The potential and limitations of cartilage-specific (V+C)− fibronectin and cartilage oligomeric matrix protein as osteoarthritis biomarkers in canine synovial fluid

SummaryObjectiveTo determine if levels of the cartilage-specific (V+C)− fibronectin isoform in the synovial fluid is associated with cartilage change during osteoarthritis.DesignSynovial fluid was collected from 26 healthy dogs presenting to the Orthopedic Surgery Clinic with unilateral cranial cruciate rupture, 22 control dogs, and 13 dogs from a colony maintained for the study of canine hip dysplasia. Total fibronectin, (V+C)− fibronectin, and cartilage oligomeric matrix protein (COMP) were quantitated by ELISA assays. Statistical analysis used Wilcoxon's signed-rank and rank-sum tests and Spearman's rank correlation.ResultsThe concentration of total fibronectin was increased in affected (P<0.0001) and contralateral (P=0.0005) knees of the clinic population (compared to unaffected knees in colony controls). Both (V+C)− fibronectin and COMP concentrations were elevated in the contralateral knees in clinical patients relative to unaffected knees in the colony controls (P=0.03 and P=0.04, respectively), and relative to the affected knees (P=0.003); however, corrections for joint effusions suggest elevated totals in the affected knees. (V+C)− fibronectin and COMP concentrations were correlated (rsp=0.74; P