The effect of synovial tissue on the synthesis of proteoglycan by the articular cartilage of young pigs.

Explants of pig articular cartilage were grown in organ culture in the presence of synovial tissue; controls consisted of paired explants that were cultivated in isolation. To find whether the synovial tissue affected synthesis of sulfated proteoglycan by the cartilage, 35SO4 was added to the medium and its incorporation into the cartilage examined by both biochemical assay and autoradiography. The synovial tissue severely inhibited the uptake of 35SO4, but if the synovium was removed after 8 days cultivation and the cartilage was grown in isolation for a further 4 days, incorporation of 35SO4 equalled and sometimes surpassed that of controls which had been grown without synovium continuously for 12 days. Synovium did not prevent the formation of new cartilage on the cut surfaces of the explants, but it reduced the incidence of newly formed cartilage.