2007 Volume 20 Issue 2 Pages 250-257
The effects of titanium surface conditions on bone-related gene expression profile in osteogenic cell culture are not fully understood. We previously reported that the expression of bone-related genes in osteoblastic cells was upregulated when cultured on titanium compared with polystyrene. However, the upregulation ranged only up to 2 times and did not seem to fully explain the biological phenomenon of osseointegration. Osteoblastic culture studies normally utilize dexamethasone in the media to induce the cells into osteoblastic lineage. We hypothesized that culturing the cells under the dexamethasone-free osteoinductive condition may increase the contrast of the effect of titanium and its surface roughness on the degree of osteoblastic differentiation. Objectives: The objective of this study was to examine the bone-related gene expression profile of bone marrow stromal cells cultured on titanium under the dexamethasone-free osteoinductive condition.
Methods: Rat bone marrow stromal cells were cultured on either polystyrene surface, machined titanium or acid-etched titanium without dexamethasone. The differentiation of the cells was evaluated by the expression of the representative bone marker genes using reverse transcriptase-polymerase chain reaction (RTPCR) at days 7, 14 and 28 of culture. Results: Osteopontin gene expression was consistently upregulated up to 3.5 times on both the titanium surfaces compared to the polystyrene, while osteocalcin was upregulated particularly on the acid-etched surface up to 38.8 times at the initial stage of day 7. The sustained gene expression at day 28 on the titanium cultures was seen for all of the genes tested (collagen I, bone sialoprotein II, osteopontin, osteocalcin). Conclusion: The positive modulation of bone-related gene expression by the presence of titanium was detected in the dexamethasone-free osteoinductive media compared to the previously reported results using the dexamethasone-containing osteoinductive media. The results suggest that these culture conditions are beneficial for bone-related gene expression profile studies.
