In vitro characterization of primary osteoblasts on titanium surfaces processed with wire-type electric discharge machining

The fixation of titanium implants in bone tissue is affected by the presence of a passive titanium oxide (TiO2) layer. Specifically, oxidation products in the amorphous TiO2 matrix enhance the mechanical properties of mineralized tissues. In addition, in vitro mineralization mediated by primary osteoblasts on amorphous TiO2 generates stiff tissues in a process that resembles pathological mechanisms connected with tumors and proceeds through hydrogen peroxide-inducible clone-5 (Hic-5) expression. However, the relationship between surface-based peroxidation and stiff mineralized tissue formation remains unclear. In this study, titanium samples were processed using wire electrical discharge machining to generate oxidation products in amorphous TiO2. The gene expression profiles of primary osteoblasts cultured on these specimens were characterized. Increased expression of Hic-5 was correlated with the presence of peroxidation products. The crystallization of amorphous TiO2 in these samples reduced the expression of both Hic-5 and lysyl oxidase, an enzyme that promotes matrix cross-linking.