Hedgehog signalling in liver regeneration

Excerpt

The adult liver has unique regenerative capabilities. Adult livers generally regenerate fully functional liver cells when injured, unlike other vital adult organs which typically respond to cell loss by forming scar tissue. The mechanisms underlying these differences are not well understood, particularly since adult livers are perfectly capable of scarring. In fact, transient scar formation normally occurs in situations that lead to efficient and complete recovery of functional liver mass, such as 70% partial hepatectomy (PH). Scarring also occurs to some extent during many types of chronic liver injury, although progressive scarring (dubbed cirrhosis) occurs in only a minority of individuals with chronic liver injury. Even in cirrhotic livers, however, scarring has been shown to regress gradually once factors driving chronic injury are alleviated. The aggregate data suggested to us that the unique regenerative capabilities of adult livers are linked to its ability to control the formation and regression of scar. Our research has focused on delineating the mechanisms that control scarring. The results will help to clarify why injured livers typically regenerate healthy parenchyma, as well as why other organs replace wounded tissue with scar. …