To describe the acute cellular response, inflammatory mediator release, and effect on chondrocyte metabolism of interleukin 1β (IL-1β) in isolated innervated or denervated equine metacarpophalangeal joints.
One metacarpophalangeal joint of 24 adult horses.
The metacarpophalangeal joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated metacarpophalangeal joint preparation. Isolated joints were assigned to 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1β. Synovial fluid was collected for cytologic examination and determination of IL (IL)-1β, (IL-6), prostaglandin E2 (PGE2), and substance P (SP) values. Synovial membrane was immunostained with SP and nerve-specific enolase (NSE) antibodies. Cartilage was collected for determination of proteoglycan (PG) synthesis and degradation.
IL-1β induced significant neutrophilic leukocytosis in synovial fluid and synovial membrane. IL-1β concentration had returned to baseline by 5.5 hours, but IL-6 concentration significantly increased throughout the study. Total SP content was significantly higher in inflamed joints. There was a significant increase in 24- and 48-hour PG degradation in inflamed innervated joints.
Cellular response to IL-1β was rapid and sustained; joint clearance of IL-1β was rapid, and endogenous production of IL-1β did not follow. The IL-6 and PGE2 concentrations significantly increased, and SP content was increased in association with inflammation but not denervation. A degradative response of cartilage to IL-1β was observed, and was enhanced by innervation. This model was useful for investigation of the articular response to acute inflammation and the influence of denervation in modulating this response. (Am J Vet Res 1998;59:88–100)
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