Cellular Homeostasis and Repair in the Mammalian Liver

The mammalian liver is one of the most regenerative tissues in the body, capable of fully recovering mass and function after a variety of injuries. This factor alone makes the liver unusual among mammalian tissues, but even more atypical is the widely held notion that the method of repair depends on the manner of injury. Specifically, the liver is believed to regenerate via replication of existing cells under certain conditions and via differentiation from specialized cells--so-called facultative stem cells--under others. Nevertheless, despite the liver's dramatic and unique regenerative response, the cellular and molecular features of liver homeostasis and regeneration are only now starting to come into relief. This review provides an overview of normal liver function and development and focuses on the evidence for and against various models of liver homeostasis and regeneration.