Bringing cardiac cell therapy with bone marrow stem cells to the clinic: where are we now?

Stem cell therapy is emerging as a potential therapeutic option for cell death-related heart diseases. Preclinical as well as early-phase human studies have demonstrated the ability for cell therapy to augment perfusion and increase myocardial contractility. In addition, recent intermediate-size randomized trials suggested the potential of bone marrow stem cells to augment left ventricular recovery after a recent myocardial infarction. In general, the effects are modest and often similar despite differences in the study design, cell number or type. Therefore, a number of issues should be addressed before stem cell therapy will become standard clinical practice. They are related to the selection of the optimal cell type, standardization of the cell processing and release criteria. Other issues include timing of the cells injections and cell homing and retention. Further research is needed to understand the mechanisms underlying observed functional and beneficial effects including optimization of myocardial biological effects. Finally, despite overall enthusiasm, safety of the cardiac stem cell therapy should remain under scrutiny. The safety profile needs to be established in the large clinical trials and in a close interaction between translational and clinical research to address conceptual or procedural issues.