Accumulation of fibronectin in articular cartilage explants cultured with TGF beta 1 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 TGF beta 1 and the sulfated fucopolysaccharide, fucoidan, accumulated fibronectin at levels comparable to those found in osteoarthritic lesions. TGF beta 1 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.