CIRRHOSIS OF THE LIVER - A REGENERATIVE PROCESS

The ancient story of Prometheus, chained to a rock for defying Zeus by stealing fire from Mount Olympus and subjected to daily tearing at his liver by an eagle, attests to the early recognition of the extraordinary regenerative capacity of the human liver. This process had remained an intriguing mystery over the millennia. In the last 20 years, following the pioneering work of Bucher (1) and Moolten et al (2), there has been an explosion of research that has clarified some of the mechanisms underlying the process of hepatic regeneration. Regeneration implies proliferation and regeneration. After the fetal and postnatal growth of the liver is completed, hepatocytes no longer proliferate actively, but they can proliferate in response to cell death or loss (3). Hepatocyte growth responses are of particular research interest because they occur in vivo and involve cells that are normally quiescent. Hepatic regeneration constitutes a highly regulated process that is best shown by the arrest of liver growth following a partial hepatectomy precisely at the moment the hepatic mass reaches the mass of the original intact liver (3). This suggests that hepatic regeneration after a partial hepatectomy is a strictly regulated nonautonomous growth process that is controlled by the same factors that are responsible for the determination and maintenance of hepatic mass in a normal individual. In response to a partial hepatectomy, hepatocytes enter the cell cycle and progress to DNA synthesis and replication but only in numbers sufficient to restore the hepatic mass. The regeneration response is both synchronized and universal in that it affects all intrahepatic cell lines, including nonparenchymal cells. The first part of the present paper deals with a review of the concepts related to the regulation of growth and regeneration following liver injury. This is followed by discussion of the process of hyperplasia and neoplasia seen in cirrhosis. The second part of this work deals with a new histopathological method used to identify hepatocellular carcinoma (HCC), which is based upon a consideration of dynamic criteria and the lessons learned from a human disease process, alpha-1-antitrypsin (AAT) deficiency.