Human embryonic stem cells for heart repair: where are we now?

Purpose of review Chronic heart failure is a multifactorial devastating, disease facing limitations in pharmacology. The human heart does, not regenerate. Thus, myocardial regeneration has been envisioned using stem cells. Few clinical trials using bone marrow stem cells have been performed without conclusive results. While it is now well established that bone marrow stem cells do not differentiate into cardiomyocytes, both paracrine effects and a potential neoangiogenesis are proposed to explain the modest benefits observed in patients. Human embryonic stem cells represent an alternative cell source to regenerate a postinfarction myocardial scar. Recent findings In terms of development, human embryonic stem cells are the most versatile stem cells capable of differentiating into all cell types of the body, including cardiomyocytes in vitro. Animal experiments have shown that human embryonic stem cell-derived cardiomyocytes engraft into a postmyocardial infarcted heart. Recently, cardiac committed human embryonic stem cells also spontaneously differentiated in vivo in rat hearts. Several limitations, including genetic and epigenetic instabilities of human embryonic stem cell lines, slow down the translation of research into the clinical arena. Summary This review gives an update on the advantages and disadvantages of human embryonic stem cells as a source in cell therapy. The remaining challenges of these cells to relieve heart failure are then presented.