Effect of glucocorticoid-induced osteoporotic-like conditions on osteoblast cell attachment to implant surface microtopographies.

OBJECTIVES: The objectives of this work were to: (1) establish methodology for pretreating osteoblast-like cells in vitro with dexamethasone to cause glucocorticoid-induced osteoporosis, (2) perform quantitative and qualitative assessments of cellular attachment of osteoporosis-like osteoblasts when grown on implant surfaces of differing roughness, (3) and explore the hypothesis that dexamethasone-treated osteoblasts have altered cell attachment properties by focal adhesion disassembly and decreased tyrosine phosphorylation of the focal adhesion tyrosine kinase. METHODS: Osteoblasts were cultured with dexamethasone (10(-7) and 10(-6) M) for up to 4 days of incubation to induce osteoporosis-like conditions. Cellular attachment assays demonstrated the effect of dexamethasone treatments on cellular attachment properties of osteoblasts. Qualitative data were obtained utilizing immunofluorescent microscopy and Western blotting. Focal adhesion kinase (FAK) immunoprecipitation and tyrosine-phosphorylation Western blots were obtained from dexamethasone-treated human embryonic palatal mesenchymal- 1486 osteoblast cultures supplemented with ascorbate and beta-glycerol phosphate medium. RESULTS: Cellular attachment was significantly greater (P < 0.05) with non-dexamethasone-treated osteoblasts (92%) as compared to dexamethasone-treated osteoblasts after 1 (72%), 2 (63%), and 4 days (53%) of exposure. Dexamethasone-treated osteoblasts were viable and capable of proliferation, suggesting that the reduction of cellular attachment may be related to these cell adhesion processes. Immunofluorescent microscopy of both dexamethasone-treated osteoblasts and non-dexamethasone-treated osteoblasts failed to show any relative difference in the disassembly of focal adhesions and actin filaments. Extended dexamethasone treatment periods (up to 3 weeks) showed changes in the levels of FAK and FAK-phosphotyrosine in human embryonic palatal mesenchymal-1486 osteoblasts. CONCLUSIONS: The protocol used in this study demonstrated a glucocorticoid-induced osteoporosis-like suppression of osteoblasts. FAK disassembly was not a significant factor in short period; however, FAK protein levels and phosphotyrosine signaling on FAK were affected after 1-week exposure to dexamethasone. Phosphorylated FAK was not associated with the rise in the level of FAK, further indicating the possibility of FAK involvement in reduced cell attachment.

Effects of implant microtopography on osteoblast cell attachment.

PURPOSE: The overall aim of this project was to study osteoblast cell attachment on titanium surfaces with varying surface roughness. MATERIALS AND METHODS: Commercially pure titanium surfaces were prepared by polishing through 600-grit sandpaper, sandblasting, or sandblasting followed by acid etching to produce surfaces of varying roughness, as determined by scanning electron microscopy and atomic force microscopy. In vitro cell attachment of MC3T3-E1 osteoblasts was performed on the prepared surfaces in both serum-containing and serum-free media conditions. RESULTS: Cell attachment was directly related to the average surface roughness, with the highest levels of cell attachment observed on sandblasted and sandblasted-acidetched surfaces. Similar patterns of cell attachment were observed when serum-free conditions were employed. CONCLUSIONS: Combined surface analytical and cell/molecular biological techniques are powerful tools to broaden our understanding of biological events occurring at the implant-tissue interface. Data acquired from these in vitro techniques provide a translational application to in vivo clinical models leading to the next generation of dental implants.