MicroRNA-21 affects mechanical force-induced midpalatal suture remodelling

miR-21 can promote osteoblast differentiation of periodontal ligament stem cells. However, the effect of miR-21 on bone remodelling in the midpalatal suture is unclear. This study aimed to elucidate the effects of miR-21 on the midpalatal suture bone remodelling by expanding the palatal sutures.

miR-21 deficient (miR-21^-/- ) and wild-type (WT) mice were used to establish animal models by expanding the palatal sutures. Micro-CT, haematoxylin-eosin (HE) staining, tartrate-resistant acid phosphatase (TRAP) staining, fluorescence labelling and immunohistochemistry were used to investigate the function of miR-21 in midpalatal suture bone remodelling. Besides, bone mesenchymal stem cells (BMSCs) derived from both miR-21^-/- and WT mice were cultured. The MTT, CCK8, EdU analysis, transwell and wound healing test were used to assess the effects of miR-21 on the characteristics of cells.

The expression of ALP was suppressed in miR-21^-/- mice after expansion except 28 days. The expression of Ocn in WT mice was much higher than that of miR-21^-/-  mice. Besides, with mechanical force, miR-21 deficiency downregulated the expression of Opg, upregulated the expression of Rankl, and induced more osteoclasts as TRAP staining showed. After injecting agomir-21  to miR-21^-/- mice, the expression of Alp, Ocn and Opg/Rankl were rescued. In vitro, the experiments suggested that miR-21 deficiency reduced proliferation and migration ability of BMSCs.

The results showed that miR-21 deficiency reduced the rate of bone formation and prolonged the process of bone formation. miR-21 regulated the bone resorption and osteoclastogenesis by affecting the cell abilities of proliferation and migration.