Efficacy of infliximab in a rabbit model of osteoarthritis.

The purpose of this study was to investigate the efficacy of intra-articular injection of infliximab in a rabbit model of osteoarthritis. In 30 New Zealand white rabbits, the cruciate ligaments and medial menisci were resected using the Hulth technique. Eight weeks postsurgery, the animals were randomly divided into three groups, and each group was given monthly intra-articular injections (0.5 ml) of 10 mg/ml infliximab, 20 mg/ml infliximab, or saline, respectively. After 3 months, the results were assessed by macroscopic observation, histological evaluation, and measurement of the levels of interleukin-1β, tumor necrosis factor-α, and nitric oxide in the synovial fluid. In the two groups of rabbits administered infliximab (10 or 20 mg/ml), the pathological changes were more attenuated than in the group administered saline. Mankin scores in the rabbits administered infliximab 10 mg/ml (2.7 ± 0.9) or infliximab 20 mg/ml (2.4 ± 0.7) were significantly lower than in the control group (6.4 ± 1.2) (p <0.05). The tumor necrosis factor-α and nitric oxide contents of the synovial fluid were also decreased significantly in the rabbits administered infliximab at both concentrations compared with the saline-injected rabbits (p <0.05). Administration of infliximab did not change the levels of interleukin-1β in the synovial fluid. Similar results were obtained for all analyses with the two concentrations of infliximab tested. This study demonstrates that intra-articular injections of infliximab can protect against the development of experimentally induced osteoarthritis.