Osteoblast integrin adhesion and signaling regulate mineralization

Integrin adhesion and signaling events may contribute to the progressive di fferentiation of the osteoblast and to the initiation of a mineralized matr ix. The purpose of our study was to begin to analyze the role of integrin r eceptors, in particular alpha2 beta1, alpha5 beta1, and alphaV beta3, regar ding mediation of the initiation of a mineralized matrix. Integrin-perturba tion assays were conducted in microdot cultures of UMR-106-01 Bone Sialopro tein (BSP) osteoblast cells. For phenotypic analysis, we performed bright-f ield microscopy and Aliziran Red S staining to analyze effects on mineraliz ation initiation. Mineralization was reduced significantly (P < 0.001) foll owing the addition of alpha5- or beta1-integrin subunit antibody by approxi mately 20% and 45%, respectively-alphaV beta3 integrin by nearly 65%, and a lpha2 beta1 integrin by nearly 95%. This effect was reversible following th e removal of the antiintegrin antibody. These results suggest that integrin adhesion and signaling events may contribute to the ability of this cell l ine to mediate the initiation of the mineralization phenotype biologically.