Human Liver Stem Cells:
Regeneration of the liver begins with growth activation of the primary hepatocyte population. Although in the adult, hepatocytes are normally quiescent and fully differentiated, they retain the capacity to proliferate on demand. The other cell types in the liver, including biliary epithelium, sinusoidal endothelium, stellate cells and Kupffer cells also proliferate, but with a lag period. In the adult, when liver damage is severe and loss of parenchymal hepatocytes is massive or for some reason are prevented from growth initiation, stem cells do however fulfill an important role. This has been studied extensively in a wide variety of experimental animal models and occurs following treatment with numerous liver toxins or carcinogens. The term oval cells was first coined by Farber to describe the cellular response in liver of animals to toxins such as acetylaminofluorene or diethylnitrosamine. More the debate has broadened to include a fourth source of stem cells with hepatic potential, namely the haematopoietic stem cell compartment.