PERCUTANEOUS TRANSLUMINAL IN-VIVO GENE-TRANSFER BY RECOMBINANT ADENOVIRUS IN NORMAL PORCINE CORONARY-ARTERIES, ATHEROSCLEROTIC ARTERIES, AND 2 MODELS OF CORONARY RESTENOSIS

Background Gene therapy has been proposed as a possible solution to th e problem of restenosis after coronary angioplasty. The current study was undertaken to assess conventional methods of gene transfer and to develop percutaneous techniques for introducing genes directly into th e coronary arteries of large mammals. Since the anticipated targets of gene therapy against restenosis include atherosclerotic and previousl y instrumented arteries, we also evaluated gene transfer in atheroscle rotic coronary arteries and in two porcine models of restenosis: one u sing intracoronary stents and a second using balloon overstretch angio plasty. Methods and Results The conventional method of using perforate d balloon catheters to deliver Lipofectin-DNA complexes directly into the coronary arteries of intact animals was applied to 18 porcine coro nary arteries including normal arteries, hypercholesterolemic arteries , and those simulating restenosis. The results of this study were cons istent with previously published results indicating that only low leve ls of luciferase gene expression could be obtained by Lipofectin-media ted gene transfer. We therefore undertook a second, parallel study to evaluate percutaneous transluminal in vivo gene transfer using a repli cation-deficient adenoviral vector. A comparison of the two studies re vealed that the mean level of reporter gene expression in the cohort u ndergoing adenoviral infection was 100-fold higher than in the cohort undergoing Lipofection. Analysis of luciferase activity over time in n ormal arteries revealed that recombinant gene expression was half-maxi mal after 1 day, peaked within 1 week, was still half-maximal at 2 wee ks, and declined to low levels by 4 weeks. Histochemical analysis of c oronary arteries treated with a second adenovirus expressing a nuclear -localized beta-galactosidase gene demonstrated gene transfer to a lim ited number of cells in the media and adventitia. Immunohistochemical analysis of Ad5-infused arteries using a monoclonal antibody directed against CD44 identified a periadventitial infiltrate composed of leuko cytes. Conclusions The recombinant adenoviral vectors proved to be far more effective than Lipofectin at delivering foreign genes directly i nto the coronary arteries of living mammals. Furthermore, the influenc es of hypercholesterolemia and arterial injury appeared to have little effect on the levels of gene expression obtained using either method. The results demonstrate that low-level recombinant gene expression, t he major obstacle impeding gene therapy for the prevention of restenos is, can potentially be overcome by using adenoviral vectors to mediate coronary gene transfer in vivo. The duration of gene expression provi ded by these vectors and their effective deployment in atherosclerotic , balloon-overstretched, and stented coronary arteries suggest that re combinant adenovirus may have potential for evaluating gene therapy in the clinically informative porcine models of coronary restenosis.