Failure of proteoglycans to form aggregates in morphologically normal aged human hip cartilage.

The macromolecular organization of proteoglycans in morphologically and histochemically normal hip cartilage from aged humans has been studied. In contrast to findings in articular and nonarticular cartilage from other sources, most of the proteoglycans in these tissues did not exist in large aggregates. Treatment with hyaluronic acid beta1 leads to 3 hydrolase failed to diminish the size of proteoglycans prepared under conditions favoring aggregation, a finding suggesting that they were not complexed with hyaluronic acid. Polyacrylamide gel electrophoresis failed to demonstrate the presence of link glycoproteins associated with the proteoglycans. After incubation in vitro with hyaluronic acid, minimal augmentation of hydrodynamic size of the preparation occurred, an indication that hyaluronate-proteoglycan interaction had not taken place. These results suggest that proteoglycan aggregation was diminished because of a defect in the core protein of the proteoglycans resulting in an impaired ability of these molecules to interact with hyaluronic acid.