Structure Function Relationships at the Tendon to Bone Insertion Site

描述（由申请人提供）：不同材料的附着是一个主要的工程挑战，因为在这样的界面上会产生高水平的局部应力。一种有效的生物解决方案可以在肌腱（一种柔顺的结构性“软组织”）与骨（一种僵硬的结构性“硬组织”）的附着上看到。在肌腱-骨愈合过程中，存在于未受伤肌腱和骨之间的独特过渡组织不会被重建。手术再附着这两种不同的生物材料因此经常失败。我们建议研究肌腱-骨插入部位的发展，并使用结果来指导肌腱-骨修复的组织工程研究。肌腱-骨插入部位是一种分层复合材料，具有复杂的结构组织、成分组成和生物力学行为。大多数先前的研究都集中在组织（即毫米尺度）和微观（即微米尺度）水平上的分析。对插入部位成分的纳米级结构知之甚少-羟基磷灰石（即矿物），纤维软骨和胶原纤维。此外，人们对肌腱-骨界面的化学和结构转变以及这些参数如何影响系统的机械响应知之甚少。我们的初步研究表明，在肌腱和骨骼之间存在矿物质和纤维软骨浓度的平滑过渡，这种过渡可以部分解释组织水平上的力学行为。在目的1中，我们将研究大鼠冈上肌腱和肱骨头之间天然肌腱-骨界面的发育。在目标2中，我们将在一个受控的体外系统中合成胶原基质，在矿物和纤维软骨中具有浓度梯度。从这两个目标收集的数据将用于测试有关矿物质和纤维软骨在肌腱到骨插入中的作用的假设。利用拉曼光谱研究羟基磷灰石与胶原蛋白的比例。胶原与羟基磷灰石之间的界面将用电子显微镜进行表征。定位基因表达将使用原位杂交技术进行评估。数据将在使用生物力学模型进行应力传递的背景下进行解释。公共卫生相关性：肌肉骨骼损伤是疼痛和残疾的常见原因，并导致巨大的医疗费用软组织损伤通常需要手术修复和肌腱-骨愈合（例如，肩袖修复2,3，前十字韧带重建4,5，屈肌腱撕脱术6）。临床结果经常令人失望（例如，据报道，在肩袖，修复后的肌腱撕裂复发率高达94%3,7,8）。这项研究将为未来的外科重建技术奠定基础，这些技术将通过再生肌腱到骨的自然插入来改善愈合。

DESCRIPTION (provided by applicant): The attachment of dissimilar materials is a major engineering challenge because of the high levels of localized stress that develop at such interfaces. An effective biologic solution to this problem can be seen at the attachment of tendon (a compliant, structural "soft tissue") to bone (a stiff, structural "hard tissue"). The unique transitional tissue that exists between uninjured tendon and bone is not recreated during tendon-to-bone healing. Surgical reattachment of these two dissimilar biologic materials therefore often fails. We propose to examine the development of the tendon-to-bone insertion site and use results to guide tissue engineering studies for tendon-to-bone repair. The tendon-to-bone insertion site is a hierarchical composite material with complex structural organization, compositional makeup, and biomechanical behavior. Most previous research has focused on analysis at the tissue (i.e., millimeter scale) and microscopic (i.e., micrometer scale) levels. Less is known about the nanoscale architecture of the insertion site constituents - hydroxyapatite (i.e., mineral), fibrocartilage, and collagen fibers. Furthermore, little is known about the transition in chemistry and structure across the tendon- to-bone interface and how these parameters affect the mechanical response of the system. Our preliminary studies indicate that there is a smooth transition in mineral and fibrocartilage concentration between tendon and bone, and that this transition may partly explain the mechanical behavior at the tissue level. In Aim 1 we will study the development of the natural tendon-to-bone interface between the rat supraspinatus tendon and humeral head. In Aim 2 we will synthesize collagen matrices in a controlled in vitro system with concentration gradations in mineral and fibrocartilage. Data gathered from these two aims will be used to test hypotheses related to the role of mineral and fibrocartilage at the tendon-to-bone insertion. The hydroxyapatite to collagen ratio will be investigated using Raman spectroscopy. The interface between collagen and hydroxyapatite will be characterized using electron microscopy. Localized gene expression will be evaluated using in situ hybridization. Data will be interpreted in the context of stress transfer using biomechanical models. PUBLIC HEALTH RELEVANCE: Musculoskeletal injuries are a common cause of pain and disability, and result in significant health care costs.1 Injuries to the soft tissues often require surgical repair and tendon-to-bone healing (e.g., rotator cuff repair2,3, anterior cruciate ligament reconstruction4,5, flexor tendon avulsion6). Clinical outcomes have frequently been disappointing (e.g., at the rotator cuff the recurrence of tears to repaired tendons has been reported to be as high as 94%3,7,8). The work in this proposal will form the foundation for future surgical reconstruction techniques that will improve healing by regenerating the natural tendon-to-bone insertion.