Mechanisms of Secondary Cartilage Induction and Maintenance in the Jaw

项目总结 目标是设计创新的疗法来治疗出生缺陷、疾病和伤害 对于颞颌关节(TMJ)的功能，需要做很多工作来揭示引导TMJ功能的机制 次级软骨的分化。次级软骨是在初级软骨发育后形成的 骨骼，在颌骨的关节和肌肉连接中起着关键的动力作用。在人类身上， 在下颌骨的髁突和冠突形成的次级软骨是正常所必需的。 TMJ的职能。下颌运动和相关的力量是诱导和维持继发性的必要因素。 软骨，但生物力学和分子信号如何整合来做到这一点仍不清楚。至 为了解决这个问题，我们提出了一系列实验，利用鸭子和 鹌鹑的胚胎。与在人类中发现的很相似，鸭在肌腱上发育出明显的次级软骨。 他们的下颌内收肌插入冠突。等同的次级软骨缺失。 鹌鹑和其他物种，如老鼠。我们利用鸭子形成这种次级软骨的事实，并将重点放在 神经脊间充质(NCM)的作用，它产生颌骨骨骼中的所有软骨和骨骼。 NCM还制造肌肉结缔组织，包括韧带和肌腱。相比之下，下巴肌肉 源自中胚层。我们已发表的和初步的研究表明，当将NCM从鹌鹑移植到 对于鸭子来说，在下巴骨骼和伴随的肌肉组织中产生类似鹌鹑的图案，这反过来又导致 冠突上次级软骨的丢失。此外，瘫痪肌肉或阻碍转化 生长因子-β(转化生长因子β)和成纤维细胞生长因子(成纤维细胞生长因子)信号也抑制继发性 冠突上的软骨生成。因此，我们假设转化生长因子β和 成纤维细胞生长因子信号、颌骨结构和机械力促进下颌骨上次级软骨的形成 鸭子与鹌鹑的冠状突起。我们用三个具体目标来检验我们的假设。在目标1中，我们评估 转化生长因子β和成纤维细胞生长因子信号在多大程度上是由NCM介导的，并使用功能的得失 准确确定这些途径何时何地在足底诱导继发性软骨形成的方法 冠状突起。在目标2中，我们研究了颌骨结构和机械力之间的联系 下颌内收肌使用从几何和材料特性研究得出的有限元模型，以及 通过实验操作进行了测试。在目标3中，我们阻断机械转导，调节胚胎 运动，并结合体内和体外实验，了解局部机械环境 调节次级软骨的分子程序。通过研究NCM介导的信号转导的影响， 肌肉骨骼解剖，以及机械力对次级软骨的诱导，本项目将提供 关于对TMJ功能至关重要的冠突模式的新见解，提供了一种潜在的手段 改善肌腱到骨的愈合，并导致再生次级软骨的新的临床策略。

PROJECT SUMMARY With the goal of devising innovative therapies to treat birth defects, diseases, and injuries that compromise the function of the temporomandibular joint (TMJ), much needs to be done to uncover mechanisms that direct the differentiation of secondary cartilage. Secondary cartilage arises after development of the primary cartilaginous skeleton and plays a critical kinetic role in the articulations and muscle attachments of the jaw. In humans, secondary cartilage that forms at the condylar and coronoid processes of the mandible is required for normal function of the TMJ. Jaw movements and associated forces are necessary to induce and maintain secondary cartilage, but how biomechanical and molecular signals become integrated to do so remains unclear. To address this question, we propose a series of experiments that leverage the distinct jaw anatomies of duck and quail embryos. Much like that found in humans, duck develop a pronounced secondary cartilage at the tendon insertion of their jaw adductor muscle on the coronoid process. An equivalent secondary cartilage is absent in quail and other species such as mice. We exploit the fact that duck form this secondary cartilage and focus on the role of neural crest mesenchyme (NCM), which produces all the cartilages and bones in the jaw skeleton. NCM also makes muscle connective tissues including ligaments and tendons. In contrast, jaw muscles are derived from mesoderm. Our published and preliminary studies show that NCM, when transplanted from quail to duck, generates quail-like pattern in the jaw skeleton and accompanying musculature, which in turn causes a loss of secondary cartilage on the coronoid process. Moreover, paralyzing muscle or blocking Transforming Growth Factor-Beta (TGFβ) and Fibroblast Growth Factor (FGF) signaling also inhibits secondary chondrogenesis on the coronoid process. Thus, we hypothesize that species-specific differences in TGFβ and FGF signaling, jaw architecture, and mechanical forces promote formation of secondary cartilage on the coronoid process of duck versus quail. We test our hypothesis with three Specific Aims. In Aim 1, we evaluate the extent to which TGFβ and FGF signaling are NCM-mediated, and use gain- and loss-of-function approaches to determine precisely when and where these pathways induce secondary cartilage at the coronoid process. In Aim 2, we investigate the link between jaw architecture and mechanical forces at the mandibular adductor using a finite element model derived from geometric and material property studies, and tested through experimental manipulations. In Aim 3, we block mechanotransduction, modulate embryonic motility, and combine in vivo and in vitro experiments to understand how the local mechanical environment regulates molecular programs for secondary cartilage. By investigating the effects of NCM-mediated signaling, musculoskeletal anatomy, and mechanical forces on the induction of secondary cartilage, this project will offer new insights on patterning the coronoid process, which is essential to TMJ function, provide a potential means to improve tendon to bone healing, and lead to novel clinical strategies for regenerating secondary cartilage.