Cardiac gene delivery with cardiopulmonary bypass

Abstract

Background - Cardiac gene therapy offers the possibility of enhancing myocardial performance in the compromised heart. However, current gene delivery techniques have limited myocardial transgene expression and pose the risk of extracardiac expression. Isolation of the coronary circulation during cardiac surgery may allow for more efficient and cardiac-selective gene delivery in a clinically relevant model. Methods and Results - Neonatal piglets (3 kg) underwent a median sternotomy and cardiopulmonary bypass, followed by aortic cross-clamping with 30 minutes of cardioplegic arrest. Adenoviral vectors containing transgenes for either β-galactosidase (adeno-β-gal, n=11) or the human β2-adrenergic receptor (adeno-β2-AR, n=15) were administered through the cardioplegia cannula immediately after arrest and were allowed to dwell in the coronary circulation during the cross-clamp period. After 1 week, the animals were killed, and their heart, lungs, and liver were excised and examined for gene expression. Analysis of β-galactosidase staining revealed transmural myocardial gene expression among animals receiving adeno-β-gal. No marker gene expression was detected in liver or lung tissue. β-AR density in the left ventricle after adeno-β2-AR delivery was 396±85% of levels in control animals (P<0.01). Animals receiving adeno-β2-AR and control animals demonstrated similar β-AR density in both the liver (114±8% versus 100±9%, P=NS) and lung (114±7% versus 100±9%, P=NS). There was no evidence of cardiac inflammation. Conclusions - By using cardiopulmonary bypass and cardioplegic arrest, intracoronary delivery of adenoviral vectors resulted in efficient myocardial uptake and expression. Undetectable transgene expression in liver or lung tissue suggests cardiac-selective expression.