Stem cell therapy for the treatment of myocardial infarction.

Despite timely reperfusion and subsequent optimal postinfarct pharmacotherapy and device-based treatment, the outcome in patients with severe myocardial infarction remains unfavourable. Myocardial salvage is incomplete, resulting in adverse left ventricular remodeling with concomitant morbidity and mortality. The combined risk of recurrent myocardial infarction, death or readmission for heart failure amounts to 25 % within the first year, highlighting the need for additional treatment strategies. Recent and rapidly evolving insights in cardiac biology, recognizing endogenous repair capabilities of the adult human heart, paved the path towards progenitor or stem cell based cardiac protection and repair strategies following ischemic injury. We critically report on the major randomized controlled clinical trials published so far concerning intracoronary transfer of autologous bone marrow cells in the setting of acute myocardial infarction. Moreover, underlying mechanisms, practical aspects, remaining questions and future challenges are highlighted. Taken together, these trials confirm the safety and feasibility of intracoronary progenitor cell transfer in the setting of myocardial infarction. Efficacy data suggests its potential to improve left ventricular function recovery beyond current state of the art therapy, but results are mixed, modest at best and do not support true cardiomyogenesis. Hence, due to its complexity, costs and remaining uncertainties, it is still too early to implement progenitor cell therapy in its current form in standard treatment strategies for ischemic heart disease. Future studies on strategies for cardiomyocyte regeneration in combination with myocardial protection are needed.