Many applications of human embryonic stem cells (hESCs) will require fully defined growth
and differentiation conditions including media devoid of fetal calf serum. To identify factors
that control lineage differentiation we have analyzed a serum-free (SF) medium conditioned
by the cell line END2, which efficiently induces hESCs to form cardiomyocytes. Firstly, we
noted that insulin, a commonly used medium supplement, acted as a potent inhibitor of
cardiomyogenesis in multiple hESC lines and was rapidly cleared by medium conditioning …