The biosynthetic response of the mature chondrocyte in early osteoarthritis

Metabolic studies in early experimental osteoarthritis (OA) have shown that the rate of proteoglycan synthesis in the diseased articular cartilage may be markedly enhanced relative to normal; elevated rates of synthesis were however accompanied by increased release of new molecules from the tissue so that the response was apparently non-reparative. Described here are experiments with immature and mature chondrocytes in culture which show that aging of chondrocytes in vivo is accompanied by a marked fall in the capacity of these cells to synthesize link protein and to assemble a proteoglycan-rich matrix. It is suggested that poor deposition of proteoglycan by mature chondrocytes in OA may result from insufficient synthesis of link protein for stabilization of aggregates.