title: BM cells giving rise to MSC in culture have a heterogeneous CD34 and CD45 phenotype.
abstract: BACKGROUND
  Mesenchymal stromal cells (MSC) isolated from adult human BM are characterized by their fibroblast-like morphology, adherent growth and capacity to differentiate into adipocytes, osteocytes, chondrocytes, cardiomyocytes and neuroprogenitors. After culturing these cells in vitro, they express the cell-surface molecules CD44, CD90, SH2 and SH3, and are negative for CD34 and the hematopoietic marker CD45. The aim of this study was to characterize the in vivo phenotype of MSC relative to the expression of CD34 and CD45.
  
  
  METHODS
  BM mononuclear cells were stained with Ab against both molecules and separated into the CD34(+), CD34(-), CD45(+) CD34(+), CD45(high+) CD34(-), CD45(med,low+) CD34(-) and CD45(-) CD34(-) subpopulations, which were then cultured under the same conditions and analyzed for growth of MSC.
  
  
  RESULTS
  A small population of MSC arose from the CD45(+) CD34(+) fraction, although the majority was obtained from the CD45(-) CD34(-) subpopulation. MSC from all fractions could be differentiated into adipocytes and osteocytes. In addition, MSC from the CD34(+) and CD34(-) fractions were shown to differentiate into chondrocytes. After in vitro culture, MSC from both fractions possessed the same phenotype, which was negative for CD34 and CD45.
  
  
  CONCLUSIONS
  MSC from the CD45(+) CD34(+) fraction change their phenotype under in vitro conditions.
authors.affiliation: Department of Hematology/Oncology, University Medical Center, Freiburg, Germany. stefankaiser2@gmx.de
authors.forename: S
authors.initials: S
authors.lastname: Kaiser
authors.forename: B
authors.initials: B
authors.lastname: Hackanson
authors.forename: M
authors.initials: M
authors.lastname: Follo
authors.forename: A
authors.initials: A
authors.lastname: Mehlhorn
authors.forename: K
authors.initials: K
authors.lastname: Geiger
authors.forename: G
authors.initials: G
authors.lastname: Ihorst
authors.forename: U
authors.initials: U
authors.lastname: Kapp
mesh_terms: D017667:Adipocytes / Q000276:immunology; D000293:Adolescent; D000328:Adult; D018952:Antigens, CD34 / Q000276:immunology*; D015415:Biomarkers / Q000032:analysis; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000276:immunology; D019070:Cell Lineage / Q000276:immunology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000276:immunology; D005260:Female; D006801:Humans; D016130:Immunophenotyping; D017493:Leukocyte Common Antigens / Q000276:immunology*; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D010011:Osteocytes / Q000276:immunology; D017154:Stromal Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism