miR-219对炎症性肠病Th17和Treg细胞增殖分化的免疫调节作用

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory conditions that are classically characterized by periods of remission and relapse. Although the etiology and pathogenesis of IBD remain elusive, emerging evidences have shown that IBD are resulted from the combination of genetic polymorphisms, environmental factors, and dysregulated immune responses to intestinal commensal microbiota. MicroRNAs (miRs) are endogenous small non-coding RNAs that impart posttranscriptional gene regulation through translational repression and mRNA degradation. miR-219 has been reported to play a crucial role in many physiological processes such as carcinogenesis and immune system modulation. However，the function of miR-219 in the pathogenesis of IBD remains unclear. In our preliminary experiments, we have demonstrated that miR-219 is markedly decreased in inflamed mucosa and peripheral blood mononuclear cells (PBMC) of IBD patients. Further investigation indicates that CD4+ T cells are the major resources of miR-219 both in intestinal mucosa and PBMC. In this study, we will explore the potential role of miR-219 in regulating CD4+ T cell immune response in intestinal mucosa of IBD, and attempt to determine the potential target genes of miR-219. Experimental colitis models in mice will be established and treated with miR-219 precursor to determine whether it could alleviate intestinal mucosal inflammation. This work will clarify the potential role of miR-219 in the pathogenesis of IBD, and provide a novel therapeutic approach for the treatment of IBD.

炎症性肠病（IBD）的病因和发病机制可能与肠道菌群失调、肠黏膜免疫应答调节异常、肠黏膜屏障缺损、环境和遗传等因素有关。microRNA（miR）是一类内源性非编码小分子RNA，通过结合靶基因的3'-UTR端，调控相关靶基因表达和功能。我们前期通过芯片筛选及荧光定量PCR验证发现miR-219在IBD患者炎症肠黏膜组织与外周血中表达降低，并且证实miR-219促进Treg细胞分化，同时抑制Th17细胞相关免疫应答。据此提出miR-219可能通过调节IBD患者Th17/Treg动态平衡参与调控肠黏膜炎症发生。本课题着重研究miR-219在IBD中的表达水平以及对肠黏膜组织CD4+ T细胞免疫调节效应，寻找miR-219的靶基因，阐明其在IBD发病过程中的免疫调节作用。构建小鼠结肠炎模型，靶向上调miR-219在结肠组织中的表达，研究肠黏膜炎症发展变化，为临床上IBD的治疗提供新靶点。

炎症性肠病（inflammatory bowel disease, IBD）是一种发生在胃肠道的慢性非特异性炎症性疾病，主要包括克罗恩病（Crohn’s disease, CD）和溃疡性结肠炎（ulcerative colitis, UC）两种临床类型，目前发病机制尚不十分清楚。许多miRNA在IBD患者肠黏膜组织中表达异常，诱导局部肠黏膜免疫功能失调，与IBD发生发展密切相关。. 本研究使用qRT-PCR方法证实miR-219a-5p在IBD患者炎症肠粘膜组织和外周血CD4+ T细胞中表达显着降低。促炎细胞因子（例如IL-6，IL-12，IL-23和TNF-α）在体外抑制CD4+ T细胞中miR-219a-5p表达，是miR-219a-5p在IBD中表达降低的重要因素。慢病毒介导的miR-219a-5p下调促进CD4+ T细胞向Th1/Th17细胞的分化，而miR-219a-5p过表达则抑制Th1/Th17细胞分化。萤光素酶报告基因实验证实ETV5是miR-219a-5p的靶基因，其表达水平在IBD患者炎症肠粘膜和外周血CD4+ T细胞中表达显著增加。ETV5通过激活STAT3和STAT4磷酸化水平促进Th1/Th17免疫反应。外源性补充miR-219a-5p可改善TNBS诱导的小鼠肠粘膜炎症反应，其特点是TNBS诱导的小鼠肠粘膜固有层中IFN-γ+ CD4+ T细胞和IL-17A+ CD4+ T细胞的浸润减少，炎症因子表达水平显著降低。. 综上所述，本研究证实miR-219a-5p通过调控ETV5抑制Th1/Th17介导的IBD肠粘膜炎症反应，为IBD发病机制研究以及临床诊断、治疗提供新的理论基础和分子靶点，补充外源性miR-219a-5p可能是治疗IBD的有用方法。