There is an ongoing discussion about the role of collagenase as a specific cartilage-degrading enzyme in the course of osteoarthritis. Using NMR microscopy, the influence of collagenase on the cartilage structure was investigated.
High-resolution MR imaging investigations were performed at 7.1 Tesla to study the influence of collagenase on the cartilage structure of pig femoral condyles. Two different contrast agents (polylysine-Gd-DTPA and liposome-entrapped contrast agents) were tested to improve the NMR microscopic visualization of the damaged cartilage regions.
The NMR microscopic investigations showed that collagenase affects only the cartilage surface. Changes within the cartilage layer were not detected. However, after the application of specific contrast agents, it was possible to detect with great sensitivity collagenase-induced damage to the collagen network on the cartilage surface and the superficial cartilage zones. The application of liposome-entrapped contrast agents improved the visualization of the collagenase-degraded superficial cartilage zone.
These findings could be of great importance when estimating the state of the articular cartilage. The degree of fibrillation of the cartilage surface in the course of osteoarthritic disease can be visualized by MR tomography with a high degree of sensitivity.