title: Endothelial outgrowth cells are not derived from CD133+ cells or CD45+ hematopoietic precursors.
abstract: OBJECTIVE
  Two types of endothelial progenitor cells (EPCs), early EPCs and late EPCs (also called endothelial outgrowth cells [EOCs]), were described in vitro previously. In this report, we dissect the phenotype of the precursor(s) that generate these cell types with focus on the markers CD34, CD133, and vascular endothelial growth factor receptor-2 (VEGFR2) that have been used to identify putative circulating endothelial precursors. We also included CD45 in the analysis to assess the relation between CD34+ hematopoietic progenitors (HPC), CD34+ endothelial precursors, and both in vitro generated EPC types. Addressing this issue might lead to a better understanding of the lineage and phenotype of the precursor(s) that give rise to both cell types in vitro and may contribute to a consensus on their flowcytometric enumeration.
  
  
  RESULTS
  Using cell sorting of human cord blood (UCB) and bone marrow (BM) cells, we demonstrate that EOC generating precursors are confined to a small CD34+ CD45- cell fraction, but not to the CD34+ CD45+ HPC fraction, nor any other CD45+ subpopulation. CD34+ CD45+ HPC generated monocytic cells that displayed characteristics typical for early EPCs. Phenotypic analysis showed that EOC generating CD34+ CD45- cells express VEGFR2 but not CD133, whereas CD34+ CD45+ HPC express CD133 as expected, but not VEGFR2.
  
  
  CONCLUSIONS
  EOCs are not derived from CD133+ cells or CD45+ hematopoietic precursors.
authors.affiliation: Department of Clinical Chemistry, Microbiology and Immunology, University of Ghent, University Hospital, B-9000 Ghent, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: Timmermans
authors.forename: Filip
authors.initials: F
authors.lastname: Van Hauwermeiren
authors.forename: Magda
authors.initials: M
authors.lastname: De Smedt
authors.forename: Robrecht
authors.initials: R
authors.lastname: Raedt
authors.forename: Frank
authors.initials: F
authors.lastname: Plasschaert
authors.forename: Marc L
authors.initials: ML
authors.lastname: De Buyzere
authors.forename: Thierry C
authors.initials: TC
authors.lastname: Gillebert
authors.forename: Jean
authors.initials: J
authors.lastname: Plum
authors.forename: Bart
authors.initials: B
authors.lastname: Vandekerckhove
mesh_terms: D000071916:AC133 Antigen; D000293:Adolescent; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D015415:Biomarkers / Q000032:analysis; D001854:Bone Marrow Cells / Q000166:cytology; D002454:Cell Differentiation; D002469:Cell Separation; D002478:Cells, Cultured; D002648:Child; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism; D005260:Female; D005312:Fetal Blood / Q000166:cytology; D005434:Flow Cytometry; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D017493:Leukocyte Common Antigens / Q000235:genetics / Q000378:metabolism*; D008297:Male; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D011336:Probability; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D015415:Biomarkers; D006023:Glycoproteins; C000606023:PROM1 protein, human; D010455:Peptides; D040301:Vascular Endothelial Growth Factor Receptor-2; D017493:Leukocyte Common Antigens