Proinflammatory Cytokine Activities, Matrix Metalloproteinase‐3 Activity, and Sulfated Glycosaminoglycan Content in Synovial Fluid of Dogs with Naturally Acquired Cranial Cruciate Ligament Rupture

Abstract

To measure and compare activities of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and matrix metalloproteinase-3 (MMP-3); as well as sulfated glycosaminoglycan (S-GAG) content in synovial fluid from dogs with cranial cruciate ligament rupture (CCLR) and dogs with clinically normal stifles. To determine whether correlations exist between demographic and disease-related variables and these synovial markers. Prospective clinical study. Dogs with CCLR (n=23) and Beagles with normal stifle joints (n=21). Synovial fluid activities of proinflammatory cytokines (IL-1beta, IL-6, and TNF-alpha) were determined by bioassay. MMP-3 activity was measured using fluorogenic substrate. S-GAG contents were determined by dimethylmethylene blue dye-binding assay. Mann-Whitney U-test was used to compare results from CCLR joints with normal controls. Spearman's rank correlation test was used to evaluate associations between demographic and disease-related markers and synovial markers. Mean values for synovial markers were significantly higher in CCLR joints compared with controls. IL-1beta and MMP-3 were positively correlated with lameness duration. Activities of proinflammatory cytokines, MMP-3 activity and S-GAG contents were significantly elevated in synovial fluid from canine stifle joints with naturally acquired CCLR. These results indicate that there is joint inflammation and increased release of GAGs into synovial fluid, suggesting that these inflammatory changes are associated with depletion of proteoglycan from articular cartilage. Medical and surgical treatments designed to decrease joint inflammation and breakdown of proteoglycans may be of value in the management of CCLR in the dog.