Characterization of a hyaluronic acid-dermatan sulfate proteoglycan complex from dedifferentiated human chondrocyte cultures.

Cells grown from human articular cartilage by an explant method were shown to be dedifferentiated chondrocytes by the failure to respond to treatment with 5-bromodeoxyuridine, vitamin A, or the addition of hyaluronic acid. The major glycosaminoglycan produced by these cells was high molecular weight hyaluronic acid. The majority of the 35S-sulfated glycosaminoglycan was copolymeric chondroitin sulfate-dermatan sulfate (Mr = 2 to 2.4 X 10(4). The dermatan sulfate was present as the 4-sulfated isomer. Labeled proteoglycans were isolated from the growth media by centrifugation in either associative or dissociative cesium chloride density gradients in the presence of protease inhibitors or by precipitation with cetylpyridinium chloride and column chromatography on Sepharose CL-2B. The proteoglycans secreted into the medium by these dedifferentiated chondrocytes were large molecular weight proteoglycans (Kav = 0.23 on Sepharose CL-2B) that were able to form specific complexes with hyaluronic acid. The material isolated by the cetylpyridinium chloride precipitation was an aggregated proteoglycan (78% aggregate) that was not displaced by exogenous proteoglycan which after reduction and alkylation gave a large proteoglycan monomer (Kav = 0.23 on Sepharose CL-2B). These findings are in direct contrast to the report of small molecular proteoglycans isolated from cultures of dedifferentiated chrondrocytes obtained from other species.