ADENOASSOCIATED VIRUS VECTORS VASCULAR GENE DELIVERY

A variety of delivery systems have been used to genetically modify vas cular endothelial cells and smooth muscle cells (SMCs), but currently available systems suffer from either inefficient in vivo gene transfer , transient episomal vector expression, or significant immune response s and inflammation. In the present study, we evaluated an alternate ve ctor system, recombinant adeno-associated virus (rAAV) for transductio n of vascular cells in culture and in vivo. Primary cultures of rabbit , monkey, and human SMCs; macaque and human microvascular endothelial cells; and human umbilical vein endothelial cells were efficiently tra nsduced at a dose of 100 to 1000 DNase-resistant particles per cell. r AAV-mediated transduction of the vasculature in vivo was observed afte r intraluminal gene delivery or after intra-adventitial injection in c arotid arteries of atherosclerotic cynomolgus monkeys. Whether vector delivery was intraluminal or adventitial, transduction was observed in the adventitia, particularly within microvessels (vasa vasorum) but n ot in cells of the intima or media. Transduction of adventitial microv essels was enhanced by balloon injury 4 days before gene transfer. Thi s was particularly true for adventitial delivery. We have previously s hown that adventitial cell proliferation increases significantly 4 day s after balloon injury (45%) in this animal model. Together, these dat a suggest that cell proliferation may enhance AAV transduction in vivo in the vasculature. AAV vectors exhibited a tropism in vivo for the m icrovascular endothelium at the doses used in the present study, which may provide the opportunity for targeting gene delivery. In summary, we have demonstrated the utility of rAAV vectors for ex vivo vascular cell gene delivery and present an initial experience with rAAV for in vivo vascular gene delivery. This alternate vector system may overcome some of the limitations hampering the development of gene therapy for vascular disorders.