【作者】 包丽娜；

【导师】 白丁；

【作者基本信息】 四川大学 ， 口腔临床医学， 2007， 硕士

【摘要】 正畸牙移动过程中，在牙槽骨发生活跃骨吸收和骨形成的同时，也存在牙骨质的吸收和修复，成牙骨质细胞在这个过程中具有重要意义。正常情况下，位于牙骨质表面的成牙骨质细胞可以抵抗破骨细胞的粘附，从而避免牙根吸收；在已吸收的牙根表面，成牙骨质细胞分泌形成新的牙骨质样组织对其进行修复。当牙根吸收与修复的平衡被打破后，牙根吸收发生。正畸牙移动过程中的牙根吸收，由于其存在的广泛性，不可预见性等特点，成为目前研究的热点。许多研究试图寻找正畸力作用下牙根吸收和修复的发生机制，已取得一定的成果，但仍未清楚。已往对牙移动过程中牙根吸收和修复的研究多集中在组织形态学上的观察，而对成牙骨质细胞的研究又多集中在牙根发育过程和牙周组织的再生工程中，关于机械应力作用下成牙骨质细胞功能变化的研究还未见报道。本课题通过研究机械应力刺激对成牙骨质细胞重要的矿化相关基因-骨涎蛋白(Bone sialoprotein BSP)和骨桥蛋白(Osteopontin OPN)表达的影响，有助于从细胞力学和分子生物学水平上进一步了解正畸牙移动过程中牙根吸收和修复的发生机制。本课题利用四点弯曲细胞力学加载装置，以体外培养的成牙骨质样细胞OCCM-30为研究对象，运用实时荧光定量PCR(real-time fluorescentquantitativePCR，FQ-PCR)技术，研究了不同性质、不同强度、不同作用时间的应力应变对成牙骨质细胞矿化相关基因BSP／OPN mRNA表达的影响。从细胞力学和分子生物学水平对正畸力作用下成牙骨质细胞的功能变化与牙根吸收和修复的关系进行了初步揭示，为进一步阐明牙根吸收和修复的机制提供实验基础。根据实验结果得出以下结论：1．2000、4000μstrain的张应力和压应力在四个时间点都抑制成牙骨质细胞BSP mRNA的表达，4000μstrain力值比2000μstrain力值对成牙骨质细胞BSP mRNA表达的抑制作用更强。表明机械张、压应力刺激均抑制成牙骨质细胞矿化功能，抑制的强弱与应力的大小和加载时间有关。2．2000、4000μstrain的压应力在作用初期促进成牙骨质细胞OPN mRNA的表达，12h后表现为抑制作用。2000μstrain和4000μstrain的张应力抑制OPN mRNA的表达，抑制作用随着加载时间的延长而增强。表明机械应力刺激可以调节成牙骨质细胞OPN mRNA的表达，进而可能影响成牙骨质细胞的矿化功能和破牙骨质细胞的粘附能力。综上所述，成牙骨质细胞是力学敏感性细胞，机械应力刺激可以调节成牙骨质细胞BSP／OPN mRNA的表达，进而可能影响成牙骨质细胞的矿化功能和破牙骨质细胞的粘附能力。机械应力刺激对成牙骨质细胞BSP／OPN mRNA表达的影响与应力的性质，大小和加载时间有关。更多还原

【Abstract】 Background and objective: During orthodontic tooth movement ,The remodeling of alveolar bone is active, Meanwile ,cementum also undergoes both resorption and deposition. Cementoblast plays an important role in the progress of root resorption and repair. Cementoblast is located on the surface of root cementum to inhibit the attachment of the osteoclast and form the new cementum-like tissue in the lacuna on the resorpted root surface. The pathologic resorption is formed when the balance of resorption and repair is disturbed. Orthodontically induced root resorption is the most frequent unwanted side effect of orthodontic tooth movement that is unavoidable. Although many researchers focus on it ,the pathogenesis of root resorption is still not clear.It is not known how orthodontic force influences the function of cementoblast and what is the relationship between the function change of cementoblast with root resorption and repair.The aim of present research is to determine the effects of the mechanical strain on the express of the mineral associated gene BSP and OPN in cementoblast in vitro.Methods: Cementoblasts OCCM30 were cultured in DMEM with 10% FBS for 48. hours, then subjected to mechanical strain by four-point bending system with tension and compression stress at 2000μstrain and 4000μstrain at 0.5Hz frequency for3h, 6h, 12h, 24h. BSPand OPN mRNA were analysed with real time quantitive RT-PCR after mechanical loading. Statistical significance was determined for each comparison using the one-way ANOVA, and p<0.05 was statistically considered significant.Results:1. Cementoblasts are sensitive cells to mechanical strain.2. 2000/4000μstrain tension and compression both suppressed BSP mRNA expression of Cementoblasts. 4000μstrain suppressed stronger than 2000μstrain.3. OPN mRNA expression of Cementoblasts was increased in response to compression stress after 31k 6h mechanical loading,then suppressed after 12h、24h loading. while Tension stress almost suppressed OPN mRNA expression all times.Conclusion:1. Mechanical strain suppressed BSP mRNA expression of Cementoblasts and is believed inhibit the capability of cementoblast to synthesize cementum matrix.2. It is suggest that cementoblast regulates the function of osteoclast by the different expression of OPNmRNA after mechanical loading .更多还原