Are intra-aortic hemopoietic cells derived from endothelial cells during ontogeny?

The aorta is recognized as an intraembryonic site that produces adult-type hemopoietic stem cells. A corpus of data indicates that hemopoietic cells arranged as clusters attached to the aortic floor derive from an endothelial intermediate. This review reports on experimental approaches carried out in the avian embryo to establish the developmental history of the aortic endothelium and trace the origin of associated hemopoietic cells.