Gene Transfer Into the Donor Heart During Cold Preservation for Heart Transplantation

Background. Ex vivo gene transfer to heart grafts may hold promise as a means of changing alloreactivity or xenoreactivity after transplantation. However, it remains to be determined how effectively gene transfer can be accomplished within a short time in cold-stored grafts that are ready to be transplanted. Methods. We performed an experimental study using a replication-defective adenovirus (Adex1CALacZ) encoding the Escherichia coli β-galactosidase (β-gal) gene to perform gene transfer to heart grafts awaiting transplantation. Thirty hearts of Wistar rats were removed and their coronary arteries were perfused with University of Wisconsin solution containing 1 × 109, 1 × 1010, or 1 × 1011 plaque-forming units of the recombinant adenovirus at 4°C for 60 minutes. As a control, other hearts were perfused with University of Wisconsin solution with an adenoviral vector that did not contain the β-gal gene (Adex1w1) for the same period. After perfusion, the grafts were implanted in the necks of syngeneic adult rats. The grafts were removed each week after transplantation and their expression of β-gal was assessed by 5-bromo-4-chloro-3-indoyl-β-image-galactoside staining. Results. Successful gene transfer and expression of the β-gal gene were demonstrated in adenovirus-perfused hearts. Gene transfer occurred preferentially in the cardiomyocytes over the endothelial cells and smooth muscle cells of the coronary vessels. In hearts perfused with 1 × 109 plaque-forming units of the adenovirus, gene expression persisted for 4 weeks after transfer, but it diminished gradually and was minimal by day 28. Histologic analyses revealed slight inflammatory reactions in the myocardium. In hearts perfused with 1 × 1010 and 1 × 1011 plaque-forming units of the adenovirus, β-gal diminished 3 weeks after transplantation and a prominent infiltration of leukocytes was recognized in the myocardium. Conclusions. This study demonstrated that the cardiomyocytes of heart grafts express an exogenous gene product after adenovirus-mediated gene transfer under hypothermic preservation conditions. However, immune or inflammatory reactions to recombinant adenoviruses must be taken into account when a large number of adenoviruses are injected into the coronary arteries.