Quantification of aggrecan within the articular cartilage explants. The proteins of the cultured explants were extracted by liquid N2 pulverization. (a) Cartilage was extracted immediately after isolation (t = 0) or after culture for 21 days with vehicle, insulin growth factor (IGF), oncostatin M plus tumour necrosis factor (OSM + TNF), or metabolically inactive (MI) control for assessing passive physiochemical release. (b) Cartilage was extracted after the three different levels of cytokine treatment followed by an identical 14 days with either vehicle or IGF. IGF significantly stimulated proteoglycan content within the cartilage explants at all time points. (c) Quantification of sulphated glycosaminoglycan (S-GAG) from all treatments over the entire experimental period. S-GAG released from cartilage explants to the conditioned medium was quantified by the Alcian blue-binding assay. The curves represent the release at days when the conditioned medium was fully replaced, and the values were accumulated over the entire period. MI, metabolically inactive; O + T, oncostatin M plus tumour necrosis factor; W/O, without stimulation (vehicle control). (d) Quantification of S-GAG turnover 2 weeks after the catabolic induction. The aggrecan release in the identical 14-day period, with or without IGF stimulation following three different periods of catabolic stimulation, was measured by the Alcian blue-binding assay. The results show the accumulated release of S-GAG during the 2 weeks with anabolic stimulation (IGF) and without stimulation (vehicle). *P < 0.05, **P < 0.01, ***P < 0.001.