EFFECTS OF KERATINOCYTE AND HEPATOCYTE GROWTH-FACTOR IN-VIVO - IMPLICATIONS FOR RETROVIRUS-MEDIATED GENE-TRANSFER TO LIVER

We have previously shown that intravenous administration of keratinocy te growth factor (KGF) induces hepatocyte proliferation, allowing for efficient and noninvasive in vivo gene transfer with high-titer retrov iral vectors in mice. The distinctive periportal distribution of trans duced cells led us to investigate the ability of virus-sized particles to perfuse the liver adequately after growth factor treatment. We fou nd that perfusion was adequate, and that transduction was limited to t he periportal region because only those cells were stimulated to divid e. Cells in this region also showed increased expression of Ram-1, the receptor for the murine Moloney leukemia virus (MoMLV) amphotropic en velope, after KGF treatment. In further studies we found that recombin ant hepatocyte growth factor (HGF) induces a different population of h epatocytes to divide and upregulate Ram-1. The differential pattern of induction suggested that combining KGF and HGF would improve gene tra nsfer efficiency further. Indeed, simultaneous delivery of both growth factors leads to an overall increase in the number of proliferating c ells. Importantly, when coupled with MoMLV delivery, efficiency of gen e transfer increased. These results confirm the utility of growth fact ors for noninvasive hepatic gene transfer in mice, and demonstrate how experiments to define the mechanism of transduction can be taken adva ntage of to develop improved gene transfer protocols.