骨髓来源巨噬细胞向肌成纤维细胞转分化：腹膜透析相关性腹膜纤维化的新机制

Peritoneal dialysis (PD)-associated peritoneal fibrosis is closely related to peritoneal inflammation, yet the underlying mechanism has not been fully clarified. Macrophages are the main effector cell type of peritoneal inflammation, with high plasticity. Recent studies have shown that macrophages can directly undergo transition into myofibroblasts (Macrophage-myofibroblast transition, MMT) under certain physiological and pathological state. Our preliminary work found that α-smooth muscle actin (α-SMA)+ myofibroblasts are co-expressing CD68 macrophage antigen in the fibrotic peritoneum, indicating that the MMT process may participate in the pathogenesis of peritoneal fibrosis. The hypothesis will be tested in this study. Firstly, peritoneal samples will be collected from PD patients and experimental PD model at various stages of the disease to identify the MMT phenomenon by immunostaining. Secondly, a myeloid cell genetically labeled mouse strain will be constructed to further characterize the MMT process, including the exact proportion and changes in secretory functions. Lastly, we will explore the regulatory mechanisms of MMT by TGF-β/Smads signaling pathway in vitro. Our study will help to elucidate the mechanisms by which peritoneal inflammation induces peritoneal fibrosis and will contribute to the understanding of the origins of myofibroblasts, thus may have clinical implications for prevention and treatment of PD-associated peritoneal fibrosis.

腹膜透析相关性腹膜纤维化的发生与腹膜炎症密切相关，但具体机制尚未完全阐明。巨噬细胞是腹膜炎症的主要效应细胞类型，具有高度可塑性。近期研究发现在某些生理病理状态下巨噬细胞可直接转分化为肌成纤维细胞(Macrophage-myofibroblast transition, MMT），我们前期工作发现腹膜组织中肌成纤维细胞可共表达巨噬细胞标志物，提示MMT过程可能也参与腹膜纤维化的发病机制。本课题拟收集处于疾病不同阶段的腹膜透析患者及动物模型的腹膜组织标本，通过免疫染色证实MMT过程在腹膜纤维化中的存在；随后，利用髓系细胞遗传标记小鼠进行巨噬细胞示踪实验，进一步证实MMT过程，明确其比例及功能变化；最后，将在体外实验探讨TGF-β/Smads信号通路对MMT过程的调控作用。本研究将有助于阐明腹膜炎症导致腹膜纤维化的机制及明确肌成纤维细胞的来源，从而为腹膜透析相关性腹膜纤维化的防治提供新思路。

腹膜纤维化的发生与腹膜炎症密切相关，巨噬细胞是腹膜炎症的主要效应细胞类型。既往研究发现在其他器官系统中巨噬细胞可通过转分化为肌成纤维细胞(Macrophage-myofibroblast transition, MMT）参与纤维化发生，本研究拟通过在临床患者腹膜活检标本、动物模型、体外细胞实验中验证在腹膜纤维化中的MMT现象并探讨其作用及发生机制。我们首先收集了我中心腹膜透析拔管患者腹膜活检标本进行巨噬细胞标志物CD68和肌成纤维细胞标志物α-SMA共定位染色，发现CD68+α-SMA+细胞占α-SMA+肌成纤维细胞的比例约为5%，证实在人腹膜纤维化标本中存在MMT现象；随后，我们利用LysM-Cre/Rosa26tdTomato小鼠构建腹膜纤维化模型进行骨髓来源巨噬细胞示踪实验，发现约10%α-SMA+肌成纤维细胞共表达骨髓来源标记巨噬细胞标志物CD68/Tomato，证实在腹膜纤维化动物模型中同样存在MMT现象，并提示可发生分化的巨噬细胞为骨髓来源；最后，利用Smad3敲除小鼠构建腹膜纤维化模型发现CD68+α-SMA+转分化细胞比例较野生型小鼠显著降低，提示TGF-β1/Smad3信号介导腹膜纤维化MMT现象的发生。本研究证实了MMT现象参与腹膜纤维化发生的新机制，将为腹透相关性腹膜纤维化的防治提供新思路。