠后期的疾病如胎儿发育不良、早产等。然而，胚胎着床的分子机制尚不清晰。我们的前期研究揭示了胚胎信号通过上皮细胞钠离子通道（ENaC），调控前列腺素（PGE2）的生成和释放，对胚胎着床有关键性作用。多重抗药性蛋白IV（MRP4）能转运PGE2，但其在胚胎着床中的作用尚未报道。我们假设， ENaC在囊胚信号激活下，调控MRP4表达和功能。MRP4将胞内合成的PGE2转运至上皮与间质间，促进蜕膜化；且进一步激活上皮细胞内PGE2合成，从而参与了胚胎着床。本项目将利用小鼠在体模型和人子宫内膜上皮、间质细胞系体外模型，对以上假设进行研究。研究结果将对胚胎着床分子机制有理论性突破。同时，将为治疗女性不孕不育、提高辅助生育成功率和预防胚胎着床源性疾病提供临床指向。

胚胎着床是人类生殖过程中最为复杂且极其关键的步骤。胚胎着床不良会导致妊娠后期的疾病如胎儿发育不良、早产等。胚胎着床障碍是限制辅助生殖受孕成功率的主要因素。然而，胚胎着床的分子机制尚不清晰。本课题在前期研究揭示了胚胎信号通过上皮细胞钠离子通道（ENaC），调控前列腺素（PGE2）的生成和释放，对胚胎着床有关键性作用的基础上，提出多重抗药性蛋白IV（MRP4）可能是ENaC相关信号转导通路的下游，并对胚胎着床有贡献。经过一系列体内外模型的实验验证和分析，本课题的研究结果表明：子宫内膜MRP4在着床期高表达并发挥从上皮细胞向间质细胞转运PGE2的作用；子宫内膜MRP4功能抑制或表达敲低导致小鼠胚胎着床率下降和蜕膜化削弱；MRP4是胚胎着床期ENaC相关信号通路调控的下游分子；MRP4参与胚胎着床期ENaC激活引起的CREB磷酸化与PGE2合成及分泌。结果首次证明了MRP4，参与了ENaC调控的胚胎着床信号转导，为理解胚胎着床的分子机制提供了新的关键性基因和因子；并为开发治疗和预防与胚胎着床相关的疾病提供了新的分子靶标。