Effects of exercise on synovial fluid and serum biomarkers of musculoskeletal diseases in horses with and without osteochondral fragmentation

Abstract

Introduction: Osteoarthritis (OA) is a common problem in horses. Measuring biomarkers (BMs) is one of the recent methods used to diagnose early OA. With OA, the levels of many BMs usually increase. In addition, many of the BMs are normally increased in body fluid with exercise. Purpose: To distinguish between changes occurring in osteochondral tissues as a result of adaptation (exercise) versus pathological conditions (osteoarthritis) based on assessing various BMs of articular cartilage and bone metabolism in the synovial fluids and sera of two-year old horses. The changes in the levels of BMs will be correlated with the results of clinical examinations and histopathology findings.

Material and Methods: Sixteen healthy 2-year-old horses were exercised on a treadmill for 91 days (5 days/week). On day 21, an osteochondral chip fragment was created in one randomly chosen intercarpal joint of eight horses. Both synovial fluid and serum samples were collected weekly from the horses. Bone and articular cartilage BMs were assessed in synovial fluid and serum. On day 91, the horses were euthanized and the pathologic changes in the joints of exercised horses with and without osteochondral fragmentation were scored and then correlated with the synovial fluid and serum BM levels.

Results: Exercise and OA significantly increased all BMs compared to baseline. In general, the increase in the levels of biomarkers was higher as a result of OA compared to exercise. This increase was seen in all BMs except serum CTXI and 234CEQ. The levels of bone markers were higher in serum than synovial fluid samples whereas the levels of articular cartilage markers were higher in synovial fluid than in serum samples. In OA, cartilage metabolism preceded bone metabolism based on BM results. Within cartilage, aggrecan turnover preceded collagen turnover. Moreover, aggrecan synthesis preceded its turnover. The first change in the biomarker levels was in CS846. There were significant correlations between articular cartilage BMs and the clinical examination, gross, and histologic changes of articular cartilage.

Conclusion: This study showed the usefulness of assessing BMs in differentiating exercise-induced changes from discrete OA pathology. Synovitis due to exercise and/or OA may be the key factor influencing the levels of biomarkers. Assessing articular cartilage biomarkers is a useful method that can be used to detect the amount of pathological changes occurred in early OA.