Definitive hematopoiesis from endothelial cells in the mouse embryo; a simple guide.

Circulation is composed of two interactive systems, the cardiovascular and the hematopoietic, which affect each other. Recently, endothelial progenitor cells/angioblasts have been identified in the circulation of the adult mouse and human. Furthermore, some hematopoietic cells (HCs) have been shown to contribute to angiogenesis, suggesting that HCs can transdifferentiate into endothelial cells (ECs). Although these concepts in adult are still controversial, understanding the mechanisms of the relationship between ECs and HCs would benefit the clinical application for cardiovascular and hematologic disorders. Both ECs and HCs are considered to be derived from a common germ layer, the mesoderm, and have more intimate relationship in embryo than in adult. Here, we describe the relationship between ECs and HCs with special attention to the hemogenic ECs in the mouse embryo.