COLLAGEN STRUCTURE AND THE TOUGHNESS OF BONE

骨骼日益脆弱是老年人保健中的一个主要问题。骨主要由坚硬的矿物相和柔顺的胶原基质组成。迄今为止，人们一直推测矿物相增加了骨的硬度，而胶原基质则增强了组织的韧性。本研究的长期目标是阐明胶原蛋白在决定骨机械完整性中的作用及其对年龄和疾病相关的骨脆性增加的贡献。在本研究中，我们假设与年龄相关的骨脆性增加可归因于骨中胶原蛋白分子和结构特性的不利变化。为了验证这一假设，将解决四个具体目标。具体目标1是开发一种新的方法来定量胶原变性在骨的非钙化和钙化的胶原部分。使用这种技术，预计能够检测标本之间非钙化和钙化胶原蛋白部分胶原变性的差异。具体目的2是确定骨中胶原变性与骨重塑的关系。Aim 1中开发的技术将用于确定骨中的胶原变性，而骨重塑将通过检查类骨（非钙化胶原基质）的体积分数和骨中继发性骨的数量和体积分数来评估。具体目标3是确定骨中非钙化和钙化胶原部分胶原变性的年龄相关变化，并探讨这种变化与胶原网络和骨的生物力学完整性的相关性。最后，具体目标4是检查骨中胶原交联浓度的变化作为年龄的函数，并探讨其与年龄相关的骨生物力学完整性恶化的相关性。在本研究中，将进行力学测试，以确定脱矿骨和骨样品的弹性模量、强度和断裂韧性。选择性消化技术将用于定量正常和变性胶原蛋白分子的数量。胶原交联浓度将采用简化高效液相色谱技术测定。这项研究将首次深入了解骨的结构-功能关系及其与年龄相关的骨生物力学完整性恶化的相关性。此外，本研究中开发的技术将促进胶原网络作为骨质量决定因素的未来研究。

Increased skeletal fragility is a major concern in the health care of the elderly. Bone primarily consists of a hard mineral phase and a compliant collagenous matrix. It has been speculated hitherto that the mineral phase imparts the stiffness to bone, while the collagenous matrix enhances the toughness of the tissue. The long-term goal of this study is to elucidate the role of collagen in determining bone mechanical integrity and its contribution to age and disease-related increases in bone fragility. In this study, it is hypothesized that age-related increase of bone fragility is attributable to the adverse changes in molecular and structural properties of collagen in bone. To test this hypothesis, four specific aims will be addressed. Specific Aim 1 is to develop a novel methodology for quantification of collagen denaturation in the non-calcified and calcified collagen portions in bone. Using this technique, it is expected to be able to detect the difference in collagen denaturation in both the non-calcified and calcified collagen portions between specimens. Specific Aim 2 is to determine the correlation of the collagen denaturation in bone with bone remodeling. The technique developed in Aim 1 will be used to determine collagen denaturation in bone, while bone remodeling will be assessed by examining the volume fraction of osteoids (non-calcified collagen matrix) and the number and volume fraction of secondary osteons in bone. Specific Aim 3 is to determine the age-related changes in collagen denaturation in both non-calcified and calcified collagen portions in bone, and to explore the correlation of such changes with the biomechanical integrity of the collagen network and bone. Finally, Specific Aim 4 is to examine changes in collagen crosslinks concentrations in bone as a function of age and to explore their correlation with the age-related deterioration in bone biomechanical integrity. In this study, mechanical testing will be performed to determine the elastic modulus, strength, and fracture toughness of the demineralized bone and bone samples. A selective digestion technique will be employed to quantify the amount of normal and denatured collagen molecules. The collagen crosslinks concentration will be determined using a simplified HPLC technique. This study will, for the first time, provide an insight into the structure-function relationship of bone and its correlation with age-related deterioration in the biomechanical integrity of bone. Also, the techniques developed in this study will facilitate future studies on the collagen network as determinants of bone quality.