Stem cell-based therapies for heart regeneration: what did the bench teach us?

Stem cell-based therapies represent a promising therapy for myocardial infarction. Pre-clinical and clinical tests performed in the last 10 years indicate that several types of stem cells and their progenies reduce infarct size and improve cardiac contractile function. The mechanism is dependent on the type of cell and involves a combination of several factors, such as: (i) the formation of new blood vessels, (ii) the release of pro-survival, pro-angiogenic and anti-inflammatory factors (paracrine effect), and (iii) the functional contribution of cardiomyocytes. With the exception of cardiac progenitor cells and pluripotent stem cells (human embryonic stem cells and inducible pluripotent stem cells) that have the unquestioned ability to give rise to cardiomyocytes, the other stem cells, including bone-marrow stem cells and fetal stem cells, have none or very limited capacity to differentiate into contractile cells. For both cases, it is of the utmost importance to develop strategies to promote cell survival and in vivo engraftment as well as to unravel the therapeutic mechanism of stem cells. This review focuses on the recent developments of stem cells and on the use of biomaterials for efficiently stem cell delivery and tracking.