Effect of polysulfated glycosaminoglycan on DNA content and proteoglycan metabolism in normal and osteoarthritic canine articular cartilage explants

Objective-To study the effect of polysulfated glycosaminoglycan (PSGAG) on proteoglycan metabolism and DNA content of control and osteoarthritic (OA) cartilage. Study Design-An in vitro study comparing the effects of PSGAG on articular cartilage explants from canine stifle joints with and without chronic OA af ter transection of the left cranial cruciate ligament. Sample Population-Five large cross-breed dogs. Methods-Cartilage explants (6 to 13 per treatment group) from the medial si de of the femoral trochlea and medial femoral condyle from both stifles of each dog were incubated in a defined medium containing 0, 0.05, 0.5, or 5 m g/mL of PSGAG. After 72 hours in culture, explants were pulsed for 6 hours with sodium [S-35]sulfate. Aminophenylmercuric acetate (APMA) was used to a ctivate endogenous neutral matrix metalloproteinases (MMPs) and induce prot eoglycan degradation in the radiolabeled explants. DNA content and radioact ivity were measured in papain-digested explants, and radioactivity was meas ured in the medium by liquid scintillation counting. Proteoglycan synthesis and degradation were calculated. Cartilage was examined histologically for signs of OA. A mixed model analysis of variance and linear contrasts were used to rest for significant (P < .05) effects of OA and treatment with PSG AC. Results-Transection of the cranial cruciate ligament produced OA in operate d joints. DNA content and proteoglycan synthesis of OA cartilage were signi ficantly lower than in cartilage from control joints. For both DNA content and proteoglycan synthesis, significant interactions occurred between the c oncentration of PSGAG and whether the articular cartilage was from OA or co ntrol joints. The two lower concentrations of PSGAG (0.05 and 0.5 mg/mL) pr edominantly increased DNA content in OA cartilage (7 and 18%, respectively, compared with 0 mg/mL PSGAG) while the highest concentration (5 mg/mL) pre dominantly increased DNA content in control cartilage (30% compared with 0 mg/mL PSGAG). PSGAG at .05 mg/mL predominantly decreased proteoglycan synth esis in OA cartilage (19% reduction compared with 0 mg/mL PSGAG) while PSGA G at .5 and 5 mg/mL predominantly decreased proteoglycan synthesis in contr ol cartilage (17 and 55% reduction, respectively, compared with 0 mg/mL PSG AG). Following activation of MMPs, PSGAG caused a dose-dependent decrease i n degradation of radiolabeled proteoglycan in both OA and control cartilage . Conclusions-OA cartilage was responsive to treatment with PSGAG at 100-fold lower concentration than control cartilage. When treated with PSGAG, artic ular cartilage explants maintained or increased DNA content at the expense of proteoglycan synthesis. Following MMP activation, proteoglycan degradati on was inhibited in OA and control explants in a dose-dependent manner. Clinical Relevance-If the results of this study extend to in vivo use, trea tment with PSGAG may modify the progression of OA in articular cartilage by maintaining chondrocyte viability or stimulating chondrocyte division as w ell as protecting against extracellular matrix degradation. (C) Copyright 2 000 by The American College of Veterinary Surgeons.