Insulin-like growth factor I gene transfer to cirrhotic liver induces fibrolysis and reduces fibrogenesus leading to cirrhosis reversion in rats

Abstract

Weinvestigated whether gene transfer of insulin-like growth factor I (IGF-I) to the hepatic tissue was able to improve liver histology and function in established liver cirrhosis. Rats with liver cirrhosis induced by carbon tetrachloride (CCl4) given orally for 8 weeks were injected through the hepatic artery with saline or with Simian virus 40 vectors encoding IGF-I (SVIGF-I), or luciferase (SVLuc). Animalsweresacrificed8weeksafter vector injection. In cirrhotic ratsweobserved that, whereas IGF-I was synthesized by hepatocytes, IGF-I receptor was predominantly expressed by nonparenchymal cells, mainly in fibrous septa surrounding hepatic nodules. Rats treated with SVIGF-I showed increased hepatic levels of IGF-I, improved liver function tests, and reduced fibrosis in association with diminished -smoothmuscle actin expression, up-regulation of matrix metalloproteases(MMPs)and decreased expression of the tissue inhibitors of MMPs TIM-1 and TIM-2. SVIGF-I therapy induced down-regulation of the profibrogenic molecules transforming growth factor beta (TGF ), amphiregulin, platelet-derived growth factor (PDGF), connective tissue growth factor (CTGF), and vascular endotheliumgrowthfactor(VEGF)andinduction of the antifibrogenicandcytoprotective hepatocyte growth factor (HGF). Furthermore, SVIGF-I-treated animals showed decreased expression of Wilms tumor-1 (WT-1; a nuclear factor involved in hepatocyte dedifferentiation) and up-regulation of hepatocyte nuclear factor 4 alpha (HNF4 ) (which stimulates hepatocellular differentiation). The therapeutic potential of SVIGF-I was also tested in rats with thioacetamide-induced liver cirrhosis. Also in this model, SVIGF-I improved liver function and reduced liver fibrosis in association with up-regulation of HGF and MMPs and down-regulation of tissue inhibitor of metalloproteinase 1 (TIMP-1). Conclusion: IGF-I gene transfer to cirrhotic livers induces MMPs and hepatoprotective factors leading to reversion of fibrosis and improvement of liver function. IGF-I gene therapy may be a useful alternative therapy for patients with advanced cirrhosis without timely access to liver transplantation.