Proteoglycan profiles obtained by electrophoresis and triple immunoblotting

Using synovial fluid of individuals with osteoarthritis as a prototypic biologic fluid containing one part proteoglycan per 100 to 1000 parts of other protein, profiles of proteoglycan were produced without preliminary purification through agarose-acrylamide gel electrophoresis, transfer to nitrocellulose, and triple immunoblotting. Chondroitin sulfate, keratan sulfate, and a hyaluronic acid binding region appear to be present on individual synovial fluid proteoglycans in variable amounts, and consequently a triple immunoblot using monoclonal antibodies to these three epitopes has the potential for developing a proteoglycan profile. The profile is assembled by means of densitometric scans of autoradiograms obtained after use of 125I-labeled anti-mouse immunoglobulin. By contrast to the profile of a relatively homogeneous proteoglycan purified from articular cartilage extracts, the proteoglycans of synovial fluid appeared to be quite heterogeneous with the bulk of keratan sulfate epitopes migrating ahead of the bulk of the chondroitin sulfate epitopes. Most of the proteoglycans appeared to possess a hyaluronate binding region.