Effects Of MMP/TIMP On Rat's Articular Cartilage Injury After Ischemia-reperfusion

Functions of joints are not always as well as they used to be though the survival rate is higher and higher after replantation．Researchs have shown that there were significantly damages of articular cartilage: unsmooth of articular cartilage surface and breaking down of cartilage matrix, and these were related with the dissatisfactory recovery of joint function after replantation． Matrix metalloproteinases (MMPs),collectively capable of degrading essential all cartilage extra cellular matrix components,play important roles in cartilage degrading．Tissue inhibitor of metalloproteinases (TIMPs), natural specific inhibitors of MMPs,can prevent MMPs from expressing and activating under physiological conditions． There is a suppression and contrasuppression balance between TIMPs and MMPs under physiological condition.We suppose that ratio of MMP/TIMP fluctuation may lead to imbalance of MMPs and TIMPs, and be an important reason for cartilage destruction and dyfuction of joint after repalntation． Doxycycline can inhibit MMPs' activity and slow down the degradation of cartilage in pathologic progression of osteoarthritis.This indicates that while ischemia-reperfusion destroyed the balance of MMPs and TIMPs, exogenesis MMPs inhibitor, such as doxycycline, may re-establish the balance , prevent cartilage from degradating and maintain cartilage's normal structure．Our research applied the method of blocking rats' femoral artery with vascular clip for 8 hours and then reflow the limb as a replantation model. We applied the technique of immunochemistry and computer image analysis system to test different expression of MMP-3 and TIMP-1 after ischemia-reperfusion and stimulately changes of proteoglycans and type Ⅱcollagen. After ectogenesis doxycyline were given to suppress the MMPs' activity, we investigated their effect on expressions of MMP-3 and TIMP-1 and articular cartilage matrix degradation. Our research trys to find out the relationship between ratio of MMP/TIMP and impairment or repairment of articular cartilage after replantation, hoping to find out new clinic treatmeant method and realization for prophylactic treatment of articular cartilage injury after replatation. Results:1. After ischemia-reperfusion, expression of MMP-3 in cartilage increased rapidly, and reached higher level copared with normal group on the 1st week,the highest level on the 3rd week,then descend,but still mantaining high level on the 8th week. Though the expression of TIMP-1 also increased, its' increasing extent is smaller than that of MMP-3, causing the ratio of MMP-3 to TIMP-1 increased and reached its' highest level on the 3rd week, too. Correpondingly, contents of PGs and type Ⅱ collagen in cartilage continuously dropped down and normal structure of cartilage and cell were destructed. The joints became osteoarthritis in the end.2. After doxycyline were given ,expression of MMP-3 decreased and no signifant changes of TIMP-1 were observed.The radios of MMP-3 to TIMP-1 in treated group are lower than those of untreated group on 1, 3 and 8 weeks after replantation. Degradation of PGs and type Ⅱ collagen were inhibited and structures of cartilage and cell were more similar to normal. Conclusions:1. Changes stimulated by ischemia-reperfusion injury destroyed the balance relationship of MMP-3 and TIMP-1.The radio of MMP to TIMP increasing may be an important reason for cartilage destruction and malfunctions of articular joints. 2. After exogenesis MMPs inhibitor reduced the radtio of MMP to TIMP by means of inhibiting the expression of MMPs, the degradations of PGs and type Ⅱcollagen in cartilage are relieved and the pathologic progression of osteoarthritis is slowed down.