title: Common endothelial progenitor cell assays identify discrete endothelial progenitor cell populations.
abstract: BACKGROUND
  Multiple measures of endothelial progenitor cells (EPCs) have been described, but there has been limited study of the comparability of these assays. We sought to determine the reproducibility of and correlation between alternative EPC assay methodologies.
  
  
  METHODS
  We simultaneously assessed EPC numbers in 140 patients undergoing cardiac catheterization using the 2 most commonly used culture techniques: endothelial cell outgrowth and colony-forming unit (CFU). In the final 77 patients, EPCs were also identified on the basis of cell surface marker expression (CD133, CD34, and vascular endothelial growth factor receptor-2 [VEGFR-2]) and aldehyde dehydrogenase (ALDH) activity.
  
  
  RESULTS
  Endothelial progenitor cell enumeration based on fluorescence activated cell sorting was more precise than culture assays. There was limited correlation between EPC numbers determined using the 2 common culture-based assays; however, endothelial CFUs correlated with VEGFR-2 and CD34/VEGFR-2-expressing cells. Endothelial progenitor cells defined by expression of CD133, CD34, CD133/CD34, and ALDH activity correlated with each other, but not with VEGFR-2(+) cells.
  
  
  CONCLUSIONS
  Endothelial progenitor cells can be broadly classified into 2 classes: VEGFR-2-expressing cells, which give rise to endothelial CFUs, and CD133/CD34 or ALDH(br) cells. These observations underscore the need for better assay standardization and a more precise definition of EPCs in cell therapy research.
authors.affiliation: Duke University Medical Center, Durham, NC 27710, USA. povsi001@mc.duke.edu
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Povsic
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Zavodni
authors.forename: Enrikas
authors.initials: E
authors.lastname: Vainorius
authors.forename: Jennifer F
authors.initials: JF
authors.lastname: Kherani
authors.forename: Pascal J
authors.initials: PJ
authors.lastname: Goldschmidt-Clermont
authors.forename: Eric D
authors.initials: ED
authors.lastname: Peterson
mesh_terms: D000071916:AC133 Antigen; D000444:Aldehyde Dehydrogenase / Q000096:biosynthesis; D015703:Antigens, CD / Q000096:biosynthesis; D018952:Antigens, CD34 / Q000096:biosynthesis; D019070:Cell Lineage; D042783:Endothelial Cells / Q000145:classification / Q000166:cytology* / Q000378:metabolism; D006023:Glycoproteins / Q000096:biosynthesis; D006801:Humans; D010455:Peptides; D015203:Reproducibility of Results; D013234:Stem Cells / Q000145:classification / Q000166:cytology* / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000096:biosynthesis
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D018952:Antigens, CD34; D006023:Glycoproteins; C000606023:PROM1 protein, human; D010455:Peptides; D000444:Aldehyde Dehydrogenase; D040301:Vascular Endothelial Growth Factor Receptor-2