补体活化/IL-21双向调控血小板生成稳态在ITP发病机制中作用

Immune thrombocytopenia (ITP) is an acquired autoimmune hemorrhagic disease. Enhanced complement activation has long been considered as one of the major pathogenesis of ITP. Bone marrow mesenchymal stem cells (MSCs) are multipotent stromal cells with multi-differentiation capacities, hematopoiesis support and immunomodulatory effects. Our previous study confirmed that enhanced complement activation could induce apoptosis and dysfunction of MSCs in ITP and consequently dynamic changed in niche CXCL12 and alternations in the location of megakaryocytes in the thrombopoietic niche in bone marrow. The results strongly indicated that enhanced complement activation in the bone marrow niche of ITP play a role in pathogenesis of ITP by influencing platelet formation. However, the roles of complement system in the maturity and differentiation of megakaryocytes, or in peripheral platelet destruction remain poorly understood. Therefore, this study aims to explore the mechanism of circ100284-miR217 induced deficient MSCs by regulating complement activation in ITP, clarify the bi-directional regulation effects of CD4+CD45RO+ T cell subsets and IL-21 expression on platelet homeostasis, provide potential targets and strategies for the prevention and treatment of ITP.

免疫性血小板减少症（ITP）是一种获得性的自身免疫性出血性疾病，补体活化是其重要发病机制之一。骨髓间充质干细胞（MSCs）是一种多能干细胞，其具有多向分化潜能、造血支持和免疫调控等功能。申请者在前期研究证实，补体活化介导MSCs凋亡增加、免疫调控异常，破坏骨髓微环境CXCL12浓度梯度，导致巨核细胞在血管微环境分布减少，强烈提示：ITP骨髓微环境补体异常活化通过影响血小板生成参与发病，但其对巨核细胞的成熟、分化及外周血小板破坏的作用机制尚缺乏研究。因此本课题拟通过体内外研究，探讨circ100284-miR217参与ITP补体异常活化介导MSCs功能损伤机制，阐明CD4+CD45RO+ T细胞亚群及相关细胞因子白介素21表达异常，对血小板生成稳态双向调控，为ITP防治提供潜在新靶点和新策略。

免疫性血小板减少症（ITP）是一种获得性的自身免疫性出血性疾病，补体活化是其重要发病机制之一。本课题在前期工作基础上，进一步论证ITP 骨髓微环境补体活化，探究MSCs功能损伤的分子调控机制；揭示补体活化介导受损MSCs对T淋巴细胞亚群比例及功能调控异常，导致骨髓微环境IL-21分泌失衡；进一步阐明ITP骨髓微环境补体活化，IL-21异常高表达影响巨核细胞成熟、分化的病理机制；初步阐明ITP MSCs高表达circ100284，诱导其对C5b-9沉积介导的细胞毒性增加，引起下游IL-21 异常高表达对巨核细胞和血小板的双向调控作用及机制。同时，本研究首次发现ITP补体阳性组MSCs NLRP3炎症小体相关基因表达升高，IL-1β和IL-18分泌增多，表明NLRP3炎症小体活化，诱导MSCs发生细胞焦亡。转录组测序揭示MSCs-ITP-C+脂肪酸代谢异常，活化NLRP3炎症小体，从而导致MSCs焦亡。骨髓微环境MSCs-ITP-C+来源的脂肪细胞分泌脂联素下降，脂联素体外促进ITP巨核细胞表达脂联素受体，以及巨核细胞分化成熟；ITP小鼠模型研究表明，脂联素增加骨髓巨核系前体细胞；并验证脂联素具有抗炎作用，调控脾脏巨噬细胞极化，减少M1型巨噬细胞，M2型巨噬细胞数量增多，从而减轻ITP脾脏血小板滞留和破坏。他克莫司体外干预MSCs-ITP-C+，发现抑制NLRP3炎症小体活化和MSCs-C+焦亡。随机对照临床研究表明，以他克莫司为主的治疗方案显著提高初治ITP患者6个月持续缓解率，患者均耐受良好，为ITP防治提供潜在新靶点和新策略。