The expression and regulation of the liver enriched transcription factors involving in liver differentiation

卵圆细胞在严重肝损伤中起代偿细胞的作用，被认为等同于肝干/祖细胞。我们从Long-Evans Cinnamon（LEC）大鼠肝脏中分离出卵圆细胞。细胞呈γ-谷氨酰转肽酶（γ GTP）阳性，甲胎蛋白阳性，细胞角蛋白18和19阳性，但细胞中白蛋白阴性。卵圆细胞移植到肝脏后可转化为肝细胞，肝富集转录因子HNF-1、HNF-3、HNF-4和C/EBP的表达与胚胎分化表型的出现一致。白蛋白基因在胚胎发生过程中肝细胞分化开始时被激活。体外实验中，卵圆细胞在EGF（10 mg/ ml）存在下，于三维胶原凝胶中培养9天后，用流式细胞仪检测细胞中HNF-3 β mRNA的表达，HNF-3 α、HNF-4、HNF-1 α和C/EBPalpha mRNA的表达。在胶原包被的培养皿中培养的卵圆细胞在视黄酸存在下，HNF-4基因和γ-GTP蛋白表达显著增加，表明LEC大鼠卵圆细胞在体内可分化为肝细胞，在体外可分化为胆汁上皮细胞。

Oval cells function as compensatory cells in severe liver injury and are thought to be equivalent to liver stem/progenitor cells. We isolated oval cells from the liver of Long-Evans Cinnamon (LEC) rats by lsopyknic centrifugation in a Percoll gradient. The cells were gamma-glutamyl transpeptidase (gammaGTP) positive alpha-fetoprotein positive, cytokeratin 18 and 19 positive, but albumin negative in the cells. When oval cells were transplanted to the liver, they were transformed into hepatocytes.The expression of the liver enriched transcription factors HNF-1 , -3, -4, and C/EBP is concordant with appearance of the differentiated phenotype in the embryos. Albumin gene is activated at the onset of hepatocyte differentiation during embyogenesis. Among liver-enriched transcription factors, only HNF-3beta mRNA was expressed, but HNF-3alpha, HNF-4, HNF-lalpha and C/EBPalpha mRNAs were undetectable.In vitro experiments, oval cells were cultured in the presence of EGF(10mg/ ml) in three-dimensional collagen gels for 9 days. they formed bile duct-like branchingtubles, On the other hand, oval cells cultured on collagen coated dishes in the presence of retinoic acid expressed HNF-4 gene and gamma GTP protein significantly.These results indicated that the oval cells isolated from LEC rats can differentiate into hepatocytes in vivo and can differentiate into bile epithelial cells in vitro.