The potential of embryonic stem cells to treat heart disease.

Cell therapy is currently receiving growing interest as a new means of repairing infarcted myocardium. Despite the encouraging experimental results yielded by autologous skeletal myoblasts and bone marrow-derived hematopoietic and mesenchymal stem cells, there is increasing evidence that the plasticity of these adult cells is more limited than initially thought and that, consequently, their conversion into cardiomyocytes is unlikely or, at best, quantitatively very limited. As the engrafted cells should electromechanically interact with host cardiac cells to form a functional syncytium, attention is now increasingly focused on cells that feature a true cardiomyogenic differentiation potential, enabling them to connect with the neighboring cardiomyocytes. In this setting, embryonic stem cells are particularly attractive, since they can be precommitted towards a cardiac lineage and complete their full maturation in vivo, possibly under the influence of host tissue-associated paracrine signaling pathways. Although a potential clinical use of embryonic stem cells is still fraught with difficulty (amplification, purification and immunogenicity), available experimental data suggest a consistent efficacy in repairing infarcted myocardium, which has stimulated efforts to address these issues.