骨硬化蛋白在非龋性硬化牙本质形成中的调控作用研究

Non-carious sclerotic dentin is a kind of reactive dentin and also highly mineralized dentin, resulted from mechanical stimulation. Non-carious sclerotic dentin acts as a natural barrier to effectively prevent external stimulation from infecting pulp, and has a good effect on protecting pulp. But how the non-carious sclerotic dentin does form is not clear until now. Sclerostin, an osteocyte-derived negative regulator of bone formation, is a mechanosensitive protein, and its expression is inhibited under the mechanical loading, which promotes the bone formation. Sclerostin can be expressed by odontoblast too, which has been reported in a latest study. Then we propose that it is sclerostin that regulate the formation of non-carious sclerotic dentin under mechanical stimulation and work as negative regulator, according to the similarity of dentin and bone. It means that the expression of sclerostin is inhibited under the mechanical loading, which promotes the mineralized dentin formation. The present study is to fully investigate and demonstrate whether formation of sclerotic dentin is regulated by sclerostin through animal model, knockout mouse and odontoblast. The aim is to make out the mechanism of dentinal self-defense under external stimulation. Moreover, it is hoped that a new strategy could be found to prevent and treat dental caries and dentine sensitivity from the perspective of regulating sclerostin.

非龋性硬化牙本质是牙本质受到机械力刺激而产生的矿化程度较高的反应性牙本质，是保护牙髓的天然屏障，但是其形成机制尚不清楚。骨硬化蛋白是骨形成的负向调节因子，作为力学负荷敏感蛋白，机械力刺激使骨硬化蛋白表达下调进而促进成骨；而最新研究表明骨硬化蛋白在成牙本质细胞中也有表达。根据骨与牙本质的诸多相似性，本课题提出了骨硬化蛋白在非龋性硬化牙本质形成中的可能调控作用：骨硬化蛋白对成牙本质细胞的调控作用与其对骨细胞的作用相似，即作为牙本质矿化的负向调节因子；在机械力刺激下骨硬化蛋白的表达受到抑制进而促进牙本质矿化并形成硬化牙本质。本课题拟通过非龋性牙本质形成的动物模型、基因敲除鼠体内实验及细胞学实验等来研究骨硬化蛋白在非龋性硬化牙本质形成中的调控作用及机制，研究机械力刺激下成牙本质细胞产生反应性变的“自我防御”机制，为牙本质龋和牙本质敏感症等牙本质疾病的预防和治疗提供新思路。

非龋性硬化牙本质（Non-carious sclerotic dentin）是牙本质受到机械刺激而产生的反应性改变，其处于“抵御外敌”的前沿阵地，是阻止外界刺激由牙本质小管传入髓腔的天然屏障，但是其形成机制尚不清楚。骨硬化蛋白（Sclerostin）表达于骨细胞中，是骨形成的负向调节因子。作为力学负荷敏感蛋白，受力可使骨硬化蛋白表达下调进而促进成骨。最新研究表明骨硬化蛋白在牙本质细胞也有表达，由此，本课题提出了骨硬化蛋白调控非龋性硬化牙本质形成的可能机制。由于牙颈部非龋性硬化牙本质主要在中老年患者中出现，本项目收集了年轻牙髓，中老年正常牙髓以及NCCLs牙髓中骨硬化蛋白的表达差异，并通过慢病毒过表达以及敲低骨硬化蛋白发现其促进牙髓细胞衰老；其次，通过构建体外拉应力模型模拟成牙本质样细胞的受力情况，证实骨硬化蛋白在拉应力刺激的成牙本质样细胞中表达下调，并进一步阐明ERK通路以及蛋白酶体通路在拉力调控成牙本质样细胞中骨硬化蛋白表达的调控机制；随后通过慢病毒过表达骨硬化蛋白证实其通过调控STAT3信号通路抑制拉应力诱导的成牙本质样细胞的矿化分化。本研究初步探讨了机械刺激下牙本质产生反应性变的“自我防御”机制，并通过骨硬化蛋白的调控作用为牙本质龋和牙本质敏感症等牙本质疾病的预防和治疗提供新思路。