Association of CXCL12 Levels in Synovial Fluid With the Radiographic Severity of Knee Osteoarthritis

Objective: Inflammation is implicated to be involved in the pathogenesis of osteoarthritis (OA). CXCL12, also known as stromal cell-derived factor, is the unique identified natural ligand of the G-protein-coupled receptor CXCR4 and exhibits both homeostatic and proinflammatory functions. This study aimsto determine whether CXCL12 levels in serum and synovial fluid (SF) of patients with knee OA are correlated with the disease severity. Methods: This study consisted of 252 patients with knee OA and 144 healthy controls. The radiological grading of OA in the knee was performed according to the Kellgren-Lawrence grading system. CXCL12 levels in serum and SF were measured by enzyme-linked immunosorbent assay. Results: Higher levels of serum CXCL12 were found in knee OA patients compared with healthy controls. The CXCL12 levels in SF of knee OA patients with KL grade 4 were significantly elevated compared with those with KL grades 2 and 3. Furthermore, knee OA patients with KL grade 3 had significantly higher SF levels of CXCL12 compared with those with KL grade 2. CXCL12 levels in SF of knee OA patients were significantly correlated with disease severity evaluated by KL grading criteria. However, there were no significant differences in the serum CXCL12 levels between patients with different KL grades. Conclusion: CXCL12 levels in SF were closely related to the radiographic severity of OA. CXCL12 levels in SF may be an alternative biomarker for the progression of OA.