311. Targeted Gene Delivery to Selected Liver Segments by Isolated Hepatic Perfusion with Clamping of the Portal Vein

Purpose: Development of targeted gene transfer technologies is essential for in vivo gene therapy. Adenoviral vectors are capable of gene transfer into a wide variety of cell types but often elicit severe immune-inflammatory responses. A serious adverse event due to systemic inflammatory response syndrome was recently reported after infusion of an adenoviral vector into the liver. To minimize toxicity to the liver, gene transfer and expression should be localized to limited liver segments. In the present study, we examined the feasibility of physical targeting to the selected liver segments using catheterization techniques. Methods: Procedure 1: A vascular clamp was placed across the portal vein (PV) between the upper and the lower segments of the liver in Wistar rats. An adenoviral vector carrying the LacZ gene, AxCALacZ, was infused through the proximal PV. The clamp was removed 5 min later. Procedure 2: Isolated hepatic perfusion technique was applied in addition to clamping as procedure 1. Both PV and the hepatic inferior vena cava (IVC) were cannulated, while the other vasculatures were all clamped. The adenovirus vector was injected through the PV catheter and unbound vector particles were washed out with PBS. The outflow solution from the circulation was collected to the IVC catheter. Results: The beta-gal activity was significantly higher in the proximal segments compared to the distal segments in both procedures. Moderate beta-gal activity was also detected in the spleen in procedure 1, while the activity was hardly detectable in procedure 2. The levels of inflammatory cytokines were reduced by isolated hepatic perfusion. Conclusion: Isolated hepatic perfusion with clamping of specific portal vein branches is useful for adenoviral-mediated local gene delivery to selected liver segments and could be applied to treatment of focal liver diseases such as liver metastases of cancer.