title: Patterns of integrin expression in a human mandibular explant model of osteoblast differentiation.
abstract: Cell-matrix interaction is crucial in regulating osteoblast differentiation and function. These interactions are themselves regulated, at least in part, by integrins. Although there are some data from mammalian models, few studies have compared integrin expression at different stages of the osteoblast lineage. Here, primary human mandibular osteoblast cultures were grown in the presence of epidermal growth factor (EGF), giving a proliferative, less differentiated phenotype, or of vitamin D(3) and hydrocortisone (D+Hc), giving a more differentiated phenotype. These cultures were compared with those of cells prepared in the absence of EGF or D+Hc by fluorescence-activated cell sorter using a panel of monoclonal antibodies to specific integrin heterodimers. To provide in vivo correlation, the same panel of antibodies was used to stain fresh-frozen, undemineralised sections of human mandibular bone. Under baseline conditions the alpha(3), alpha(5), alpha(v), alpha(v)beta(3), beta(3) and beta(1) integrin subunits were expressed strongly by the cells, with low-level expression of the alpha(1), alpha(2) and alpha(4) subunits. In the presence of EGF there was increased alpha(2) expression. With D+Hc, alpha(3) and alpha(5) expression was elevated. Immunohistochemical analysis demonstrated alpha(2), alpha(3), alpha(5), alpha(v)beta(3), beta(1) and beta(3) subunits in cells of the osteoblast lineage; alpha(2) staining was restricted to cells close to the bone surface whilst alpha(v)beta(3) and beta(3) were most frequently localised in the osteocytes. The results provide evidence that cells at successive stages of the osteoblast lineage show different patterns of integrin expression. These integrins may be important in cell-matrix interactions leading to osteoblast differentiation.
authors.affiliation: Department of Oral Pathology, Eastman Dental Institute for Oral Healthcare Sciences, University College London, 256 Grays Inn Road, WC1X 8LD, London, UK. j.bennett@eastman.ucl.ac.uk
authors.forename: J H
authors.initials: JH
authors.lastname: Bennett
authors.forename: D H
authors.initials: DH
authors.lastname: Carter
authors.forename: A L
authors.initials: AL
authors.lastname: Alavi
authors.forename: J N
authors.initials: JN
authors.lastname: Beresford
authors.forename: S
authors.initials: S
authors.lastname: Walsh
mesh_terms: D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D019070:Cell Lineage; D002478:Cells, Cultured; D002762:Cholecalciferol / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005109:Extracellular Matrix / Q000502:physiology; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology; D039423:Integrin alpha1; D039421:Integrin alpha2; D039422:Integrin alpha3; D039441:Integrin alpha4; D039482:Integrin alpha5; D039564:Integrin alphaV; D019012:Integrin beta1 / Q000235:genetics; D039661:Integrin beta3; D016023:Integrins / Q000032:analysis / Q000235:genetics*; D008334:Mandible / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010011:Osteocytes / Q000378:metabolism / Q000502:physiology; D010641:Phenotype; D010980:Platelet Membrane Glycoproteins / Q000235:genetics; D019030:Receptors, Vitronectin / Q000235:genetics
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D039423:Integrin alpha1; D039421:Integrin alpha2; D039422:Integrin alpha3; D039482:Integrin alpha5; D039564:Integrin alphaV; D019012:Integrin beta1; D039661:Integrin beta3; D016023:Integrins; D010980:Platelet Membrane Glycoproteins; D019030:Receptors, Vitronectin; D039441:Integrin alpha4; D002762:Cholecalciferol; D004815:Epidermal Growth Factor; D006854:Hydrocortisone