Oval cells, putative hepatic stem cells, could potentially provide a novel solution to the severe shortage of donor livers, because of their ability to proliferate and differentiate into functional hepatocytes. We have previously demonstrated that oval cells can be induced to differentiate into cells with morphologic, phenotypic, and functional characteristics of mature hepatocytes. In this study, we have established a new model combining ethionine treatment with partial hepatectomy to activate oval cells, then developed a procedure utilizing selective enzymatic digestion and density gradient centrifugation to isolate and purify such cells from heterogeneous liver cell population. We identified oval cells by their morphological characteristics and phenotypic properties, thereby providing definitive evidence of the presence of hepatic stem-like cells in adult rat livers. Viewed by transmission electron microscopy, they were small cells with ovoid nuclei, a high nucleus/cytoplasm ratio and few organelles, including mitochondria and endoplasmic reticulum. Flow cytometric assay showed that these cells highly expressed OV-6, cytokeratin-19 (CK-19) and albumin. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis displayed that the freshly isolated cells co-expressed albumin, cytokeratin-7 (CK-7) and CK-19 mRNA, indicating that they were essentially bipotential hepatic stem-like cells. Furthermore, we set up a culture system containing growth factors and a fibroblast feeder layer, to provide nourishment to these cells. Thus, we were able to culture them in vitro for more than 3 months, with the number of cells doubling 100 times. Gene expressions of albumin, CK-7 and CK-19 in the cells derived from the expanding colonies at day 95 were confirmed by RT-PCR analysis. These data suggested that the hepatic oval cells derived from adult rat livers possess a high potential to proliferate in vitro with a large increase in number, while maintaining the bipotential nature of hepatic stem cells.

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Physiological levels of cortisol stimulate intestinal polyamine synthesis, Interestingly, some herbal extracts contain glycyrrhetinic acid (GA), which has a chemical structure similar to that of cortisol. Twenty piglets with similar BW (2.9 kg) were assigned randomly to one of the 4 treatment groups, which received supplementation with 0, 0.01, 0.02 or 0.04% GA to the milk powder for 12 d. BW was measured on d 0, 5, and 12 for all treatments. On d 12, the blood was collected for an analysis of plasma amino acids and serum hormone concentration, and the jejunum samples were obtained for an analysis of ODC activity and morphology from the control and 0.02% GA treatment groups. Dietary supplementation with 0.02% GA resulted in the highest ADG among all of the treatment groups (P<0.05). Compared with the control, dietary supplementation with 0.02% GA increased feed intake by 14.8% (P>0.05), ADG by 20% (P<0.05), decreased the feed: gain ratio by 3.3% (P>0.05), improved the plasma arginine concentration(P<0.05), and increased the ODC activity in the jejunum on d 21 (P<0.05), but there was no effect on the other plasma amino acids and serum cortisol, GH and insulin concentration (P>0.05). Villus height in pigs treated with 0.02% GA was greater than that in the control pigs (P <0.05) on d 21 These results suggest that 0.02%GA increases endogenous arginine provision and ODC activity, and improves the morphology in the jejunum, and enhances growth performance in milk‐fed piglets.