How Embryonic Stem Cells Can More Effectively Treat Ischemic Heart Disease
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Regeneration of heart muscle tissue cannot be accomplished by adult cardiomyocytes because these cells have withdrawn permanently from the cell cycle. And so, cardiomyocytes seemed to have been irreplaceable in the past. Now, fetal cardiomyocytes may be able to differentiate once transplanted into infarcted tissue, but as is so often the case, sufficient amounts of fetal tissue cannot be obtained. An alternative source of cardiomyocytes is needed (18).

It is common for researchers to aggregate ES cells into embryoid bodies (EBs) before exposing them to growth factors for differentiation. In current research, these EBs can be directed to produce spontaneously contracting areas containing cardiac muscle-specific antigens and transcription factors (13).

Therefore, ES cell-derived cardiac muscle cells may constitute a sorely-needed source of cells in transplantation for heart muscle damaged by ischemic heart disease or for myogenic heart disorders. However, adult stem cells may also be able to repopulate regions affected by myocardial ischemia after differentiation into cardiac tissue (18).

 
(39) On another note, the lack of a suitable in vitro model continues to hamper the study of human cardiac tissue development. It is impossible to study the human embryo after implantation because of ethical reasons. Without such a model, scientists lack an efficient way of gathering information on the differentiation of early human cardiac precursor cells, the development of excitability, excitation-contraction coupling, and the molecular signals for the two processes. Much information on the development of the heart has recently been learned from experiments with murine ES cells but human ES cells could further elaborate on that knowledge of heart development if not also regenerate cardiac muscle tissue (13).

Problems To Be Overcome For Embryonic Stem Cells To Provide A Viable Treatment:
(37) 1) The cardiomyocytes generated from ES cells need to be enriched and purer in makeup. For example, the cardiomyocytes in this study were found to be a mixed population of myocytes with fast and slow cell characteristics - atrial, ventricular, and sinus nodal cells (13).
2) Different strategies to counter immune rejection must be established.
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