Regulated Assembly of the Tendon Extracellular Matrix

描述(申请人提供)：肌腱连接肌肉和骨骼，在传递和承受拉伸负荷方面具有主要功能。肌腱容易受伤，因为它们承受着大的和/或重复的载荷。这些损伤会导致严重的疼痛和残疾，在运动、工作环境和衰老中很常见。肌腱特异性细胞外基质的组装和功能性肌腱的发育所涉及的调控机制是目前应用的重点。所获得的数据将为了解正常肌腱的发育、生长、成熟以及与衰老、损伤和修复相关的变化提供重要参数。我们的一般假设是肌腱基质组装是一个多步骤的过程，每一步都需要特定的调控相互作用。我们以前的工作已经确定了肌腱基质组装的三个关键步骤：肌原纤维组装的成核；未成熟纤维中间体的沉积和稳定以及它们进入生长期；以及线状和侧向纤维生长，产生肌腱功能所需的成熟纤维。我们假设这些步骤的调控包括：异型V/XI型胶原与I型胶原的相互作用；改变与面胶原XII和XIV型胶原的相互作用；以及与富含亮氨酸的小分子蛋白多糖(SLRP)的相互作用，涉及两个SLRP类别，即核心蛋白聚糖和二聚糖；以及鲁米肯和纤维调节蛋白。其具体目的是：(1)确定涉及I型胶原和V/XI型胶原的异型相互作用在肌腱原纤维组装成核中的作用(S)；(2)确定(Facit)XII和XIV型胶原在纤维沉积和进入纤维生长过程中稳定纤维中间体的功能作用；以及(3)确定纤维与SLRPs相互作用在调节纤维生长步骤中的功能作用。V/XI型异构体表达的小鼠模型为空，将使用Facit胶原XII和XIV以及SLRPs。有单一或复合缺陷的小鼠将在发育过程中使用超微结构和形态计量学方法进行分析。这些方法将与生化、免疫化学和分子分析相结合，以确定特定的功能相互作用。肌腱特异性基质组装中调控步骤的定义为我们进一步了解肌腱修复/再生、病理变化及其调控过程奠定了基础。

DESCRIPTION (provided by applicant): Tendons connect muscle to bone and have a primary function in transmitting and withstanding tensile loads. Tendons are prone to injury because they are subjected to large and/or repetitive loads. These injuries cause significant pain as well as disability and are common in sports, work environments and aging. The regulatory mechanisms involved in tendon-specific extracellular matrix assembly and development of a functional tendon are the focus of the current application. The data obtained will provide important parameters for understanding normal tendon development, growth, maturation as well as changes associated with aging, injury and repair. Our general hypothesis is that tendon matrix assembly is a multi-step process, with each step requiring specific regulatory interactions. Our previous work has identified 3 key steps in tendon matrix assembly; nucleation of fibril assembly; deposition and stabilization of immature fibril intermediates as well as their entrance into the growth phase; and linear and lateral fibril growth, generating the mature fibrils required for tendon function. We hypothesize that the regulation of these steps involve: heterotypic type V/XI collagen interactions with type I collagen; changing interactions with FACIT collagen types XII and XIV; and interactions with small leucine-rich proteoglycans (SLRPs) involving 2 SLRP classes, decorin and biglycan; and lumican and fibromodulin. The specific aims are to: (1) determine the role(s) of heterotypic interactions involving collagens type I and type V/XI in nucleation of tendon fibril assembly; (2) identify the functional roles of (FACIT) collagen types XII and XIV in stabilization of fibril intermediates during deposition into fibers and entrance into fibril growth; and (3) determine the functional roles of fibril interactions with SLRPs in the regulation of fibril growth steps. Mouse models null for typeV/XI isoform expression, FACIT collagen types XII and XIV and SLRPs will be utilized. Mice with single or compound deficiencies will be analyzed during development using ultrastructural and morphometric approaches. These approaches will be integrated with biochemical, immunochemical and molecular analyses to define specific functional interactions. Definition of the regulatory steps in tendon-specific matrix assembly provides a foundation to further our understanding of tendon repair/regeneration, pathological changes and the modulation of these processes.