Perspective:

Cell replacement trials for repair of infarcted myocardium have met with limited success. However, it may be that the cell type and delivery methods have been suboptimal. Based on promising preclinical studies, these investigators generated a highly purified population of cardiovascular progenitor cells from hESCs and then mixed them with fibrinogen and thrombin to form a fibrin gel that could be placed into a pericardial pocket. The mechanism by which this model might improve wall motion is unclear, but could involve secretion of salutary extracellular vesicles by the transplanted cells. Identification of the mechanism(s) is critical, as this will guide future therapies that could be more feasible and effective. The first step may be to expand this intriguing feasibility study with adequate numbers and controls to further establish safety and efficacy.