MAGNETIC-RESONANCE-IMAGING AND MORPHOMETRIC QUANTITATION OF CARTILAGEHISTOLOGY AFTER CHRONIC INFUSION OF INTERLEUKIN-1 IN RABBIT KNEES

Cartilage pathology in rabbit knees was monitored by noninvasive magne tic resonance imaging (MRI) and evaluated using morphometric histologi c measurements. Infusion of rabbit knees with the cytokine interleukin 1 induces cartilage degradation and inflammation. A miniosmotic pump was implanted subcutaneously to deliver interleukin 1 through a polyet hylene catheter inserted into the rabbit knee. Rabbit knees were image d using MRI and prepared for histologic examination at 5 and 12 days a fter chronic infusion of interleukin 1. MRI obtained 0.7-mm sections f or three-dimensional reconstruction of cartilage image. Cartilage dete rioration near the site of infusion was visible on MRI. MRI measuremen ts indicated a reduction in cartilage thickness. Histology revealed a loss of staining of cartilage matrix proteoglycan, synovial hypertroph y, and perichondral bone resorption. Morphometric analysis of cartilag e histology indicated a reduction in both cellularity (chondrocytes/mm u2 area) and cell to matrix area ratio. These observations suggest tha t a loss of proteoglycan, an early event in cartilage degeneration, ca n be detected by MRI.