Osteoprotegerin play an important role in experimental orthodontic force-induced osteoclastogenesis

Objectives: Many studies have demonstrated that human periodontal ligament (hPDL) cells have important roles in the tooth movement induced by orthodontic force. However, the roles of human gingival fibroblasts (hGFs) during bone remodeling are undefined. To define precise roles of hGFs on bone resorption which occurs during orthodontic tooth movement, we investigated RNA and protein expression of receptor activator nuclear factor κB ligand (RANKL), Osteoprotegerin (OPG) and the effects to osteoclastogenesis on hGFs during experimetal tooth movement.

Methods: hGFs were subjected to centrifugal force for 90 min in the presence and absence of bone marrow cells. After various times, the cells were processed for the analyses. bone-resorption factor expression and osteoclastogenesis were analysed by reverse transcriptase-polymerase chain reaction (RT-PCR), Enzyme-linked immunosorbent assay (ELISA), immunoflourescence staing, Tartrate resistant acid phosphatase (TRAP) positive stainig.

Results: Application of the cells to centrifugal force increased the expression of receptor activator nuclear factor κB ligand (RANKL), Interleukin-1 beta, and Tumor necrosis factor-alpha, which are the important regulators related to the osteoclastic activation. Unexpectedly however, centrifugal force also induced osteoprotegerin (OPG) expression. In addition, anti-OPG antibody significantly increased the formation of osteoclasts. Expecially with anti-OPG antibody hGFs under centrifugal force expressed less TRAP-positve cells than non forced hGFs.

Conclusions: This study suggests that orthodontic force-mediated teeth movement increse OPG and RANKL expression on hGFs. expecially OPG expression was significant on hGFs than RANKL. Interleukin-1 beta, and Tumor necrosis factor-alpha also faciliated OPG expression in hGFs.In conclusion OPG of hGFs play an important role in orthodontic force-induced osteoclastogenesis.