Effects of hyaluronan on proteoglycan content of osteoarthritic chondrocytes in vitro

To investigate the effect of hyaluronic acid (HA) on proteoglycan (PG) concentration in alginate cultures of human osteoarthritic chondrocytes and to analyze whether HA exhibit anti-degradative effects in the presence of the cytokine IL-1beta.

Cartilage samples from ten patients with osteoarthritis of the knee were harvested and chondrocytes were cultivated in alginate beads. Four groups were cultured: control group with and without IL-1beta (500 pg/ml) and HA group (100 microg/ml) with and without IL-1beta (500 pg/ml). PG concentration was estimated by a dimethylmethylene blue assay. To assess cell proliferation, we measured DNA content fluorometrically.

The proliferation rate (DNA) was unchanged in all culture groups. In the control-group PG/DNA (ng/ng) concentration was 27.1 +/- 7.2. Supplementation of the medium with HA decreased PG concentration to 25.3 +/- 6.9 (p < 0.05). After administration of IL-1beta PG/DNA concentration dropped to 23.1 +/- 6.0 (p < 0.01). By contrast HA treatment of IL-1beta stimulated chondrocytes did not further decrease PG concentration (23.9 +/- 6.1). In fact the negative effect of isolated HA application was inverted if HA was given with IL-1beta (p < 0.05).

In osteoarthritic chondrocytes cultured phenotypically stable, HA could exhibit protective effects only in the presence of the degradative cytokine IL-1beta. Thus, the reported anti-inflammatory effects of HA to cartilage matrix seem to be more indirect by blocking degradative effects of cytokines to the matrix.