Delayed Tooth Movement in MicroRNA-29 Sponge Transgenic Mice

Objectives: Movement of teeth through bone depends on osteoclast activities that are strictly controlled at transcriptional, post-transcriptional and translational levels and interferences of these events affect the rate of tooth movement. MicroRNAs (miRs), short non-coding RNAs, are important regulators of post-transcriptional gene expression and certain miRs play a crucial role in osteoclast differentiation/function. In this study, we focused on miR-29 family, which promotes osteoclastogenesis and their expression patterns in human periodontal ligament cells corresponded to different orientations of forces. The aims of study were to investigate tooth movement of miR-29 sponge transgenic mouse, which possesses lower expression level of miR-29 family and gain some insights into a possible mechanism of miR-29 on tooth movement in vivo.
Methods: Methods: Ten weeks old miR-29 sponge transgenic and wildtype control mice (n=16) were used for the study. The tooth movement was achieved using a 2-cN expansion spring on mouse’s mandibular first molar for 2 weeks. The measurement of tooth movement was evaluated using Faxitron® radiography. H&E and TRAP staining techniques were performed to investigate the activity and numbers of osteoclasts in both groups. In addition, RT-realtime PCR was performed to evaluate the level of expression of miR-29a, b and c in each animal.
Results: Results: The average distance of tooth movement in the miR-29 sponge mice (160+42μm) were significantly less than the one in the control mice (211+33μm) (P<0.05). The expression of miR-29 family in the miR-29 sponge mice was 0.2-0.6 fold lower than the one in the control mice (P<0.05). In addition, histological studies demonstrated markedly less numbers of osteoclasts in the miR-29 sponge mice compared to the ones in the control mice (P<0.05).
Conclusions: Conclusions: The underexpression of miR-29 family decreased osteoclast numbers in alveolar bone leading to delayed tooth movement in mice.