Diacerein protects against iodoacetate-induced osteoarthritis in the femorotibial joints of rats

The present study was undertaken to investigate the effect of diacerein on the histopathology of articular cartilage and subchondral bone of the femorotibial joint in rats. Osteoartbritis was induced in rats after single intra-articular injection of sodium iodoacetate. Rats were sacrificed 1, 2, 4, and 8 weeks post intra-articular injection to evaluate the progression of histopathogenesis of osteoarthritis. Diacerein was orally administered （15 mg/kg） once daily post 1 and 2 weeks of iodoacetate injection in two groups, respectively, for up to 12 weeks. Articular cartilage and sub- chondral bone of the rats of both groups were examined after 8 and 12 weeks, respectively. Quantitative histological analyses were performed by scoring these sections as per the OARSI system. Chondroitin sulfate was also estimated in articular cartilage by decrease in absorbance of methylene blue on complexation with chondroitin sulfate using a spectrophotometer. Intra-articular injection of iodoacetate induced loss of articular cartilage with progressive sub- chondral bone sclerosis and degeneration. Based on histopathological and biochemical findings, diacerein treatment showed chondroprotective effect. Furthermore, the chondroprotective effect of diacerein was found to be more pro- nounced after 12 weeks as compared to 8 weeks in both cases （i.e., post 1 and 2 weeks of iodoacetate injection）. Similar results were observed by investigation of chondroitin sulfate during biochemical study, showing the chon- droprotective effect. In conclusion, diacerein exhibits chondroprotective effect in rats with late onset of action.