Effective gene transfer in the rat myocardium via adenovirus vectors using a coronary recirculation model

Background: Gene therapy promises to play an important role in the treatment of heart disease and in transplantation. The limited effectiveness of gene transfer, however, remains an unresolved problem. The aim of the study was to create a model for more effective gene transfer using adenovirus vectors carrying the lacZ-reporter gene (AdV-lacZ). 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 AdV-lacZ 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 degrees C and the hearts were subsequently transplanted heterotopically in syngeneic rats. This method was compared to AdV-lacZ injection into cardioplegic hearts. The hearts were harvested after 2, 7, or 14 days and evaluated histologically for expression of the lacZ gene. Results: Maximal gene expression was achieved after 7 days by the recirculation model. There was less efficient gene expression at day 2 and at day 14. No evidence of ischemic injury of the myocardium was noticed histologically. Almost no successful gene expression was seen in the arrested hearts. Conclusion: This novel recirculation method lets the vector be repeatadly exposed to the endothelium, resulting in an effective gene expression after 7 days incubation time rather than after 14, when a decline has set in presumably due to immunologic response.