Establishment and application of an experimental model of human fetal hepatocytes for investigation of the protective effects of silybin and polyporus umbellalus polysaccharides

AIM: To establish a new experimental model system of human fetal hepatocytes to study the mechanisms underlying the protective effect of silybin and polyporus umbellalus polysaccharides (PSP) on the cellular ultrastructure.

METHODS: Human fetal hepatocytes were obtained from the liver of a human fetus that resulted from a medically necessary induced labor; the mother provided informed consent for sampling, experimental use and publication of findings. The hepatocytes were cultured and then pretreated with silybin or PSP or without either (control), after which the treated cells were exposed to CCl₄ for 4 h. Changes in cellular ultrastructure were observed by scanning electron microscopy and transmission electron microscopy, and changes in alanine aminotransferase (ALT), aspartate aminotransferase (AST) and superoxide dismutase (SOD) were assayed.

RESULTS: Levels of ALT and AST were significantly decreased, and level of SOD was elevated in the two pretreatment groups following CCl₄ exposure, as compared to the control group. The cellular integrity and ultrastructure were well preserved in the two pretreatment groups but were seriously damaged in the control group.

CONCLUSION: The CCl₄-induced hepatotoxic cell model system of human fetal hepatocytes is an effective tool for studying the hepatoprotective effect of drugs and may be applicable for studies to screen medicines for treatment of hepatitis.

In vitro evidences of epithelial to mesenchymal transition in low cell-density cultured human fetal hepatocytes

Culturing fetal hepatocytes in high cell-density allowed stabilization of the hepatocyte phenotype up to 8 weeks, including the maintenance of liver-specific functions. On the other hand, when cultured at low cell-density, fetal hepatocytes underwent morphological modifications and acquired fibroblastic morphology. Since a switch from E-cadherin to vimentin expression accompanied these changes, we hypothesized the occurrence of epithelial-to-mesenchymal transition when fetal hepatocytes were cultured at low cell-density. Changes in gene expressionsuch as up-regulation of fibrosis-related geneswere also observed, suggesting that the low cell-density culture system promoted the acquisition of a profibrotic phenotype in cultured hepatocytes. The origin of fibrogenic cells in the liver is not well known, and the role of hepatocytes as a source of fibrogenic cells is controversial. Therefore, we hypothesized that hepatocytes undergoing epithelial-to-mesenchymal transition could have a central role in liver fibrosis as a source of fibrogenic cells. To conclude, the high cell-density culture system could be a useful model for in vitro studies requiring long-term cultures of hepatocytes, such as the development of pharmaceutical drugs and mechanisms of viral infections. The low cell-density culture system may provide additional insights into the origin of fibrogenic cells in the liver, thus contributing to the development of novel therapeutic approaches.

Alternative Cell Sources to Adult Hepatocytes for Hepatic Cell Therapy

Adult hepatocyte transplantation is limited by scarce availability of suitable donor liver tissue for hepatocyte isolation. New cell-based therapies are being developed to supplement whole-organ liver transplantation, to reduce the waiting-list mortality rate, and to obtain more sustained and significant metabolic correction. Fetal livers and unsuitable neonatal livers for organ transplantation have been proposed as potential useful sources of hepatic cells for cell therapy. However, the major challenge is to use alternative cell sources for transplantation that can be derived from reproducible methods. Different types of stem cells with hepatic differentiation potential are eligible for generating large numbers of functional hepatocytes for liver cell therapy to treat degenerative disorders, inborn hepatic metabolic diseases, and organ failure. Clinical trials are designed to fully establish the safety profile of such therapies and to define target patient groups and standardized protocols.