title: Dissociation between stem cell phenotype and NOD/SCID repopulating activity in human peripheral blood CD34(+) cells after ex vivo expansion.
abstract: OBJECTIVE
  The relationship between phenotype and function in ex vivo-cultured human hematopoietic stem cells (HSC) remains poorly understood. We investigated the effects of a short-term serum-free culture on the relationship between stem cell phenotype, cell division history, and function in human CD34(+) cells.
  
  
  METHODS
  G-CSF-mobilized peripheral CD34(+) cells were cultured for 4 days with stem cell factor, flt-3 ligand, and thrombopoietin. The phenotype (CD34, CD38, HLA-DR, c-kit), cell division history, colony-forming cell (CFC), long-term culture-initiating cell (LTC-IC), and NOD/SCID repopulating activities were evaluated at Day 0 and 4.
  
  
  RESULTS
  We observed a loss of CD38, HLA-DR, and c-kit surface expression resulting in a drastic increase in CD34(+)CD38(-), CD34(+)HLA-DR(-), and CD34(+)c-kit(-/low) cells at Day 4. In contrast, the frequency of Thy-1(+) cells was maintained. We observed a 1.3-fold expansion of CFC, a 4.8-fold increase in LTC-IC, and an overall maintenance of the NOD/SCID repopulating cell activity. CD34(+)CD38(-) and CD34(+)HLA-DR(-) cells detected at Day 4 displayed the most active pattern of division (4 to 5 divisions) whereas 60% of CD34(+)Thy-1(+) cells divided 0 to 2 times during the same period. At Day 4, the NOD/SCID repopulating activity was associated with Thy-1(+) cells with no more than 2 divisions.
  
  
  CONCLUSIONS
  Our results show that the relationship between stem cell phenotype and function is dramatically altered in cultured CD34(+) cells. Thy-1 expression and cell division history appear to be superior to CD38, HLA-DR, and c-kit, or to homing molecules (CXCR4, VLA-4) as predictors of the repopulating activity of cultured peripheral CD34(+) cells.
authors.affiliation: Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6160, USA. gdanet@mail.med.upenn.edu
authors.forename: G H
authors.initials: GH
authors.lastname: Danet
authors.forename: H W
authors.initials: HW
authors.lastname: Lee
authors.forename: J L
authors.initials: JL
authors.lastname: Luongo
authors.forename: M C
authors.initials: MC
authors.lastname: Simon
authors.forename: D A
authors.initials: DA
authors.lastname: Bonnet
mesh_terms: D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D015703:Antigens, CD; D018952:Antigens, CD34 / Q000032:analysis*; D000943:Antigens, Differentiation / Q000032:analysis; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D019650:Hematopoietic Stem Cell Mobilization; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009244:NAD+ Nucleosidase / Q000032:analysis; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000235:genetics; D012016:Reference Values; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D013926:Thrombopoietin / Q000494:pharmacology; D013997:Time Factors; D014183:Transplantation, Heterologous / Q000502:physiology*
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D008562:Membrane Glycoproteins; D019718:Receptors, CXCR4; D016179:Granulocyte Colony-Stimulating Factor; D013926:Thrombopoietin; D019009:Proto-Oncogene Proteins c-kit; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; C498155:Cd38 protein, mouse; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1