Cell trafficking, mediator release, and articular metabolism in acute inflammation of innervated or denervated isolated equine joints.

The research article discusses how the release of interleukin 1 beta (IL-1 beta), an inflammatory mediator, affects the cellular response, inflammatory mediator release, and effects on chondrocyte metabolism in horse joints, comparing the responses in innervated and denervated joints.

Research Methodology

• The research was conducted on a single metacarpophalangeal joint of 24 adult horses.
• Each of these horse joints was isolated for six hours in a pump-perfused, auto-oxygenated, innervated, or denervated joint preparation.
• The isolated joints were categorized into four groups: control, control-denervated, inflamed, and inflamed-denervated.
• Inflammation was induced by an intra-articular injection of IL-1 beta.
• Samples of synovial fluid were collected for cytological examination and to determine the levels of interleukin-1 beta (IL-1 beta), interleukin 6 (IL-6), prostaglandin E2 (PGE2), and substance P (SP).
• Through immunostaining the synovial membrane, levels of SP and nerve-specific enolase (NSE) were determined.
• Cartilage was collected for the determination of proteoglycan (PG) synthesis and degradation.

Research Findings

• IL-1 beta triggered significant neutrophilic leukocytosis (increased number of neutrophils) in synovial fluid and synovial membrane.
• IL-1 beta concentrations increased rapidly, then returned to baseline at 5.5 hours, but IL-6 concentrations significantly rose throughout the study.
• The total content of Substance P (SP), a neuropeptide involved in pain perception, was notably higher in the inflamed joints.
• There was a significant increase in PG degradation, over a period of 24 and 48 hours, in inflamed innervated joints.

Conclusions

• The cellular response to IL-1 beta was quickly triggered and sustained over time. The clearance of IL-1 beta from the joint was also rapid. Endogenous production of IL-1 beta did not follow the rapid clearance trend.
• The concentrations of IL-6 and PGE2 significantly increased, alluding to a systemic inflammatory response.
• The content of Substance P (SP) also increased in conjunction with inflammation but not with denervation.
• The introduction of IL-1 beta resulted in cartilage degradation. This degradation was further enhanced in the presence of neural innervation, suggesting a possibly detrimental effect of innervation in inflammation scenarios.
• The experimental model allowed effective investigation of the articular response to acute inflammation and the influence of denervation in modulating this response.