Stem cells in hepatology

The liver is the only human parenchymal organ that has the capacity for self regeneration. Endogenous hepatocytes and hepatic progenitor cells, called oval cells, usually ensure liver repair after injury, but when the extent of liver damage is too severe, these mechanisms appear to be insufficient and liver transplantation is the only therapeutic option. However, the insufficient number of donor organs available for orthotopic liver transplantation worldwide makes it urgent to find new therapies for acute and chronic liver disease. In vivo tissue engineering, involving isolated liver cell transplantation into the liver and/or other ectopic sites, and in vitro tissue engineering, using an extracorporeal hepatic support system or bio-artificial liver, represent promising approaches to the treatment of liver failure. Nowadays, stem cells are emerging as a potential source of liver cells that may overcome the problems associated with the shortage of human hepatocytes available for transplantation. Human umbilical cord blood, the umbilical cord itself and the placenta have been proposed as non-controversial and readily available sources of multipotent stem cells capable of proliferating for lengthy periods of time and of differentiating into various adult cell lines. Stem cells differentiated into hepatocytes could be used alone or in support systems, such as human liver acellular matrix, for the treatment of liver failure.