Purpose

The purpose of the current study was to analyze the synovial fluid concentrations of known inflammatory biomarkers in the setting of symptomatic OA and assess for any differences in biomarker concentrations based on the extent of radiographic disease.

Methods and Materials

Patients presenting with knee complaints were invited to provide synovial fluid samples from the symptomatic knee during their initial visit. For this study, a subset of patients with OA was analyzed. The concentration of 16 synovial fluid biomarkers was measured, including TIMP-1, TIMP-2, TIMP-3, MMP-13, IL-6, MCP-1, MIP-1β, VEGF, bFGF, eotaxin, IL-1Ra, MMP-1, MMP-3, MMP-9, RANTES, and TSG-6. Samples were analyzed using a multiplex magnetic bead immunoassay. Patients were divided into a low-grade cartilage damage group (K-L <= 2 or OARSI <= 1) or a high-grade cartilage damage group (K-L > 2 or OARSI > 1).

Results

101 patients were included in this analysis. There was a significant difference in log-transformed MIP-1β (p=0.025) and bFGF (p=0.015) concentrations between OARSI grade groups. The high-grade joint space narrowing group had significantly greater concentrations of MIP-1β (p=0.022) and bFGF (p=0.003).

There was a significant difference in log-transformed MIP-1β concentration between K-L grade groups (p=0.013). The high-grade K-L group had a significantly greater concentration of MIP-1β (p=0.020).

Conclusion

The synovial fluid concentrations of two synovial fluid biomarkers were found to differ significantly based on the extent of radiographic OA. bFGF is a growth factor that is known to promote chondrogenesis, angiogenesis, wound healing, and granulation tissue formation. As the severity of OA worsens, it is possible that this growth factor is upregulated in an attempt to counteract the cartilage degeneration. Continued study of synovial fluid biomarkers in the setting of symptomatic OA may improve our understanding of the pathogenesis of disease and identify treatment targets in an attempt to halt disease progression.