Embryonic stem cells as a model for cardiogenesis.

Embryonic stem (ES) cells are derived from the inner cell mass of mouse blastocysts. These cells, when placed upon a suitable fibroblast feeder layer, continue to proliferate without overt differentiation and remain totipotent. Cells in this state are competent for gene targeting via homologous recombination. Hence, they hold the possibility of developing defined animal models of human cardiovascular disease. When removed from the feeder layer, ES cells undergo differentiation and development into large, multicellular structures, termed embryoid bodies (EBs). Morphologic, biochemical, and molecular genetic analyses indicate that during EB development some early aspects of cardiogenesis are recapitulated. Thus, EB development in culture is useful for studying certain early cardiogenic events.