Mechanism of BMP‐2 stimulated adhesion of osteoblastic cells to titanium alloy

Abstract

Cell adhesion is dependent on many factors, including the repertoire of extracellular matrix (ECM) proteins and their receptors, e.g. integrins, synthesized by the cell, the composition of the ECM adsorbed to the surface, and the intrinsic chemistry of the surface. Factors that govern bone cell, i.e. osteoblast, adhesion and ECM elaboration significantly influence its re-modeling into mature bone, and ultimately its ability to integrate with biomaterials used for orthopedic prostheses. In this study, we have investigated how treatment with bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor-beta (TGF-beta) superfamily that promotes ectopic bone formation, modulates the organization and expression of osteoblastic cell proteins. Specifically, we analyzed how BMP-2 treatment affects cytoskeletal components, ECM, and alpha 5 and beta 1 integrin receptor subunits in osteoblastic cells plated on Ti6A14V, a titanium alloy widely used for orthopedic implants that interacts with bone cells in vitro and in vivo. Osteoblastic cells were pre-treated with BMP-2 for 12 h prior to plating; BMP-2 treatment stimulated adhesion and proliferation of osteoblastic cells and this adhesive advantage was reflected in enhanced long-term matrix mineralization in the BMP-2 pretreated cultures. Confocal laser scanning microscopic analysis of BMP-2 treated cells showed that enhanced cytoskeletal organization and focal contact formation occurred. These changes were accompanied by a concomitant increase in the spatial organization of fibronectin, whereas vitronectin, collagen type I, osteopontin, and osteocalcin showed little change. The changes in ECM organization correlated with increased fibronectin, alpha 5 and beta 1 integrin subunit, and focal adhesion kinase (p125FAK) expression, as well as increased p125FAK phosphorylation. By confocal microscopy, the alpha 5 integrin subunit was more concentrated in lamellipodia after BMP-2 treatment. These results demonstrate that BMP-2 significantly altered osteoblastic cytoskeletal and ECM organization and enhanced expression of fibronectin and of specific integrin receptor subunits, with concomitant changes in the levels and phosphorylation of p125FAK. These effects may contribute to downstream cellular responses important for bone cell function, and growth.

PLGA-Based Microparticles for the Sustained Release of BMP-2

“…The cells display no orientation inclination around the non-BMP-2 containing spheres nor do they avoid growing adjacently to them, as depicted in Figure 4. The addition of exogenous BMP-2 has reportedly increased osteoblast attachment to titanium alloy by inducing a more extensive extracellular matrix thereby increasing surface contact of the cells with the alloy [38]. A similar process may be positively influencing cell attachment to the microparticles that are releasing BMP-2.…”

Characterization of Multipotential Mesenchymal Progenitor Cells Derived from Human Trabecular Bone

“…Specifically, we have compared the performance of two basal media, Dulbecco's modified Eagle's medium (DMEM), widely used for the culture of various cell types including bone marrow-derived MPCs [14,18,19], and DMEM with Kaighn's modification of Ham's F12 (F12K) supplemented with ascorbic acid and L-glutamine, which has been routinely used in studies involving cells derived from trabecular bone [9,20,21].…”

Direct and indirect induction of apoptosis in human mesenchymal stem cells in response to titanium particles

“…50 mM NaCI. 3 mM MgCL, and 0.5% Triton X-100 for 5 min [34]. After blocking with 5'%i bovine serum albuniin/l'% sheep seruni/PBS.…”