类风湿关节炎微环境成纤维滑膜细胞表达共刺激分子ICOSL对Tfh细胞亚群分化和免疫病理损伤的作用机制

Inducible costimulator (ICOS) signal play important role in regulating immune response and autoimmunity. In our previous work, we found ICOS ligand (ICOSL) were upregulated in peripheral blood and in inflammatory synovium of rheumatoid arthritis patients and CIA mice, which were finely correlated with the progression and prognosis of arthritis. And we found the ICOSL protein were upregulated in fibroblast-like synoviocytes of inflammatory tissue either. However, its biological significance is still unknown and need to be further investigated. In this proposed research project, we intend to perform the following experiments to explore the role of ICOSL signal in the pathogenesis of rheumatoid arthritis and mechanisms involved by combining with clinical and animal experimental study: (1) ICOSL modulate the biological capacity of rheumatoid arthritis fibroblast-like synoviocytes. (2) Inflammatory cytokines stabilize ICOSL to mediate the transformation of fibroblast-like synoviocytes in arthritic disease. (3) The impact of ICOSL signal on autoantibody production by regulation expression of T follicular helper (Tfh) cells. (4) The impact of ICOSL signal on tissue damage by regulation expression of autoreactive T cells. In summary, interventions with these signals may contribute to immune homeostasis and offer potentially promising approach for the treatment of rheumatoid arthritis.

正性共刺激分子ICOS/ICOSL是参与免疫应答和自身免疫病理的重要的免疫分子。我们前期研究发现类风湿关节炎（RA）及CIA小鼠外周免疫细胞和关节微环境ICOS/ICOSL分子呈上调表达，且与免疫病理进程密切相关，体外干预该信号可以显著缓解关节炎症。同时我们发现RA炎性微环境滑膜成纤维细胞（FLS）上调表达ICOSL，但其作用机制尚不清楚。鉴此，本项目以RA和CIA为研究对象，从ICOSL信号对滑膜成纤维细胞功能的调节和对Tfh细胞分化介导组织损伤相互作用切入，展开以下研究：（1）ICOSL调控FLS生物学功能的分子机制；（2）炎性微环境FLS中ICOSL表达上调的调控机制；（3）ICOSL信号介导FLS通过调控炎性微环境异位淋巴结Tfh细胞分化促进自身抗体产生的作用和机制；（4）ICOSL信号促进自身反应T细胞活化的作用和机制。从而为针对该分子为靶点的免疫治疗提供实验依据。

类风湿关节炎(RA)是一种重要的自身免疫性疾病，滑膜炎性微环境中 Tfh 细胞异常活化介导的自身抗体产生在 RA 发病过程中发挥重要作用。RA成纤维样滑膜细胞( Fibroblast-like synoviocyte，FLS)在其中起着重要的作用。RAFLS表面ICOSL的表达及对RA免疫病理的作用未见报道。本项目以表达 ICOSL 的滑膜成纤维细胞与 Tfh 相互作用为切入点，围绕 RA 关节滑膜炎性浸润和自身抗体产生的关键环节，从分子水平、细胞水平、动物水平、RA 患者等层面通过体内外实验，研究发现：(1)类风湿关节炎患者炎性微环境滑膜成纤维细胞(RAFLS)表面ICOSL表达上调，ICOSL信号可以通过促进RAFLS增殖、侵袭迁移和分泌细胞因子。ICOSL分子主要调控RAFLS受体配体相关信号通路、蛋白骨架信号通路、代谢相关信号通路从而影响RAFLS的生物学功能。（2）RAFLS表面ICOSL表达受RA炎性微环境调控，关节腔滑膜积液可以显著促进ICOSL的表达，促进RAFLS粘附、趋化淋巴细胞、中性粒细胞相关功能、促进RAFLS对炎症因子、生长因子等结合能力从而重塑RA炎性微环境。（3）类风湿关节炎患者和CIA小鼠B淋巴细胞表面ICOSL上调表达并与临床病理特点和疗效密切相关， CD19+ICOSL+B淋巴细胞过继转移可以促进CIA小鼠关节炎进展，提示这群B细胞可被视作RA诊断和预后判断的新临床免疫指标。（4）ICOSL阻断抗体干预可以显著抑制关节炎病理进程， 通过靶向抑制小鼠脾脏GC、PC、Tfh细胞亚群，抑制IFN-γ、IL-4和IL-17等细胞因子分泌缓解疾病进程。提示ICOSL作为干预靶点具有潜在应用价值。本项目为选择新的类风湿关节炎治疗靶点提供了实验依据，为RA的免疫治疗拓展新的途径。