Analysis of Cartilage Morphology and sGAG Content via Contrast Enhanced Micro-CT

描述（由申请人提供）：骨关节炎（OA）是一种潜在的关节衰弱性疾病，其特征是软骨细胞外基质逐渐但进行性降解。对OA发病机制和用于测试疾病修饰疗法的模型的兴趣已经促使了许多小动物关节退行性变模型的开发。然而，虽然可以通过组织学和大体生化分析来评估此类模型中的基质变化，但确定有关基质变化的详细空间信息充其量是具有挑战性的。一种能够对软骨形态和基质成分进行高分辨率、非破坏性定量的技术可能会彻底改变这种小动物模型的评价。这项探索性/发展性研究资助提案的目标是开发一种新的成像方法，利用对比度增强微计算机断层扫描（UCT）获得高分辨率，三维（3D）数据描述的形态和硫酸化糖胺聚糖分布的小动物关节软骨。虽然UCT是骨和各种生物材料的定量形态学和显微结构分析的有力工具，但由于其X射线衰减最小，因此对于软骨或其他软组织的分析并不有用。我们最近对一种新型UCT应用进行了初步验证，用于定量离子型造影剂UCT（EPIC-UCT）的平衡分配，该应用依赖于从具有更大负固定电荷密度（主要是由于蛋白聚糖上的硫酸化糖胺聚糖（sGAG））的组织区域优先排除带负电荷的不透射线造影剂。拟定研究的具体目的是：（1）评价使用EPIC-UCT定量大鼠关节软骨形态学的情况;（2）评价使用EPIC-UCT定量大鼠关节软骨sGAG分布的情况;（3）评价使用EPIC-UCT通过直接关节内注射造影剂原位评价完整大鼠膝关节中关节软骨的情况。在这个为期2年的项目中，我们的目标是开发一种适合于在小型啮齿动物模型中对关节软骨进行终末期分析的方法，并为将这种方法扩展到纵向、体内跟踪软骨基质变化的研究奠定基础。

DESCRIPTION (provided by applicant): Osteoarthritis (OA) is a potentially debilitating condition of articular joints characterized by a gradual but progressive degradation of the cartilage extracellular matrix. Interest in OA pathogenesis and in models for testing disease modifying therapies has motivated the development of numerous small animal models for joint degeneration. However, while matrix changes in such models can be evaluated via histology and gross biochemical analysis, determination of detailed spatial information regarding matrix changes is challenging at best. A technique capable of high resolution, nondestructive quantification of cartilage morphology and matrix composition could revolutionize the evaluation of such small animal models. The goal of this Exploratory/Developmental Research Grant proposal is to develop a novel imaging methodology utilizing contrast-enhanced microcomputed tomography (UCT) to obtain high resolution, three-dimensional (3D) data describing the morphology and sulfated glycosaminoglycan distribution of small animal articular cartilage. While a powerful tool for quantitative morphological and microstructural analysis of bone and a variety of biomaterials, UCT has not been useful for analysis of cartilage or other soft tissues because of their minimal X-ray attenuation. We have recently performed preliminary validation of a novel UCT application for quantification of the Equilibrium Partitioning of an Ionic Contrast agent UCT (EPIC-UCT) that relies on preferential exclusion of a negatively charged, radio-opaque contrast agent from tissue regions with a greater negative fixed charge density (primarily due to sulfated glycosaminoglycans (sGAGs) on proteoglycans). The specific aims of the proposed research are to (1) evaluate the use of EPIC-UCT to quantify the morphology of rat articular cartilage; (2) evaluate the use of EPIC-UCT to quantify the sGAG distribution of rat articular cartilage; and (3) evaluate the use of EPIC-UCT for in situ evaluation of articular cartilage in intact rat knees using direct intraarticular injection of the contrast agent. In this 2-year project, we aim to develop a methodology suitable for end-stage analysis of articular cartilage in small rodent models and to have laid the groundwork for studies extending this methodology to longitudinal, in vivo tracking of cartilage matrix changes.