Integrin adhesion and signaling events may contribute to the progressive differentiation of the osteoblast and to the initiation of a mineralized matrix. The purpose of our study was to begin to analyze the role of integrin receptors, in particular α2β1, α5β1, and αVβ3, regarding mediation of the initiation of a mineralized matrix. Integrin-perturbation assays were conducted in microdot cultures of UMR-106-01 Bone Sialoprotein (BSP) osteoblast cells. For phenotypic analysis, we performed bright-field microscopy and Aliziran Red S staining to analyze effects on mineralization initiation. Mineralization was reduced significantly (P < 0.001) following the addition of a5- or β1-integrin subunit antibody by approximately 20% and 45%, respectively—αVβ3 integrin by nearly 65%, and α2β1 integrin by nearly 95%. This effect was reversible following the removal of the anti-integrin antibody. These results suggest that integrin adhesion and signaling events may contribute to the ability of this cell line to mediate the initiation of the mineralization phenotype biologically.
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