IL-22 is involved in liver regeneration after hepatectomy

Hepatocyte proliferation following partial hepatectomy is an important component of liver regeneration, and recent in vitro studies have shown that IL-22 is involved in cellular proliferation in a variety of cell types, including hepatocytes. IL-22 functions through IL-10Rbeta and IL-22Ralpha. The goal of this study was to investigate the potential role of IL-22 in liver regeneration after 70% hepatectomy. Following 70% hepatectomy, done under general anesthesia in mice, serum IL-22 and hepatic IL-22Ralpha mRNA were significantly increased. Although administration of exogenous IL-22 prior to hepatectomy did not increase hepatocyte proliferation, administration of anti-IL-22 antibody before hepatectomy did significantly decrease hepatocyte proliferation. Furthermore, IL-22 treatment prior to 70% hepatectomy induced stat-3 activation; no significant changes were seen in ERK1/2 activation, stat-1 activation, or stat-5 activation. IL-22 pretreatment also significantly increased hepatic and serum IL-6 levels. In addition, animals treated with anti-IL-22 antibody also expressed less TGF-alpha. In conclusion, these data suggest that IL-22 is involved in liver regeneration and this may be due to interaction with IL-6 and TGF-alpha cascades.