Effect Of Matrix Metalloproteinase-13 On Articular Cartilage Of Rat Hindlimb Suffered From Ischemia And Reperfusion

Objective. To investigate the expression of matrix metalloproteinase-13 (MMP-13) and type Ⅱ collagen (COLⅡ) in the Wistar rat model for the purpose of elucidating their roles in the destruction of articular cartilage of limbs suffered from ischemia and reperfusion (IR) and of presenting theoretical proofs to prevent the dysfunction of replanted joints.Methods. Articular cartilage samples were obtained from femoral condylus and tibial plateau of left hindlimb knees of IR rats and of normal rats. Specimens were promptly fixed in paraformaldehyde, processed, embedded in paraffin, sectioned, stained with HE for histological changes and using immunohistochemistry (SP) method to examine MMP-13 and COLⅡ in articular cartilage. Tiger 920 image analyze system was used to evaluate the optical density (OD) of the sections of cartilage examined. Normal group and IR Groups were compared using a one-way analysis of variance (ANOVA) of the OD scores. Results. Using light microscope, we found that, in the earlier period of IR, the articular surface was flat while lots of chondrocytes were necrotic. Between 2w and 8w, articular facet gradually became rough. There had been an abnormal increase in the number of chondrocytes, which were scattered and in disorder. Calcification layer was thickened with antedisplacement of tide line.Under transmission electronic microscope, in the earlier period of IR, the swelled mitochondria and dilated reticulum appeared in the plasma of chondrocytes. Large amounts of chondrocytes necrosed membrane-lysis and nucleus-fragmentation. At late stage, there were a few of chondroblasts and neonate chondrocytes in articular cartilage. Under scanning electronic microscope, at late stage of IR, the articular facet was rough and even some crackles appeared which were broadening and deepening gradually. MMP-13 was abundant in the IR groups, increased from 3 days and reach its maximum at 14 days after reperfusion (P<0.01), then decreased slightly but was at higher level compared with that in the controlled group till 60 days after reperfusion (P<0.01).There was no difference of COLⅡ between the experiment group and the controlledgroup in the earlier period of IR, but from 3 days after reperfusion, COLⅡ reduced remarkably in the experiment groups compared with the controlled group (P<0.01).Conclusion. Due to the ischemia and reperfusion, there appeared the degeneration and necrosis of chondrocytes in the articular cartilage. Later, responsible to some cytokines, such as TNFαand IL－1β, MMP-13 expressed strongly in the cartilage, coincident with COLⅡ. It suggested that MMP-13 play some roles in the destruction of COLⅡ, which may lead to matrix degradation and, at last, chronic arthritis.