Development of selective induction system for functionally specified cardiomyocytes using embryonic stem cells

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Previously, we have established an embryonic stem (ES) cell differentiation system that can systematically induce cardiovascular cells from common progenitor cells that express Flk1, a vascular endothelial growth factor receptor. In this proposal, we have tried to selectively induce functionally specified cardiomyocytes, such as pacemaker cells and ventricular cells, using our ES cell system. 1)Effective induction method of cardiomyocyte differentiation : When Flk1^+ cell were cocultured on OP9 stroma cells, Flk1^+ cells could give rise to cardiomyocytes, as well as endothelial cells. Approximately 10-18% of ES-derived cells were αMHC-GFP^+ cardiomyocytes, which was more than 2-3 times higher in induction efficiency than that of the conventional embryoid body method. 2)Global analysis of cardiomyocyte differentiation process : Among intermediate stages of cardiomyocyte differentiation, Flk1^+/CXCR4^+/vascular endothelial cadherin^- (FCV) cells specifically possessed cardiac progenitor potentials. We purified undifferentiated ES cells, Flk1^+ mesoderm cells, FCV cardiac progenitor cells, and αMHC-GFP^+ cardiomyocytes, and then generated global gene profile during cardiomyocyte differentiation using DNA chip. 3)Induction of functionally specified cardiomyocytes : We confirmed that, in addition to ventricular myosin^+ cells, HCN4^+ pacemaker cells, and connexin40^+ Purkinje cells were observed in induced cardiomyocytes. 4)Cardiomyocyte differentiation from human ES cells : Our research project for cardiomyocyte differentiation using human ES cells has been approved by the ministry (MEXT) in Japan, and we have launched human ES cell culture in our laboratory. We have already succeeded in inducing spontaneously beating colonies from human ES cells.