A method of directly differentiating pluripotent human embryonic stem cells (hES cells) into cells of a cardiac lineage, comprising:
- (i) providing a culture of hES cells in a defined medium comprising bFGF, insulin, ascorbic acid, and activin-A, wherein said defined medium is free of serum, free of feeder cells, and free of feeder cell conditioned medium;
- and
- (ii) adding nicotinamide (NAM) to the culture, wherein the hES cells are cultured in the presence of NAM for a period of time sufficient to induce the expression of cardiac specific transcription factor (CSX) Nkx2.5 and cause the hES cells to directly differentiate into cells of cardiac lineage.