牙周膜细胞初级纤毛感应和传导正畸应力刺激的研究

The capacity of periodontal ligament cells (PDLC) in response to different mechanical force plays a critical role in orthodontic tooth movement. Extensive research has not fully revealed the mechanisms on the PDLC respond to mechanical force. Many studies showed that primary cilia have demonstrated a mechanosensory role in tissues such as the kidney, live, where cilium deflection under shear stress triggers a celluar response. The preliminary study confirmed that primary cilia exist on the cell membranes of the PDLC, and the Runx2, an essential transcription factor for the regulation of osteoblast differentiation and α-tubulin, a major microtublin in primary cilia are increasing under the tensile stress. Therefore, the hypotheses of our study is proposed: the primary cilia functions as a dual sensor, the mechanosensors and the chemosensors, to coordinate the activation of PDLC under orthodontic force. In this study, we explore the mechanisms about how primary cilia induce the physiological morphology and the function of PDLC under different mechanical stimuli both in vitro and in vivo. Further study analyzes the influence of primary cilia knockdown on the function of PDLC in orthodontic tooth movement. This study will significantly help understanding the mechanism of periodontal tissues remodeling under mechanical stimuli. Moreover, it will provide important theoretical foundations for a better orthodontic treatment plan.

牙周膜细胞（PDLC）是正畸应力作用的直接效应细胞，对机械应力可作出不同的生物化学反应，机械力学信号是如何传导到PDLC内引起生物化学反应的确切机制尚不明了。肾病学等领域研究发现，初级纤毛是多数细胞膜上的力学感应器，可对流体应力作出感应并转导力学信号到胞内。本课题组预实验发现PDLC胞膜上存在初级纤毛，且在张应力作用下PDLC初级纤毛主要微管蛋白α-tubulin和成骨转录因子RUNX2的表达均增强。因此，本项目提出研究假设：初级纤毛在正畸应力调控PDLC活性中起力学感应和信号转导作用。本课题拟通过体外和体内实验，来探寻张应力和压应力作用后PDLC初级纤毛的特征变化，以及与PDLC成骨/破骨相关分子表达之间的信号联系，初级纤毛RNAi后对PDLC受应力调控活性的影响及其对正畸牙移动的影响。这将有助于明确力学刺激在牙周组织改建中的调控机理，为正畸治疗中更加科学合理使用矫治力提供理论依据。

初级纤毛是一种细胞膜上的力学感应器，在力学刺激下将力学信号传递给胞内的细胞骨架，进行而引起胞内的生化反应，牙周膜细胞表面的初级纤毛可能参与了正畸应力调控下牙周膜细胞的力学感应和信号转导。本研究首先在人牙周膜组织和人牙周膜细胞中观察到初级纤毛结构，然后通过体外实验观察了静压应力和拉应力刺激下牙周膜细胞表面的初级纤毛的变化和牙周膜细胞成骨功能的关系。结果发现，人牙周膜细胞在循环拉应力作用24小时后，纤毛率无明显差异，初级纤毛长度缩短。牙周膜细胞中初级纤毛的形态可能不受静压应力的影响。初级纤毛相关基因IFT88的敲降可有效减少牙周膜细胞中初级纤毛的数量；在压应力刺激后，牙周膜细胞中COX2基因的转录水平显著上升，OPG基因的转录水平下降，它们的变化不受初级纤毛基因IFT88敲降的影响；但初级纤毛相关基因IFT88的敲降后，阻碍了牙周膜细胞的成骨分化功能。转录组实验研究发现，牙周膜细胞在压应力刺激24h后有368个基因差异表达，其中有两个基因MCHR1和DFNB31是初级纤毛基因，差异表达基因多与炎症反应有关，其有可能通过pathways in cancer, Cytokine-cytokine receptor interaction pathway 和insulin signaling pathway这三个信号通路参与牙周膜细胞对压应力的感知反应。这提示，可以通过干预初级纤毛基因表达来影响正畸效应细胞——牙周膜细胞的功能，这将丰富目前的正畸理论和正畸机理探讨。