6-Shogaol promotes bone resorption and accelerates orthodontic tooth movement through the JNK-NFATc1 signaling axis.

INTRODUCTION: Corticotomy is widely used in clinical practice to accelerate tooth movement and shorten the duration of orthodontic treatment. It is effective, but an invasive surgery is needed to induce alveolar bone osteopenia that enable rapid tooth movement. In this study, we discovered the potential of 6-shogaol as a more patient-friendly non-invasive alternative to induce transient osteopenia and accelerate tooth movement. MATERIALS AND METHODS: The effects of 6-shogaol on the bone marrow macrophages (BMM) proliferation and osteoclast differentiation, and bone resorption were determined in vitro. Sprague-Dawley rats were distributed into three groups: CON, IPinj or Localinj and euthanized at day 28. Micro-CT, histology, immunohistological, and TUNEL analysis were performed to evaluate the tooth movement acceleration effect of 6-shogaol. RESULTS: In vitro, 6-shogaol promotes osteoclast differentiation and functional demineralization of alveolar bone. RANKL-induced mRNA expression of osteoclastic-specific genes was significantly higher in the presence of 6-shogaol. A dose-dependent increase in the area of TRAP-positive cells was observed with 6-shogaol treatment. F-actin ring formation and increased bone resorption confirmed that osteoclasts treated with 6-shogaol were mature and functional. 6-shogaol stimulated JNK activation and NFATc1 expression during osteoclast differentiation. In vivo, 6-shogaol promotes alveolar bone transient osteopenia and accelerates orthodontic tooth movement. Alveolar bone mass was reduced, more osteoclasts were observed in bone resorption lacunae on the compression side, and the expression of RANKL and sclerostin were higher than the control group. In conclusion, our results suggest that 6-shogoal accelerates tooth movement by inducing osteopenia by a mechanism similar to surgically induced bone injury.

Postnatal Development of the Spheno-occipital Synchondrosis: A Histological Analysis.

The spheno-occipital synchondrosis (SOS) in cranial base is an important growth center for the craniofacial skeleton, and also is a guide rail for development of the maxilla, midface, and mandible. Previous studies showed that SOS may be a treatment target for youngsters with midfacial hypoplasia and small cranial vault secondary to craniosynostosis. However, most of studies about the SOS are based on imaging data. In this study, we try to explore the characteristics of postnatal development of the mouse SOS based on histological analysis. Our findings showed that the width of the SOS in mice were gradually decreased from newborn mice to adult mice, and the SOS cartilage was gradually became small, then almost completely ossificated in adult mice. The resting and proliferative layers in SOS cartilage were gradually decreased, and almost only hypertrophic chondrocytes while no resting and proliferative layer chondrocytes in adult mice. The proliferative ability of SOS chondrocytes also gradually decreased. These findings will be of benefit for the further clinical treatment for patients with midfacial hypoplasia or small cranial vault secondary to craniosynostosis. Further evidence-based research about the clinical implication is necessary in future.