Healthy adult livers exhibit little hedgehog activity. In the presence of liver injury, hepatocytes are subject to cellular stress and in some cases undergo apoptosis. In this setting of injury, hedgehog ligand production increases resulting in the appropriate expansion and differentiation of progenitor cells allowing for liver reconstruction. As the insult is removed, Hh pathway activity slowly declines, and the progenitor population gradually dwindles away with recovery of liver health.
