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, p70S6K, mTOR and GSK-3β 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.