Effect of activated equine neutrophils on sulfated proteoglycan metabolism in equine cartilage explant cultures.

OBJECTIVE

To determine the influence of activated equine neutrophils on sulfated glycosaminoglycan metabolism of equine articular cartilage in vitro.

ANIMALS

Articular cartilage explants harvested from the metacarpophalangeal joints of 7 horses.

PROCEDURE

Proteoglycan degradation and synthesis were measured by release of glycosaminoglycan from the explants, and incorporation of [35S]sulfate into newly synthesized glycosaminoglycan.

RESULTS

Activated equine neutrophils significantly increased the release of glycosaminoglycan from explant matrix and the magnitude of that response was influenced by duration of exposure. This response varied significantly between horses, but was detected as early as 3 hours after co-cultures were initiated. In addition to enhancing degradation, incubation of explants with activated neutrophils for 3 days caused significant inhibition of glycosaminoglycan synthesis during a subsequent 3-hour pulse-labeling period. This response varied significantly between individual animals, but age was not a predictive factor.

CONCLUSION

Neutrophils may have a critical role in the process of cartilage degradation during equine inflammatory joint disease.