Quantitative MR microscopy of enzymatically degraded articular cartilage

Structural changes in bovine patellar articular cartilage, induced by compo nent selective enzymatic treatments, were investigated by measuring tissue T-2 relaxation at 9.4 T. This MRI parameter was compared with Young's modul us, a measure of elastic stiffness and loadbearing ability of cartilage tis sue. Collagenase was used to digest the collagen network and chondroitinase ABC to remove proteoglycans, Polarized light microscopy and digital densit ometry were used to assess enzyme penetration after 44 hr of enzymatic dige stion. T-2 relaxation in superficial cartilage increased significantly only in samples treated with collagenase. A statistically significant decrease in Young's modulus was observed in both enzymatically treated sample groups . These results confirm that T-2 of articular cartilage is sensitive to the integrity of collagen in the extracellular matrix. Nonetheless, it does no t appear to be an unambiguous indicator of Cartilage stiffness, which is si gnificantly impaired in osteoarthrosis. Magn Reson Med 43: 676-681, 2000, ( C) 2000 Wiley-Liss, Inc.