RANKL/OPG信号通路在PTH促进SFA正颌外科术后颌骨改建和正畸加速中的调控效应研究

In recent years, the prospect of surgery-first approach (SFA) in surgical-orthodontic treatment of skeletal malocclusion and the administration of parathyroid hormone (PTH) to facilitate orthodontics and bone remodeling have attracted the close attention of researchers. However, the mechanisms of SFA orthognathic surgery and PTH in accelerating tooth movement and bone remodeling have not been elucidated.Our previous study showed that the RANKL/OPG signaling pathway played an important role on the bone turn over and bone remodeling process through the intermitent administration of PTH in a rabbit mandibular defect model. In this study, a rabbit model of first molar orthodontics and bi-maxillary orthognathic surgery will be established. After the bi-maxillary orthognathic surgery, the upper and lower first premolars will mesially tracted with a traction force of 80cN, and the intermittent or continuous administration of PTH will be administrated through subcutaneous injection. During the orthodontics process, the orthodontic tooth mobility will be analysed, and bone remodeling will be assessed through histomorphological and morphometric analysis of alveolar bone tissue, serum levels of bone turnover detection, tartrate-resistant acid phosphatase (TRAP) staining positive osteoclasts number calculation and osteoclastogenic activity analysis at the orthodontic compression and tension sites. In addition, the molecular expression and transcription in RANKL/OPG signaling system,which plays an important role between bone remodeling and tooth movemnt, will be detected through PCR, Western blotting, ELISA and IHC analysis. The purpose of this study is to examine the feasibility of using PTH and SFA orthognathic surgery to promote the tooth movement and bone remodeling, and to titrate the optimal mode and dosage of PTH in accelerating tooth movement during orthognathic surgery, and to provide a preliminary investigation of the underlying mechanisms of this phenomenon. The specific aims of the study are provide theoretical support and an experimental basis for the clinical application of PTH and SFA orthognathic surgery in accelerating the tooth movement and shortening the entire treatment period in skeletal dento-facial deformities.

以手术优先（Surgery-first approach，SFA）的正颌外科-正畸联合治疗以及应用甲状旁腺素（parathyroid hormone, PTH）加速牙颌面畸形术后正畸牙移动的机制尚不清楚。课题组前期研究发现RANKL/OPG信号通路在PTH调控骨转换水平而加速骨改建过程中起重要作用。本研究通过建立兔第一磨牙正畸矫治模型和上下颌骨正颌外科手术模型，术后持续性或间隙性给予不同剂量的PTH。研究SFA正颌外科对正畸牙移动速度的影响、正畸牙张力侧和压力侧破骨细胞活化和牙槽骨组织形态学改变、骨转换生化标志物水平检测，以及RANKL/OPG信号通路中关键分子信号的表达效应。探索SFA正颌外科加速正畸牙移动和颌骨改建的调控机制，PTH能否进一步加速正颌外科术后正畸牙移动及其效应机制，筛选适宜的PTH给药方式和剂量。为推广SFA正颌外科并应用PTH缩短骨性牙颌面畸形疗程提供理论和实验依据。

如何缩短骨性牙颌面畸形患者的治疗时间成为国内外研究的热点。虽然先行正颌手术再正畸治疗的手术优先方法（surgery-first approach, SFA）可在治疗初期可使患者面部畸形得到明显改善，但进一步加速术后正畸牙移动和骨愈合成为了需探索解决的问题。本研究猜想在正颌外科术后应用甲状旁腺激素（parathyroid hormone, PTH），不仅有利于正颌外科手术后截骨部位骨愈合，同时加速正畸牙的移动，从而缩短正畸疗程。本实验通过建立228只兔上下颌截骨术和上下颌第一磨牙正畸移动模型，术后牵引第一磨牙近中移动，实验组术后间隙性皮下注射不同剂量PTH。在加载正畸力后测量第一磨牙近中移动速度。CBCT观察分析截骨线间隙内新骨生成和骨愈合情况。HE染色观察正畸牙牙周组织形态学变化，成骨细胞和破骨细胞染色并计数数量变化。免疫组织化学法检测牙周组织中OPG、RANKL、RUNX2和Collagen I表达；qPCR检测正畸牙压力侧牙槽骨中OPG、RANKL、RUNX2、M-CSF、SOST及BMP-2 mRNA的表达。.结果：下颌升支截骨术和上颌前部截骨术后实验组正畸牙近中移动速度快于对照组。正畸牵引14天内，实验组正畸牙压力侧牙周组织RANKL表达均大于对照组及阴性对照组（P<0.05），而OPG、RUNX2表达均小于对照组及阴性对照组；加力21天时，实验组RANKL和RUNX2的表达与对照组比较差异无统计学意义（P>0.05）。正畸牵引第5、7、21天时实验组正畸牙压力侧RANKLmRNA的表达均高于对照组（P<0.05）；第14天时，实验组正畸牙压力侧RANKLmRNA的表达与对照组比较，差异无统计学意义（P>0.05）；而OPG、RUNX2mRNA表达均低于对照组（P<0.05）。实验组压力侧牙周组织中M-CSF及SOST的mRNA表达大于对照组（ P<0.05），而实验组BMP-2 mRNA表达小于对照组（ P<0.05）。实验组下颌骨截骨区愈合及骨痂生成、改建情况优于对照组。CBCT影像学检测结果显示术后实验组截骨区骨痂成骨情况优于对照组。.结论：下颌升支截骨术和上颌前部截骨术术后间隙性给予PTH可早期激活牙周组织中的破骨和成骨活性，加速骨的分解和合成代谢，加速正畸牙移动并促进截骨区骨愈合，从而缩短SFA疗程。