Mechanisms regulating afferent innervation in the dental pulp

项目摘要/摘要 由于牙齿暴露在环境刺激下，牙齿的神经支配对它们的终身保护和我们- 年龄。牙齿主要由三叉神经节(TG)的感觉神经纤维支配，这些感觉神经纤维有助于促进牙齿的发育。 通过传递有害刺激来保护牙齿器官。在出生后的发育过程中，牙髓(DP)分泌 神经营养因子，以高度调控的方式引导轴突在牙齿内穿透和萌发。 转化生长因子β(转化生长因子β)超家族在牙齿发育过程中起着重要的调节作用。 包括矿化和神经支配。转化生长因子β信号下游的分泌型磷蛋白骨桥蛋白 (OPN)，是一种主要的细胞外蛋白，调节牙齿矿化，也促进轴突生长。 牙齿损伤后，DP细胞释放神经营养因子，调节轴突生长和牙本质修复。 有趣的是，OPN-/-小鼠在牙髓愈合过程中不会形成修复性牙本质，这表明OPN在牙髓愈合过程中起着关键作用。 在这一进程中发挥社会作用。这个项目的长期目标是了解保护 牙齿通过感觉神经支配。总体目标是确定来自牙间膜的信号的作用- 调节牙齿神经的食糜。我们的中心假设是牙齿间充质中的TGFBR2调控 OPN旁分泌信号引导牙齿感觉神经支配。我们实验室已经建立了一种小鼠模型 其中TGFBR2在使用Osterix启动子的产生成牙本质细胞的间充质中被有条件地删除- 驱动Cre重组酶(Tgfbr2cko)。这些小鼠在出生后存活下来，但它们的骨骼有明显的缺陷 还有牙齿。我们进行了一系列实验，以确定DP系膜中的TGFBR2信号是否- 乳糜酶在牙齿发育过程中调节它们的分化和引导轴突生长的能力。我们发现 OPN-/-小鼠没有表现出最初假设的P7神经支配减少，但确实表现出障碍。 破坏了轴突靶向。神经突起在调节反应性和修复性牙本质中的作用 DP细胞的矿化能力是否受损仍不清楚。在这些数据的指导下，我们将测试 我们的假设有以下两个具体目标：1)分析OPN管理的信号级联在 牙间充质在发育过程中对牙齿感觉神经的调节；2)建立 与牙本质修复相关的轴突生长受TGFBR2和/或OPN信号的调节 DP间充质细胞。在第一个目标下，我们将进行对照和OPN-/-DP的mRNA序列分析 以确定哪些信号可能扰乱传入组织。在第二个目标中，我们将使用 Tgfbr2cko、OPN-/-和WT小鼠体内牙齿损伤模型和神经元再生的研究。这个 拟议的研究具有重要意义，因为它有望促进和扩大对DP如何 细胞通过轴突引导机制保护牙齿器官。这些信息将加强我们的联合国- 了解牙齿中间充质-神经元相互作用的复杂相互作用 为将来的预防、治疗和再生策略奠定基础，以改善牙髓的保存性 牙齿。

Project Summary/Abstract Since teeth are exposed to environmental stimuli, tooth innervation is crucial to their lifelong protection and us- age. The tooth is primarily innervated with sensory nerve fibers from the trigeminal ganglion (TG) that help pro- tect the tooth organ by relaying noxious stimuli. During postnatal development, the dental pulp (DP) secretes neurotrophic factors to guide axonal penetration and sprouting within the tooth in a highly regulated manner. The transforming growth factor β (TGFβ) superfamily regulates many developmental processes in teeth, in- cluding mineralization and innervation. A secreted phosphoprotein downstream of TGFβ signals, osteopontin (OPN), is a major extracellular protein that regulates tooth mineralization and also promotes neurite outgrowth. Following tooth injury, DP cells release neurotrophic factors that modulate neurite growth and dentin repair. Interestingly, OPN-/- mice do not form reparative dentin during pulpal healing, suggesting that OPN plays a cru- cial role in this process. The long-term goal of this project is to understand the cellular mechanisms that protect teeth via sensory innervation. The overall objective is to determine the role of signals from the dental mesen- chyme that regulate tooth innervation. Our central hypothesis is that Tgfbr2 in the dental mesenchyme governs paracrine signaling via OPN to guide tooth sensory innervation. Our laboratory has established a mouse model in which Tgfbr2 is conditionally deleted in odontoblast-producing mesenchyme using an Osterix promoter- driven Cre recombinase (Tgfbr2cko). These mice survive postnatally, but have significant defects in their bones and teeth. We performed a series of experiments to determine whether Tgfbr2 signaling in the DP mesen- chyme regulates their differentiation and ability to guide neurite outgrowth during tooth development. We found that OPN-/- mice do not demonstrate reduced innervation at P7 as originally hypothesized, but do exhibit dis- rupted axonal targeting. The role of neurite outgrowth in regulating reactionary and reparative dentine when the mineralization capacity of the DP cells is compromised remains unknown. Guided by these data, we will test our hypothesis with the following two specific aims: 1) To analyze the OPN-governed signaling cascades in the dental mesenchyme regulating tooth sensory innervation during development; 2) To establish the degree to which the neurite outgrowth associated with dentin repair is regulated by Tgfbr2 and/or OPN signaling in the DP mesenchyme. Under the first aim, we will perform an mRNA Sequence Analysis of control and OPN-/- DP tissue to determine what signals could be disrupting the afferent organization. In the second aim, we will use an in vivo dental injury model and investigate neuronal regeneration in Tgfbr2cko, OPN-/-, and WT mice. The proposed research is significant because it is expected to advance and expand the understanding of how DP cells protect the tooth organ via mechanisms involving axonal guidance. Such information will enhance our un- derstanding of the complex interplay of mesenchymal-neuronal interactions in the tooth that could serve as a basis for future preventive, therapeutic, and regenerative strategies in endodontics to improve the preservation of teeth.