The Proteoglycan Metabolism of Articular Cartilage in Joint-Scale Culture

Understanding and controlling chondrocyte and cartilage metabolism in osteochondral tissues may facilitate ex vivo maintenance and application, both for allografts and tissue-engineered grafts. The hypothesis of this study was that maintenance of chondrocyte viability and matrix content and release of sulfated glycosaminoglycan (sGAG) in the articular cartilage of joint-scale osteochondral fragments are temperature and metabolism dependent. The aims were to assess, for adult goat joints, the effects of incubation temperature (37°C vs. 4°C) on cartilage chondrocyte viability and tissue matrix content and mechanical function, and the effects of temperature and cellular biosynthesis on sGAG release. Chondrocyte viability was maintained with 37°C incubation for 28 days, but decreased by ∼30% with 4°C incubation. Concomitantly, with 37°C incubation, cartilage sGAG was depleted by ∼52% with the lost sGAG predominantly unable to aggregate with hyaluronan, whereas collagen content, tissue thickness, and tissue stiffness were maintained. The depletion of sGAG was diminished by slowing metabolism, with 4°C decreasing release by ∼79% compared with 37°C incubation, and cycloheximide inhibition of cell metabolism at 37°C decreasing release by ∼47%. These results indicate that the articular cartilage of joint-scale grafts have enhanced chondrocyte viability with incubation at 37°C, but may need anabolic stimuli or catabolic inhibitors to maintain sGAG content