NF-κB信号通路介导Tcf4调控牙骨质再生的作用机制研究

Periodontitis is a worldwide chronic disease characterized by destruction of gingival and periodontal ligament, resorption of alveolar bone as well as cementum exposure, leading to loss of the affected teeth, thus the ideal goal of periodontal treatment is complete regeneration of the soft and hard tissues lost due to periodontitis. In addition, it is important to promote appropriate PDL tissue orientation, involving the perpendicular insertion of collagen fibers into both new cementum and alveolar bone. With regarding to periodontal tissue engineering and regeneration, cementum regeneration is a critical and challenging phase in the formation of functional PDL. Increasing evidence has demonstrated that the activation of canonical Wnt signaling pathway can promote the regeneration of various tissues, and also regulate the cementum formation and cementoblasts differentiation. However, the regulation mechanism of cementum regeneration by T cell factor 4 (Tcf4), an important transcription factor of canonical Wnt signaling pathway, is still poorly understood. Interestingly, we found that enhanced cementum formation was associated with increased Tcf4 expression in our previous studies. Furthermore, it has been reported that increased Tcf4 expression may contribute to cartilage degeneration in osteoarthritis by augmenting nuclear factor-κB (NF-κB) signaling, and NF-κB signaling pathway was involved in the differentiation and apoptosis of cementoblast. Thus, a hyposthesis that Tcf4 may regulate the cementum formation and regeneration via activation of NF-κB signaling pathway has been proposed. To test the hypothesis, we firstly use a Tcf4 over-expression transgenic mice model and a conditional gene knock-out mice model to evaluate the role of Tcf4 in regulating cementum formation and regeneration, followed by the in vitro assessment to analyze the role of Tcf4 in affecting proliferation and differentiation of cementoblasts. Furthermore, a series of cytological experiments and an animal model with bilateral mandibular cementum defects established as reported previously will be adopted to explore the regulation mechanisms of Tcf4 in regulating cementum formation and regeneration via NF-κB signaling pathway. We expect that the outcomes will provide great potential for cementum regeneration in teeth affected by periodontitis, and the identification of new molecular mechanism will give a remarkable significance in its translation from bench to bedsides.

牙周病会导致牙周膜胶原纤维的溶解破坏，牙槽骨的吸收缺陷和根面牙骨质的暴露，严重危害人类健康。牙周再生治疗的关键步骤是牙骨质的再生。研究显示Wnt信号通路在牙骨质形成过程中发挥重要作用。本课题组的前期研究提示：Tcf4，作为经典Wnt通路中的关键转录因子，参与调控牙骨质的形成。另有研究发现Tcf4能够通过激活NF-κB信号通路来发挥作用，而NF-κB通路参与成牙骨质细胞的代谢调控。我们据此提出假设：NF-κB信号通路介导Tcf4调控牙骨质的再生。为验证此假设，本项目拟首先观察Tcf4和NF-κB信号通路在牙骨质发育和重建中的表达特点；然后通过细胞学实验探讨Tcf4在成牙骨质细胞的增殖和分化过程中扮演的角色，同时利用转基因小鼠确证Tcf4在牙骨质的形成过程中起重要作用；最后，分别通过细胞实验和动物模型探讨NF-κB信号通路介导Tcf4调控牙骨质形成和再生的机制，为寻找牙周再生方法提供理论依据。

牙周病是人群中最广泛流行的慢性感染性疾病，是成年人失牙的首要原因。据统计， 60%的拔牙患者是因为牙周病的侵袭，同时牙周病还可危害其他器官：如患牙周炎的心脏病人发生心梗的危险更高；患感染性心内膜炎的患者中约 8%与牙周病有关；此外，牙周炎还可能导致孕妇早产。牙周病对人类的健康危害如此之大，是因为它会引起牙龈和牙周膜胶原纤维进行性溶解破坏、牙槽骨的吸收缺陷以及根面牙骨质的暴露。牙周再生治疗的目的就是功能性重建包括牙龈、牙周膜、牙槽骨和根面牙骨质等在内的多种组织。牙周再生非常困难，是业内公认的难题。目前国内外的研究者一直尝试用再生性手术、组织工程及局部使用重组生长因子等方法促进牙周组织再生，但常常忽略了根面牙骨质的再生。实际上，牙周组织再生的关键步骤就是高度有序的连接纤维重新附着于新形成的牙骨质内，研究表明成功的牙骨质再生是牙周组织再生的金标准。.本项目聚焦牙骨质的形成和再生进行研究。在基金项目的前期研究中，发现Wnt信号通路的重要转录因子Tcf7l2参与成牙骨质细胞的分化调节，并在牙骨质的形成过程中发挥重要作用，文献分别证实：Tcf7l2能够通过调控NF-κB信号通路来发挥作用，并且NF-κB信号通路参与成牙骨质细胞的代谢调控，因此假设NF-κB 信号通路介导 Tcf4 对牙骨质形成和再生的调控。为了验证这个假设，我们从组织学、细胞学和动物实验方面设计实验，发现①Tcf7l2在牙骨质发育区域表达；②Tcf7l2在成牙骨质细胞矿化过程中发挥正向调控作用；③在成牙骨质细胞代谢过程中，Tcf7l2对NF-κB信号通路有正向调控作用；④Tcf7l2缺失会使牙骨质厚度降低，p-p65表达降低。最终得到结论：Tcf7l2能够通过激活NF-κB信号通路促进牙骨质的形成。所撰写论文发表在Journal of Cellular Physiology杂志上。.本项目的发现使得我们在探知牙骨质形成的分子机制方向又迈进了一步，为临床上治疗牙周炎和实现真正意义上的牙周组织再生提供了新的理论依据。

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