Biomarker profiling of biologic fluids and tissues from horses with induced carpal osteoarthritis : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand
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2024-09-04
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Massey University
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Abstract
Osteoarthritis (OA) is a progressive, irreversible disease of synovial joints associated with chronic pain, which negatively impacts on the quality of life of millions of people worldwide. Similarly, OA in horses is common and has a major financial impact on the equine industry, in treatment costs, time lost to training and animal wastage.
Diagnosis of OA generally relies on clinical examination and imaging findings. However, there is a poor correlation between them, and imaging modalities have low sensitivity and specificity, and high costs. Extensive research has been conducted to identify possible molecular biomarkers of OA in early disease, stratify the likelihood of progression, and explore new interventions. Despite significant advancements in biomarker research, the adoption and validation of candidate biomarkers within a clinical practice setting is yet to be established due to the lack of consistency, the limited practicality of the tests, and the relatively high costs when used as a tool for disease surveillance. There is a need for non-invasive, cost effective, repeatable diagnostic and screening tests with high sensitivity and specificity for early disease diagnosis. The primary objective of the body of research presented in this dissertation was to investigate alternative economical, and potentially more accurate techniques for the determination of biomarker profiles of equine OA.
An established surgical and exercise model was used in this study to induce carpal OA in nine of seventeen young female Thoroughbred horses. Weekly blood and synovial fluid samples were collected for 9 weeks after induction of OA and joint tissue samples were collected at the end of the study.
The first study (Chapter 3) assessed the use of cell-free DNA (cfDNA) as a potential biomarker of OA. The results showed that cfDNA concentrations were significantly higher in synovial fluid from horses with OA than in the control group at 4 and 9 weeks. Conversely, cfDNA concentrations in plasma did not significantly differ between groups. It was concluded that plasma cfDNA measurement is not sufficiently sensitive for early diagnosis of OA, while measurement of this biomarker in joint fluid may be useful.
The second and third studies (Chapters 4 and 5) investigated the use of infrared (IR) spectroscopy techniques to determine the serum and synovial fluid biomarker profiles of the same group of horses with induced OA and controls. Although serum IR spectroscopy profiles were not significantly different between groups, this technique showed good accuracy when used with synovial fluid.
Raman spectroscopy (Chapter 6) was used to assess the biochemical profiles of cartilage and bone samples obtained from the same cohort of horses. This technique successfully identified clear differences between articular cartilage and bone but failed to detect significant differences between diseased and healthy joints for both cartilage and bone.
Overall, the results of these studies showed that with the described model of equine OA, the techniques and methodologies used proved more useful to identify biomarker profiles of horses with OA when used on synovial fluid compared with blood (serum or plasma). This suggests that biomarkers concentrations (cfDNA) and profiles (IR signals) are excessively low in the peripheral circulation for the detection threshold of these techniques, and that more invasive methodologies of sampling (arthrocentesis) are the preferred method for this model of OA. Raman spectroscopic analysis of tissues failed to detect significant differences in spectroscopic profiles between groups, possibly due to the nature of the OA model used, with a relatively short duration and the potential confounding effect of exercise and lameness.
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osteoarthritis, biomarkers, horses, synovial fluid, serum, plasma, spectroscopy, cell-free DNA