The effect of centrifugal force on expression levels of matrix metalloproteinase-8 and ¨C9 in cultured human gingival fibroblasts

Objective:previous studies showed that most patients with fixed orthodontic appliances experienced an increased incidence of gingivitis during treatment and up-regulate of matrix metalloproteinase-8 and ¨C9( MMP-8 and ¨C9) in gingival crevicular fluid were associated with gingival inflammation. In the present study, in order to find a plausible explanation at the molecular level, the effect of centrifugal force on expression levels of MMP-8 and ¨C9 in cultured human gingival fibroblasts was investigated. Methods:Gingival fibroblast cell culture flasks were centrifuged at 167g for 10, 20, 30, 60, 90 and 120min by horizontal microplate rotor, which simulates the commonly used orthodontic force. The effect of force on mRNA and protein expression levels of MMP-8 and ¨C9 were analyzed by semi-quantitative RT-PCR and flow cytometric assay respectively. Results:Increased mRNA and protein expression levels of MMP-8 and ¨C9 were indicated during 60, 90 and 120min of application of force, and the expression level was positively correlated with the pressure of force. Conclusion:Centrifugal force elevated the expression levels of MMP-8 and ¨C9 at the transcriptional and translational levels in cultured human gingival fibroblasts. It suggests that application of orthodontic force may partly contribute to the gingival inflammation occurring during fixed orthodontic treatment.