Cardiac differentiation from human embryonic stem cells. (a) A staged protocol to induce cardiac differentiation from human embryonic stem (hES) cells . (b) Modeling early human heart formation using hES cells. hES cells were induced as embryoid bodies using the protocol shown in (a). Day 6 embryoid bodies were dissociated and the KDRlow/C-KITneg population represents the multipotent cardiovascular progenitor cells with a transcriptional signature of ISL1+, TBX5+ and NKX2.5+. The KDRlow/C-KITneg population was further specified into major cardiovascular lineages, including cardiomyocytes, smooth muscle cells and endothelial cells. bFGF, basic fibroblast growth factor; BMP, bone morphogenetic protein; DKK1, Dickkopf homolog 1; ES, embryonic stem; KDR, kinase insert domain protein receptor; VEGF, vascular endothelial growth factor.