母胎界面蜕膜NK细胞的表型和功能特征

In the process of embryonic development, special maternal-fetal interface is needed to protect the normal development of the fetus. Decidualization is the process of converting endometrial stromal cells into decidual cells and is the main characteristics of forming the maternal-fetal interface. In the deciduas of the first trimester, 30-40% of the total cells are immune cells, among which NK cells account for almost 70% of all the immune cells. Why such a large number of immune cells do not launch an immune response but maintain immune tolerance? Researches about this question will have great importance in our understanding in the immune tolerance mechanisms of the normal pregnancy and the pathogenesis of immune disorders mediated by pregnancy-related disease. In the recent ten years, we have researches on the differentiation and functional polarization of human decidual NK cells, and further identified four novel NK subsets. In this project, we will further discuss the following important issues: verify that decidual NK cells are special NK population with CD56brightCD49a+ phenotype and directly regulated by Lnc-56 and Lnc-49; focus on one or two key negative regulatory molecules on decidual NK cells and analyze their core role in maintaining maternal-fetal immune tolerance; explore how the decidual CD56brightCD49a+ NK cells accept educations of maternal or paternal HLA class I molecules and form tolerance for the allogenic cells; analysis of the binding sites and binding abilities between KIRs on NK cells and HLA-C from different individuals, and its correlation with normal pregnancy/pregnancy related diseases. Through these researches, we hope to eventually understand the dynamic characteristics of immune cells in decidual microenvironment, especially the main mechanism of the development, differentiation, mature, migration, education, activation and function of NK cells. These studies will hopefully establish the decidual NK cells dominated, novel immune cells network in maternal-fetal interface, which will further promote the comprehensive understanding of pregnancy-related disease pathogenesis.

早孕蜕膜组织中免疫细胞占细胞总数的30-40%，其中NK细胞又占蜕膜免疫细胞总数的70%，如此大数量免疫细胞为何没有启动免疫应答，反而维持免疫耐受？回答该问题对认识正常妊娠的免疫耐受机制，以及免疫失常介导的妊娠相关疾病发病机理，会有重要指导意义。近十年来，我们对人蜕膜NK细胞已进行发育分化、功能极化研究并界定四种NK细胞亚群，本课题将进一步探讨以下问题：证明dNK细胞为CD56brightCD49a+ 特殊细胞群体，并受Lnc-56和Lnc-49的直接调控；聚焦1-2个dNK细胞关键负调分子，分析它们在维持母胎免疫耐受中的核心作用；探讨蜕膜dNK细胞如何接受HLA-I类分子的教育，形成对同种“异体”细胞的耐受，及其与正常妊娠/妊娠相关疾病的关联性。最终希望了解蜕膜微环境中免疫细胞尤其是NK细胞的动态特征，建立以dNK细胞为主体的母胎免疫界面细胞网络，促进对妊娠相关疾病发病机理的全面认识。

母胎界面富含蜕膜NK细胞，其表型和功能特征、发育分化和转录调控机制尚不明确，本课题发现在人和小鼠早期妊娠蜕膜组织局部，存在大量CD49a+Eomes+NK细胞亚群，通过分泌生长因子PTN、OGN等，促进胚胎的发育。胚胎来源的绒毛外滋养层细胞表达的HLA-G与蜕膜NK细胞相互作用，诱导NK细胞大量表达这些生长因子。缺失这种可以分泌生长因子的NK细胞，会出现胚胎生长受限现象。在反复流产病人中蜕膜NK细胞表达生长因子能力显著下降，不能支持早期胚胎的正常发育。为了挽救由于NK细胞分泌生长因子减少导致的胚胎生长受限，在体外用骨髓造血干细胞诱导出蜕膜样NK细胞，并对小鼠进行静脉过继转输，转输后的老龄鼠和生长因子缺陷鼠妊娠结局明显改善，胚胎生长受限缓解。. 生物信息学分析提示，人dNK细胞特异性高表达同源结构域家族转录因子PBX1，在dNK细胞产生的生长因子（PTN、OGN）基因启动子区富含多个PBX1结合位点，沉默人蜕膜NK细胞PBX1表达，蜕膜NK细胞表达生长因子显著减少。通过构建NK细胞发育早前期（Vav1-Cre）和中后期（Ncr1-Cre）pbx1基因条件型敲除小鼠模型，显示两种Pbx1条件型敲除小鼠dNK细胞分泌生长促进因子显著减少，妊娠结局差，胚胎生长受限十分严重。表现为胎鼠体重、体长显著低于正常小鼠；骨骼染色实验说明Pbx1条件型敲除小鼠胎鼠硬骨发育不良。我们的实验结果揭示转录因子PBX1通过调节蜕膜NK细胞表达生长因子PTN/OGN，促进胚胎的早期发育。该研究对于基于NK细胞促进胚胎发育，改善妊娠相关疾病的结局具有重要意义。