lncRNA H19/miRNA-675与let-7在调控正畸牙骨质动态平衡中的对话机制研究

The dynamic balance of cementum is an important issue of periodontal remodeling during orthodontic tooth movement. The disruption of this balance leads to orthodontically induced root resorption. LncRNA H19, which is highly conserved with a very low mutation rate, promotes osteogeneic differentiation via TGF-β1/Smad3/HDAC and miRNA-141/miRNA-22/Wnt signaling pathways. This effect is partially mediated by miRNA-675 which is encoded by exon 1 of lncRNA H19. Interestingly, a negative feedback loop was reported between lncRNA H19 and let-7 which is a positive osteogenic regulator just similar as lncRNA H19. These reports indicate lncRNA H19 and let-7 probably also play key roles in the dynamic balance maintaining of cementum. This project will study the following issues 1) how cementoblast is regulated by lncRNA H19 and the underline mechanisms; 2) how cementoblast is regulated by let-7; 3) the cross-talk between let-7 and lncRNA H19 in maintaining the dynamic balance of cementum; 4) explore the role of lncRNA H19 and let-7 in orthodontically induced root resorption.

牙骨质动态平衡是正畸牙移动牙周组织改建的重要内容，其破坏将导致正畸诱导性根吸收的发生。高度保守和极低突变率的lncRNA H19能够通过TGF-β1/Smad3/HDAC及miRNA-141/miRNA-22/Wnt双信号轴促进成骨分化，且部分效应由其外显子1编码的miRNA-675介导。有趣的是同样正向调控成骨分化的let-7 却被证实与lncRNA H19之间存在着微妙的负反馈调控。这些报道提示lncRNA H19与let-7很可能在牙骨质动态平衡维持中也发挥着关键调控作用。本项目拟以lncRNA H19对牙骨质动态平衡的维持为主线着重探讨1）lncRNA H19对成牙骨质细胞的调控作用及机制；2）let-7对成牙骨质细胞的调控作用；3）let-7与lncRNA H19在维持牙骨质动态平衡中的交互对话机制；4）正畸牙移动过程中lncRNA H19与let-7在牙根吸收发生中的作用。

正畸矫治力引发的正畸诱导性牙根吸收是正畸治疗中常见并发症之一，理解牙骨质代谢机理有助于探索防止牙根吸收的有效方法。本项目研究发现lncRNA H19的表达在成牙骨质细胞的矿化过程中逐步上升，通过腺病毒过表达及小RNA敲减技术显示lncRNA H19可以正向调控osterix、OCN和BSP矿化指标的表达。miRNA-675-5p在其他细胞中发现与lncRNA H19之间存在一定的交互机制。因此，我们的研究进一步探索了在成牙骨质细胞分化中miRNA-675-5p的表达变化，并通过敲低和过表达实验发现miRNA-675-5p负向调控成牙骨质细胞的分化矿化。此外，本课题组发现炎症因子IL-1β会通过上调MMP-9和MMP-13的表达促进成牙骨质细胞对细胞外基质的降解；TNF-α通过stat3信号分子调控成牙骨质细胞自噬，然而miR-146a-5p可以通过TRAF6/IRAK1/NFkB信号轴负向调控成牙骨质细胞炎症因子的表达。本课题组还发现miR-145a-5p参与circRNA Lrp6调控的成牙骨质细胞分化及矿化的生物学过程中。这些研究为我们认识非编码RNA在成牙骨质细胞代谢中的作用提供了帮助，为治疗正畸诱导性牙根吸收等临床应用提供参考依据,并为牙周组织再生的实现提供了理论基础。