Interleukin-6 augments hepatocyte growth factor-induced liver regeneration; involvement of STAT3 activation

In liver regeneration, quiescent hepatocytes need to be primed before they can fully respond to growth factors such as hepatocyte growth factor (HGF). Recently, interleukin-6 (IL-6) has been shown to play an important role in initiating liver regeneration via activating signal transducer and activator of transcription 3 (STAT3). We therefore investigated the effect of IL-6 on liver regeneration and examined STAT3 activation following IL-6 and/or HGF treatment in rats.

The animals underwent portal branch ligation (PBL) of the left lateral and median branches. They were intravenously treated with either IL-6 (500 microg/kg), HGF (50 microg/kg), both, or vehicle alone on and every 12 h after PBL. The degree of compensatory hypertrophy in unoccluded lobes was examined by measuring the wet weight ratios of the unoccluded lobes to the whole liver and the 5-bromo-2'-deoxyuridine labeling index of hepatocytes in each group. STAT3 expression in regenerating liver was examined by Western blotting and immunohistochemistry.

Coadministration of IL-6 and HGF most effectively increased both the wet weight of the unoccluded lobes and the hepatocellular DNA synthesis. HGF as well as IL-6-treated animals showed moderate STAT3 activation in hepatocytes throughout the experiment.

IL-6 augmented HGF-induced liver regeneration and hepatocellular replication. Liver regeneration stimulated by HGF treatment may be closely involved with STAT3 activation in a different manner induced by IL-6 treatment.