Abstract

Safety in gene therapy is an important issue since both viral and non-viral vectors have toxic side effects. Not only vectors themselves, but also distributions of produced proteins affect safety in gene therapy; thus, development of target-selective gene transfer methods is rational. We have developed organ-, region- and cell-selective gene transfer methods using non-viral vectors. To deliver foreign gene to liver parenchymal cells (hepatocytes), galactosylation of cationic liposome/plasmid DNA complex is useful strategy. Based on analyses for intrahepatic disposition characteristics and interaction with blood components, we formulated novel galactosylated lipoplex with regulated salt concentration to reduce particle size of lipoplex and to stabilize lipoplex simultaneously; as a consequence, we succeeded in improvement of hepatocyte-selective gene transfer after intraportal injection of the lipoplex in mice. On the other hand, administration routes are important for target-selective gene transfer. We discovered that simple instillation of naked plasmid DNA onto organ surface (the liver, kidney, spleen, stomach and lung) in mice and rats could result in effective and region-selective transgene expression. Neither physical force nor carriers are necessary for gene transfer onto organ surface mesothelial cells. To rationally improve transfection efficiency, mechanism of gene transfer should be elucidated. We clarified that Rac-mediated macropinocytosis was required for naked plasmid DNA transfer in gastric mesothelial cells.