588. Hepatic HB-EGF (Heparin-Binding EGF-Like Growth Factor) Gene Therapy for Fulminant Hepatic Failure in Mice: More Potent Protective and Mitogenic Effects for Hepatocytes Than HGF (Hepatocyte Growth Factor)
Authors: Ken-ichiro Kosai, Ngin Cin Khai, Tomoyuki Takahashi
Journal: Molecular Therapy (2006)

Background/Aims: We have found that HGF (hepatocyte growth factor) can be a therapeutic agent for liver disorders, including fulminant hepatic failure, regardless administrations of recombinant protein or the gene therapy strategy (Ref 1-3). On the other hand, heparin-binding epidermal growth factor-like growth factor (HB- EGF), a unique membrane-anchored growth factor, is more rapidly increased after liver injury than HGF, suggesting another hepatotrophic factor. However, the therapeutic potential of HB- EGF for liver disorders has not yet been studied. A biologically important point is that the first HB-EGF gene therapy trial for heart disorders by us did not exert therapeutic effects but rather exacerbated the unfavorable remodeling (Ref 4) although HB-EGF is also cardiotrophic factor. In this context, this study explores the potential of hepatic HB-EGF gene therapy in comparison with HGF.Methods: Mice received an intraperitoneal injection of the agonistic anti-Fas antibody 72 hours after an intravenous injection of either adenoviral vector (1x10E11 particles) expressing human HB-EGF (Ad.HB-EGF), human HGF (Ad.HGF) or no gene (Ad.dE1.3), and were sacrificed 24 or 36 hours later to assess liver injury and regeneration.Results: Exogenous HB-EGF was predominantly localized on the membrane, suggesting the initial synthesis of proHB-EGF in hepatocytes. The control Ad.dE1.3-treated mice represented remarkable increases in serum ALT and AST levels and histopathologically severe liver injuries with numerous apoptosis, but a limited number of mitogenic hepatocytes. In contrast, the liver injuries and apoptotic changes were significantly inhibited, but the mitogenic hepatocytes remarkably increased, in both the Ad.HB- EGF- and Ad.HGF-treated mice. More mitogenic hepatocytes and milder injuries were observed in the Ad.HB-EGF-treated mice.Conclusions: HB-EGF has more potent protective and mitogenic effects for hepatocytes than HGF, at least for the present conditions. In vivo hepatic HB-EGF gene transduction is therapeutic for Fas-induced liver injury. These facts are useful for establishing the effective gene therapy for several liver disorders, as well as understanding biological and pathological roles of HB-EGF.References:(1)Biochem. Biophys. Res. Commun. 244: 683-690, 1998. (2)Hepatology 30: 151-159, 1999. (3) Int J Oncol 27: 77-86, 2005. (4) Lab Invest 85: 862-873, 2005.Fig. (A)Experimental schedule. Liver enzyme (B) and regenerating hepatocytes (C) after either gene therapy for Fas-induced liver injury. White and black bars represent 24 and 36 h after the anti-Fas injection, respectively (* P<0.01, either Ad.HB-EGF or Ad.HGF vs. control Ad.dE1.3: # P<0.01, Ad.HB-EGF vs. Ad.HGF). Background/Aims: We have found that HGF (hepatocyte growth factor) can be a therapeutic agent for liver disorders, including fulminant hepatic failure, regardless administrations of recombinant protein or the gene therapy strategy (Ref 1-3). On the other hand, heparin-binding epidermal growth factor-like growth factor (HB- EGF), a unique membrane-anchored growth factor, is more rapidly increased after liver injury than HGF, suggesting another hepatotrophic factor. However, the therapeutic potential of HB- EGF for liver disorders has not yet been studied. A biologically important point is that the first HB-EGF gene therapy trial for heart disorders by us did not exert therapeutic effects but rather exacerbated the unfavorable remodeling (Ref 4) although HB-EGF is also cardiotrophic factor. In this context, this study explores the potential of hepatic HB-EGF gene therapy in comparison with HGF. Methods: Mice received an intraperitoneal injection of the agonistic anti-Fas antibody 72 hours after an intravenous injection of either adenoviral vector (1x10E11 particles) expressing human HB-EGF (Ad.HB-EGF), human HGF (Ad.HGF) or no gene (Ad.dE1.3), and were sacrificed 24 or 36 hours later to assess liver injury and regeneration. Results: Exogenous HB-EGF was predominantly localized on the membrane, suggesting the initial synthesis of proHB-EGF in hepatocytes. The control Ad.dE1.3-treated mice represented remarkable increases in serum ALT and AST levels and histopathologically severe liver injuries with numerous apoptosis, but a limited number of mitogenic hepatocytes. In contrast, the liver injuries and apoptotic changes were significantly inhibited, but the mitogenic hepatocytes remarkably increased, in both the Ad.HB- EGF- and Ad.HGF-treated mice. More mitogenic hepatocytes and milder injuries were observed in the Ad.HB-EGF-treated mice. Conclusions: HB-EGF has more potent protective and mitogenic effects for hepatocytes than HGF, at least for the present conditions. In vivo hepatic HB-EGF gene transduction is therapeutic for Fas-induced liver injury. These facts are useful for establishing the effective gene therapy for several liver disorders, as well as understanding biological and pathological roles of HB-EGF. References:(1)Biochem. Biophys. Res. Commun. 244: 683-690, 1998. (2)Hepatology 30: 151-159, 1999. (3) Int J Oncol 27: 77-86, 2005. (4) Lab Invest 85: 862-873, 2005. Fig. (A)Experimental schedule. Liver enzyme (B) and regenerating hepatocytes (C) after either gene therapy for Fas-induced liver injury. White and black bars represent 24 and 36 h after the anti-Fas injection, respectively (* P<0.01, either Ad.HB-EGF or Ad.HGF vs. control Ad.dE1.3: # P<0.01, Ad.HB-EGF vs. Ad.HGF).