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-1<f>β</f>.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-1<f>β</f> (500 <f>pg/ml</f>) and HA group (<f>100 μg/ml</f>) with and without IL-1<f>β</f> (500 <f>pg/ml</f>). 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 <f>PG/DNA (ng/ng)</f> concentration was <f>27.1±7.2</f>. Supplementation of the medium with HA decreased PG concentration to <f>25.3±6.9 (p<0.05)</f>. After administration of IL-1<f>β</f> <f>PG/DNA</f> concentration dropped to <f>23.1±6.0 (p<0.01)</f>. By contrast HA treatment of IL-1<f>β</f> stimulated chondrocytes did not further decrease PG concentration (<f>23.9±6.1</f>). In fact the negative effect of isolated HA application was inverted if HA was given with IL-1<f>β</f> (<f>p<0.05</f>).Conclusions: In osteoarthritic chondrocytes cultured phenotypically stable, HA could exhibit protective effects only in the presence of the degradative cytokine IL-1<f>β</f>. 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. [Copyright &y& Elsevier]