Tri-iodothyronine and a deleted form of hepatocyte growth factor act synergistically to enhance liver proliferation and enable in vivo retroviral gene transfer via the peripheral venous system

Retroviral vectors integrate into the target cell genome in a stable manner and therefore offer the potential for permanent correction of the genetic diseases that affect the liver. These vectors, however, usually require cel l division to occur in order to allow provirus entry into the nucleus. We h ave explored clinically acceptable methods to improve the efficiency of ret roviral gene transfer to the liver, which avoid the need for liver damage. Tri-iodothyronine (T3) and recombinant hepatocyte growth factor have previo usly been used to induce hepatocyte proliferation in rat livers and allow i n vivo retroviral gene transfer. We investigated the combined effects of th ese growth factors, with their differing mechanisms of action, on hepatocyt e proliferation in vivo and assessed their effectiveness in priming cells f or retroviral gene transfer. During the phase of hepatocyte proliferation r etrovirus was administered via either the portal or tail vein. Acting syner gistically, T3 and a truncated form of recombinant hepatocyte growth factor (dHGF) induced 30% of hepatocytes in normal rat liver to enter DNA synthes is at 24 h. This increased proliferation enabled the liver to be transduced in vivo by retroviral vectors via either the portal or peripheral venous s ystem, achieving transduction efficiencies of 6.9 +/- 1.6% and 4.3 +/- 0.4% respectively. Thus, the liver can be simply and conveniently transduced in vivo with integrating vectors, introduced via the peripheral venous system during a wave of growth factor-induced proliferation, pointing the way to clinically applicable gene transfer techniques.