|Budget Amount *help
¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 1998 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1997 : ¥2,100,000 (Direct Cost : ¥2,100,000)
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.