RESUMO
OBJECTIVE: Osteoarthritis (OA) is a major cause of disability and represents the most common disease in the aging population. Although the course of the disease is generally assessed using standard radiographic images, biochemical markers may be employed to detect the disease and determine the degree of severity. We developed an enzyme linked immunosorbent assay (ELISA) system using a monoclonal antibody specific for the large-splice variants of tenascin-C (TN-C) and examined whether TN-C in synovial fluid (SF) is an adequate biochemical marker of OA progression. METHODS: SF samples were obtained from knees of 74 patients with OA and 16 without OA. Based on the radiographic grading of the OA severity, the knees were divided into 3 groups: mild, moderate, and severe OA. Expression of TN-C splice variants was examined using immunoblotting. TN-C concentrations were determined by ELISA. RESULTS: Western blotting showed the presence of large TN-C variants in SF from severe OA. TN-C levels were 5-fold higher in OA samples compared to subjects without OA (p < 0.0001). TN-C levels were not different between control cases and mild OA, but increased significantly in moderate (p = 0.0244) and severe OA (p < 0.0001). After adjusting TN-C levels for age, body mass index, and sex, TN-C levels correlated with radiographic progression of knee OA (R2 = 0.404, p < 0.0001). CONCLUSION: TN-C, including the large-variant subunits, is a useful biochemical marker for OA progression in the later stages of disease.
