SIRPα介导的巨噬细胞功能调控在肝细胞移植中的作用和机制

Hepatocyte transplantation is an effective technique for the treatment of liver disease. Promoting the colonization and proliferation of hepatocytes in the recipient liver is the key problem in the treatment of hepatocyte transplantation. We found that the clearance of macrophages could improve the integration rate of hepatocyte transplantation. However, the mechanism and specific role of macrophages in hepatocyte transplantation are rarely reported. Previous studies have shown that SIRPα has a "checkpoint" regulation on macrophages, and downregulation of SIRPα induced by LPS can promote the activation of macrophages. So we hypothesized that macrophage is the key point to influence the colonization and proliferation of transplanted hepatocytes. The mechanism may be expressed as downregulated of SIRPα by HMGB1 promote the activation of macrophage, increase the phagocytosis and secretion of inflammatory factors and finally inhibit the colonization and proliferation of transplanted cells. This study will verify the hypothesis mentioned above mainly through the activation or inhibition of HMGB1 or SIRPα by using Fah deficient mice model and macrophage cell line. And this project will elucidate the function and mechanism of SIRPα mediated macrophage regulation in hepatocyte transplantation and provide theoretical basises for the clinical application of hepatocyte transplantation.

肝细胞移植是治疗肝病的有效技术，促进移植的肝细胞在受体肝脏中的定植和增殖，改善受体肝脏功能是肝细胞移植治疗的关键。我们近期发现清除巨噬细胞可显著提高肝细胞移植的整合率，但巨噬细胞在肝细胞移植中的具体作用和机制尚不清楚。前期研究显示SIRPα对巨噬细胞具有“检查点”样调控作用，LPS诱导SIRPα下调可促进巨噬细胞活化。鉴于HMGB1已被证明在各种类型的肝损伤中均发挥重要作用，因此我们提出假说：巨噬细胞是影响移植的肝细胞定植和增殖的关键，机制可能为内源性炎症因子HMGB1下调SIRPα表达，促进巨噬细胞活化，增加其吞噬以及分泌炎性因子等作用而抑制移植细胞的定植和增殖。本项目采用Fah基因缺陷小鼠肝细胞移植模型和巨噬细胞系，通过活化/抑制HMGB1或SIRPα等干预手段验证上述假说，阐明SIRPα介导的巨噬细胞功能调控在肝细胞移植中的作用和机制，为肝细胞移植的临床应用提供重要的理论和应用依据。

越来越多的证据表明，巨噬细胞在肝脏免疫微环境中发挥了重要作用，针对巨噬细胞功能的特异性调控可有效提高肝细胞移植的整合率、缓解各种因素导致的急、慢性肝损伤。本研究以巨噬细胞功能调控为主线，以肝前体细胞（HepLPCs）为工具，通过对Fah基因缺陷小鼠移植HepLPCs发现巨噬细胞的活化阻碍了移植细胞的定植和增殖，而清除巨噬细胞则可提高移植细胞的整合效率；进一步我们采用HepLPCs条件培养基(HepLPCs-CM)与不同极化状态的巨噬细胞共培养，在体外实验中发现HepLPCs可有效抑制巨噬细胞炎性活化（M1型巨噬细胞相关指标如IL6/IL1β/iNOS、TNFa/MCP1均明显下降），同时促进修复性巨噬细胞产生（M2型巨噬细胞相关指标CD206/IL10/ARG1均显著上升）；紧接着，我们采用小鼠非酒精性脂肪肝炎（NASH）疾病模型在体内进行了验证，结果发现，较对照组相比，HepLPCs移植治疗组肝脏组织CD163（M2型巨噬细胞）表达明显增加，并伴随着肝细胞空泡样变性和纤维化程度均明显降低，提示HepLPCs移植治疗可显著促进NASH模型小鼠肝脏组织中修复型巨噬细胞的产生，从而延缓甚至逆转非酒精性脂肪肝炎进程。本研究从巨噬细胞功能调控的角度出发，阐明了HepLPCs移植治疗在肝脏疾病中的治疗效果和机理，为各类肝病的临床治疗提供了一个全新的思路，有望开创肝病治疗的新领域。