| Objective: In this investigation we utilized rabbit mono-side-hindlimb-IR-model, to observe the pathological changes of articular cartilage and detect the apoptosis of chondrocytes and the expression of matrix metalloproteinase-3 (MMP3) in joint tissues. The aim was to elucidate the influence of ischemia-reperfusion to articular cartilage and the potential function of MMP3 in the cartilage degradation. This will be useful to explore the mechanism of degeneration of articular cartilage of limbs suffered from the ischemia-reperfusion and offer theoretical proofs to prevent joint dysfunction after the replantation of limb.Methods: 35 adult New Zealand white rabbits (BW:3.0 + 0.5Kg) were randomly grouped into 7. Except femoral artery, femoral vein, femoral nerve and sciatic nerve, all the other soft tissues of the left hindlimbs were cut off. Then the femoral blood vessels were clamped by vessel clamps. The right hindlimbs were treated as auto-control. After 8 hours of ischemia, the left hindlimbs were reperfused. Then at Iday, 3days, 7days, 2weeks, 4weeks, Sweeks and 12weeks, the grouped rabbits were killed respectively. The articular cartilage, synovium, and meniscus were excised from the knee joints of both sides. Using paraffin section we observed the pathological changes of articular cartilage and synovium under light microscope and electron microscope. TUNEL method was used to detect the apoptosis of chondrocyte. Expressions of MMP3 and proteoglycan (PG) in articular cartilage were examined with immunohistochemistry technic (SP). At the same time, we detected the MMP3mRNA level in meniscius tissue with ISH (in situ hybridization) technic. Tiger920 image analyses system was used to estimate the optical density (OD) of upper staining results. We also counted thequantities of apoptosised chondrocytes. In the end, with SPSS software, we analysed the outcomes of this experiment in statistics method.Results: Under light microscope, in the earlier period of IR, the surface of articular cartilage was flat and the chondrocytes in column layer were well-arranged, but large amounts of chondrocytes were necrotic. There were many hemorrhagic spots in synovium with infiltration of inflammation cells and the surface of synovium was destructed. Between 2w and 12w, articular facet was roughenss and chondrocytes broke off from the surface. In column layer, chondrocytes were sparsity and in disorder. Calcification layer was thickened with antedisplacement of tide line. The surface of synovium was repaired with the hyperplasia of synoviocytes. There were a mass of fibroblasts in interstitial of synovium and it was similar to granulation tissue and thickened entirely with amount of occluded capillary vessels. Under transmissive electron microscope, in the earlier period of IR, there were swelled mitochondria, dilated reticulum and a mass of lipid droplet in plasm of chondrocytes. Large amounts of chondrocytes necrosed with membran-lysis and nuclear-fragmentation. At late stage, there were a few of chondroblasts and neonate chondrocytes in articular cartilage and lots of necrosis as well. Under scanning electron microscope, at late stage of ischemia-reperfusion, the articular facet was rough and even some cracks on it, which were broadening and deepening gradually with the collagen fiber exposed. Apoptosis occurred very earlier following ischemia-reperfusion of limbs and reached the maximum in 3d. During the early period of ischemia-reperfusion, the level of MMP3 mRNA in meniscus chondrocytes was significantly increased, then decreased 2w later. Strong expression of MMP3 were examined in articular cartilage, which increased from 3d and reach maximum at 2w (P<0.01) , then failed slightly and sustained at higher level compared with control side until 12w following IR (P<0.05 ) . There was no difference of PG between experiment side and control side in the early period of IR, but from 2w it significantly reduced in experiment side compared with control side (P<0.05) .Conclusions:1. At early stage of IR, degeneratio...
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