Gene Delivery of Sarcoplasmic Reticulum Calcium ATPase Inhibits Ventricular Remodeling in Ischemic Mitral Regurgitation

Abstract

Background-Mitral regurgitation (MR) doubles mortality after myocardial infarction (MI). We have demonstrated thatMR worsens remodeling after MI and that early correction reverses remodeling. Sarcoplasmic reticulum Ca ϩ2 -ATPase (SERCA2a) is downregulated in this process. We hypothesized that upregulating SERCA2a might inhibit remodeling in a surgical model of apical MI (no intrinsic MR) with independent MR-type flow. Methods and Results-In 12 sheep, percutaneous gene delivery was performed by using a validated protocol to perfuse both the left anterior descending and circumflex coronary arteries with occlusion of venous drainage. We administered adeno-associated virus 6 (AAV6) carrying SERCA2a under a Cytomegalovirus promoter control in 6 sheep and a reporter gene in 6 controls. After 2 weeks, a standardized apical MI was created, and a shunt was implanted between the left ventricle and left atrium, producing regurgitant fractions of Ϸ30%. Animals were compared at baseline and 1 and 3 months by 3D echocardiography, Millar hemodynamics, and biopsies. The SERCA2a group had a wellmaintained preload-recruitable stroke work at 3 months (decrease by 8Ϯ10% vs 42Ϯ12% with reporter gene controls; PϽ0.001). Left ventricular dP/dt followed the same pattern (no change vs 55% decrease; PϽ0.001). Left ventricular end-systolic volume was lower with SERCA2a (82.6Ϯ9.6 vs 99.4Ϯ9.7 mL; Pϭ0.03); left ventricular end-diastolic volume, reflecting volume overload, was not significantly different (127.8Ϯ6.2 vs 134.3Ϯ9.4 mL). SERCA2a sheep showed a 15% rise in antiapoptotic pAkt versus a 30% reduction with the reporter gene (PϽ0.001). Prohypertrophic activated STAT3 was also 41% higher with SERCA2a than in controls (PϽ0.001). Proapoptotic activated caspase-3 rose Ͼ5-fold during 1 month in both SERCA2a and control animals (PϭNS) and decreased by 19% at 3 months, remaining elevated in both groups. Conclusions-In this controlled model, upregulating SERCA2a induced better function and lesser remodeling, with improved contractility, smaller volume, and activation of prohypertrophic/antiapoptotic pathways. Although caspase-3 remained activated in both groups, SERCA2a sheep had increased molecular antiremodeling "tone." We therefore conclude that upregulating SERCA2a inhibits MR-induced post-MI remodeling in this model and thus may constitute a useful approach to reduce the vicious circle of remodeling in ischemic MR. (Circ Heart Fail. 2010;3:627-634.)

Cardiac gene therapy in large animals: bridge from bench to bedside

“…5 This beneficial effect was further confirmed in sheep 7,25 and dog 23 models of pacing-induced heart failure, chronic ischemia pig 79 and sheep model of myocardial infarction with mitral valve regurgitation model. 6 Consistent beneficial effects of SERCA2a gene transfer in different etiology of heart failure models support its significance in a failing heart. SERCA2a gene transfer was also shown to increase coronary flow by increased endothelial nitric oxide synthase expression, 9 and attenuates myocardial apoptosis.…”

“…In fact, most of the large animal studies that targeted calcium cycling used adenoassociated virus to demonstrate the chronic efficacy. [5][6][7]23,25,79,83 The importance of this vector is growing with the increasing attention to treat heart failure with gene therapy.…”

“…To increase the transduction efficiency, various approaches have been taken. Slow injection of the vectors 5 or interruption of antegrade coronary flow in combination with venous occlusion 6,8,28 were aimed at prolonged vector attachment to the vessel. V-focus system, 7,24,25 which allows recirculation of the vectors through closed circuit, also increases the vector exposure while minimizing extra-cardiac expression.…”

“…Indeed, the efficacy of virus-mediated sarcoplasmic reticulum calcium ion (Ca 2+ ) ATPase (SERCA2a) gene transfer, which led to the initiation of the aforementioned clinical trial, was supported by a large amount of preclinical data with remarkable effect in large animals. [3][4][5][6][7][8][9] In this review, we discuss the current status of cardiac gene therapy focusing on large animal studies, with emphasis on animal models, targeted genes, vector types and delivery methods.…”

Gene Therapy in Heart Failure

“…Antegrade coronary infusion with a short occlusion of both a coronary artery and a coronary vein enhanced myocardial gene expression 58,59 ( Figure 3c). This method preserved left ventricular function and inhibited ventricular remodeling in a large animal model of heart failure 59 .…”