Demonstration of increased proteoglycan turnover in cartilage explants from dogs with experimental osteoarthritis

Abstract

The turnover of proteoglycans (assessed by the release into the medium of newly synthesised [³⁵S]‐proteoglycan) in explant cultures of articular cartilage from various anatomical sites of the knee joints (stifle) of mature beagles with experimental osteoarthritis has been studied with the following findings: (a) The proportion of newly synthesised proteoglycans released from cartilage explants maintained in vitro was generally increased for cartilage from operated compared with nonoperated control joints. (b) At 3 weeks after surgery there was a significant increase in the release of [³⁵S]‐proteoglycans from explants of the lateral and medial tibial plateaux of operated joints compared with sham‐operated joints but not from other sites. On the other hand, when this comparison was made at 3 to 6 months after surgery, significant increases in the release of [³⁵S]‐proteoglycans were observed from cartilage of all anatomical areas except the patellar groove. (c) The release of [³⁵S]‐proteoglycan from cartilage explant cultures was dependent on live chondrocytes, since freeze‐thawing the tissue immediately after labelling markedly reduced the release from both normal and osteoarthritic cartilage.