Abstract 45

OSTEOGENIC SIGNAL TRANSDUCTION PATHWAYS IS MODULATED BY SURFACE CHEMISTRY MODIFICATION OF TITANIUM IMPLANTS

Zreiqat, H¹, Valenzuella, S2, Evans, P3,

¹ University of New South Wales, School of Medical Sciences, Sydney, 2052, N.S.W, Sydney, Australia

This study was undertaken to assess possible mechanism(s) by which surface chemistry modification of commonly used orthopaedic material (titanium alloy (Ti-6Al-4V)) with magnesium affect the adhesion, proliferation and differentiation of human bone derived cells (HBDC).

Primary HBDC were obtained from outgrowths of normal trabecular bone removed at primary hip replacement. Bone chips were cultured in _-minimal essential media supplemented with 10% fetal calf serum and 0.1 M L-ascorbic acid phosphate. Highly polished disks (Ti-6Al-4V, 15mm diameter x 1mm thick) modified with either Mg were used. HBDC were plated on implant disks in serum-free media for 2, 4 and 6 hrs. Scanning electron microscopy (SEM) was performed to determine cell morphology on the different materials. At the predetermined time points, cells were lysed on the specific surfaces, total proteins were extracted and equal protein amounts were separated by SDS/PAGE. Subsequently, Western blotting with anti- type I collagen, -alkaline phosphatase, -actin, -phospho-Erk1/2 and c-fos, and -fra-2 antibodies were conducted.

HBDC cultured on Mg-modified Ti-6Al-4V had a different activation pattern of protein and cytoskeletal elements as well as in the signalling pathway studied. These signalling pathways regulate gene expression for establishing an osteogenic phenotype. Incorporation of Mg into commonly used orthopaedic implants leads to changes in signalling transduction in osteoblasts which may contribute to their increased ability to synthesize matrix proteins and form bone on implant materials. Therefore, surface chemistry modification of metallic implants with divalent cations may alter the molecular component of implant surface and promote optimal osteogenesis

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