Gene Expression profile of Osteoblasts on Micro-arc Oxidation Modified Ti-5Zr-3Sn-5Mo-15Nb

Objectives: Ti-5Zr-3Sn-5Mo-15Nb titanium alloy (TLM) was modified using micro-arc oxidation (MAO) technique. The morphology of osteoblasts cultured on samples was observed and the expression of several genes important in bone turnover was evaluated to get a better understanding of the molecular mechanism under cell-material interaction.

Methods: MAO process was conducted at two different final voltages. Cell morphology on them was visualized by SEM. The mRNA expression of Cbfa1, osteopontin (OPN), collagen type I á2-chain (Coll-Iá2), fibronectin (FN), osteocalcin (OCN), BMP-2 and BMP-4 was evaluated via semi-quantitative RT–PCR.

Results: Two porous bioactive surfaces of different dimension were grown on TLM substrate via MAO. 3 days post-seeding, osteoblasts on MAO surfaces, especially on the surface formed at high voltage, were more spread with more lamellipodia coming out from the cells compared with those on the polished surface. MAO treatment had no obvious affection on the mRNA expression of Cbfa1, OPN, Coll-Iá2 and FN at day 1, 3 and 5, while the OCN mRNA level was strikingly elevated on MAO surfaces, with the highest OCN expression on MAO surface formed at higher voltage at day 3. Interestingly, MAO treatment exhibits an up-regulation effect on BMP-2 and BMP-4 mRNA expression of osteoblasts on TLM surface.

Conclusion: MAO process can form porous structure on TLM, whose surface characteristics are dependent on the MAO final voltage applied. Osteoblasts spread is enhanced by MAO treatment, which could be ascribed to the Ca element incorporated by MAO. The OCN expression is induced by MAO, indicating promoted differentiation of osteoblasts at terminal stage of cell differentiation, which may lead to faster osseointegration. The up-regulation of BMP-2/-4 expression may be a reason for the enhanced functions of osteoblasts cultured on MAO modified TLM surfaces.