iTreg的表观调控及其在自身免疫性疾病中的作用机制

Forkhead box P3 (FoxP3)+ CD4+ regulatory T (Treg)-cells can be divided into natural Treg (nTreg)-cells and adaptive Treg (iTreg)-cells. iTreg-cells are generated outside the thymus, and require TCR signaling and the cytokines TGF-beta1 and IL-2. In contrast to nTreg-cells, iTreg-cells are more effective in controlling established inflammatory diseases, and more resistant to the conversion to T helper (Th)1-, Th17-, and follicular helper T (Tfh)-cells under inflammatory conditions. Despite the mechanisms of iTreg-cell generation have been intensively focused in the past, our understanding of molecular mechanisms, particularly microRNA (miRNA)-mediated epigenetic regulation involved in the iTreg-cell generation is lacking. Our prliminary data we showed that microRNA-31 (miR-31), a small non-coding RNA, decreased over 100 folds in TGF-beta1-induced iTreg-cells compared to controls. We created miR-31 overexpression transgenic and miR-31flox/flox/CD4-Cre conditional knockout mice. We found that miR-31 overexpression inhibited iTreg-cell induction, and facilitated autoimmunity. This project intends to carry out further investigations: 1) the target gene(s) of miR-31; 2) the contribution and mechanism of conditional knock-out of miR-31 in development and differentiation of iTreg-cells, and in the development of autoimmunity; 3) the transcription signaling pathway(s) regulating miR-31; 4) The utility of targeting miR-31 in translational research. The clarification of these issues may be conducive to enhancing our understanding of the apparent regulatory networks of Treg-cells, and may lead to create novel ideas and strategies for both diagnosis and treatment of autoimmune disorders.

调节性T细胞（Treg）分为nTreg和iTreg。iTreg产生于胸腺之外，需要TCR信号、TGF和IL-2。与nTreg相比，iTreg较稳定，不易向Th1、Th17和Tfh细胞转变，对治疗慢性疾病的疗效更好。尽管过去对iTreg研究较多，但microRNA介导的表观调控机制至今未见报道。课题组前期研究发现：miR-31在iTreg分化前后相差100倍以上。课题组首次完成了miR-31过表达和miR-31条件性基因剔除小鼠的构建。预实验发现miR-31过表达导致iTreg的分化被显著抑制，同时促进自身免疫性疾病发生。该项目拟进一步求证：1）miR-31靶基因；2）miR-31对iTreg细胞及疾病的作用机制；3）miR-31转录的信号网络；4）靶向miR-31诱导iTreg分化用于转化医学研究。这些问题的阐明有利于增强对iTreg表观调控的理解，为自身免疫性疾病的诊治提供新思路新方法。

本项目以严重危害我国人民健康的自身免疫性疾病：银屑病和多发性硬化症为核心，以免疫细胞表观调控与自身免疫性疾病发生发展之间关系为基点，深入研究免疫负调控细胞iTreg和相关致炎免疫细胞、靶细胞的表观调控在自身免疫性疾病中的作用机制。项目负责人在自身免疫性疾病免疫学机理和治疗新靶点领域取得了系列创新成果：（一）揭示了利多卡因和miR-31正负调控外周Treg分化，被认为是自身免疫性疾病的重要致病机制之一（Nat Commun 2015；JACI 2015）；（二）揭示了自身免疫性疾病中“皮肤干细胞-免疫抑炎细胞/免疫致炎细胞”稳态的调控新机制（Stem Cells TM 2016；Stem Cells 2014；ZL 201210002750.3；ZL 201210002647.9），为临床应用干细胞治疗自身免疫性疾病提供了理论依据；（三）发现病毒感染激发了自身免疫性疾病的发生发展（EMBO MM 2017），提出寻常型银屑病是由病毒感染激发，抗病毒免疫应答中易感基因促进表皮细胞与免疫细胞互作异常而导致疾病发生发展的病因学假说，为银屑病等自身免疫性疾病诊治提供了新思路；（四）鉴定出表皮细胞增殖负调节子SFRP4、pp6和MAT2a为银屑病治疗全新靶点（J Immunol 2015；Nat Commun 2015；EBioMed 2018；ZL 2013106233142）；这些研究发表通讯作者论文11篇，合计IF：77.7，授权专利3项。同时在本项目的资助下，项目负责人2017年获得国家杰出青年基金的支持。本项目中免疫学新机制的阐明和新靶点的发现有利于增强对负调控分子和负调控细胞表观调控的理解，为自身免疫性疾病的诊治提供新思路新方法。