Gene transfer to coronary artery bypass conduits

Background. Gene therapy is a rational approach to prevention of stenosis in saphenous vein grafts used as conduits for coronary artery bypass grafting. To explore this possibility we developed methods for adenoviral-mediated gene transfer to canine saphenous veins. Methods. During a single procedure, autogenous canine saphenous vein segments were transduced ex vivo and used as coronary artery bypass grafts. The proximal end of each vein was ligated, adenovirus containing the Escherichia coli β-galactosidase gene (Ad.CMVLacZ) was delivered at titers of 2.5 × 10⁹ or 5 × 10⁹ plaque-forming units (pfu)/mL to the lumen through a distal heparin lock, and the segment was immersed in the viral solution for 1 hour at 37°C. Control segments were exposed to diluent alone in an identical manner. Aortocoronary anastomoses were made using cardiopulmonary bypass. Transgene expression was assessed qualitatively and quantitatively after 3 days. Results. β-Galactosidase levels showed a dose-dependent increase: 0.00 ± 0.00 ng/mg total protein for controls; 5.60 ± 2.27 ng/mg total protein for a viral titer of 2.5 × 10⁹ pfu/mL and 11.97 ± 6.14 ng/mg for 5 × 10⁹ pfu/mL. The two dosage groups differed significantly from each other (p = 0.035) and from controls (p = 0.003). X-gal staining demonstrated mostly endothelial and scattered adventitial transgene expression. Conclusions. Transgene expression after ex vivo gene transfer into saphenous vein grafts in a canine coronary artery bypass model indicates that this method may be useful for delivery of therapeutic genes to prevent or retard vein graft arteriosclerosis.