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疾病，其特征是软骨细胞外基质的逐渐但渐进的降解。对OA发病机制和疾病修饰疗法测试模型的兴趣推动了许多关节变性小动物模型的发展。然而，虽然这些模型中的基质变化可以通过组织学和总体生化分析来评估，但确定关于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、无损量化的技术可能会彻底改变这种小动物模型的评估。这项探索性/发展性研究拨款提案的目标是开发一种新的成像方法，利用对比增强的微计算机断层扫描（UCT）来获得描述小动物关节软骨形态和硫酸氨基聚糖分布的高分辨率三维（3D）数据。虽然UCT是骨和各种生物材料的定量形态学和微观结构分析的有力工具，但由于其x射线衰减很小，因此它不适用于软骨或其他软组织的分析。我们最近对一种新的UCT应用进行了初步验证，该应用用于定量离子造影剂UCT （EPIC-UCT）的平衡分配，该造影剂依赖于优先排除带负电荷的、放射不透明的造影剂，使其从具有较大负电荷固定密度的组织区域（主要是由于蛋白聚糖上的硫酸化糖胺聚糖（sGAGs））。拟议研究的具体目的是：(1)评估EPIC-UCT用于量化大鼠关节软骨形态的应用；(2)评价EPIC-UCT量化大鼠关节软骨sGAG分布的应用；(3)通过直接关节内注射造影剂，评估EPIC-UCT在完整大鼠膝关节关节软骨原位评估中的应用。在这个为期2年的项目中，我们的目标是开发一种适合小型啮齿动物模型关节软骨终末分析的方法，并为将该方法扩展到软骨基质变化的纵向、体内跟踪的研究奠定基础。

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.