Quantitative MR microscopy of enzymatically degraded articular cartilage

Structural changes in bovine patellar articular cartilage, induced by component selective enzymatic treatments, were investigated by measuring tissue T2 relaxation at 9.4 T. This MRI parameter was compared with Young's modulus, a measure of elastic stiffness and loadbearing ability of cartilage tissue. Collagenase was used to digest the collagen network and chondroitinase ABC to remove proteoglycans. Polarized light microscopy and digital densitometry were used to assess enzyme penetration after 44 hr of enzymatic digestion. T2 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 T2 of articular cartilage is sensitive to the integrity of collagen in the extracellular matrix. Nonetheless, it does not appear to be an unambiguous indicator of cartilage stiffness, which is significantly impaired in osteoarthrosis. Magn Reson Med 43:676–681, 2000. © 2000 Wiley‐Liss, Inc.