CD11c(high)MHC-II+树突状细胞在牙周炎症微环境中对Treg/Th17细胞分化的作用及机制研究

The immune mechanism of inflammation is a hot topic in research field on periodontal disease. Dendritic cells, which perform as immune antigen presentation, play an important biological role in many process of the human immune response. CD4+ T helper cells can differentiate into distinct subsets, including Regulatory T (Treg) and Th17 accompanied with specific effective cytokines production. Treg cell subsets are specialized CD4+ T cells that function to maintain self-tolerance and immune homeostasis by secreting specific cytokines TGF-β. While Th17 subset recently discovered, mainly marked by producing IL-17 family cytokines. In periodontal inflammatory microenvironment, the CD11c(high)MHC-II+ dendritic cells may regulate CD4+T lymphocyte differentiating into Treg/Th17 cells, under certain immune response and cytokine cocktail in periodontitis. The applicant's previous study of periodontitis patients showed, as strong antigen-presenting cells dendritic cells can significantly produce cytokines increased IL-6, MHC, and decreased TGF-β, indicating the dendritic cells may play an important role on CD4+T lymphocytes to Treg/Th17 cell differentiation in network of periodontal inflammatory microenvironment. However, in progress of chronic periodontitis, the interaction and possible regulatory mechanism of CD11c(high)MHC-II+ dendritic cells to Treg/Th17 have not yet be clearly elucidated. This project intends to use the mouse periodontitis model, further studying the abnormal expression of mouse derived CD11c(high)MHC-II+ dendritic cells in periodontal inflammation, and to explore the molecular mechanisms underlying its regulation on Treg/Th17 differentiation, and clarify its role and value as potential therapeutic targets. The implementation of this project will not only add new insights to the development of dendritic cells in regulating inflammatory diseases, but also provide new ideas for the prevention and treatment of periodontal disease.

免疫炎症机制是牙周炎研究热点，树突状细胞在牙周炎症免疫应答各环节发挥重要作用。申请者前期研究发现，牙周炎患者外周血树突状细胞数量增多，MHC-II表达增强，分泌IL-6增多，而TGF-β减少，同时CD4+T淋巴细胞向Th17方向分化增多而Treg比例下降，提示树突状细胞可能参与调控CD4+T淋巴细胞向Treg/Th17分化，但机制尚不明确。本项目拟研究：(1) CD11c(high)MHC-II+树突状细胞体外生物学功能及其对Treg/Th17细胞分化调控作用；(2) CD11c(high)MHC-II+树突状细胞调控Treg/Th17细胞分化的胞外细胞因子途径及胞内信号通路；(3)构建C57BL/6小鼠牙周炎模型，验证CD11c(high)MHC-II+树突状细胞体内调控Treg/Th17细胞分化的分子机制。研究结果将为明确树突状细胞作为牙周炎治疗靶标的可行性，为牙周炎症防治提供新思路。

免疫炎症机制是牙周炎的研究热点，树突状细胞在牙周炎症免疫应答各环节发挥重要作用。申请者前期研究发现，牙周炎患者外周血中树突状细胞数量增多， MHC-II表达增强，同时CD4+T淋巴细胞向Th17方向分化增多，而Treg细胞比例下降，提示树突状细胞可能参与调控CD4+T淋巴细胞向Treg/Th17分化，本课题按照原定计划开展了如下实验，顺利完成了预定目标。（1）研究发现了活化的强抗原递呈树突状细胞在牙周炎中的表达和分布，CD4+T淋巴细胞高表达IL-6、MHC-II等炎性因子，同时下调TGF-β因子表达，牙龈固有层中发现了增高的标记为 CD11c和MHC-II树突状细胞。牙周炎牙龈组织中MHC-II和CD11c的表达水平也高于正常对照组织。（2）对树突状细胞和CD4+T淋巴细胞共培养后发现CD4+T淋巴细胞向Th17细胞方向分化，而Treg细胞比例下降，提示树突状细胞可能通过调控Th17/Treg淋巴细胞及其特异性因子的分泌进而参与牙周炎症的发生发展。（3）通过构建牙周炎小鼠动物模型，体内实验进一步发现，CD11c+MHC-II+ 树突状细胞可以显著增加结扎诱导的牙周炎小鼠牙周组织局部破骨细胞数量。并且CD11c+MHC-II+ 树突状细胞注射组可进一步促进牙周炎症这个过程，骨吸收速度大于单纯牙周炎症组。另一方面，阿司匹林作为预防骨质疏松的药物，可以有效通过NF-κB/NFATc1途径抑制牙周炎症微环境下，树突状细胞向破骨细胞方向分化。综上结果提示CD11c+MHC-II+树突状细胞作为抗原呈递并活化调控Th17/Treg细胞，其介导的细胞免疫应答是机体免疫应答的重要组成部分，与牙周炎症的发生和发展密切相关。