Stem and progenitor cells are promising new treatment options to enhance muscular growth and restore cardiac ventricular function in diseased heart. To date, many cell types from different sources (embryonic, bone marrow, induced pluripotent, endogenous cardiac stem cells, mesenchymal stem cells) have been used with a perspective to restore cardiac muscle after myocardial infarction and to enhance cardiac function.1 This has resulted in several studies approaching the feasibility and experimental as well as clinical benefit of modifying cardiac function by cytotherapy. Although, in clinical trials, data on long-term effects of cell transplantation in hearts with myocardial infarction are still missing, and potential side effects like generation of arrhythmias and restricted cardiac growth can still not be excluded, some of the trials both in clinical and in experimental settings have promising results regarding the partial restoration of ejection fraction after myocardial infarction.2 3 However, it remains unclear whether stem or progenitor cells contribute directly to recovery processes in failing hearts by integrating into the heart tissue and participating in contraction. Thus, it was shown that after myocardial infarction, only poor engraftment is achieved, utilising mononuclear and mesenchymal bone marrow …