Nitrite and nitrotyrosine concentrations in articular cartilage, subchondral bone, and trabecular bone of normal juvenile, normal adult, and osteoarthritic adult equine metacarpophalangeal joints.

This research paper studies nitrite and nitrotyrosine concentrations in different parts of the equine metacarpophalangeal joints. The study found higher levels of these substances in horses suffering from osteoarthritis compared to healthy adult and juvenile horses. However, nitrite concentration cannot distinguish between normal and pathological conditions. Increased nitrotyrosine levels in the subchondral bone are suggestive of early or moderate osteoarthritis, indicating a role of oxidative stress in disease progression.

Research Methods and Sample Groups

• The research involved the study of nitric oxide (NO) end products in different tissue layers of equine joint, specifically in articular cartilage, subchondral bone, and the underlying trabecular bone. These elements constitute the bearing surface of the joint, providing an essential framework for the study.
• Nitrite, as a proxy for NO, and nitrotyrosine were measured in the joint tissue of three distinct groups of horses – 15 healthy mature horses aged 5-18 years, 15 mature horses suffering from osteoarthritis aged 8-22 years, and 13 juvenile horses aged 6 months-4 years with no joint issues.
• An examination of the extent of cartilage damage was carried out using the Cartilage Degeneration Index, and the data obtained was correlated with the nitrite and nitrotyrosine measurements.

Results and Findings

• Across all the three tissue layers under examination, osteoarthritic joints showed a higher concentration of nitrite compared to the joints of healthy horses. This was statistically significant for the articular cartilage and both subchondral and trabecular bone.
• Nitrite concentration was significantly higher in the cartilage and subchondral bone of juvenile horses than in mature horses, regardless of health status.
• Nitrotyrosine levels were significantly higher in the subchondral bone of horses affected by osteoarthritis compared to healthy controls. In contrast, these concentrations were significantly lower in the trabecular bone of young horses.

Conclusions and Implications

• The results demonstrate a similarity in nitrite and nitrotyrosine concentrations across the three tissue layers, supporting the idea of the joint’s bearing surface as a functional entity.
• While nitrite concentration appears to correspond to tissue metabolic activity, it does not differentiate between physiological processes in young animals and pathological processes in osteoarthritic animals.
• The increased concentration of nitrotyrosine in the subchondral bone of osteoarthritic horses indicates the potential for early or moderate osteoarthritis. It implies the role of oxidative stress in the disease’s development.