Accumulation of Fibronectin in Articular Cartilage Explants Cultured with TGFβ1 and Fucoidan

Fibronectin is a glycoprotein involved in cell matrix interactions. In osteoarthritis, fibronectin levels in the lesion cartilage are elevated up to 20-fold above control levels. In these experiments, explants of disease-free cartilage cultured in the presence of a combination of TGFβ1 and the sulfated fucopolysaccharide, fucoidan, accumulated fibronectin at levels comparable to those found in osteoarthritic lesions. TGFβ1 increased fibronectin synthesis, most of which was released to the medium. The addition of fucoidan favored retention of the newly synthesized fibronectin within the matrix. The fibronectin which accumulated as a result of these treatments was similar to the fibronectin in normal and osteoarthritic cartilage with respect to the ED-B+ alternative splice form. No change in the proteoglycan content of the cartilage explants with elevated fibronectin levels was detected.