Enhancement of retrovirus-mediated gene transfer to rat liver in vivo by infusion of hepatocyte growth factor and triiodothyronine

Abstract

Background/Aims: Gene transfer using recombinant Moloney murine leukemia viruses (rMoMuLV) requires mitosis of the target cell. Previously, we and others have used partial hepatectomy for induction of hepatocellular proliferation for gene transfer to the liver in vivo by exsanguineous perfusion with rMoMuLV. We hypothesized that induction of hepatocellular proliferationby combined administration of two hepatocellular mitogens, hepatocyte growth factor (HGF) and triiodothyronine (T3), should permit rMoMuLV-mediated gene transfer into liver without invasive approaches.Methods: HGF (1 mg/kg) was perfused continuously into the portal vein of Wistar male rats and T3 (2 mg/kg) was injected subcutaneously. Twenty-four hours after injecting HGF and T3, the state of proliferation of hepatocytes was estimated from the incorporation of 5′-bromo-2′-deoxy-uridine (BrdU). The amphotropic retroviral receptor (Ram-1) expression of liver was evaluated at different time points after injecting HGF and T3 by means of Northern blotting using Ram-1 cDNA probe. In order to evaluate the role of hormone treatment on gene transfer, the liver was perfused exsanguineously with rMoMuLV 24 h after injection with hormones.Results: Rats treated with a combination of HGF and T3 expressed BrdU and β-galactosidase in 8.3% and 0.7% of hepatocytes, respectively. On the other hand, there was near absence of gene transfer in untreated rats perfused with rMoMuLV. Twenty-four hours after the initial manipulation, abundant expression of Ram-1 mRNA was observed in rat hepatocytes treated with HGF plus T3.Conclusions: Stimulation of hepatocellular mitosis and upregulation of Ram-1 expression by HGF and T3 augment retrovirus-mediated gene transfer into hepatocytes.