Optimal compressive force induces bone formation via increasing bone sialoprotein and prostaglandin E2 production appropriately

Although orthodontic tooth movement can promote bone formation, the molecular mechanism that underlies this phenomenon is not fully understood. The purposes of this study were to determine how mechanical stress affects the osteogenic response of human osteoblastic cells (Saos-2), and also examine the optimal compression for osteogenesis in vitro. Saos-2 cells cultured with or without continuously compressive force (0.5∼3.0 g/cm2). The expression of bone sialoprotein (BSP), osteopontin, and cyclooxygenase-2 (COX-2) were measured using real-time PCR, Western blot analysis and immunoassay. The calcium content in the mineralized nodules was determined using Calcium C-Test kit. Only one loading with 1.0 g/cm2 of compressive force significantly increased the expression of BSP mRNA and protein, COX-2 mRNA expression and PGE2 synthesis. Indomethacin, an inhibitor of PGE2 synthesis, inhibited the compression-induced above phenomenon. Moreover, the conditioned medium from 1.0 g/cm2 of compressive force apparently stimulated calcium content in mineralized nodules. This study demonstrates that an optimal compressive force stimulates in vitro mineralization by BSP synthesis through the autocrin action of PGE2 production.