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

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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.