Activin-A and Bmp4 Levels Modulate Cell Type Specification during CHIR-Induced Cardiomyogenesis
We previously reported that chick anterolateral endoderm (AL endoderm) induces cardiomyogenesis in mouse embryoid bodies. However, the requirement to micro-dissect AL endoderm from gastrulation-stage embryos precludes its use to identify novel cardiomyogenic factors, or to scale up cardiomyocyte numbers for therapeutic experiments. To circumvent this problem we have addressed whether human definitive endoderm (hDE) cells, which can be efficiently generated in large numbers from human embryonic stem cells (hESCs), can mimic the ability of AL endoderm to induce cardiac myogenesis. Results demonstrate that both hDE cells and medium conditioned by them induce cardiac myogenesis in pluripotent hESCs, as indicated by rhythmic beating and immunohistochemical/quantitative polymerase chain reaction monitoring of marker gene expression. The cardiomyogenic effect of hDE is enhanced when pluripotent hESCs are preinduced to the mes-endoderm state. Because this approach is tractable and scalable, it may facilitate identification of novel hDE-secreted factors for inclusion in defined cardiomyogenic cocktails.