Abstract
Our understanding of the process of self-renewal has both progressed and changed over the last few decades. For many years, the assumption was that the liver regenerates primarily through the division of hepatocytes. However, over the last few years there has been increasing evidence of the participation of immature cells. Stem cell-fed liver regeneration comprising extensive cell proliferation within the portal areas of the liver lobules occurs when the proliferation of mature hepatocytes is massively impaired, as seen in chronic and severe liver injury. The tissue-determined progenitor cells, termed “oval cells” owing to their predominant morphology, may develop from dormant stem cells located in the canal of Hering. They proliferate and extend into the surrounding parenchyma, differentiating into hepatocytes and bile duct cells. The variable antigen profiles imply that the intrahepatic progenitor cells constitute a dynamic cell compartment, which contains a multitude of cells expressing not only hepatic, but also extrahepatic markers. Selecting one or even several markers to identify and isolate oval cells always determines the choice of target cell. In the search for an alternative source of cells for transplantation purposes, the appropriate stimulus to prepare the host liver for oval cell repopulation as a clinically viable form of treatment remains to be determined.