A COMMON PRECURSOR FOR HEMATOPOIETIC AND ENDOTHELIAL-CELLS

Embryonic stem cell-derived embryoid bodies contain a unique precursor population which, in response to vascular endothelial growth factor, gives rise to blast colonies in semi-solid medium, Upon transfer to li quid culture with appropriate cytokines, these blast colonies generate both hematopoietic and adherent, stromal-type cells, Cells within the adherent population display characteristics of endothelial lineage in cluding the expression of CD31, flk-1, flt-1, tie-2, the capacity to t ake up acetylated LDL and the presence of cytoplasmic Weibel-Palade bo dies, Mixing studies demonstrated that the hematopoietic and endotheli al precursors within the blast colonies develop from the same cell, th e blast colony-forming cell, Kinetic analysis showed that the blast co lony-forming cell represents a transient cell population that develops early and is lost quickly during embryoid body development, These fin dings provide strong evidence that the blast colony-forming cell repre sents the long-hypothesized hemangioblast, the common precursor of the hematopoietic and endothelial lineages.