Restricted and coordinated expression of β3-integrin and bone sialoprotein during cultured osteoblast differentiation

In this study, the expression of beta(3)-integrin was examined in relationship to the restricted expression of bone sialoprotein (BSP), Immunohistochemical analysis indicated that the alpha(v)beta(3)-integrin was coincident and proximal to BSP expression in the fetal mandible bovine osteoblast culture model. alpha(v)beta(3)-integrin expression was expressed predominantly in a region proximal to, but not including, the substrate adherent cells, In comparison, the alpha(5)beta(1)-integrin was expressed in a generalized pattern throughout the culture layers in a coordinated fashion to fibronectin, The temporal expression of beta(1)- and beta(3)-integrin was evaluated using RT-PCR and southern blot analysis. Unlike the generalized expression of beta(1)-integrin, beta(3)-integrin was restricted to days 3 and 5 of the culture period. The previous demonstration of similar restriction of BSP expression and the present colocalization of BSP suggests the potential coordinated expression of a specific extracellular matrix ligand with a select integrin, beta(3)-integrinnsSP adhesion-mediated signaling may play a significant role in the process of osteoblast morphodifferentiation. (C) 1999 by Elsevier Science Inc. All rights reserved.