Efforts to improve bone response to biomaterials have focused on ligands that bind ␣5␤1 integrins. However, antibodies to ␣5␤1 reduce osteoblast proliferation but do not affect differentiation when cells are grown on titanium (Ti). ␤1-silencing blocks the differentiation stimulus of Ti microtopography, suggesting that other ␤1 partners are important. Stably ␣2-silenced MG63 human osteoblast-like cells were used to test whether ␣2␤1 specifically mediates osteoblast response to Ti surface micron-scale structure and energy. WT and ␣2-silenced MG63 cells were cultured on tissue culture polystyrene (TCPS) and Ti disks with different surface microtopographies: machined pretreatment (PT) surfaces [mean peak to valley roughness (R a) < 0.02 m], PT surfaces that were grit-blasted and acid-etched (SLA; R a ‫؍‬ 4 m), and SLA with high surface energy (modSLA). Alkaline phosphatase (ALP), ␣2 and ␤1 mRNA, but not ␣5, ␣v, ␤3, type-I collagen, or osteocalcin, increased on SLA and modSLA at 6 days. ␣2 increased at 8 days on TCPS and PT, but remained unchanged on SLA and modSLA. ␣2-protein was reduced 70% in ␣2-siRNA cells, whereas ␣5-mRNA and protein were unaffected. ␣2-knockdown blocked surface-dependent increases in ␤1 and osteocalcin and decreases in cell number and increases in ALP and local factors typical of MG63 cells grown on SLA and modSLA [e.g., prostaglandin E 2, osteoprotegerin, latent and active TGF-␤1, and stimulatory effects of 1␣,25(OH)2D3 on these parameters]. This finding indicates that ␣2␤1 signaling is required for osteoblastic differentiation caused by Ti microstructure and surface energy, suggesting that conclusions based on cell behavior on TCPS are not predictive of behavior on other substrates or the mechanisms involved.␣-2 integrin siRNA ͉ MG63 human osteoblasts ͉ titanium surface roughness T itanium (Ti) and Ti alloys are commonly used as biomaterials because their surface properties provide a biocompatible interface with peri-implant tissues. Strategies for modifying the nature of this interface frequently involve changes to the surface, thereby affecting protein adsorption, cell-substrate interactions, and tissue development (1). A common modification has been to create micron-scale and submicron scale roughness. Preclinical and clinical studies (2-12) show that these surfaces support greater bone-to-implant contact than smooth surfaces.How surface microstructure promotes an osteogenic response is an important question, because bone-forming osteoblasts preferentially colonize bone surfaces that have been preconditioned by bone-resorbing osteoclasts (13), resulting in complex micron-scale and submicron-scale morphologies (14). In vitro experiments using model surfaces indicate that migration, growth, and colony morphology of rat bone marrow cells (15) and osteoblasts (16-18) are sensitive to microstructure. These observations suggest that structural elements can modulate the spatial organization of cells and their ECM.The topography of osteoclast resorption pits in bone can be modeled by using Ti subs...

Enterococcus faecalis LTA could upregulate the expression of RANKL and OPG at different rates, suggesting a potential role for LTA in the bone resorption process of refractory apical periodontitis through the regulation of RANKL and OPG. In addition, IRAK1/4 and p38MAPK signalling involving RANKL/OPG may contribute to inflammatory responses from PDL cells.