Stem cell therapy after myocardial infarction: ready for clinical application?

The discovery of stem cells capable of generating angiogenic or contractile cells and structures might offer new treatment options for patients suffering from heart disease. In particular, embryonic stem cells are considered to have great potential for regenerative medicine and tissue engineering. Studies suggest that delivery or mobilization of stem and progenitor cells might improve tissue perfusion and contractile performance of the damaged heart; however, the underlying mechanisms are poorly understood. Fusion or trans-differentiation into cardiomyocytes or vascular cells are considered rare events of cellular engraftment, and adult stem cells are now considered as 'regenerator cells', acting via paracrine effects of cytokines, or by activation of resident stent cells, thereby supporting the myocardial healing mechanisms after injury. Administration of autologous hematopoietic stem cells or mobilization of endogenous stem cells has been shown to be safe after myocardial infarction or cardiomyopathies, whereas skeletal myoblasts are considered to be hazardous due to the occurrence of life-threatening arrhythmias. This review focuses on the use of adult human stem cells for treating myocardial infarction and cardiomyopathy, and discusses recent preliminary efficacy data, which suggest that 'regenerator cells' might have the potential to improve myocardial perfusion and contractile performance in patients suffering from myocardial infarction, severe ischemic heart disease and chronic heart failure.