Cardiac stem cells and progenitors: developmental biology and therapeutic challenges.

Discovery of embryonic and adult stem cells holds great promise for the treatment of cardiovascular disease. Embryonic stem (ES) cells differentiate into cardiac myocytes as well as multiple other cell lineages in vitro and when transplanted into the heart. However, their clinical application is limited by their pleuripotent nature, capacity to form teratomas and ethical concerns. Several groups have reported that bone marrow-derived cells differentiate into cardiac myocytes, though these findings remain controversial requiring further examination. Nevertheless, injection of bone marrow-derived cells in the setting of experimental models of myocardial infarction has demonstrated functional benefit. Similarly, small phase I/II clinical trials of bone marrow derived mononuclear cell infusions in the setting of acute myocardial infarction have generally demonstrated short term functional benefit. Most recently, several distinct populations of resident stem cells have been identified in the heart. Further elucidation of cardiovascular stem cell biology is a crucial first step in translating the promise of cardiac stem cells and progenitors into the clinical reality.