Effects of glucosamine on proteoglycan loss by tendon, ligament and joint capsule explant cultures

SummaryObjectiveTo investigate the effect of glucosamine on the loss of newly synthesized radiolabeled large and small proteoglycans by bovine tendon, ligament and joint capsule.DesignThe kinetics of loss of 35S-labeled large and small proteoglycans from explant cultures of tendon, ligament and joint capsule treated with 10 mM glucosamine was investigated over a 10-day culture period. The kinetics of loss of 35S-labeled small proteoglycans and the formation of free [35S]sulfate were determined for the last 10 days of a 15-day culture period. The proteoglycan core proteins were analyzed by gel electrophoresis followed by fluorography. The metabolism of tendon, ligament and joint capsule explants exposed to 10 mM glucosamine was evaluated by incorporation of [3H]serine and [35S]sulfate into protein and glycosaminoglycans, respectively.ResultsGlucosamine at 10 mM stimulated the loss of small proteoglycans from ligament explant cultures. This was due to the increased loss of both macromolecular and free [35S]sulfate to the medium indicating that glucosamine affected the release of small proteoglycans as well as their intracellular degradation. The degradation pattern of small proteoglycans in ligament was not affected by glucosamine. In contrast, glucosamine did not have an effect on the loss of large or small proteoglycans from tendon and joint capsule or large proteoglycans from ligament explant cultures. The metabolism of cells in tendon, ligament and joint capsule was not impaired by the presence of 10 mM glucosamine.ConclusionsGlucosamine stimulated the loss of small proteoglycans from ligament but did not have an effect on small proteoglycan catabolism in joint capsule and tendon or large proteoglycan catabolism in ligament, tendon or synovial capsule. The consequences of glucosamine therapy at clinically relevant concentrations on proteoglycan catabolism in joint fibrous connective tissues need to be further assessed in an animal model.