MicroRNA-425对炎症性肠病Th17和Treg细胞增殖分化的免疫调节作用

Crohn’s disease (CD) and ulcerative colitis (UC), are two major types of inflammatory bowel diseases (IBD), which is well known as a chronic inflammatory disorder of the gastrointestinal tract. Dysregulated immune responses in intestinal mucosa toward commensal microbiota, impaired mucosal barrier, genetic and environmental factors may contribute to the pathogenesis of human IBD. MicroRNAs (miR) are a group of small, non-coding RNAs (approximately 18-22 nucleotides), which are able to posttranscriptionally modulate gene expression by binding to the 3'-untranslated region of target mRNAs, resulting in mRNA degradation or translational inhibition. It has been well reported that miR play a crucial role in many autoimmune diseases, including IBD. Our microarray data have shown that miR-425 was significantly increased in the inflamed mucosa tissues of patients with IBD. Additionally, our preliminary experiments have shown that miR-425 was also markedly increased in peripheral blood mononuclear cells (PBMC) of IBD patients. We also found that Th17 cells exhibited high level of miR-425 expression, which was found to be much lower in Treg cells. Thus, miR-425 is supposed to be involved in the regulation of Th17/Treg balance, and the development of in intestinal inflammation, particularly in human IBD. In this study, we will study the expression of miR-425 in the PBMC and inflamed mucosa of IBD patients. We will also investigate the potential role of miR-425 in regulating Th17 cell immune responses and Treg function in intestinal mucosa, and attempt to determine the potential target genes of miR-425. Acute and chronic colitis in mice will be indcued and administrated through blockage of miR-425 with antisense in vivo to investigate whether it could alleviate intestinal inflammation. This work will demonstrate the function of miR-425 in the regulation of IBD development, and provide an novel theoretical basis for IBD immune therapy.

炎症性肠病（IBD）是一种胃肠道的慢性非特异性炎症性疾病，其发病机制尚不完全明确，可能与肠黏膜免疫调节异常、遗传和环境等因素有关。microRNA（miR）是一类非编码的小分子RNA，通过结合靶基因的3’-UTR端，调控其表达。研究发现miR在多种自身免疫性疾病中发挥了重要的调节作用。我们前期通过基因芯片检测发现miR-425在IBD患者肠黏膜内表达升高，并发现Th17细胞显著高表达miR-425，而抑制调节性T细胞（Treg）内其表达水平较低，据此提出miR-425可能参与调节肠粘膜内Th17/Treg动态平衡，促进肠道炎症发生。本课题着重探索miR-425对IBD肠黏膜组织Th17、Treg细胞免疫调节效应，阐明miR-425在IBD发生过程的免疫调控作用。建立小鼠结肠炎模型，体内靶向阻断miR-425应答，观察肠黏膜炎症变化，为IBD病理机制研究及临床上靶向生物治疗提供新的思路。

炎症性肠病（IBD）是一种胃肠道的慢性非特异性炎症性疾病，其发病机制虽尚不完全明确，但肠黏膜免疫调节异常被认为是发病的中心环节。我们收集了IBD患者及健康对照者（HC）外周血单个核细胞（PBMC）及肠黏膜组织，qRT-PCR发现IBD患者PBMC与肠黏膜组织中miR-425表达较HC显著上调。无论外周血细胞或肠黏膜细胞，CD4+ T细胞均是miR-425表达的主要来源之一，其中Th17细胞表达miR-425水平显著高于较其他亚型。我们使用表达miR-425的lentivirus（LV-miR-425）转染T细胞，并诱导分化为Th17后，发现miR-425过表达显著上调Th17分化及致病因子表达，提示miR-425能够促进致病性Th17的分化。经数据库分析以及荧光素酶报告基因分析；发现Foxo1是miR-425全新的靶基因，并在IBD患者外周血及肠黏膜样本中发现Foxo1表达明显下降。此外，我们构建了以lentivirus为载体的siRNA，借此抑制CD4+ T细胞中Foxo1表达后，CD4+ T细胞向Th17分化以及致病因子表达显著上调。不仅如此，我们建立了小鼠结肠炎模型，当小鼠结肠miR-425被抑制后，结肠炎症明显减轻，结肠Th17细胞数量减少。基于以上，我们证实了miR-425可能通过靶向抑制Foxo1，上调肠黏膜内致病性Th17分化以及其介导的免疫病理损伤应答过程，由此促进肠道炎症的发生发展。通过这些工作，为IBD发病机制的研究提供新的思路，并为临床上靶向生物治疗提供了新的理论依据。

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