Effects of four NSAIDs on proteoglycan turnover and content of OA cartilage. Shown are the following measures of proteoglycan turnover: (a) percentage change in proteoglycan synthesis rate (compared with untreated osteoarthritic cartilage of the same donor), as a measure of cartilage matrix synthesis (proteoglycan synthesis); (b) percentage release of newly formed proteoglycans (new proteoglycan release), as a measure of retention of newly formed proteoglycans (normalized to the synthesis of these proteoglycans); (c) percentage total release of proteoglycans (total proteoglycan release), measured as the percentage release of glycosaminoglycans (normalized to the glycosaminoglycan content); and (d) proteoglycan content (proteoglycan content). White bars represent effects of indomethacin (10 μmol/l); light grey bars represent naproxen (300 μmol/l), dark grey bars represent aceclofenac (0.03 μmol/l) and black bars represent celecoxib (1 μmol/l). The results are presented as means of five experiments (with each cartilage sample from the different donors) ± standard error. Statistically significant differences for the effect of an NSAID compared with OA cartilage of the same donors is calculated using nonparametric paired analysis (*P < 0.05). Difference between percentage changes for the two nonselective NSAIDs compared with the (more) selective NSAIDs (n = 10 versus n = 10) is calculated by nonparametric, nonpaired analysis (P values are given for each of the parameters). NSAID, nonsteroidal anti-inflammatory drug; OA, osteoarthritis.