Table_1_The Differential and Dynamic Progression of Hepatic Inflammation and Immune Responses During Liver Fibrosis Induced by Schistosoma japonicum or Carbon Tetrachloride in Mice.docx

Liver fibrosis can result from various causes and could progress to cirrhosis and cancer; however, there are no effective treatments due to that its molecular mechanism is unclear. liver fibrosis model made by Schistosoma japonicum (S. japonicum) infection or Carbon tetrachloride (CCl4) intraperitoneal injection is a conventional model used in liver fibrosis-related studies for mechanism or pharmaceutical research purposes. But the differences in the pathological progression, immune responses and the underlying mechanism between the two liver fibrosis model have not been carefully compared and characterized, which hinders us from correctly understanding and making better use of the two models. In the present study, the pathological changes to the liver, and the cytokines, inflammatory factors, macrophages, and lymphocytes subsets involved were analyzed in the liver fibrosis model of S. japonicum infection or CCl4 intraperitoneal injection. Additionally, the pathological progression, immune responses and the underlying injury mechanism in these two models were compared and characterized. The results showed that the changing trend of interleukin-13 (IL-13), transforming growth factor beta (TGF-β), inflammatory factors, and M1, M2 macrophages, were consistent with the development trend of fibrosis regardless of whether liver fibrosis was caused by S. japonicum or CCl4. For lymphocyte subsets, the proportions of CD3+ T cells and CD4+ T cells decreased gradually, while proportion of CD8+ T cells peaked at 6 weeks in mice infected with S. japonicum and at 12 weeks in mice injected with CCl4. With prolonged S. japonicum infection time, Th1 (CD4+IFN-γ+) immunity converted to Th2 (CD4+IL-4+)/Th17 (CD4+IL-17+) with weaker regulatory T cell (Treg) (CD4+CD25+FOXP3+) immunity. However, in liver fibrosis caused by CCl4, Th1 cells occupied the dominant position, while proportions of Th2, Th17, and Treg cells decreased gradually. In conclusion, liver fibrosis was a complex pathological process that was regulated by a series of cytokines and immune cells. The pathological progressions and immune responses to S. japonicum or CCl4 induced liver fibrosis were different, possibly because of their different injury mechanisms. The appropriate animal model should be selected according to the needs of different experiments and the pathogenic factors of liver fibrosis in the study.

肝纤维化（Liver fibrosis）可由多种诱因引发，且可进展为肝硬化乃至肝癌；但由于其分子机制尚未阐明，目前尚无有效的治疗手段。由日本血吸虫（Schistosoma japonicum, S. japonicum）感染或四氯化碳（Carbon tetrachloride, CCl4）腹腔注射构建的肝纤维化模型，是肝纤维化相关机制研究与药物研发中常用的经典模型。但目前尚未对这两种模型的病理进程、免疫应答及潜在分子机制进行系统的比较与表征，这阻碍了我们对这两种模型的正确认知与合理应用。本研究中，我们分别对日本血吸虫感染及四氯化碳腹腔注射诱导的肝纤维化模型的肝脏病理变化，以及相关细胞因子、炎症因子、巨噬细胞及淋巴细胞亚群的变化进行了分析。此外，我们还对这两种模型的病理进程、免疫应答及潜在损伤机制进行了比较与表征。结果显示，无论由日本血吸虫还是四氯化碳诱导肝纤维化，白细胞介素-13（interleukin-13, IL-13）、转化生长因子-β（transforming growth factor beta, TGF-β）、炎症因子的变化趋势，以及M1、M2型巨噬细胞的动态变化，均与纤维化的发展趋势相符。对于淋巴细胞亚群而言，CD3+ T细胞与CD4+ T细胞的占比均呈逐渐下降趋势；而CD8+ T细胞的占比在日本血吸虫感染小鼠中于6周时达到峰值，在四氯化碳注射小鼠中则于12周时达到峰值。随着日本血吸虫感染时长的延长，Th1（CD4+IFN-γ+）免疫应答逐渐向Th2（CD4+IL-4+）/Th17（CD4+IL-17+）免疫应答转换，调节性T细胞（regulatory T cell, Treg）（CD4+CD25+FOXP3+）的免疫活性则有所减弱。而在四氯化碳诱导的肝纤维化模型中，Th1细胞占据主导地位，Th2、Th17及Treg细胞的占比则逐渐下降。综上，肝纤维化是受一系列细胞因子与免疫细胞共同调控的复杂病理过程。日本血吸虫与四氯化碳诱导的肝纤维化，其病理进程与免疫应答存在显著差异，这可能与二者的损伤机制不同有关。本研究提示，应根据不同实验的研究需求及肝纤维化的致病诱因，选择合适的动物模型。