Abstract 25: Ultrasound Cavitation Mediated Gene Delivery of ApoAI to the Artery Wall for Modulating Plaque Content

Abstract

Gene therapy is a potential approach for inhibiting many of the processes that occur during atherogenesis, particularly when targeting key molecular regulators that have multiple adverse downstream signaling pathways. Local expression of human-apoAI in the artery wall has been shown to protect against atherosclerosis in mice, without affecting systemic HDL levels. We hypothesized that focal gene delivery in arterial plaque is possible using ultrasound (US)-mediated cavitation of acoustically-active cationic microbubble gene carriers. Lipid-shelled cationic microbubbles (MB) with a decafluorobutane gas core were prepared. Bicistronic plasmids (luciferase with either GFP or apoAI) were charge coupled to the MB and injected intravenously in 12 LDLR -/- mice fed high-fat diet for 8 weeks. The thoracic aortic root was exposed to US at 1.6MHz, a pulsing interval of 1Hz, and a mechanical index of 1.3 in order to produce repetitive cavitation of MB. In vivo optical imaging showed a focal luciferase activity only at the site of UMGD starting from a day after the procedure and lasting for 7-10 days. Activity was subsequently localized to the aortic root on ex vivo optical imaging. Immunohistochemistry of the aortic root confirmed luciferase transfection of both endothelial cells of the aortic root and base of the aortic cusps, and intramural cells in atherosclerotic lesions, likely macrophages. We further show that gene therapy with the luciferase-apoAI plasmid, results in migration of cells to the thymus 6-8 days after transfection. These results indicate that local US-mediated gene therapy approach for controlling atherosclerosis is feasible in this pre-clinical model.