Gene Therapy Strategy for Long-Term Myocardial Protection Using Adeno-Associated Virus-Mediated Delivery of Heme Oxygenase Gene

Abstract

Background — Ischemia and oxidative stress are the leading mechanisms for tissue injury. An ideal strategy for preventive/protective therapy would be to develop an approach that could confer long-term transgene expression and, consequently, tissue protection from repeated ischemia/reperfusion injury with a single administration of a therapeutic gene. In the present study, we used recombinant adeno-associated virus (rAAV) as a vector for direct delivery of the cytoprotective gene heme oxygenase-1 (HO-1) into the rat myocardium, with the purpose of evaluating this strategy as a therapeutic approach for long-term protection from ischemia-induced myocardial injury. Methods and Results — Human HO-1 gene (hHO-1) was delivered to normal rat hearts by intramyocardial injection. AAV-mediated transfer of the hHO-1 gene 8 weeks before acute coronary artery ligation and release led to a dramatic reduction (>75%) in left ventricular myocardial infarction. The reduction in infarct size was accompanied by decreases in myocardial lipid peroxidation and in proapoptotic Bax and proinflammatory interleukin-1β protein abundance, concomitant with an increase in antiapoptotic Bcl-2 protein level. This suggested that the transgene exerts its cardioprotective effects in part by reducing oxidative stress and associated inflammation and apoptotic cell death. Conclusions — This study documents the beneficial therapeutic effect of rAAV-mediated transfer, before myocardial injury, of a cytoprotective gene that confers long-term myocardial protection from ischemia/reperfusion injury. Our data suggest that this novel “pre-event” gene transfer approach may provide sustained tissue protection from future repeated episodes of injury and may be beneficial as preventive therapy for patients with or at risk of developing coronary ischemic events.

Pre-emptive gene therapy using recombinant adeno-associated virus delivery of extracellular superoxide dismutase protects heart against ischemic reperfusion injury, improves ventricular function and prolongs survival

“…The difference in survival between SOD versus LacZ treated rats cannot be due to deleterious effect of LacZ expression since our previous work has shown no significant difference in infarct sizes of the saline versus the LacZ treated animals. 31 In vivo studies on aging and I/R in rats have shown to have no effect on mitochondrial, cytosolic or total SOD activity. Myocardium is a rich source of mitochondrial DNA and consequently a significant source of ROS during I/R.…”

“…Potential 'area at risk' after acute I/R injury was estimated by Evans blue exclusion as previously described. 31 The 5-0 Ticron blue polyester sutures were used to close the chest wall. The respirator and the endotracheal tube were then removed and animal was allowed to recover under a warm heat lamp.…”

“…31. Briefly, after 24 h of reperfusion, LAD was religated and 1% Evans blue was injected into the heart to determine potential 'area at risk' based on dye exclusion.…”

“…We have previously reported that recombinant adeno-associated virus (rAAV) is effective for direct myocardial gene transfer. 31 Along with the ability for long-term expression of antioxidant enzyme in vivo, one can administer the therapeutic gene months in advance of the injury for future myocardial protection, thereby providing an effective approach to preventive therapy. Thus, the goal of this in vivo SOD study was to use rAAV, obtain efficient Ec-SOD gene expression and assess following acute I/R injury, the survival and long-term pre-emptive protection of the myocardium.…”

Augmentation of AAV-mediated cardiac gene transfer after systemic administration in adult rats

“…5,16 AAV serotype 2 vectors have been most intensively studied and have been successfully used in several experimental therapeutic approaches such as protection from ischemia/reperfusion injury in a rat model 17 or gene replacement therapy in cardiomyopathic hamsters 18,19 and revealed beneficial effects on neoangiogenesis, infarct size and cardiac function in a murine model of myocardial ischemia. 20 However, to achieve highly selective transduction of myocardial tissue, AAV vectors were administered by intramyocardial injection or selective perfusion of coronary arteries.…”