The circadian expression of osteogenic factors in periodontal tissue loading mechanical force: new concepts of the personalized orthodontic care
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The need for orthodontic treatment continues to increase. Strategies that shorten the treatment course and reduce discomfort are most welcome in clinic. Circadian rhythm plays important role in various physiological processes, including bone formation. This study intended to depict a possible circadian releasing property of the osteogenic factors within the periodontal tissue during orthodontic treatment, which may direct a more efficient and satisfactory orthodontic treatment to the patient.
Primary periodontal ligament cells (PDLCs) were obtained from the Sprague-Dawley (SD) rats. An equibiaxial strain value of 12% was applied on rat PDLCs (rPDLCs). After 2 h stimuli of 10−7 M dexamethasone (DX), the osteogenic genes’ expressions were detected by real-time polymerase chain reaction (RT-PCR) at Zeitgeber times 0, 4, 8, 12, 16, 20, and 24. An orthodontic appliance was placed on 45 SD rats. Animals were maintained under 12-h light/dark periods and euthanized at 9 time points over the diurnal cycle. The orthodontic sensitive tissues of the mesial root of the maxillary first molar were collected for RT-PCR and immunohistological assay.
The rPDLCs displayed typical fibroblastic spindle shape, and subcultured steadily in vitro. Induced by DX, the mRNA expression of Col-1, OPN, and IBSP within the loaded/unloaded rPDLCs oscillated as that of the main clock gene Per-1. The osteogenic genes’ expressions as well as the protein releases sustained a circadian oscillation trend in vivo.
This study indicates the existence of a circadian rhythm of the osteogenic factors within the orthodontic sensitive tissues, which highlights the importance of precise timing of force loading in further orthodontic treatment. Thus, a periodicity pattern of orthodontic traction at night may prove a more efficient tooth movement while minimizing the treatment window and discomfort complains.
KeywordsCircadian rhythm Orthodontic tooth movement Osteogenesis Animal study Mechanical force Predictive preventive personalised medicine Prognosis Biomarker panel Expression pattern Animal model Personalized orthodonic care
The authors would like to thank the Tongji Medical College Animal Center, Anyi Li and the Stomatology faculty of Tongji Medical College Zuojiao Yin for technical support.
The study was funded by the National Science Foundation of China (No. 81170986 and No.81800891).
Compliance with ethical standards
All procedures concerning animal use were conformed to the guidelines of the Animal Ethics Committee of Huazhong University of Science and Technology (Wuhan, China)
The authors declare that they have no competing interests.
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