Repair characteristics of the articular cartilage surface following acute inflammatory arthritis

To investigate the repair characteristics of the surface protein in an acute arthritis of short duration.

Knee arthritis in rabbits was induced by intraarticular (ia) injection of 20 micrograms E. coli endotoxin into one knee of 12 rabbits. The contralateral knee served as control. Four animals were killed 3, 6, and 10 days after ia injection. The articular cartilage surface was probed by quantitation of anticollagen type II (anti-CII) antibody binding. The suprapatellar bursae were washed, and the recovered cells counted.

A significant increase in anti-CII antibody binding compared to control was measured 3 days after ia injection, coinciding with evidence of acute arthritis (injected joint: 1.1 x 10(7), control: 4.2 x 10(4) cells/joint; percent increase in anti-CII binding: 36.7 +/- 10.7; p < 0.02). Six days after ia injection, the acute arthritis showed a major decrease in intensity whereas anti-CII binding was still abnormal (injected joint: 1.7 x 10(6) cells/joint; percent increase in anti-CII binding: 24.7 +/- 19.6; p < 0.05). On Day 10, there was minimal evidence of arthritis in 3 of 4 rabbits, and anti-CII antibody binding returned to normal (injected joint: 1.9 x 10(5) cells/joint; percent anti-CII binding: -5.8 +/- 3.9). There was a strong positive correlation between individual synovial fluid cell counts and the percent increase in anti-CII binding (R = 0.72, p < 0.02).

The magnitude of binding of anti-CII antibodies to the articular cartilage surface constitutes a sensitive probe for the detection of early damage following a transient inflammatory insult. Our studies indicate that after acute injury, the cartilage surface may show evidence of damage for at least 6 days when probed with anti-CII antibodies.