Effects of hyaluronan on proteoglycan content of osteoarthritic chondrocytes in vitro

Purpose: 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-1β.

Methods: 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-1β (500 pg/ml) and HA group (100 μg/ml) with and without IL-1β (500 pg/ml). PG concentration was estimated by a dimethylmethylene blue assay. To assess cell proliferation, we measured DNA content fluorometrically.

Results: 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-1β PG/DNA concentration dropped to 23.1 ± 6.0 (p < 0.01). By contrast HA treatment of IL-1β 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-1β (p < 0.05).

Conclusions: In osteoarthritic chondrocytes cultured phenotypically stable, HA could exhibit protective effects only in the presence of the degradative cytokine IL-1β. 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.