Compensatory recovery of liver mass by Akt-mediated hepatocellular hypertrophy in liver-specific STAT3-deficient mice

Background/Aims: Liver regeneration following hepatectomy is complicated and involves a variety of interacting factors. The present study was designed to study the roles of proliferation and hypertrophy of hepatocytes in liver regeneration following hepatectomy in liver-specific STAT3-knockout (LS3-KO) mice lacking mitogenic activity. Methods: Partial hepatectomy was performed in LS3-KO and control mice. Liver regeneration was estimated by the liver weight, cell proliferation and cell size, and the related cellular signals were analyzed. Results: Proliferation of hepatocytes following PH was markedly suppressed in LS3-KO mice with reduced cyclinD1 transcript. However, liver mass recovered sufficiently following PH in LS3-KO mice almost equal to that of control mice. Analysis of hepatocellular growth revealed that cell size following hepatectomy was significantly larger in LS3-KO mice than in control mice. Hepatectomy induced immediate but transient phosphorylation of Akt, p70(S6K), mTOR and GSK-3 beta in LS3-KO mice much more than in control mice. Additionally, adenoviral transfection of dominant negative mutant of Akt to control and LS3-KO mice led to insufficient liver regeneration following hepatectomy. Conclusions: PI3-K/Akt-mediated responsive hepatocellular hypertrophy may be essential for liver regeneration following hepatectomy and sufficiently compensated liver regeneration even in STAT3-deficient liver, in which cell proliferation is impaired. (c) 2005 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.