Influence of polysulfated polysaccharides on aggrecans synthesized by differentiated human articular chondrocytes

Objective, Synthesis rates of aggrecans by phenotypically stable human arti cular chondrocytes and the immobilization of these aggrecans in large aggre gates have been used as variables reflecting the capability of these calls to restore the extracellular matrix of articular cartilage in vitro. The ef fects of heparin, chondroitin polysulfate, and xylosan polysulfate on these variables were investigated. Methods, Human articular chondrocytes were maintained in culture in gelled agarose. After 2 weeks of culture, the media were supplemented for one week with 10 mu g/ml each of heparin, chondroitin polysulfate, and xylosan poly sulfate. Synthesis of aggrecans was investigated using (Na2SO4)-S-35 as a r adioactive precursor during the last 24 h of exposure to polysaccharides. S ize exclusion chromatography was used to assay the proportions of aggrecans immobilized in aggregates. Native aggrecan aggregates accumulated during c ulture were liberated in associating conditions by agarase digestion of the artificial agarose matrix and studied by electron microscopy, Hyaluronan s ynthesis was studied in monolayer cultured chondrocyte derived fibroblasts, The cells were exposed to H-3 glucosamine for 24 h after the nutrient medi a were supplemented with 3 polysaccharides for one week, Size exclusion chr omatography was used to assess the length of the hyaluronan filaments. Results. Xylosan polysulfate and chondroitin polysulfate but not heparin si gnificantly increased total S-35 incorporation rates in aggrecan. Electron microscopy study of aggrecan aggregates showed that xylosan and chondroitin polysulfate but not heparin significantly increased aggrecan aggregate siz es, The same polysulfated polysaccharides increased the synthesis of high m olecular weight hyaluronan by chondrocyte derived fibroblast-like cells. Conclusion. Polysulfated polysaccharides significantly increased the synthe sis rates and the accumulation of aggrecan in aggregates in the extracellul ar environment in this in vitro system.