Correlation of dickkopf-1 concentrations in plasma and synovial fluid to the severity of radiographic signs of equine osteoarthritis.

The study sought to determine the relationship between dickkopf-1 (Dkk-1) levels in bloodstream and synovial fluid, and observable signs of osteoarthritis in horses as seen on radiographs. However, no significant correlation was identified between Dkk-1 concentrations and radiographic signs of osteoarthritis. Nonetheless, the study found that the concentrations of Dkk-1 were significantly higher in low-motion joints compared to high-motion joints.

Objective and Methodology

• The research set out to investigate if there was a correlation between the circulating and intra-synovial Dkk-1, a protein that modulates tissue development, and radiographic signs of equine osteoarthritis.
• The researchers measured circulating and intra-synovial Dkk-1 levels in clinical cases using a commercially available human Dkk-1 ELISA. The ELISA test is a plate-based assay technique designed for detecting and quantifying substances such as peptites, proteins, antibodies, and hormones.
• Radiographs (X-rays) were taken of the joints from which fluid was collected. These radiographs were assessed and scored by a professional radiologist for various signs of osteoarthritis: joint narrowing, subchondral bone sclerosis, subchondral bone lysis, and periarticular modelling.
• The results were analyzed by comparing radiographic scores and the concentrations of Dkk-1 using a Kruskal-Wallis one-way ANOVA, a type of inferential statistical test that is used to determine if there are any statistically significant differences between two or more groups of an independent variable on a continuous or ordinal dependent variable.
• Correlations were further assessed using Kendall’s statistic, a measure of association between two measured quantities.

Results

• A total of 42 synovial fluid samples from 21 horses were collected and used in the analysis.
• No significant correlation was observed between Dkk-1 concentrations and radiographic signs of osteoarthritis.
• However, the study found that intra-synovial Dkk-1 concentrations were significantly higher in joints that performed limited motion (averaging 232.68 pg/mL) when compared to high-motion joints (averaging 28.78 pg/mL).

Conclusions

• The study concluded that low-motion joints have significantly higher concentrations of Dkk-1 compared to high-motion joints. This could potentially indicate a role of Dkk-1 in osteoarthritis specifically related to low-motion joints.
• However, as no significant correlation was identified between Dkk-1 concentrations and radiographic signs of osteoarthritis, the role of Dkk-1 in the pathogenesis of osteoarthritis is still unclear.
• Further research is needed to understand the importance of the finding and to determine if there are potential diagnostic or therapeutic applications of Dkk-1 in horses.