Cardiac stem and progenitor cell identification: different markers for the same cell?

For a long time the heart has been considered a terminally differentiated organ without any regenerative potential. The latter has been classically based on the terminally differentiated nature of cardiomyocytes and the absence of a pool of tissue-specific stem cells. This view has been radically changed due to the discovery of resident cardiac stem and progenitor cells in the adult mammalian heart. However, at minimum, 5 apparently different cardiac stem and/or progenitor cell types have been described so far. Thus, we have changed from a view of the heart as a static tissue to an organ with the highest number of tissue-specific stem cell populations. Most likely, the different putative adult cardiac stem and progenitor cells represent different developmental and/or physiological stages of a unique resident adult cardiac stem cell. Notably, it is not yet known the origin of all these cells. A better understanding of the origin, biology and physiology of the myocardial stem and progenitor cells will impact the development of regenerative medicine as an effective therapy for heart disease and failure.