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能够有效地将负荷从肌肉传递到骨骼。形成 肌腱发育和愈合过程中的肌腱依赖于多尺度调控的协调 从胶原分子形成纤维，组装成纤维束形成纤维的过程，以及 纤维的募集以形成束。XII胶原蛋白是一种具有三个间断结构的原纤维相关胶原 螺旋(Facit)，主要在肌腱生长发育和损伤后表达。 XII胶原蛋白与I型胶原纤维和细胞表面的相互作用及其定位形成柔性桥 在胶原纤维之间暗示其在调节I型胶原纤维形成、纤维组织和 与其他细胞外基质成分的相互作用。此外，XII胶原蛋白在损伤和 再生反应。例如，XII胶原蛋白与I型胶原蛋白和其他基质成分共定位 在组织再生过程中存在，这表明它在组织凝聚力中发挥作用。最近的数据显示，胶原蛋白 XII缺乏症破坏了小鼠和人类疾病的肌腱结构和功能特性，表明 XII胶原蛋白的调节在肌腱的发育和愈合中起着至关重要的作用。然而，通过这些机制 在出生后发育过程中，XII型胶原缺乏会破坏肌腱层次结构的形成，并且 受伤后的这种等级结构的重述，仍然未知。因此，这样做的目的是 建议建立涉及胶原XII对肌腱分级结构的调节机制， 机械功能和组成在出生后发育和愈合过程中的整个过程。我们假设 XII胶原蛋白介导的机制是建立肌腱结构和功能所必需的，这些 在受伤后，对调节机制进行了简要介绍。为了测试这一点，我们将使用我们的新型肌腱靶向 COL12a1基因敲除和可诱导的COL12a1基因敲除小鼠模型的研究 XII胶原蛋白贯穿跟腱的整个发育和愈合过程。我们将进行全面的多尺度 在以下方面使用我们创新的鼠标模型进行结构、功能和成分分析：目标1： 阐明XII胶原在调节肌腱分层组装中的机制作用 在出生后的发育过程中发挥作用。目的2：明确XII胶原蛋白的调节机制 治愈。利用我们创新的鼠标模型，我们将定义特定于肌腱的调节机制，包括 为XII胶原蛋白的获得提供了一个基本的了解肌腱的结构和功能及其 在康复过程中重建。全面、严谨地评估肌腱多尺度结构， 功能和组成将决定XII胶原蛋白在出生后发育过程中的作用 发展和受伤后的愈合反应。本提案所描述的活动提供了强有力的 科学研究基金会，为我作为一名独立的调查员做出宝贵的贡献做好准备。

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.