Patterns of integrin expression in a human mandibular explant model of osteoblast differentiation

Cell-matrix interaction is crucial in regulating osteoblast differentiation and function. These interactions are themselves regulated, at least in par t, by integrins. Although there are some data from mammalian models, few st udies have compared integrin expression at different stages of the osteobla st lineage. Here, primary human mandibular osteoblast cultures were grown i n the presence of epidermal growth factor (EGF), giving a proliferative, le ss differentiated phenotype, or of vitamin D-3 and hydrocortisone (D + He), giving a more differentiated phenotype. These cultures were compared with those of cells prepared in the absence of EGF or D + He by fluorescence-act ivated cell sorter using a panel of monoclonal antibodies to specific integ rin heterodimers. To provide in vivo correlation, the same panel of antibod ies was used to stain fresh-frozen, undemineralised sections of human mandi bular bone. Under baseline conditions the alpha (3), alpha (5), alpha (v) a lpha (v)beta (3), beta (3) and beta (1) integrin subunits were expressed st rongly 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 a, expre ssion. With D + He, alpha (3) and alpha (5) expression was elevated. Immuno histochemical analysis demonstrated alpha (2), alpha (3), alpha (5), alpha (v)beta (3), beta (1) and beta (3) subunits in cells of the osteoblast line age; alpha (2) staining was restricted to cells close to the bone surface w hilst alpha (v)beta (3) and beta (3) were most frequently localised in the osteocytes. The results proc ide evidence that cells at successive stages o f the osteoblast lineage show different patterns of integrin expression. Th ese integrins may be important in cell-matrix interactions leading to osteo blast differentiation. (C) 2001 Elsevier Science Ltd. All rights reserved.