Fig. 2.

Stem cells in liver regeneration and therapy. Under physiological conditions, the division and proliferation of mature hepatocytes maintain hepatocyte number, i.e. liver mass. In humans and rodents, a 75% partial hepatectomy can be regenerated by this capacity. Under experimental conditions or carcinogenic changes, hepatocyte proliferation can be blocked. In this case, resident hepatic stem/progenitor cells (rHSPC) proliferate and differentiate into hepatocytes. The recent literature suggests the existence of an extra-hepatic stem cell pool that contributes to liver regeneration. Bone-marrow-cell-derived cells, e.g. mesenchymal stem cells, can give rise to hepatocytes in distinct experimental settings. Cell transplantation of adult and fetal hepatocytes has been established at the stage of phase-I clinical trials in patients with metabolic liver disorders or acute liver failure. Embryonic-stem-cell-derived hepatic cells are currently being investigated as a transplantable cell source in order to overcome limitations in cell number and tissue compatibility for future therapeutic strategies