MicroRNA-34 expression in gingival crevicular fluid correlated with orthodontic tooth movement

Objectives: To explore the expression of miR-34a and its effect on expression of matrix metalloproteinases (MMPs) during orthodontic tooth movement (OTM). Materials and Methods: Twenty patients, age 12-18 years old, who underwent orthodontic treatment were enrolled. The expression of miR-34a and MMPs (MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, and MMP-14) were detected in gingival crevicular fluid by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction at different time points. The miR-34a mimics or inhibitors were transfected into human periodontal ligament (hPDL) cells, and the MMP expression was measured by ELISA. Results: The miR-34 expression in GCF on both the tension and pressure sides after orthodontic treatment were significantly downregulated, while the levels of MMPs were significantly upregulated compared with baseline level. The levels of miR-34 and MMPs returned to baseline level 3 months after orthodontic treatment. The expression of miR-34 was negatively correlated with the expression of MMP-2, MMP-9, and MMP-14. After transfection with miR-34, the MMP-2, MMP-9, and MMP-14 expression by hPDL cells were significantly downregulated compared with miR-control and miR-34 inhibitor. Conclusions: Downregulated miR-34 expression was positively correlated with MMP-2, MMP-9, and MMP-14 expression. The miR-34a transfection into hPDL cells inhibited expression of MMPs. The results suggest that miR-34a is involved in expression of MMPs during OTM.