Investigations on the quantitative and qualitative protein content in serum and synovial fluid of dogs with osteoarthritis

Background: The diagnosis of osteoarthritis in dogs remains a diagnostic challenge due to the lack of appropriate biomarkers. Therefore, this study was performed a proteomic approach to compare the protein patterns in dogs’ synovial fluid and serum that might be helpful in elucidating pathways involved in joint damage and the identification of new diagnostic biomarkers. Material and methods: SF was collected from dogs suffered from OA (n = 41) and healthy control dogs (n = 8), and serum was collected from OA dogs (n = 13) and healthy controls (n = 16). Protein concentrations were measured by Bradford analysis and were separated using SDS polyacrylamide gel electrophoresis. Proteins that were different between OA and healthy samples were digested by trypsin, analysed by MALDI-TOF mass spectrometry and compared with SwissProt database. A commercially available ELISA kit was used to evaluate Apo AI as diagnostic biomarker in SF and serum. Results: Total protein concentrations were significantly higher (P < 0.001) in dogs with OA compared to control dogs. Serum albumin and Apolipoprotein A-I (Apo AI) were significantly identified in SF. Apo A-I was further confirmed in serum and SF by significantly higher (P < 0.001) concentration in dogs with OA compared to healthy controls. Conclusion: The quantification of total protein and Apolipoprotein A-I concentrations in SF might be potential diagnostic biomarkers in canine OA.