The synthesis and immobilisation of cartilage-specific proteoglycan by human chondrocytes in different concentrations of agarose.

Chondrocytes were cultured in agarose gels of different concentrations. In this in vitro model these cells synthesize tissue-specific proteoglycans. The rate of proteoglycan synthesis was not dependent on the concentration of the surrounding gel. The immobilisation of these macromolecules in monomeric and in aggregated form were studied. 0.5% to 1.0% of agarose failed to retain important amounts of proteoglycan. Proteoglycan monomers and even aggregates diffused to the incubation medium. 2.0% and 4.0% of agarose immobilised the bulk of the aggregates and approximately 50% of the monomeric proteoglycans. Low-molecular proteoglycan species or break-down products freely moved out of the gel. The reproducibility of the variables concerning proteoglycan metabolism was very good.