肝纤维化中氧化固醇7α,25-HC/GPR183调控枯否细胞和肝星状细胞活化及交互作用的致病机制研究

Liver fibrosis is the underlying pathophysiological process in the terminal stage of most liver diseases. Kupffer cell (KC) activation, hepatic stellate cell (HSC) activation and their interactions are the crucial biological events in liver fibrosis. Liver is the most important lipid metabolic organ. Cholesterol metabolite - oxysterols as signal molecules can couple with the corresponding receptors and plays important roles in immune/inflammatory response and various liver diseases. In our preliminary experiments, we found that the oxysterol 7α, 25-HC/GPR183 signaling, cholesterol metabolism enzyme CH25H and CYP7B1 were increased in the fibrosis liver tissue of CCl4 induced mouse model. And 7α, 25-HC was also increased in the serum of liver fibrosis patients. Inhibition of GPR183 can promote PPAR-γ expression in RAW cells, suppress HSC autophagy and Wnt5a secretion, and alleviate liver fibrosis in mice. However, the specific mechanism remains unclear. On the previous results, we proposed to focus on the abnormal cholesterol metabolism in liver fibrosis, and systematically explore that 7α, 25-HC/GPR183 regulates KC, HSC and their interaction which may in turn promote ECM deposition and inflammation; investigate the regulation of 7α, 25-HC/GPR183 by targeting the synthesis of 7α, 25-HC in liver; clarify the correlation between 7α, 25-HC/GPR183 and the clinical pathological characteristics of liver fibrosis, and the role of 7α, 25-HC/GPR183 in the prevention and treatment of liver fibrosis. Therefore, provide theoretical and experimental basis for novel strategies in the treatment and diagnosis of liver fibrosis through targeting 7α, 25-HC/GPR183 signal pathway.

肝纤维化是肝病终末期病症的基础。枯否细胞（KC）和肝星状细胞（HSC）活化及交互作用是肝纤维化的重要事件。肝脏是重要脂代谢器官，胆固醇代谢物-氧化固醇信号在免疫炎症反应和肝病中起重要作用。我们目前研究发现肝纤维化患者外周血中7α,25-HC、小鼠纤维化肝组织中氧化固醇7α,25-HC及受体GPR183等上调；抑制GPR183可抑制HSC自噬和促进巨噬细胞PPAR-γ表达，并缓解小鼠肝纤维化，然其机制尚不清楚。为此拟进一步以肝脏胆固醇代谢异常为切入点，系统研究和明确氧化固醇7α,25-HC/GPR183信号异常影响KC和HSC及其交互作用致肝纤维化的作用和机制；揭示调控7α,25-HC/GPR183的规律；明确7α,25-HC/GPR183作为临床肝纤维化评价新指标与肝纤维化病理特征的相关性；明晰靶向干预7α,25-HC/GPR183对防治肝纤维化的作用，为形成肝纤维化诊疗新策略奠定基础。

本项目按照计划书执行，已达到预期目标。明确了氧化固醇7α,25-HC/GPR183信号调控HSC和KC活化促进肝纤维化的作用与机制。发现7α,25-HC/GPR183信号在肝纤维化患者和小鼠肝纤维化模型肝组织中均表达上调；发现肝HSC和KC细胞均表达GPR183，且较正常组相比，模型组HSC和KC细胞中GPR183表达呈上升趋势；抑制7α,25-HC/GPR183信号能够显著抑制HSC和KC活化进而缓解肝纤维化进程。进一步研究发现，肝纤维化在衰老环境中肝前体细胞动员减少。探究其机制发现，肝纤维化衰老机体内一些胞外基质蛋白显著下降。肝脏中的基质蛋白主要是由肝星状细胞产生。由此发现，衰老小鼠肝脏中HSC活化功能下降，其产生的胞外基质蛋白成份下降，导致卵圆细胞的动员能力下降，进而对肝脏损伤修复不良。通过对其中关键因子和信号通路的调控，以期能寻找临床治疗肝脏损伤相关疾病的新策略。发现了肝纤维化进程中，影响肝脏前体细胞分化与增殖的调控机制。研究主要阐明了BEX1在肝前体细胞动员中的作用并初步探讨了BEX1调控肝前体细胞的机制，有望为慢性肝病的治疗提供新的策略。同时明晰了Dlk1随着肝脏干细胞发育的动态变化特征，Dlk1M的缺失是肝脏干细胞向胆管前体细胞分化的标志性事件，不仅为肝脏干细胞的应用提供了理论指导，也为肝脏相关疾病如胆管细胞癌等的发病机理研究提供了启示。以通讯作者发表标注资助的SCI论文8篇，培养博士研究生3名。