The hepatocyte has a florid regenerative potential.In experimental partial resection in the rat,the remaining liver tissue starts to regenerate within a few hours.In 14-15 hours DNA replication is seen.In 20-21 hours mitoses appear.In 32 hours mitoses are at the pick.In 2 weeks the remaining liver tissue has reached the weight that had before resection. Cell division takes place in the periportal zone.In pathological conditions,dead liver cells are replaced by proliferation of surviving liver cells.Hepatocytes,Kupffer cells,endothelium,bile ducts,vessels,all proliferate.If the supportive reticular framework is presrved,the lost cells are replaced and the regeneration is "ad integrum". If however, the reticulum is damaged,healing can be accomplished only by scar formation,"fibrosis", which may produce more damage by inducing rearrangement of the blood circulation that leads to cirrhosis. Morphological evidence of liver cell regeneration either normal or abnormal is given by the presence of mitoses,large polyploid nuclei,binucleation, multinucleation and hyperplastic changes.
The factor(s) stimulating proliferation of remaining hepatocytes are not known.Tey may be humoral. Indeed: 1)blood from a partially hepatectomized animal induces a proliferative response in the liver of a non- operated animal. 2)partial hepatectomy in one of two rats joined by carotid artery/jugular vein anastomosis induces proliferative response in the liver of the other rat.3)in heterotropic liver autografts supplying arterial blood through the hepatic vein instead of th portal vein, hepatocyte regeneration occurs around the central lobular vein instead of around portal tracts.
As in every other organ, exagerated regeneretion may induce hyperplastic changes (see the discussion on hyperplasia from table of contents).