Institute of Digestive Disease, Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, CUHK Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong SAR.
Institute of Liver Disease, The Seventh Medical Centre of PLA General Hospital, Beijing, PR China.
J Pathol. 2019 Aug;248(4):488-500. doi: 10.1002/path.5275. Epub 2019 May 7.
The role of macrophages in fibrosing steatohepatitis is largely unclear. We characterized the origin and molecular mechanisms of macrophages and its targeted therapy of fibrosing steatohepatitis. Fibrosing steatohepatitis was established in Alms1 mutant (foz/foz) and C57BL/6J wildtype mice fed high-fat/high-cholesterol or methionine- and choline-deficient diet. Bone marrow transplantation was performed to track the macrophage origin in fibrosing steatohepatitis. Macrophages were depleted using liposomal clodronate. Primary macrophages were isolated from bone marrow for adoptive transfer into mice. We found that macrophage infiltration is induced in two mouse models of fibrosing steatohepatitis and human nonalcoholic steatohepatitis-fibrosis patients. Bone marrow-derived macrophages (BMMs) contribute to the hepatic macrophage accumulation in experimental fibrosing steatohepatitis. Depletion of hepatic BMMs by liposomal clodronate during liver injury attenuated fibrosing steatohepatitis, whilst BMMs depletion after liver injury delayed the regression of fibrosing steatohepatitis. The pro-fibrotic effect of macrophages was associated with reduced activation of hepatic stellate cells (HSCs), collagen deposition and hepatic expression of key pro-fibrotic factors (TIMP1, TIMP2, and TGFβ1) and endoplasmic reticulum stress markers (GRP78, IRE1α, and PDI). Conversely, adoptive transfer of BMMs significantly aggravated fibrosing steatohepatitis. Moreover, macrophage-conditioned medium directly promoted the phenotypic transition of primary quiescent HSCs to activated HSCs; it enhanced activation and proliferation but decreased apoptosis of HSC cell lines (LX-2 and HSC-T6). The effect of BMMs in promoting fibrosing steatohepatitis was mediated by inducing key pro-fibrosis factors and signaling pathways including cytokine/chemokine, TGFβ and complement cascade as assessed by cDNA expression array. Complement 3a receptor (C3ar1) was a predominant effector of macrophage mediated fibrosing steatohepatitis. Knockout of C3ar1 in mice blunted development of fibrosing steatohepatitis. In conclusion, BMMs promoted the progression of fibrosing steatohepatitis during injury, whereas macrophages reduced fibrosing steatohepatitis in the recovery phase of liver injury. Increasing anti-fibrotic macrophages and decreasing pro-fibrotic macrophages are promising approaches for fibrosing steatohepatitis. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
巨噬细胞在纤维性脂肪性肝炎中的作用在很大程度上尚不清楚。我们描述了巨噬细胞的起源和分子机制及其靶向纤维性脂肪性肝炎的治疗方法。在高脂肪/高胆固醇或蛋氨酸和胆碱缺乏饮食喂养的 Alms1 突变（foz/foz）和 C57BL/6J 野生型小鼠中建立纤维性脂肪性肝炎。进行骨髓移植以追踪纤维性脂肪性肝炎中巨噬细胞的起源。使用脂质体氯膦酸盐耗竭巨噬细胞。从骨髓中分离原代巨噬细胞进行过继转移到小鼠中。我们发现，两种纤维性脂肪性肝炎的小鼠模型和非酒精性脂肪性肝炎纤维化患者中均诱导了巨噬细胞浸润。骨髓来源的巨噬细胞（BMM）有助于实验性纤维性脂肪性肝炎中肝巨噬细胞的积累。在肝损伤期间，用脂质体氯膦酸盐耗竭肝 BMMs 可减轻纤维性脂肪性肝炎，而在肝损伤后耗竭 BMMs 则延迟纤维性脂肪性肝炎的消退。巨噬细胞的促纤维化作用与肝星状细胞（HSCs）的活化减少、胶原沉积以及肝表达关键促纤维化因子（TIMP1、TIMP2 和 TGFβ1）和内质网应激标志物（GRP78、IRE1α 和 PDI）有关。相反，BMM 的过继转移显著加重了纤维性脂肪性肝炎。此外，BMM 条件培养基直接促进原代静止 HSCs 向活化 HSCs 的表型转变；它增强了 HSC 细胞系（LX-2 和 HSC-T6）的活化和增殖，但降低了其凋亡。通过 cDNA 表达谱评估，BMMs 通过诱导关键的促纤维化因子和信号通路（包括细胞因子/趋化因子、TGFβ 和补体级联）在促进纤维性脂肪性肝炎中发挥作用。补体 3a 受体（C3ar1）是巨噬细胞介导的纤维性脂肪性肝炎的主要效应因子。在小鼠中敲除 C3ar1 可减弱纤维性脂肪性肝炎的发展。总之，BMM 在损伤期间促进纤维性脂肪性肝炎的进展，而巨噬细胞在肝损伤的恢复阶段减少纤维性脂肪性肝炎。增加抗纤维化巨噬细胞和减少促纤维化巨噬细胞是治疗纤维性脂肪性肝炎的有前途的方法。
