上皮钠通道ENaC通过miRNA介导的COX-2表达调控参与胚胎着床的机制研究

Embryo implantation remains a poorly understood process. Implantation is initiated by the attachment of the embryo to the epithelial layer of the endometrium lining the uterine lumen, and followed by a differentiation process in the endometrial stroma beneath the epithelial layer, the so-called decidualization, which is considered a maternal prerequisite for embryo implantation and successful pregnancy. However, it remains unclear how signals from the embryo at the endometrial surface are converted into chemical signals, leading to decidualization in the stromal cells that do not have direct contact with the embryo. Our preliminary study has revealed that ENaC, a sodium channel abundantly expressed in the endometrial epithelial cells during implantation, plays a critical role in implantation. ENaC can be activated by serine protease derived from embryos and regulate the decidulization-inducing molecules COX2/PGE2, as well as the miRNAs targeting COX-2 (miR101 and miR199a*). These prompt us to hypothesize that during implantation, activation of ENaC in epithelial cells by embryo signals may lead to suppression of miR101/miR199a*, thus upregulation of their target COX2 and PGE2 release, which initiate the decidulization in the stromal cell. In this project, we aim to demonstrate the involvement of miR101/miR199a* in the role of ENaC in decidualization and implantation and the underlying mechanism by using intrauterine interference animal model and endometrial epithelial cell and stromal cell model. The findings of the study may shed new light on the treatment for infertility caused by implantation failure, improvement of assisted reproductive technologies, and development of new generation of contraceptive agents.

胚胎着床是生殖和避孕的重要环节。着床时胚胎贴附到子宫内膜上皮后，引发上皮下的间质细胞发生的蜕膜化是着床的必要条件。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转换成蜕膜化信号，从而引起间质细胞的蜕膜化，而妊娠失败病人的子宫内膜ENaC的表达是异常的，说明其在着床中的关键作用。我们发现ENaC激活后引起钙内流，从而激活CREB及蜕膜化的关键分子COX-2；ENaC的激活可以调节两个调控COX-2的miRNAs-miR101和miR199a*的表达。由此推测，ENaC参与着床的其中一个作用机制可能是通过调节这两个miRNA, 增强靶基因COX-2表达和PGE2分泌。本项目通过宫内干预动物模型，上皮-间质共培养和分子克隆，证明miR101和miR199a*参与ENaC在着床中的作用及其分子机制。研究的成果对于着床性不育的治疗和辅助生育成功率的提高和新的避孕靶点的开发有重要指导意义。

胚胎着床是生殖和避孕的重要环节。着床时胚胎贴附到子宫内膜上皮后，引发下方的间质细胞发生的蜕膜化是着床的必要条件。然而迄今为止，关于胚胎信号如何通过上皮细胞转换成蜕膜化信号传递给下方的间质细胞，引起其发生蜕膜化，这一着床机制中的关键问题一直没有解决。我们的前期研究发现一个着床时在内膜上皮高表达的钠离子通道ENaC可以被来自胚胎的蛋白酶激活，调节蜕膜化的关键分子COX-2/PGE2，并在着床过程中起重要作用。本项目研究结果表明：子宫内膜上皮细胞ENaC激活后，可以通过CREB依赖性机制，导致两个COX2靶向的microRNAs——miR-101和miR-199a-3p——的改变；CREB活化引起的对miR-101和miR-199a-3p的这一抑制作用，有助于子宫COX2上调，从而对胚胎着床发挥了关键性作用。这些结果进一步阐明ENaC和COX-2/PGE2相关的信号转导通路在胚胎着床过程中的重要作用和完善该通路的分子途径，并提出了microRNAs在其中新的重要作用，以及揭示了CREB在介导ENaC调控microRNA以及胚胎着床中的重要作用。另外，本课题还揭示并首次提出了离子通道（ENaC）作为细胞膜蛋白，在介导细胞外信号，调节microRNA表达，从而调控细胞内表观遗传学改变的重要作用，该作用的揭示将对胚胎着床以外的其它生理、病理过程的发生机制的研究有重要的指导性意义。