Chemical Structure Effects on Bone Response to Mechanical Load

描述（由申请人提供）：我们将使用固态魔角旋转核磁共振波谱（MAS-NMR）来测量机械载荷下骨组织化学结构的变化。MAS-NMR将允许我们检查超微结构对骨质量的贡献，迄今为止，使用传统成像技术或其他生物物理技术是无法获得的。使之成为可能的进步是一种特殊的核磁共振单元，可以进行压缩载荷和位移测量。高分辨率结构信息将与成熟小鼠胫骨标本在单轴压缩下变形时的骨组织应变相关。在Aim 1中，我们将使用几种不同的1D和2D固态核磁共振脉冲序列来评估骨矿物晶格的畸变，因为矿物离子间距和水迁移率的变化。我们还将研究负载引起的一系列合成碳酸磷灰石的变化，这些磷灰石是骨矿物的模型化合物，可以指导我们的骨矿物结果的解释，并使同位素富集核（特别是43Ca）的测量成为可能。在这些简化的模型化合物中，我们可以准确地测量相互作用距离、矿物杂质的运动和局部对称性的重组，并解决更复杂的生物矿物测量中的不确定性。在目标2中，我们将通过氢键和焓稳定来研究水在稳定矿物和基质成分中的作用。胶原二级结构的变化将通过13C共振测量。我们将使用一种独特的方案来控制胶原蛋白和矿物质的紊乱，通过部分和完全取代天然基质水的氧化氘，形成较弱的氢键。核磁共振将探测水桥和甘氨酸-脯氨酸键，以及矿物变化，与测量的应变和施加的载荷的相关性。在Aim 3中，我们将研究不同年龄小鼠原生和受损骨组织中矿物变形、胶原构象变化和氢键的加载响应，以了解矿物和基质的年龄相关变化如何损害骨组织的机械能力。用氘离子控制氢离子的部分置换将用于提供一系列胶原构象的改变。

DESCRIPTION (provided by applicant): We will apply solid-state magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR) to measure changes in the chemical structure of bone tissue under mechanical load. MAS-NMR will allow us to examine ultrastructure contributions to bone quality that have, to date, been unobtainable using traditional imaging techniques or other biophysical techniques. The enabling advance is a special NMR cell that allows compressive loading and displacement measurements. High-resolution structural information will be correlated to strain of bone tissue from mature murine tibiae as the specimens are deformed under uniaxial compression. In Aim 1 we will assess distortion of the bone mineral lattice as changes in the mineral ion spacings and water mobility using a several different 1D and 2D solid-state NMR pulse sequences. We will also study load- induced changes in a series of synthesized carbonated apatites, which are model compounds for bone mineral to guide interpretation of our bone mineral results and to enable measurements with isotopically enriched nuclei, especially 43Ca. In these simplified model compounds we can accurately measure inter-ion distances, movement of mineral impurities, and reorganization of local symmetry and resolve uncertainties in the measurements of the more complex biomineral. In Aim 2 we will investigate the role of water in stabilizing both the mineral and matrix components via hydrogen bonding and enthalpic stabilization. Changes in collagen secondary structure will be measured through 13C resonances. We will use a unique protocol for controlled disordering of the collagen and mineral by partial and complete displacement of native matrix water with deuterium oxide, which forms weaker hydrogen bonds. NMR will probe water bridges and glycine-proline bonds, as well as mineral changes, with correlations to measured strain and applied load. In Aim 3 we will examine the loading response of mineral deformation, collagen conformation changes and hydrogen bonding in native and damaged bone tissue from mice of various ages in order to understand how age-related changes in the mineral and matrix compromise the mechanical competence of bone tissue. Controlled partial replacement of hydrogen ion with deuterium ion will be used to provide a range of collagen conformation changes. PUBLIC HEALTH RELEVANCE: Fragility fractures are a major health threat in aging populations and understanding the factors that contribute to bone failure is vitally important to the development of new interventional approaches. Through the development of methods for measuring NMR spectra of bone under compressive load, this project, for the first time, brings to this problem the power of solid-state nuclear magnetic resonance spectroscopy to understand the changes in bone structure when subjected to mechanical loading.