α7 nAChR及Wnt/Ca2+信号通路在替牙期乳牙根吸收发生发展中的作用及机制研究

Shedding of deciduous tooth, which ensures the regular process of primary and permanent tooth replacement, is a common physiological phenomenon in the development of tooth. And it is an important guarantee for the successful establishment of permanent dentition. However, the mechanisms behind this process are still not well understood. Our previous studies demonstrated that deciduous DPSCs (dental pulp stem cells) can regulate the process of root resorption through RANKL/OPG. In addition, activation of α7 nAChR (α7 nicotinic acetylcholine receptor) could regulate the destruction of alveolar bone and it is closely related with Wnt/Ca2+ signaling pathway. Moreover, there’s differential expression of α7 nAChR and endogenous α7 nicotinic acetylcholine receptor allosteric ligand, SLURP-1, in human deciduous DPSCs from different periods of root resorption. All these results indicating that SLURP-1 could affect the process of root resorption through Wnt/Ca2+ signaling pathway. This study is designed to investigate roles of α7 nAChR and Wnt/Ca2+ signaling pathway in the process of root resorption. And we shall provide new ideas and datas for further study of the process of the regulation of osteoclastic reactions in deciduous tooth root resorption.

乳牙脱落是牙齿发育过程中正常生理现象，是保证恒牙列顺利建立的重要条件，但其具体机制尚不明了。我们前期已证实乳牙牙髓干细胞（DPSCs）可能通过RANKL/OPG途径调控乳牙生理性根吸收过程；同时还证实α7亚型乙酰胆碱受体（α7 nAChR）可通过调节经典Wnt信号通路介导骨破坏过程；另外，α7 nAChR作为一种重要的钙离子通道，与Wnt/Ca2+通路密切相关。预实验又证实α7 nAChR及其内源性配体SLURP-1在根吸收不同时期人乳牙牙髓干细胞中存在差异性表达。由此推测，SLURP-1可能通过α7 nAChR调节乳牙牙髓干细胞Wnt/Ca2+信号通路，进而参与乳牙生理性根吸收过程。本课题拟以人乳牙牙髓干细胞和小型猪为实验模型，从分子、细胞、组织和整体等多种水平系统探讨α7 nACh及Wnt/Ca2+信号通路在乳牙根吸收过程中的作用及相关机制，为探索乳牙根吸收的调控机理提供新思路。

乳牙生理性根吸收是乳恒牙替换及恒牙咬合顺利建立过程中的重要阶段。在乳恒牙替换过程中, 究竟是什么因素导致了乳牙生理性根吸收的发生, 目前尚无统一、公认的观点。以往的研究表明继承恒牙牙胚及其萌出时的机械压力、继承恒牙牙囊、咬合力及牙周膜等因素可能与乳牙生理性根吸收有着密切联系。且大多数研究都集中于牙根外表面的吸收，如牙周膜干细胞对牙根吸收的调控。然而在生理性根吸收期，乳牙牙髓腔内面也存在吸收。此外，在继承恒牙胚先天缺失的情况下,牙根同样能发生吸收,其速度相对缓慢,且吸收多起始于牙根髓腔侧。因此研究乳牙牙髓干细胞(deciduous dental pulp stem cells, DDPSCs) 在生理性根吸收过程中对破骨细胞分化的调节作用具有重要意义。既为乳牙生理性根吸收过程和乳恒牙替换机制的研究提供理论依据，也为临床上防治乳牙滞留以及保留继承恒牙胚缺失的乳牙提供新的思路。该项目对根吸收不同时期DDPSCs和恒牙牙髓干细胞（dental pulp stem cells, DPSCs）进行了分离、培养与鉴定。明确了各组DDPSCs和DPSCs诱导破骨细胞形成能力的差别。并进一步通过实时定量PCR和Western blot的方法检测了各组DDPSCs和DPSCs中RANKL、OPG、α7亚型烟碱型乙酰胆碱受体（Alpha7 Nicotinic Acetylcholine Receptors, α7 nAChR）、分泌型哺乳动物Ly-6尿激酶型纤溶酶原激活物受体相关蛋白-1（Secreted mammalian leukocyte antigen 6/urokinase-type plasminogen activator receptor-related protein-1, SLURP-1）以及核转录因子κB (Nuclear factor-kappa B, NF-κB) p65亚基的表达情况，发现了其之间的相关性，提示DDPSCs中α7 nAChR被SLURP-1激活后，通过上调NF-κB，调节破骨能力相关因子RANKL、OPG的表达比例，进而调控破骨细胞形成分化能力，参与乳牙生理性根吸收进程。