Bone Matrix Maturation in a Rat Model of Intra-Cortical Bone Remodeling

 描述（由申请人提供）：本项目的目的是开发哈弗氏重建的大鼠和小鼠类似物，以促进对成人皮质骨转换过程中基质成熟的更好理解。我们的目标是开发和验证一种啮齿动物模型，其中多个骨骼网站可以使用从基因到力学的分层评价策略进行询问。骨基质的有机相和无机相的变化影响材料性能。这些性质与基质在空间中的分布相结合，决定了骨作为组织和器官的整体强度、刚度和失效能量。皮质骨约占总骨骼质量的80%，对长骨的机械强度有重要贡献。由于骨重建在整个生命过程中持续进行，因此重要的是检查在成人骨骼中形成的新骨是如何成熟的，特别是考虑到各种代谢性骨疾病（包括骨质疏松症）的治疗方法的存在，其中一些可能会对骨基质材料特性产生负面影响。虽然我们现在对骨质疏松症药物如何影响骨吸收、形成和结构有了相当多的了解，但我们对这些药物如何影响骨作为一种材料的信息却很少。特别是，骨基质从类骨质到完全矿化基质的成熟过程还不完全清楚。研究界的一个主要限制是缺乏研究皮质骨重塑的小鼠或大鼠模型。我们建议筛选三种大鼠模型，其中皮质骨吸收诱导后的恢复阶段时，板层骨填充在诱导的皮质骨吸收空间。基于严格的先验模型选择标准，我们将仔细验证模型，并确定它是否可以转化为小鼠，以便未来的研究可以利用小鼠遗传工具。主要关注的是基质成熟（例如，矿化速率），如通过组合的荧光染料标记、反向散射扫描电子显微镜和傅立叶变换红外成像测定的。其他终点包括微计算机断层扫描、偏振光显微镜、基因和蛋白质表达、血清标志物、纳米压痕和全骨机械测试。将通过与兔（正常发生哈弗氏体重塑的物种）和大鼠和小鼠（通过其他方式诱导哈弗氏体重塑）进行比较来验证该模型。为了证明实用性，我们将确定该模型是否复制硬化蛋白抗体治疗期间哈弗氏骨矿化的加速，这是我们最近在非人灵长类动物模型中发现的。该项目的成功完成将为研究人员提供一种在体内研究哈弗氏骨基质成熟的新方法，从而提供一种新的方法来筛选影响骨骼的药物或其他治疗方法，并研究基质成熟的机制以及基质中的改变如何有助于骨强度。因此，我们预计新的模型将有助于在体内研究如何在成人骨骼中保持骨质量的机制。

 DESCRIPTION (provided by applicant): The purpose of this project is to develop rat and mouse analogs of Haversian remodeling to facilitate improved understanding of matrix maturation during adult cortical bone turnover. Our objective is to develop and validate a rodent model in which multiple skeletal sites can be interrogated using a hierarchical evaluation strategy from genes to mechanics. Variations in the organic and inorganic phases of the bone matrix affect material properties. These properties, in combination with the distribution of the matrix in space, determine the overall strength, stiffness and energy-to-failure of the bone as a tissue and organ. Cortical bone makes up ~80% of the total skeletal mass and contributes significantly to the mechanical strength of long bones. Because bone remodeling continues throughout life it is important to examine how the new bone which forms in the adult skeleton matures, particularly in light of the existence of treatments for various metabolic bone diseases including osteoporosis, some of which may negatively affect bone matrix material properties. While we now have considerable knowledge of how osteoporosis drugs affect bone resorption, formation and structure, we have little information on how these drugs affect bone as a material. In particular, the maturation process of the bone matrix from osteoid to fully mineralized matrix is incompletely understood. A major limitation for the research community is the lack of mouse or rat models for studying cortical bone remodeling. We propose to screen three rat models in which cortical resorption is induced followed by a recovery phase when lamellar bone fills in the induced cortical resorption spaces. Based on strict a priori criteria for model selection, we will carefully validate the model and will determine if it can be translated to mice so that future studies can take advantage of mouse genetic tools. The primary focus is on matrix maturation (e.g., the rate of mineralization) as determined by combined fluorochrome labeling, backscatter scanning electron microscopy, and Fourier transform infrared imaging. Other endpoints include micro-computed tomography, polarized light microscopy, gene and protein expression, serum markers, nanoindentation, and whole bone mechanical testing. The model will be validated by comparison with rabbits, a species in which Haversian remodeling normally occurs and in rats and mice in which Haversian remodeling is induced by other means. To demonstrate utility we will determine if the model replicates acceleration of Haversian bone mineralization during sclerostin antibody treatment, which we recently found in a non-human primate model. Successful completion of the project will offer researchers a new way to study Haversian bone matrix maturation in vivo, thereby providing a novel approach to screen drugs or other treatments affecting the skeleton and to study mechanisms of matrix maturation and how alterations in the matrix contribute to bone strength. Thus, we anticipate the new model will facilitate in vivo research into mechanisms of how bone quality is maintained in the adult skeleton.