Embryonic Stem Cells and the Cardiovascular System

Human embryonic stem (ES) cells are pluripotent cells isolated from the inner cell mass of blastocyst-stage embryos. These cells are capable of self-renewal and can differentiate into many cell types. In vivo, human ES cells injected into immune-deficient mice yield teratomas with ectodermal, mesodermal, and endodermal cell derivatives. In vitro, spontaneous aggregation of human ES cells results in the formation of embryoid bodies (EBs) comprised of differentiated cells from the three embryonic germ layers. The addition of growth factors can induce the differentiation of human ES cells into specific populations of cells, among them the cells of the cardiovascular system, cardiomyocytes, and endothelial cells. Functional cardiomyocytes caused the EBs to exhibit rhythmic contractions. The cells of the cardiovascular system were distinguished by molecular markers and by their structural and functional characteristics. Human ES cells may serve as a source of cells for cellular transplantation in different pathologies, among them cardiovascular diseases, and as a model to study the embryonic development of human beings.