Biosynthesis and turnover of proteoglycans in organ culture of bovine articular cartilage.

The biosynthesis and turnover of proteoglycans (PG) in organ cultures of bovine metacarpalphalangeal cartilage are described. After a few days in the presence of fetal calf serum, the amount of PG in the tissue is maintained at a constant level and the rate of PG biosynthesis is maintained at a high rate. Under these "steady state" conditions PG biosynthesis and turnover must be in balance. Exposure of tissue to lipopolysaccharides reduces the rate of synthesis while increasing the rate of turnover, thereby yielding net loss of PG from the matrix. After an initial mild trypsin digestion to remove PG from the matrix, turnover of PG is reduced in the cultures and a net increase of PG occurs with time. It is suggested that viable chondrocytes can regulate local concentrations of PG in their surrounding matrix by altering both biosynthetic and turnover parameters.