High-mobility group box chromosomal protein 1 as a potential inflammatory biomarker of joint injury in Thoroughbreds.

The research article examines the relationship between osteochondral injury in horses and the levels of high-mobility group box chromosomal protein 1 (HMGB-1) found in synovial fluid. The results show that injuries were linked to significantly raised levels of HMGB-1, making it a potential marker for joint injuries.

Objective and Methodology

In this study, the researchers aimed to determine the effects of osteochondral injury, damage affecting cartilage and the underlying bone, on the levels of HMGB-1 in synovial fluid of Thoroughbreds. The study group comprised of 40 clinically normal Thoroughbreds and 45 Thoroughbreds with a racing-induced osteochondral injury.

• The synovial fluid, a lubricating fluid reducing friction in joints, was sourced from different joints including the metacarpophalangeal (MCP), metatarsophalangeal (MTP), middle carpal and radiocarpal joints.
• For the group with joint injury, radiographic and arthroscopic scores were also determined to measure the severity of the joint injury.
• In all horses, concentrations of HMGB-1 in the synovial fluid were determined using an ELISA (Enzyme-linked Immunosorbent Assay), a plate-based assay technique designed for detecting and quantifying substances such as peptides, proteins, antibodies, and hormones.

Findings and Results

The study showed that synovial fluid concentrations of HMGB-1 in the osteochondral-injured MCP-MTP and carpal joints were significantly higher compared to the synovial fluid of normal, injury-free joints.

• There was, however, no correlation found between the severities of joint injury – as determined by radiographic and arthroscopic scores – and the levels of HMGB-1 in the synovial fluid.
• The researchers identified that HMGB-1 concentrations above or equal to 11 ng/mL for MCP-MTP joints and above or equal to 9 ng/mL for carpal joints effectively differentiated osteochondral-injured joints from normal ones.
• Horses that had HMGB-1 concentrations over or equal to these levels in respective joints were more likely to have osteochondral injuries. Specifically, Thoroughbreds were twice and four times as likely to have an injury with above or equal concentrations in MCP-MTP and carpal joints respectively.

Conclusion

The presence of an osteochondral injury in Thoroughbreds was related to a significant increase in synovial fluid concentrations of HMGB-1 in MCP-MTP and carpal joints. As a result, the analysis of HMGB-1 concentrations could be useful for evaluating joint injury in horses. The researchers concluded that larger studies might help confirm these findings and determine the clinical usefulness of this potential biomarker.