Chondroitin sulfate modulation of matrix and inflammatory gene expression in IL-1β-stimulated chondrocytes – study in hypoxic alginate bead cultures

SummaryObjectiveTo determine the effect of avian chondroitin sulfate (CS) on interleukin-1β (IL-1β)-induced expression of genes related to catabolic, anabolic and inflammatory aspects in chondrocytes cultured in hypoxic alginate beads.DesignArticular chondrocytes from bovine metacarpal joint were isolated and cultured in alginate beads, using low oxygen atmosphere (5% O2). After 1-week exposure to CS (1, 10 and 100μg/ml), they were treated by recIL-1β (10ng/ml) for 24 or 48h, in the presence of CS. RNA was extracted and used to determine, by quantitative reverse transcription-polymerase chain reaction, the steady-state levels of mRNAs encoding several genes related to anabolic, catabolic and inflammatory aspects. Glycosaminoglycan (GAG) synthesis was also assayed by 35S-sulfate incorporation.ResultsCS decreased IL-1β-induced expression of matrix metalloproteases-1, -3 and -13 and aggrecanases-1 and -2. It slightly enhanced the aggrecan core protein mRNA and the GAG synthesis. Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA levels were found to be reduced by CS treatment. However, no CS-induced decrease of NO was observed in IL-1β-treated chondrocytes, whereas prostaglandin E2 production was diminished in correlation with the COX-2 mRNA amounts. Furthermore, CS was capable of counteracting IL-1β-depressed expression of transforming growth factor-β (TGF-β) receptors.ConclusionsCS can repress expression of genes encoding proteolytic enzymes involved in cartilage degradation. It also inhibits IL-1β-induced expression of the pro-inflammatory genes iNOS and COX-2 and restores TGF-β receptors I and II (TGF-βRI and RII) mRNA levels. These data suggest that CS may exert both chondroprotective and anti-inflammatory limited effects on articular cartilage that could have long-term beneficial action on the osteoarthritic process