Changes in proteoglycans in osteoarthritis: biochemistry, ultrastructure and biosynthetic processing.

The loss of proteoglycans from articular cartilage is a hallmark of the osteoarthritic process. Compensatory biosynthesis of proteoglycans is evident by histochemical analysis, characterized by significant metachromasy in the pericellular region of the matrix, at a time when proteoglycans are apparently lost from the interterritorial matrix. Changes, occurring in the pericellular region demonstrating a loss in metachromasy, suggest that depletion of specific proteoglycans surrounding the chondrocyte may be of significance in the early osteoarthritic lesion. Organ culture studies of human and animal cartilage indicated that synthesis of proteoglycans occurs normally, but that postsynthesis processing, allowing for efficient formation of proteoglycan aggregates, may be impaired. In addition, recent experiment data is consistent with proteolytic degradation of newly synthesized proteoglycan core protein which significantly reduces proteoglycan aggregate formation.