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 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.

Elastase in gingival crevicular fluid from smokers and non-smokers with chronic inflammatory periodontal disease.

OBJECTIVE: To compare elastase concentrations in gingival crevicular fluid (GCF) from individual sites of smokers and non-smokers. MATERIALS AND METHODS: Twelve pairs of smokers and non-smokers with untreated, moderate to advanced chronic inflammatory periodontal disease were matched for gender, age, ethnicity and the clinical and radiographic extent of disease. Durapore filter strip samples were collected over 30 s from two mesiopalatal sites on upper left posterior teeth. Samples were analysed for: 1) polymorphonuclear neutrophil leucocyte (PMNL) cell counts; 2) PMNL elastase-alpha 1-antitrypsin complex in the GCF supernatant by ELISA; and 3) functional elastase, free or bound to alpha 2-macroglobulin, estimated from activity against N-tert-butoxycarbonyl-alanyl-prolyl-norvalyl-p-chlorothiobenzyl ester in supernatant and lysates of GCF PMNLs. RESULTS: There were no differences in disease parameters between groups except that bleeding on probing was less extensive in smokers (P<0.001). Cell counts and elastase content of crevicular PMNLs showed no differences between groups. Lower concentrations of elastase were found in GCF supernatants from smokers than non-smokers. This difference was observed for functional elastase (mean [s.d.] = 30.21 [17.60] against 73.77 [75.26] ng microliter(-1), p<0.05) and elastase complexed with alpha 1-antitrypsin (8.97 [6.54] ng microliter(-1) against 25.71 [22.07] ng microliter(-1), p<0.001). CONCLUSIONS: Smokers have lower elastase concentrations in GCF than non-smokers. Further investigation is required to elucidate the underlying cause and its relationship with periodontal disease.