Concentration of collagen, aggrecan and cartilage oligomeric matrix protein (COMP) in synovial fluid from equine middle carpal joints.

The researchers examined the concentration of specific proteins in the joint fluid of 73 horses in order to investigate joint metabolic activity and injury response. Results indicated changes in the levels of the proteins when injury was present, which may offer insights into the nature of equine joint diseases.

Objective of the Research

• This study aimed to investigate the metabolic activity of the third carpal bone in horses, and how this is affected by injury. Specifically, they wanted to understand the release of three types of proteins – cartilage oligomeric matrix protein (COMP), aggrecan and collagen type II – into the joint fluid and blood serum in horses of two different breeds with different physical activity profiles.

Research Methods

• The researchers examined samples taken from the middle carpal joints of 73 horses, 52 of which were Standardbred trotters (STB) and 21 were Swedish Warmblood riding horses (SWH), which were known to have varying types of cartilage lesions.
• They measured the levels of the three proteins in the joint fluid (synovial fluid) and serum using specific types of ELISA (enzyme-linked immunosorbent assay), a common laboratory technique for measuring the concentration of a substance in a liquid.

Findings of the Research

• The researchers discovered that in STB horses with moderate cartilage lesions, the concentrations of COMP and aggrecan in the joint fluid were lower compared to normal joints.
• The COMP concentration in the serum was also reduced in these horses, indicating a systemic response to the joint injury.
• In SWH horses, however, the serum COMP level was slightly higher in those with moderate cartilage lesions when compared to normal joints.
• Interestingly, they noted a breed difference in the ratio of aggrecan to COMP in the joint fluid of horses with moderate lesions. The ratio was higher in STB horses than in SWH horses, which could reflect different load characters or stresses on the joints of different breeds.
• Furthermore, they found that the level of collagen type II in the joint fluid was higher in SWH horses than in STBs, but this did not correlate with the joint damage severity.
• There was a marked difference in COMP synthesis between healthy and osteoarthritic cartilage, with the latter producing less COMP.

Conclusion of the Research

• The research concluded that the metabolic activity of the third carpal bone and the response to injury in horses is reflected in the release of these proteins into the joint fluid and blood serum. Therefore, these measures could be useful indicators of joint health in horses.
• The findings also suggest breed differences in response to joint injury. These novel findings are significant in the study of equine arthritis and may have implications for the treatment and management of this disease.