Structure Function Relationships at the Tendon to Bone Insertion Site

描述（由申请人提供）：不同材料的连接是一个主要的工程挑战，因为在这种界面处会产生高水平的局部应力。这个问题的有效生物解决方案可以在肌腱（一种柔顺的结构性“软组织”）与骨骼（一种坚硬的结构性“硬组织”）的连接处看到。在肌腱-骨愈合过程中，未受伤肌腱和骨之间存在的独特过渡组织不会重新生成。因此，这两种不同生物材料的手术再附着常常失败。我们建议检查肌腱-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-骨插入部位是一种具有复杂结构组织、成分组成和生物力学行为的分层复合材料。大多数先前的研究集中在组织处的分析（即，毫米尺度）和微观（即，微米尺度）水平。对插入位点成分-羟基磷灰石（即，矿物质）、纤维软骨和胶原纤维。此外，关于肌腱-骨界面上的化学和结构的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，肌腱和骨之间的矿物质和纤维软骨浓度有一个平滑的过渡，这种过渡可能部分解释了组织水平上的力学行为。目的1：研究大鼠冈上肌腱与肱骨头之间自然腱-骨界面的发育。在目标2中，我们将在受控的体外系统中合成胶原基质，其中矿物质和纤维软骨的浓度梯度。从这两个目标收集的数据将被用来测试有关的矿物和纤维软骨在肌腱骨插入的作用的假设。将使用拉曼光谱法研究羟基磷灰石与胶原蛋白的比例。将使用电子显微镜表征胶原蛋白和羟基磷灰石之间的界面。将使用原位杂交评价局部基因表达。将使用生物力学模型在应力转移的背景下解释数据。公共卫生相关性：肌肉骨骼损伤是疼痛和残疾的常见原因，并导致显著的医疗保健成本。1软组织损伤通常需要手术修复和腱-骨愈合（例如，肩袖修复2、3例，前交叉韧带重建4、5例，屈肌腱撕脱6例。临床结果经常令人失望（例如，据报道，在肩袖处，修复肌腱撕裂的复发率高达94% 3，7，8）。本提案中的工作将为未来的外科重建技术奠定基础，这些技术将通过再生自然的肌腱-骨插入来改善愈合。

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.