Liver- and Lobe-Specific Gene Transfer Following the Continuous Microinstillation of Plasmid DNA onto the Liver Surface in Mice: Effect of Instillation Speed

Development of technology to deliver foreign gene(s) to a specific organ/tissue is one of the major challenges in gene therapy. Here, we show liver- and lobe-specific gene transfer following the continuous microinstillation of plasmid DNA (pDNA) onto the liver surface in mice. Naked pDNA was continuously instilled onto the right medial liver lobe using syringe pump in male ddY mice. Our previous studies showed liver- and lobe-selective gene expression after instillation of 30m l of pDNA solution onto the liver surface, but gene expression was also found in the other liver lobe, kidney and spleen. To improve target site selectivity of gene expression, the instillation volume was decreased; however, non-specific gene expression in the other liver lobe and diaphragm was still detected. To prevent immediate diffusion of the pDNA solution, we performed continuous microinstillation of pDNA using a syringe pump; as a result, target site selectivity was greatly improved. As for instillation speed, 5 min infusion was enough to prevent diffusion of pDNA solution. Furthermore, transfection efficiency in the target site was maintained when instillation speed was slowed. Wiping off residual pDNA solution from the applied liver lobe resulted in a further improvement in selectivity, suggesting not only immediate diffusion, but also gradual diffusion, are important factors for successful target site-specific gene transfer. Information in this study will be useful for further development of an effective gene delivery system targeted to a specific organ/tissue by use of other non-viral or viral vectors