Old dogmas and new hearts: a role for adult stem cells in cardiac repair?

The vast developmental repertoire of embryonic stem cells is well recognised. These primitive stem cells can differentiate in vivo and in vitro into cells of all three embryonic germ layers (endoderm, mesoderm, ectoderm), making them attractive potential agents to target for enhanced tissue repair and regeneration. Adult stem cells on the other hand are considered more restricted in their lineage differentiation capabilities. Recent research has challenged this dogma with the finding that bone marrow-derived stem cells can differentiate into a wide variety of cell types including muscle (skeletal and cardiac). Furthermore, although the myocardium has for decades been regarded as a post-mitotic organ, a series of studies has indicated that a population of stem cells exists which is capable of at least partial reconstitution of the myocardium following an ischaemic insult. It is therefore now accepted that adult stem cells could be used to enhance myocardial repair. This review discusses the current status of adult stem cell research in the light of its potential for improving myocardial repair.