title: Thrombospondin is synthesized and secreted by human osteoblasts and osteosarcoma cells. A model to study the different effects of thrombospondin in cell adhesion.
abstract: In this study we have shown by both immunofluorescence and immunoprecipitation techniques that human osteoblasts and osteosarcoma cells synthesize and secrete thrombospondin, a 450-kDa glycoprotein initially found in platelets. Immunofluorescence with a mouse monoclonal antibody to human platelet thrombospondin yielded specific granular staining within the cytoplasm of human osteoblasts. SDS/polyacrylamide gel electrophoresis analysis of immunoprecipitates obtained with polyclonal and monoclonal anti-thrombospondin antibodies allows the identification of thrombospondin in the cellular lysates and the culture media of biosynthetically labelled osteoblasts and osteosarcoma cells. Kinetic and dose/response studies of osteoblasts and of two osteosarcoma cell lines (MG-63, SaOs-2) were performed to assess the ability of these cells to adhere to thrombospondin and type-I collagen. Thrombospondin promoted the attachment of human osteoblasts whereas it inhibited the adhesion of MG-63 and SaOs-2 cells, both when it was directly adsorbed to plastic and when it was bound to type-I collagen. Therefore osteoblasts and osteosarcoma cells may be valuable tools to study the role of thrombospondin in cell adhesion.
authors.affiliation: Laboratoire d'Hémobiologie, INSERM U-63, Faculté de Médecine Alexis Carrel, Lyon, France.
authors.forename: P
authors.initials: P
authors.lastname: Clezardin
authors.forename: H
authors.initials: H
authors.lastname: Jouishomme
authors.forename: P
authors.initials: P
authors.lastname: Chavassieux
authors.forename: P J
authors.initials: PJ
authors.lastname: Marie
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis; D002448:Cell Adhesion / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007120:Immunochemistry; D007700:Kinetics; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000494:pharmacology; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism*; D012516:Osteosarcoma / Q000378:metabolism*; D019699:Thrombospondins; D014407:Tumor Cells, Cultured
chemical_list: D000906:Antibodies; D008562:Membrane Glycoproteins; D019699:Thrombospondins