Myocardial protection: is there a role for gene therapy?

Skeletal myoblast transplant in heart failure

Despite recent advances in the prevention and treatment of ischemic heart disease (IHD), treatment of patients with heart failure secondary to myocardial infarction remains a therapeutic challenge. Heart transplantation has emerged as a viable option but is fraught with problems of supply. Mechanical assist devices are extremely expensive and dynamic cardiomyoplasty has shown only limited success in the clinical setting. Recent insights into the pathogenesis of myocardial diseases and the progress made in the field of molecular biology have resulted in the development of new strategies at molecular as well as cellular levels for cardiac muscle repair. One such strategy is to augment ventricular function by means of cellular cardiomyoplasty through intracardiac cell grafting using adult and fetal cardiomyocytes, stem cells, and autologous skeletal myoblasts.

Gene interventions in the beta-adrenergic system for treating heart failure

Cardiovascular disease accounts for nearly 40% of all deaths annually in this country. Prevention management and advances in medical treatments have dramatically reduced the overall mortality rate due to heart disease. However, death due to chronic heart failure (HF) continues to rise, and effective therapy, particularly for end-stage HF, has been elusive. The myocardial beta-adrenergic receptor (betaAR) system is critical not only in chronic HF but also in acute settings where cardiac function is compromised. Adding to its importance is the fact that drugs that act by altering betaAR signal transduction are at the forefront of conventional HF therapeutic strategies. Accordingly, the ability to genetically manipulate betaAR signaling in the heart is of great interest since it may provide unique inotropic support and improve existing therapeutic strategies for HF.

Development of an in vivo ischemia-reperfusion model in heterotopically transplanted rat hearts

BACKGROUND

Heart transplantation has been extensively used in animal models, including studies on gene therapy for myocardial preservation. We investigated the feasibility of in situ left coronary artery (LCA) ligation as a physiological system for the examination of strategies to modulate myocardial tolerance against ischemia-reperfusion injury, such as gene therapy, using heterotopically transplanted rat hearts.

METHODS

Lewis rat hearts that had been transplanted into syngeneic recipients' abdomens were subjected to 30-min ischemia, by occluding the LCA, and subsequent blood reperfusion by releasing the suture in situ (I/R group). Transplanted hearts in the sham group underwent laparotomy only.

RESULTS

At 24 hr of reperfusion, the size of the ischemic region was 40.1+/-3.1% of the total left ventricular mass, and the infarct size was 47.5+/-3.3% of the area at risk in the I/R group. Cardiac function was reduced in the I/R group compared with the sham group, associated with higher myeloperoxidase activity (5.12+/-1.35 vs. 0.97+/-0.33 U/g wt) and higher incidence of apoptosis as defined by TUNEL (29.8+/-3.2 vs. 3.8+/-0.7%) and DNA ladder. In the I/R group, up-regulation of Bax, Bak, and caspase-3 was observed.

CONCLUSIONS

These data on myocardial damage of transplanted hearts are consistent and equivalent to those of the usual LCA occlusion model, suggesting that this method is useful to investigate strategies for modulating myocardial tolerance against ischemia-reperfusion injury using heterotopically transplanted rat hearts in a more physiological blood-perfused model.