Fig. 6

Changes in the expression levels and localization of the β1 integrin subunit during differentiation of HBDCs. a Analysis of representative gels. The levels of GAPDH and β1 integrin subunit mRNA are shown in the charts. Results are normalized to the level of the housekeeping gene (GAPDH). 0 – cell cultured under undifferentiating conditions in standard medium; 7, 14, 21 – cells cultured under osteogenic conditions in differentiating medium. b, c, d Immunolocalization of the β1 integrin subunit on days 7 (b), 14 (c) and 21 (d) of HBDC differentiation. Three independent experiments were performed and representative images are shown. Scale bar: 100 μm. e Immunofluorescence staining for osteoblasts terminating in focal adhesion contacts as shown by FAK localization (on day 21 of HBDC culture). Focal adhesion plaques indicated by a white arrowhead. Three independent experiments were performed and representative images are shown. Scale bar: 100 μm. f–h Localization of actin in differentiating HBDCs on days 7 (f), 14 (g) and 21 (h) of culture. Three independent experiments were performed and representative images are shown. Scale bar: 100 μm. i Cell adhesion to ECM proteins is mediated through integrin receptors, which are clustered within adhesive cellular structures known as focal adhesion or focal contact plaques. Focal adhesion plaques are supramolecular assemblies containing structural (talin, vinculin, tensin, actin filaments) and signaling components (FAK, Src, paxilin) regulating cell functions via integrins