The relationship between the serum and synovial fluid osteopontin (OPN), cartilage oligomeric matrix protein (COMP), and the severity of knee osteoarthritis (KOA) assessed by radiology

Objective: To investigate the relationship between the serum and synovial fluid osteopontin (OPN), cartilage oligomeric matrix protein (COMP), and the severity of knee osteoarthritis (KOA) assessed by radiology. Methods: 108 patients with KOA in our hospital were enrolled in a study group (SG). 108 patients in the same period were included in a control group (CG). The patients in the CG needed knee surgery due to a meniscus injury or other trauma. An enzyme linked immunosorbent assay (ELISA) was used to determine the expression levels of OPN and COMP. The Kellgren-Lawrence (KL) system was adopted to grade the development of KOA. The correlation between the OPN and COMP expression levels and the KL grades was analyzed using a Spearman correlation coefficient. The Pearson correlation coefficient was introduced to analyze the correlation between the OPN and COMP expressions. Results: The serum and synovial fluid COMP and OPN expression levels in the SG were higher than those in the CG (P < 0.05). The expression trend of COMP and OPN in patients with different K-L grades was as follows: Grade IV expression > grade III expression > grade II expression > grade I expression (P < 0.05). Both the serum COMP and OPN expression levels were positively correlated with the K-L grades (r=0.723, P < 0.05; r=0.799, P < 0.05). Both the synovial fluid COMP and OPN had a positive correlation with the K-L grades (r=0.701, P < 0.05; r=0.784, P < 0.05). There was a positive correlation between the COMP and OPN expression levels in the SG (r=0.340, P < 0.05; r=0.612, P < 0.05). Conclusions: COMP and OPN are highly expressed in the serum and synovial fluid of patients with KOA. The expression levels are positively correlated with the disease severity as assessed using radiology, which may be a biological measure to evaluate the conditions of patients with KOA.