Effects of hyaluronic acid on the release of proteoglycan from the cell matrix in rabbit chondrocyte cultures in the presence and absence of cytokines

Objective. To investigate the effects of hyaluronic acid (HA) on the release of proteoglycan by cultured rabbit chondrocytes. Methods. Articular cartilage chondrocytes were isolated from the knee joints of New Zealand white rabbits. Proteoglycan synthesis after incubation with HA was determined by measuring ³⁵S-sulfate incorporation. Cells incubated with HA were labeled with ³H-glucosamine and applied to a Sepharose CL-2B column. After incubation of confluent cells with ³⁵S-sulfate and then with HA in various concentrations in the presence or absence of cytokines, proteoglycan release from the cell matrix layer was measured. Results. HA (M_r 3 × 10⁵ to 19 ×10⁵), at 10 μg/ml to 1 mg/ml, had little effect on the incorporation of ³⁵S-sulfate or ³H-glucosamine into cartilage matrix proteoglycans, or on the hydrodynamic size of proteoglycan monomers, in rabbit chondrocyte cultures. However, at 10-1,000 μg/ml, HA suppressed the release of ³⁵S-proteoglycans from the cell matrix layer into the medium in the presence and absence of interleukin-1, tumor necrosis factor α, or basic fibroblast growth factor. Conclusion. These results suggest that HA is a potent inhibitor of the displacement of matrix proteoglycan into culture medium.