title: Role of beta(1)-integrins and their associated tetraspanin molecules in fibronectin-enhanced megakaryopoiesis.
abstract: BACKGROUND
  We have shown previously that fibronectin (FN) together with megakaryocyte (Mk) growth and development factor (MGDF) enhanced generation of Mk progenitors determined by colony-forming unit (CFU)-Mk assay. MGDF can activate beta(1)-integrins on progenitor cells and increase binding to FN. We studied the role of beta(1)-integrin-tetraspanin complexes by which FN may enhance megakaryopoiesis.
  
  
  METHODS
  Cord blood CD34(+) cells were cultured for up to 8 days in serum-free medium containing IL-3, IL-6 and SCF with or without MGDF in the presence or absence of FN. Immunofluorescence flow cytometry was used to monitor changes in beta(1)-integrin-tetraspanin complexes. CFU-Mk assay was used to assess Mk commitment.
  
  
  RESULTS
  The cocktail of cytokines irrespective of the presence of MGDF altered the percentage expression of beta(1)-integrins CD49d and CD49e on CD34(+) cells. CD49d expression fell initially (98% to 15%) and then rose to 75%, whereas CD49e progressively increased over the 8 days of culture, from 5.4% to 22%. However, with the addition of FN, similar changes in the expression of beta(1)-integrins were observed but the expression was maintained at a higher level. MGDF and FN increased expression of tetraspanin molecules, CD63 and CD151, as well as their co-expression with the beta(1)-integrins on both the CD34(+) and CD34(-) cells (e.g. and increase from 0% to 80% co-expression of CD49d and CD151 on CD34(+)). Blocking of beta(1)-integrins or the tetraspanin CD151 with the respective MAb reduced Mk progenitor generation in a stromal cell model.
  
  
  CONCLUSIONS
  FN enhanced Mk progenitor generation through modulation of beta(1)-integrin-tetraspanin complexes, such as CD151/CD49d.
authors.affiliation: Department of Haematology, Women's and Children's Hospital, North Adelaide, South Australia, Australia.
authors.forename: P
authors.initials: P
authors.lastname: Han
authors.forename: Xh
authors.initials: X
authors.lastname: Guo
authors.forename: C
authors.initials: C
authors.lastname: Story
mesh_terms: D015703:Antigens, CD / Q000502:physiology*; D018952:Antigens, CD34 / Q000378:metabolism; D002454:Cell Differentiation; D049109:Cell Proliferation; D005353:Fibronectins / Q000037:antagonists & inhibitors / Q000502:physiology*; D006410:Hematopoiesis; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology*; D008533:Megakaryocytes / Q000166:cytology*; D008562:Membrane Glycoproteins / Q000737:chemistry; D013234:Stem Cells / Q000502:physiology; D013926:Thrombopoietin / Q000037:antagonists & inhibitors / Q000502:physiology
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D005353:Fibronectins; D019012:Integrin beta1; D008562:Membrane Glycoproteins; D013926:Thrombopoietin