Focal arterial transgene expression after local gene delivery

BACKGROUND: Gene therapy for the treatment of vascular disease is limited b y a low transfection efficiency and/or undesired biological responses. OBJECTIVE: To determine the transfection efficiency of delivering a liposom e/DNA complex into balloon-injured rabbit arteries systematically or using a local delivery catheter. METHODS: The cationic liposomes N-[1-(2,3,diotcoyloxy) propyl]-N,N,N-trimet hylammonium methyl-sulphate and dioleoyl-phosphatidylethanolamine were mixe d 1:1 (wt/wt) and combined with the plasmid pCMV-AP containing the human pl acental alkaline phosphatase (AP) reporter gene. Before initiating the in v ivo experiments, the optimal ratio of liposome to DNA complex and the persi stence of transgene expression were determined in cultured vascular smooth muscle cells (SMC). In vivo, a Dispatch catheter was used for local deliver y of the liposome/DNA complex into rabbit iliac arteries that had been ball oon injured five days previously. The contralateral iliac or renal artery w as also balloon injured, and liposomes with normal saline were delivered as a negative control. For the systemic delivery group, the liposome/DNA comp lex was delivered through an ear vein. RESULTS: AP expression in transfected SMC persisted for 28 days in vitro, a lthough the percentage of transfected cells declined with time (eg, at 24 h it was 27.3%+/-2.9%, at 28 days it was 0.4%+/-0.1%). SMC proliferation in vitro enhanced the transfection efficiency 12-fold. In vivo, local delivery resulted in low levels of transfection in arteries harvested one day postd elivery; however, six of seven arteries harvested three days postdelivery h ad multiple regions of focal transgene expression involving all three arter ial layers, For the systemic delivery group, two of nine arteries expressed the transgene. No transgene expression was found in uninjured arteries in either the local or systemic delivery groups. However, with both local and systemic delivery, balloon-injured arteries that received liposomes and sal ine showed low levels of AP expression in either the neointima, media or ad ventitia, presumably due to systemic recirculation of the liposome/AP const ruct. CONCLUSIONS: Liposome-mediated gene transfection can be successfully perfor med to all vessel layers in vivo by using a local delivery catheter, and ma y provide a therapeutic opportunity for modulating atherosclerosis and rest enosis. Unwanted transfection at a distance may occur with catheter-based l ocal delivery and requires further refinement.