Regulatory Mechanisms of Collagen XII in Establishing Achilles Tendon Hierarchical Structure and Function in Postnatal Development and Healing

项目摘要 肌腱的层次结构决定了它有效地将负荷从肌肉传递到骨骼的能力。形成 肌腱在发育和愈合过程中依赖于多尺度调控的协调 例如由胶原分子形成原纤维、原纤维束组装形成纤维的过程，以及 纤维的补充以形成纤维束。胶原蛋白XII是一种纤维相关的胶原蛋白，具有中断的三重结构 螺旋（FACIT），主要在肌腱生长发育和损伤后表达。 胶原XII与胶原I原纤维和细胞表面及其定位相互作用，形成柔性桥 胶原纤维之间的相互作用暗示了其在调节胶原I纤维形成、纤维组织和 与其他细胞外基质成分的相互作用。此外，胶原蛋白XII在损伤中具有关键作用， 再生反应例如，胶原XII与胶原I和其他基质组分共定位 在组织再生过程中存在，表明在组织凝聚中的作用。最近的数据显示，胶原蛋白 XII缺乏会破坏小鼠和人类疾病的肌腱结构和功能特性，这表明， 胶原蛋白XII调节在肌腱发育和愈合中是关键的。然而， 胶原蛋白XII缺乏会破坏出生后发育过程中肌腱分级结构的形成， 损伤后这种等级结构的重演仍然未知。因此，这一目标 建议是建立涉及胶原XII调节肌腱分级结构的机制， 在整个出生后发育和愈合过程中的机械功能和组成。我们假设 胶原蛋白XII介导的机制是建立肌腱结构和功能所必需的， 在损伤后再现调节机制。为了测试这一点，我们将使用我们的新的肌腱靶向 Col12a1基因敲除和诱导型Col12a1基因敲除小鼠模型用于研究 胶原XII在跟腱发育和愈合过程中的作用。我们将执行全面的多尺度 使用我们的创新小鼠模型进行以下结构、功能和组成分析：目的1： 阐明胶原蛋白XII在调节肌腱的分级组装中的机制作用， 在出生后的发育过程中发挥作用。目的2：定义在细胞周期中涉及胶原XII的调节机制。 治愈利用我们创新的小鼠模型，我们将定义肌腱特异性调节机制，包括 胶原蛋白XII提供对肌腱结构和功能及其获取的基本了解 在康复期间重建。对肌腱多尺度结构进行全面、严格的评估， 功能和组成将定义胶原蛋白XII在整个出生后发育过程中的作用。 发展和损伤后的愈合反应。本提案所述的活动提供了一个强有力的 科学探究的基础，准备我作为一个独立的研究者作出有价值的贡献。

Project Abstract Tendon hierarchical structure dictates its ability to effectively transmit loads from muscle to bone. Formation of tendon during tendon development and healing is reliant on coordination of multiscale regulatory governing processes such as formation of fibrils from collagen molecules, assembly of fibril bundles to form fibers, and recruitment of fibers to form fascicles. Collagen XII is a Fibril-Associated Collagen with Interrupted Triple Helices (FACIT) and is primarily expressed during tendon growth and development and following injury. Collagen XII interacts with collagen I fibrils and cell surfaces and its localization to form flexible bridges between collagen fibrils implicates its role in regulating collagen I fibrillogenesis, fibril organization, and interactions with other extracellular matrix constituents. Further, collagen XII has critical roles in the injury and regenerative responses. For instance, collagen XII co-localization with collagen I and other matrix components is present during tissue regeneration, suggesting a role in tissue cohesion. Recent data showed that collagen XII deficiency disrupts tendon structural and functional properties in mice and human disease, suggesting that collagen XII regulation is critical in tendon development and healing. However, the mechanisms by which collagen XII deficiency disrupts formation of tendon hierarchical structure during postnatal development, and recapitulation of this hierarchical structure after injury, remain unknown. Therefore, the objective of this proposal is to establish the mechanisms involving collagen XII regulation of tendon hierarchical structure, mechanical function and composition throughout postnatal development and healing. We hypothesize that collagen XII-mediated mechanisms are required for establishing tendon structure and function and that these regulatory mechanisms are recapitulated after injury. To test this, we will use our novel tendon-targeted Col12a1 knockout and inducible Col12a1 knockdown mouse models for investigation of the regulatory roles of collagen XII throughout Achilles tendon development and healing. We will perform comprehensive multiscale structural, functional, and compositional assays using our innovative mouse models in the following: Aim 1: Elucidate the mechanistic roles of collagen XII in regulating hierarchical assembly of tendon required for function during postnatal development. Aim 2: Define the regulatory mechanisms involving collagen XII during healing. Utilizing our innovative mouse models, we will define tendon-specific regulatory mechanisms involving collagen XII to provide a fundamental understanding of the acquisition of tendon structure and function and its re-establishment during healing. Comprehensive, and rigorous assessments of tendon multiscale structure, function, and composition will define the role of collagen XII throughout the progressive stages of postnatal development and the post-injury healing response. Activities described by this proposal provide a strong foundation for scientific inquiry, preparing me to make valuable contributions as an independent investigator.