Assessment of serum Syndecan-4 in patients with knee osteoarthritis and its correlation with disease severity

Abstract Background Osteoarthritis (OA) is the most common degenerative joint disease and a leading cause of pain and disability worldwide. Currently, the diagnosis and severity of OA are based on clinical and radiological criteria which usually fail to detect the disease early. Syndecan-4 (SDC-4) is a transmembrane heparan sulfate proteoglycan involved in extracellular matrix interactions, inflammatory signaling and regulation of cartilage-degrading enzymes such as ADAMTS-5 and MMPs. The shed, soluble form of SDC-4 has been detected in osteoarthritic synovial fluid and linked to radiographic severity, however evidence on circulating (serum) SDC-4 is more limited, despite its possible role as an early biomarker being involved in OA pathogenesis. The purpose of this study was to evaluate serum SDC-4 concentrations in individuals with knee osteoarthritis (KOA) and to investigate its association with both clinical symptoms and radiological indicators of disease severity. Methods This prospective case-control study was conducted on 45 KOA patients fulfilling EULAR criteria and 45 matched healthy controls. Clinical assessment included WOMAC scores, and physical examination. SDC-4 serum levels were measured using ELISA. Radiographic severity was evaluated by Kellgren–Lawrence (KL) grading, osteophytes, joint space narrowing (JSN), bone contour deformity, and subchondral sclerosis. Statistical analyses included t-tests, ANOVA, and correlation tests. Results Serum SDC-4 levels were markedly increased in KOA patients compared to controls (15.9 ± 7.5 vs. 5.3 ± 2.6 ng/ml, p  < 0.001). Higher SDC-4 levels correlated positively with WOMAC pain, stiffness, physical function, and total scores ( p  ≤ 0.05). Radiographic features including osteophytes, JSN, bone contour deformity, and subchondral sclerosis were all correlated with higher SDC-4 levels ( p  < 0.001). Moreover, SDC-4 levels increased with higher KL grading, showing significant differences between grades 2, 3, and 4 ( p  < 0.001). Conclusion Elevated serum SDC-4 is correlated with clinical symptoms and radiographic severity of KOA; thus, SDC-4 could be a potential biomarker for KOA assessment.