CD81介导滋养细胞抑制Treg细胞分化参与子痫前期发病的机制研究

The differentiation of peripheral organs naïve CD4+ T cells to regulatory T cells (Treg) at the maternal-fetal interface is an important mechanism in the formation of immune tolerance in pregnancy. Treg deficiency is considered as the important factor in development of preeclampsia (PE). As well known, trophoblast cells play a leading role in the regulation of maternal immune cell differentiation and induction of maternal-fetal immune tolerance. In our previous studies, we found that tetraspanin CD81, an important regulatory molecule in T cell activation and differentiation, is significantly increased in trophoblast cells and peripheral blood of patients with PE; moreover, CD81 inhibits the PI3K/Akt signaling pathway, which is related to FOXP3 expression. FOXP3 is the key transcription factor for differentiation of peripheral Treg. We suppose that the abnormally high expressed CD81 in placental trophoblast cells acts on naïve CD4+ T cells via cell recognition, cell debris and exosomes to inhibit PI3K/Akt signaling pathway, then inhibits Treg cell differentiation from naïve CD4+ T cells, which results in insufficient number of Treg cells and defect of maternal-fetal immune tolerance, and finally lead to PE. In this project, we want to clarify the new regulatory mechanism of trophoblast cells on maternal-fetal immune tolerance.

外周初始CD4+T细胞分化为调节性T细胞（Treg）是维持正常妊娠免疫耐受的重要前提，而Treg数不足与子痫前期（PE）发病密切相关。普遍认为滋养细胞在调节母体免疫细胞分化及诱导母胎免疫耐受中起主导作用，但滋养细胞如何调控Treg细胞的机制不明。我们发现参与T细胞活化及分化的重要分子CD81在PE患者滋养细胞及外周血中显著升高；且CD81可明显抑制PI3K/Akt信号通路，而该信号通路与诱导Treg形成的转录因子FOXP3表达有关。我们假设：PE患者滋养细胞异常高表达CD81，CD81可能通过细胞识别、细胞碎片和外泌体形式作用于初始CD4+T细胞抑制其PI3K/Akt信号通路，减少母体初始 CD4+T细胞向Treg细胞的分化，导致母胎界面Treg细胞不足及免疫耐受缺陷。本研究从细胞间分子信息传递及整体动物实验入手，研究滋养细胞通过CD81调控Treg分化的机制，为PE防治提供新靶点。

子痫前期（preeclampsia，PE）是一种妊娠期特有的疾病，其发病机制尚不完全明确，但与母体免疫系统对妊娠产物的适应不良关系密切。Treg-Th17免疫平衡在建立和维持母体对胎儿和胎盘这一同种半异体移植物的免疫耐受方面起重要作用。CD81是四次跨膜蛋白家族（TM4SF）的成员之一，能够协调细胞膜上蛋白的相互作用，并且接收细胞外刺激后向细胞内传递信号。但其在胎盘发育过程和妊娠相关疾病中的研究目前尚未见报道。本项目研究发现：1、CD81在早发型重度PE（sPE）患者滋养细胞、蜕膜和血清中异常增高；2、CD81抑制CTBs的侵袭，高表达CD81的CTBs抑制HUVECs的成环；3、sPE患者蜕膜及外周血中Treg细胞数量及其特异性转录因子FOXP3明显下降，Th17细胞数量及特异性转录因子RORC明显上升。且外周血中CD81含量与Th17细胞功能因子IL-17呈正相关；4、 滋养细胞HTR-8高表达CD81培养上清可抑制初始T细胞向Treg细胞分化，促进向Th17细胞分化；5、CD81高表达可活化NF-kB信号通路，促进细胞因子IL-6的表达与分泌，中和IL-6后可明显逆转CD81高表达上清引起的Treg-Th17分化失衡；6、高表达CD81腺病毒尾静脉注射诱导妊娠大鼠PE样表型，此模型中蜕膜及外周血中FOXP3表达量、Treg细胞数量明显下降，RORC表达量、Th17细胞数量明显上升；7、IL-6的中和抗体可成功逆转CD81诱导的妊娠大鼠Treg-Th17免疫失衡，并改善其PE样症状。这些结果表明，早发型重度PE患者滋养细胞中异常高表达的CD81通过激活NF-kB信号通路，增加IL-6的表达与分泌，来促进IL-6/STAT3/IL-17信号通路，并抑制FOXP3，从而促进Th17抑制Treg细胞，破坏母胎界面的免疫耐受状态，最终导致PE的发病。本研究深入探讨了CD81参与PE的免疫学发病机制，为早期预测及治疗子痫前期提供了理论基础。