Adult human circulating CD34-Lin-CD45-CD133- cells can differentiate into hematopoietic and endothelial cells

A precise identification of adult human hemangioblast is still lacking. To identify circulating precursors having the developmental potential of the hemangioblast, we established a new ex vivo long-term culture model supporting the differentiation of both hematopoietic and endothelial cell lineages. We identified from peripheral blood a population lacking the expression of CD34, lineage markers, CD45 and CD133 (CD34-Lin-CD45 -CD133- cells), endowed with the ability to differentiate after a 6-week culture into both hematopoietic and endothelial lineages. The bilineage potential ofCD34-Lin-CD45-CD133 - cells was determined at the single-cell level in vitro and was confirmed by transplantation into NOD/SCID mice. In vivo,CD34 -Lin-CD45-CD133- cells showed the ability to reconstitute hematopoietic tissue and to generate functional endothelial cells that contribute to new vessel formation during tumor angiogenesis. Molecular characterization of CD34-Lin -CD45-CD133- cells unveiled a stem cell profile compatible with both hematopoietic and endothelial potentials, characterized by the expression of c-Kit and CXCR4 as well as EphB4, EphB2, and ephrinB2. Further molecular and functional characterization of CD34-Lin -CD45-CD133- cells will help dissect their physiologic role in blood and blood vessel maintenance and repair in adult life.