慢性肝损伤纤维化时前体细胞活跃。我们的前期研究发现病人纤维化减轻时，肝脏前体细胞常与星状细胞伴行并抑制其活化增生。这种作用与前体细胞发生的上皮－间质转化(EMT)后的逆转，即间质－上皮转化(MET)有关，但机制尚不清楚。本课题首先利用体外前体细胞和星状细胞共培养体系，观察前体细胞MET转化对星状细胞活化、凋亡和对细胞外基质的影响；第二通过检测前体细胞MET的三种主要信号通路 Wnt/?-catenin，Notch和Hedgehog，及上清液中细胞因子的变化探讨作用机制；第三利用四氯化碳大鼠纤维化及自发逆转模型，多标记荧光和组化染色分别观察前体细胞自发的MET及BMP-7诱导后的MET对星状细胞活化的影响；第四用细胞示踪技术将GFP和E-cad启动子/lacZ双重标记MET转化后的前体细胞回输纤维化大鼠体内，观察对星状细胞及纤维化消退的影响。本研究将为探讨纤维化中前体细胞的作用提供实验依据。

In chronic injured liver, a large number of hepatic stellate cells (HSC) are activated, while hepatic progenitor cells (HPC) are seen periportally adjacent to HSC. Our previous studies found that co-culture of HPCs and activated HSCs led to a significant inhibition of HSC activation and proliferation. Those effects could be enhanced by the reversion of HPC epithelial-mesenchymal transition (EMT), which is named as mesenchymal-epithelial transition (MET), in addition to apoptosis of activated HSC. Accordingly, we hypothesized that HPC could modulate the activation of HSC through MET transition. .In this study we will first use the in vitro co-culture system of primary HPC and HSC. Comparing with HPC undergoing proliferation, differentiation and EMT by different growth factors, chemical substance or transforming growth factor-β (TGF-β), MET of HPC will be induced by TGF-β on-off withdraw (spontanous EMT turnover). HSC activation, proliferation and apoptosis, as well as extracellular matrix expression will be detected. Second, we will detect the three main MET signals Wnt/?-catenin，Notch and Hedgehog, and cytokines in the supernatant to explore the mechnisams and signaling of the MET effects on HSC. Third, to expend the understanding of the influence of HPC on HSC in vitro, we will use carbon tetrachloride (CCl4)induced liver fibrosis and regression rat model. By obseving HPC spontanous MET and BMP-7 induced MET, HSC activation and fibrosis marker will be evaluated. Finally, by cellular tracing assay we will doule label MET transited HPC with green fluorescence protein and E-cadherin promoter driven lacZ in vitro, and inject into fibrosis rat via portal vein. Histology, biochemical parameters of fibrogenesis and fibrolysis, most importantly the location and interaction of HPC on HSC by multi-fluoresence stain through confocal microscope, will be detected and evaluated. This study will help to understand the function of HPCs and their MET transition in liver fibrosis.