Partial restoration of myocardial function and perfusion by cell therapy following myocardial infarction

Purpose of review In animals, both skeletal myoblasts and stem cells partially restore myocardial function after MI. This review provides a critical analysis of the initial clinical trials of these two therapeutic strategies. Recent findings Direct injection of autologous skeletal myoblasts into the peri-infarct area has been performed at bypass surgery and by subendocardial injection in the catheterization laboratory. Both approaches appear to improve function significantly. Nonetheless, ventricular arrhythmias occur quite frequently in the first week after myoblast injection. In contrast, stem cells can be delivered to the injured myocardium by direct injection, by IV injection, or by bone marrow stimulation. The incidence of ventricular arrhythmia does not seem to increase. The magnitude of absolute improvement in cardiac ejection fraction, however, is only about 7%. The potential limitations of stem cell therapy are cell fusion, creating genetically abnormal cells, and the ability to deliver sufficient numbers of cells to have an important biologic effect. Summary Cell replacement therapy after MI has considerable promise for restoration of cardiac function. Nonetheless because important theoretical and practical questions remain unanswered, the methodology is not yet ready for widespread clinical application.