RÉSUMÉ
BACKGROUND:Synovitis plays an important role in the occurrence and development of early knee osteoarthritis.OBJECTIVE:To compare synovial inflammation in a rabbit mode of knee osteoarthritis induced by injecting low concentration of papain at different time points,thus providing reference for the study on synovitis in knee osteoarthritis.METHODS:Twenty-four New Zealand white rabbits were divided randomly into four groups,and received the injection of 0.5 mL mixture of 2％ papain with 0.03 mol/L L-cysteine into the right knee at 1,4 and 7 days,respectively.The model rabbits were respectively sacrificed at 1,2 and 3 weeks after the last injection,and the rabbits in the blank control group were killed at 3 weeks.The local skin temperature and circumference of the knee were recorded,and the synovium and infrapatellar fat pad were separated from the right knees for histopathological observation and ELSA.RESULTS AND CONCLUSION:At the 1stweek after modeling,joint effusion was significantly increased,local skin temperature and circumference of knee joint were higher than those at the 2nd,and 3rd weeks.The levels of interleukin-1,tumor necrosis factor-α and matrix metalloproteinase-13 in the synovium in the three experimental groups were higher than those in the blank control group at 1,2 and 3 weeks after modeling;the levels peaked in the 1st week,but no significant fluctuation appeared in the 2nd and 3rd weeks.There were synovial tissue hyperplasia,thickening,and inflammatory cell infiltration in the 1st,2nd and 3rd weeks,and the proliferation of synovial tissue increased significantly with time.These findings indicate that the intra-articular injection of low concentration of papain and 0.03 mol/L L-cysteine mixtures contributes to a rabbit model of knee synovial inflammation within 1 week,with significantly joint effusion.However,significant synovial tissue thickening and vascular hyperplasia are observed;meanwhile,the joint effusion is decreased obviously.