Identification of a complex between fibronectin and aggrecan G3 domain in synovial fluid of patients with painful meniscal pathology

Abstract

Objectives: We previously described a panel of four cytokines biomarkers in knee synovial fluid for acute knee pain associated with meniscal pathology. The cytokine biomarkers included interferon gamma (IFN-gamma), interleukin 6 (IL-6), monocyte chemotactic protein 1 (MCP-1), and macrophage inflammatory protein-1 beta (MIP-1beta). Validation studies using other immunologic techniques confirmed the presence of IL-6, MCP-1 and MIP-1beta, but not IFN-gamma. Therefore we sought the identity of the IFN-gamma signal in synovial fluid.

Methods: Knee synovial fluid was collected from patients with an acute, painful meniscal injury, as well as asymptomatic volunteers. A combination of high-pressure chromatography, mass spectrometry and immunological techniques were used to enrich and identify the protein components representing the IFN-gamma signal.

Results: A protein complex of fibronectin and the aggrecan G3 domain was identified in the synovial fluid of patients with a meniscal tear and pain that was absent in asymptomatic controls. This protein complex correlated to the IFN-gamma signal. A novel enzyme-linked immunosorbent assay (ELISA) was developed to specifically identify the complex in synovial fluid.

Conclusions: We have identified a protein complex of fibronectin and aggrecan G3 domain that is a candidate biomarker for pain associated with meniscal injury.