MSCs外泌体通过STING信号通路调控巨噬细胞极化在治疗NASH中的作用及机制研究

Inflammation and immune response play important roles in the pathogenesis of nonalcoholic steatohepatitis (NASH). Our preliminary data indicated that treatment of NASH mice with mesenchymal stem cells (MSCs) exosome reduced liver inflammation and adipogenesis, decreased the expression level of stimulator of interferon genes (STING), a key immunomodulatory factor, and changed the macrophage polarization. The underlying mechanisms remain to be explored. Firstly, to understand the role of macrophage polarization in the treatment of NASH, we aimed to investigate the effect of macrophage polarization on the treatment of NASH with MSCs exosome by clearing macrophages and inhibiting their polarization. Secondly, the STING inhibitor, CRISPR-CAS9 gene knockout cell model and gene knockout mice will be applied to explore the effect of inhibiting STING signaling pathway on the treatment of NASH and to clarify whether the MSCs exosome regulated macrophage polarization through STING signaling pathway. Thirdly, we planned to investigate whether MSCs exosome could regulate the STING signal pathway through its miRNA to influence the macrophage polarization and play a therapeutic role by overexpressing or inhibiting expression of miR-24-3p in MSCs exosome. This study is helpful to clarify the mechanism of MSCs exosome therapy for NASH, and provide a new strategy for clinical application.

炎症与免疫应答在非酒精性脂肪性肝炎（NASH）致病过程中有重要作用。我们前期发现，间充质干细胞（MSCs）外泌体处理NASH小鼠后，其肝脏炎症及脂肪变减轻，并伴免疫调节关键因子干扰素基因刺激蛋白（STING）表达下调，巨噬细胞极化改变；提示MSCs外泌体可能通过STING信号通路影响巨噬细胞极化从而发挥作用，但具体机制尚待研究。我们拟通过观察清除巨噬细胞和抑制其极化后对MSCs外泌体治疗NASH的影响，了解巨噬细胞极化在外泌体治疗NASH中的作用；利用通路抑制剂，CRISPR-Cas9基因敲除细胞模型及基因敲除小鼠，观察阻断STING信号通路对外泌体治疗NASH的影响，研究外泌体是否经STING通路调控巨噬细胞极化；采用过表达或干扰前期初步筛选得到的miR-24-3p，研究外泌体是否通过miRNA调控STING信号通路影响巨噬细胞极化从而发挥治疗作用。本研究旨在为NASH治疗提供新思路。

炎症与免疫应答NASH的发生发展过程中有重要作用。既往研究提示，调控巨噬细胞的极性分化可能成为调节肝脏炎症、治疗NASH的重要手段。间充质干细胞（Mesenchymal stem cells，MSCs）是一类具有高度自我更新能力和多向分化潜能的干细胞，MSCs外泌体可参与调节糖脂代谢，改善胰岛素抵抗。我们前期研究发现，MSCs外泌体可减轻NASH小鼠的脂肪肝程度，但是其机理尚不清楚。本课题研究提示1.MSCs外泌体减轻小鼠脂肪肝，改善NASH小鼠的血糖及胰岛素水平，减少内脏脂肪，缓解脂肪肝。2.免疫信号通路紊乱是NASH发病机制中的重要因素;巨噬细胞在NASH肝组织中分布数量增多,是NASH发生过程中的重要免疫调控细胞。3.巨噬细胞是MSCs外泌体缓解NASH小鼠脂肪肝的重要功能细胞。4.MSCs外泌体促进巨噬细胞发生M2极化，其潜在机制可能是下调STING信号通路。本项目有助于阐明MSCs外泌体治疗NASH的作用机理，具有重要的科学价值与临床意义。