Fibronectin in synovial fluid and tissue in rheumatoid arthritis

Abstract

Fibronectin is a glycoprotein found in body fluids, loose connective tissue matrix and in basement membranes. Fibronectin in rheumatoid arthritis synovial fluid was immunologically indistinguishable from the plasma form, as shown by double‐diffusion analysis. Fibronectin isolated from rheumatoid synovial fluid by affinity chromatography on gelatin‐Sepharose had a polypeptide pattern similar to that of plasma fibronectin in SDS‐polyacrylamide gel electrophor‐esis. In fifty‐one patients with rheumatoid arthritis and related diseases fibronectin concentrations in synovial fluid were 445 ±103 μg/ml (mean ±SD) and within normal range, 335±52 μg/ml, in plasma. Immuno‐fluorescence staining showed a prominent increase of fibronectin in the proliferating synovial connective tissue in rheumatoid arthritis as compared to normal synovial membrane. The results suggest an increased local production of fibronectin in rheumatoid synovial tissue.