Adult Liver Stem Cells

In mammals, the adult liver contains many cell types of various embryological origins. Nevertheless, the terms "liver stem cell" and "hepatic stem cell" are used only for precursors of the two epithelial liver cell types, the hepatocytes and the bile duct epithelial cells. The liver consists of several separate lobes and represents about 2% of human and 5% of mouse body weight. It is the only organ with two afferent blood supplies. The portal vein brings venous blood rich in nutrients and hormones from the splanchnic bed (intestines and pancreas), and the hepatic artery provides oxygenated blood. The hepatic artery, portal vein, and common bile duct enter the liver in the same location, the porta hepatis. The role of liver stem cells in regeneration has been controversial, but many of the apparent inconsistencies can be reconciled by considering the different definitions used for these cells replacement by endogenous cells (regeneration) and must be distinguished from reconstitution by transplanted donor cells (repopulation). These small cells, which eventually become differentiated hepatocytes, are termed oval cells because of their morphology. Importantly, oval cells are not derived from hepatocytes, instead, they are the offspring of a cell in the canal of Hering.