Notch信号调控骨髓来源巨噬细胞ly6Chigh向ly6Clow亚群转变在肝损伤修复中的作用及机制研究

According to their origin and function, hepatic macrophages can be classified into different subsets, which exert very complicate roles during the liver injury and repair. Bone marrow-derived macrophages (BMDMs) can be divided further into two subsets based on their differential expression of ly6C. Ly6Chigh BMDMs exhibit a pro-inflammatory and tissue-damaging phenotype, in contrast, ly6Clow BMDMs show an anti-inflammatory and tissue-protective phenotype. Moreover, ly6Chigh BMDMs can switch to ly6Clow BMDMs during the liver injury and repair. At the previous work, We found that macropahge-specific RBP-J depletion lead to increase of the ratio and the number of ly6Clow BMDMs in murine fibrotic liver and liver regeneration after PHx. On the basis of the preliminary work, this project intents to clarify the role of Notch signaling in the ly6Chigh to ly6Clow Bone marrow-derived macrophages transition, though employing macropahge-specific RBP-J knockout mice combined cell depletion, adoptive transfer and parabiosis. Our study will provide potential molecular targets for the regulation of different macrophage subsets in the treatment of liver disease, and is of great significance.

在肝损伤修复中，巨噬细胞根据其起源和功能可以分为不同亚群，发挥不同的功能。骨髓来源巨噬细胞可以进一步分为ly6Chigh和ly6Clow两个不同功能状态的亚群，ly6Chigh巨噬细胞表现为促损伤作用，而ly6Clow巨噬细胞由ly6Chigh巨噬细胞转变而来，表现为促修复作用。申请者前期研究发现巨噬细胞特异Notch阻断促进肝纤维化和肝切后再生中肝脏巨噬细胞ly6Clow巨噬细胞亚群比例和数量的增加。本项目拟在前期研究的基础上，利用巨噬细胞特异性RBP-J基因敲除小鼠以及细胞清除、过继移植、联体共生等多种实验方法，明确Notch信号对骨髓来源巨噬细胞ly6C亚群转变的调控及其对肝损伤修复的影响。本项目将为干预肝脏巨噬细胞亚群治疗肝损伤促进肝再生提供新的靶点，具有重要意义。

在肝损伤修复中，巨噬细胞根据其起源和功能可以分为不同亚群，发挥不同的功能。骨髓来源巨噬细胞可以进一步分ly6Chigh和ly6Clow两个不同功能状态的亚群，ly6Chi巨噬细胞表现为促炎促损伤作用，而ly6Clo巨噬细胞由ly6Chi巨噬细胞转变而来，表现为促修复作用。本项目在前期研究的基础上，利用髓系细胞特异性RBP-J基因敲除和（或）Notch信号激活小鼠四氯化碳肝损伤纤维化模型和标准2/3肝切除模型，探索了Notch信号对骨髓来源巨噬细胞ly6C亚群转变的调控机制及其对肝损伤修复再生的影响。研究结果表明，1. 在肝切后再生过程中，不同起源及不同功能巨噬细胞亚群的数量显著变化，ly6Chi和ly6Clo巨噬细胞亚群分别在促进肝细胞增殖和血管内皮细胞增殖重塑中发挥重要作用；2.髓系RBP-J敲除不影响肝切后再生整体进程，但促进骨髓来源巨噬细胞ly6Chi促炎表型向ly6Clo促修复表型转变，该过程虽然不影响肝再生中肝细胞增殖，却促进血管内皮细胞增殖；3.髓系Notch信号的敲除/激活，促进/抑制骨髓来源巨噬细胞从促炎型ly6Chi向促修复型ly6Clo亚群转变，进而减轻/加重胶原沉积，影响肝纤维化进程，进一步分子机制的研究表明，Notch信号可通过下游Hes1与CCAAT增强子结合蛋白α（CCAAT/enhancer binding protein α, C/EBPα）基因转录起始位点上游位点相结合，抑制C/EBPα的表达，进而抑制骨髓来源巨噬细胞从ly6Chi向ly6Clo的表型转变。填补了相关理论空白，为靶向肝脏巨噬细胞亚群治疗肝损伤促进肝再生提供新的靶点。