Sulphate (35SO4) Fixation by Human Articular Cartilage compared in the Knee and Shoulder Joints

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Abstract
Thirty-eight paired specimens of adult articular cartilage from the upper end of the humerus and from the patella were obtained from human autopsy material. Their ability to fix sulphate in vitro, using 35SO4, was studied by radiochemical assay and autoradiography. In the absence of osteo-arthritis, the cartilage from the patella tended to be less active in utilizing sulphate than that from the humerus. Grade I osteo-arthritis did not significantly increase this activity in either cartilage. Osteo-arthritis of Grades II to IV, encountered only in specimens of patella, led to enhanced uptake of sulphate by the affected cartilage and to the situation in which, in paired specimens, the patellar cartilage became quantitatively more active than that from the humerus. Autoradiographic studies confirmed the quantitative results and showed a heavy uptake of labelled sulphate by clumps of chondrocytes bordering the fissures of fibrillated osteo-arthritic cartilage. The sex of the patient had no influence on the results. In the case of cartilage from the humerus, the age of the patient did not affect the mean results. In the case of the patella, the increase of chondro-cyte activity in older patients could not be dissociated from the increasing incidence of osteoarthritis. It is concluded, therefore, that the ability of the cells of adult human articular cartilage to synthesize sulphated mucopolysaccharides is uninfluenced directly by ageing. The enhancement of chondrocyte activity, seen for example in many specimens of patella with damaged cartilage, appears to be a reactive phenomenon to local conditions and the loss of mucopolysaccharide from the matrix associated with the process of osteo-arthritis within the affected joint.