Uniform long-term gene expression using adeno-associated virus (AAV) by ex vivo recirculation in rat-cardiac isografts

Background: Gene therapy in cardiovascular disease promises to be of great impact. The ideal vector for the therapeutic gene transfection remains to be determined. The aim of the present study was to investigate the efficacy of gene transfer using adeno-associated virus vectors carrying the lacZ-reporter gene (AAV-IacZ) in a previously described coronary recirculation model. Methods: Beating Lewis rat hearts perfused with oxygenated Krebs-Henseleit solution were harvested, after which an atrial septal defect (ASD) was created. All vessels were tied, and AAV-IacZ was injected into the aortic root. The solution was recirculated through the ASD to the left side of the heart and pumped back to the coronary arteries by the left ventricle. Incubation was allowed for 20 min at 15°C, and the hearts were subsequently transplanted heterotopically in syngeneic rats. Three increasing doses (109, 1010, 1011 e.u.) of AAV-IacZ virus vectors were used to study the rate of gene transfer. All hearts were harvested after 7-60 days and evaluated histologically for expression of the lacZ-gene. Results: Dose-dependent gene transfer was observed. Even after 60 days, there was no obvious decline in gene expression. Conclusion: Adeno-associated virus vectors offer effective and uniform gene transfer in the myocardium after transcoronary injection and recirculation. Due to the lack of immune response previously described, no decrease in gene expression can be observed up to 60 days after injection.