ROLE OF CHONDROITIN SULFATE HYALURONAN INTERACTIONS IN THE VISCOELASTIC PROPERTIES OF EXTRACELLULAR MATRICES AND FLUIDS

The purpose of this study was to investigate the role of chondroitin s ulfate-hyaluronan interactions in the viscoelastic properties of tissu es and fluids, using capillary and cone-on-plate viscometers. Chondroi tin sulfate markedly increased the viscosity of hyaluronan solutions a t a wide range of hyaluronan mass (50-1900 kDa) under physiological co nditions of pH, temperature, ionic strength and glycosaminoglycan conc entration (0.5-40 mg/ml), although the viscosity of the chondroitin su lfate solutions themselves was very low. In the assay using a cone-on- plate viscometer, chondroitin sulfate increased the viscosity of hyalu ronan solutions at various shear rates. At low shear rates, the viscos ity of a chondroitin sulfate (5 mg/ml)-hyaluronan (0.5 mg/ml) mixture was about 40%?a of that of an aggrecan (5 mg/ml)-hyaluronan (0.5 mg/ml ) mixture, and at 2.8-fold higher concentrations, chondroitin sulfate elicited the same effect on the viscosity of hyaluronan solutions (5 m g/ml) as an aggrecan monomer. In the presence of oscillatory motion, t he addition of aggrecan increased the elasticity (storage) modulus G' and the viscosity (loss) modulus G '' of hyaluronan solutions and mark edly decreased the loss tangent G ''/G' at frequencies corresponding t o normal joint movements. In contrast, chondroitin sulfate had only a marginal effect on the loss tangent G ''/G', although it increased G' and G ''. These findings demonstrated that chondroitin sulfate, as wel l as aggrecan, increases the viscosity of hyaluronan solutions, althou gh chondroitin sulfate has less effect on the elasticity of hyaluronan solutions than that of aggrecan, and suggest that chondroitin sulfate may play an important physiological role in determining the viscoelas tic properties of extracellular matrices and fluids. (C) 1998 Elsevier Science B.V.