Synthesis of articular cartilage proteoglycans by isolated bovine chondrocytes. Effect of autogenous conditioned synovial medium in vitro.

It was previously reported that bovine conditioned synovial medium (SM) has a catabolic activity on articular cartilage proteoglycans in an organ culture system. The question thus arose whether SM had an anabolic effect as well on articular cartilage proteoglycans. In this report it is shown that addition of autogenous SM to isolated bovine articular chondrocytes inhibited the synthesis of proteoglycans as measured by the incorporation of radiosulphate. Already after 4 hours an inhibition was seen in the pericellular (matrix) chondroitin sulphate (MA-CS) fraction, and in the culture medium chondroitin sulphate (CM-CS) fraction it was significant after 72 hours. When the synovial tissue was cultured with indomethacin (1.4 X 10(-5) mol/l) and this indo-SM was added to the chondrocyte cultures, the ability of the chondrocytes to incorporate [35S]sulphate was decreased further. It therefore seems evident that the products from the synovial tissue influences the behaviour of the chondrocyte in such a way that not only is the degradation enhanced but also the synthesis of cartilage proteoglycans is inhibited.