Electrochemical modification of titanium alloy influences osteoblast morphology and activity of cadherin-11 and rho-family GTPases

Ti alloy surfaces that ranged from rough (average Ra 1.65 .m) to smooth (Ra 0.03 μm) were created by electrochemical processing. Rat osteoblasts were cultured on the Ti alloy for up to 7 days and cell adhesion events (24 hours) demonstrated significant differences in cell polarity, area, mean focal adhesion area and mean number of focal adhesions per unit cell area between untreated and electrochemically polished Ti alloy. To address the mechanisms underlying phenotypic differences between cells on these surfaces, the activities of Rho-family GTPases and the localisation of cadherin-11 were investigated. Elevated RhoA activity was detected in cells on the smoother surfaces whilst on all surfaces inhibition of both RhoA and Rac1 compromised cell morphology but this was especially pronounced on the rougher surfaces. Significant differences in staining for cadherin-11 were observed in cells cultured for 7 days. On rougher surfaces, there was little evidence of cadherin-11 positive structures at the periphery of the cells however on the smoother surfaces there were extensive adherens junctions. These data illustrate that modifying implant surface structure not only influences initial cell adhesion but also has consequences for the cellular activity of intracellular mediators and the way in which cells interact with each other.