巨噬细胞极化诱导肾微血管周细胞转分化在移植肾间质纤维化形成中的作用及机制研究

Allograft interstitial fibrosis has been considered as the crucial cause leading to the chronic allograft dysfunction (CAD), while the accumulation of myofibroblasts contributed mainly to the pathogenesis of interstitial fibrosis. However, the origin and its related mechanism still remain unclear. Our previous studies have observed the remarkable polarization of macrophages into M2 subtype in the area of allograft interstitial fibrosis, which may be interpreted by activation of β-catenin in the nuclear of M2 macrophages; while the pivotal role of renal microvascular pericyte-to-myofibroblast (PMT) in the renal allograft tissues of recipients with CAD was also suggested. Moreover, we also observed the potential crosstalk between macrophages and renal macrovascular pericytes in vitro study. Accordingly, we put forward the hypothesis that, the polarization of macrophages into M2 subtype mediated by β-catenin may promote the pathogenesis of renal microvascular PMT, subsequently accelerated the progression of renal allograft interstitial fibrosis and CAD following kidney transplantation. To verify the hypothesis, we established the cell model and allogenic mice renal interstitial fibrosis model, as well as the conditional β-catenin knockout mice, to extensively explore the influence and mechanism of polarization of macrophages into M2 subtype promoted by the activation of β-catenin on the renal microvascular PMT and afterwards, to investigate the impact on the renal allograft interstitial fibrosis and CAD pathogenesis. The expected results will contribute to the intervention and prevention measures of renal allograft interstitial fibrosis and CAD targeting the polarization of macrophages.

移植肾间质纤维化是慢性移植肾失功（CAD）的重要病因，而肌成纤维细胞聚集是其关键机制，但其来源尚不明确。申请人在CAD患者移植肾中观察到显著的M2巨噬细胞极化，且β-catenin在核内明显活化；且肾微血管周细胞向肌成纤维细胞转分化（PMT）过程可能在CAD中发挥重要作用；体外研究还发现巨噬细胞可能与肾微血管周细胞间存在交联作用。据此，申请人提出假说：β-catenin活化介导的M2巨噬细胞极化可诱导肾微血管PMT过程，进而促进移植肾间质纤维化的形成和CAD的进展。为验证上述假说，本课题拟通过细胞实验、选择性巨噬细胞β-catenin基因敲除小鼠及同种异体小鼠肾移植慢排模型，深入探讨M2巨噬细胞对肾微血管PMT的影响，进而探究其对移植肾间质纤维化形成和CAD的作用。本研究预期成果将为以巨噬细胞极化为靶点，研究CAD的防治措施提供坚实的实验基础。

移植肾间质纤维化形成的主要病理特点是细胞外基质产生过多，并在移植肾间质中过度沉积。本研究团队的前期工作基础提示巨噬细胞极化和周细胞-肌成纤维细胞转分化（PMT）过程可能在移植肾间质纤维化形成中发挥重要作用。为探讨PMT及巨噬细胞极化在移植肾间质纤维化形成中的作用及相关机制，本研究团队通过构建同种异体小鼠肾移植慢排模型、人体组织、生物信息学、细胞实验等多种方法深入探究上述问题。总结本研究成果，我们得到以下结论：移植肾间质纤维化形成过程中存在显著的PMT过程。PMT过程可能显著促进了移植肾间质纤维化的形成，且这一作用与Hippo/YAP通路被激活有关；移植肾间质纤维化形成过程中存在明显的M1型和M2型巨噬细胞极化过程，并可能参与了间质纤维化的形成；M1型巨噬细胞极化可能通过分泌包含Prdx1的外泌体，诱导血管周细胞发生PMT过程，进而促进了移植肾间质纤维化形成，相反，M2型巨噬细胞极化对PMT过程无明显作用；M1型巨噬细胞极化可能与β-catenin信号通路有关。本研究成果不仅为研究移植肾间质纤维化形成的机制研究提供新线索，更为以M1型巨噬细胞极化为靶点探讨移植肾间质纤维化形成的临床防治方法奠定理论基础。