Nanotexturing of titanium-based surfaces upregulates expression of bone sialoprotein and osteopontin by cultured osteogenic cells

Bone formation around implants is influenced by surface geometry. Since cell/matrix/substrate interactions associated with cell signaling occur in the nanoscale dimension, we have evaluated the influence of nanotexturing of titanium-based surfaces on the expression of matrix proteins by cultured osteogenic cells at initial time points. Cells were obtained by enzymatic digestion of newborn rat calvaria and grown on titanium and titanium alloy discs with nanotextured or machined surfaces, and on glass coverslips for periods of 6 h, 1 day, and 3 days, under standard culture conditions. Cultures were processed for single or dual immunolabeling with monoclonal and/or polyclonal antibodies against bone sialoprotein (BSP), fibronectin (FN), osteopontin (OPN), type-I pro-collagen, or tubulin, followed by corresponding fluorophore-conjugated secondary antibodies. Some samples were processed for scanning electron microscope analysis of morphology and immunogold labeling. After 6 h, nanotextured surfaces exhibited up to a nine-fold increase in the proportion of cells with peripheral OPN labeling. At day 3, the proportion of OPN and BSP labeled cells was higher, and the intensity of immunoreactivity dramatically increased. No significant differences were observed in the expression pattern and the proportion of cells immunoreactive for FN or type-I pro-collagen. Our results demonstrate that nanotexturing of titanium-based surfaces upregulates the early expression of BSP and OPN in osteogenic cell cultures.