In vivo quantification of proteoglycan synthesis in articular cartilage of different topographical areas in the murine knee joint.

We developed a method of quantitative measurement of the synthesis of proteoglycans in different areas of the patella and the tibial plateau of the mouse. After incorporation of radioactive sulfate in vivo, the patella was divided with a punch into a central and a peripheral part. A central medial and a central lateral part were taken from the tibial plateau to measure the synthesis of proteoglycans. The synthesis was determined in normal joints and at different intervals after intra-articular injection of sodium iodoacetate and was compared with autoradiographs of whole joint sections. Although considerable variation in sulfate incorporation was found within a group on particular days after induction of osteoarthritis, the variation among experiments was low. Comparison with autoradiographs showed that this new method makes it possible to quantify proteoglycan synthesis by incorporation of radioactive sulfate in different topographical areas of the murine knee joint.