| ObjectiveThe aging trend of China's population has begun to emerge nowadays. The relevant epidemiological study found that incidence of osteoarthritis (Osteoarthritis, OA) which has become one of the major reasons depriving the physical working capacity of adult males in china is increasing. The main characteristics of osteoarthritis pathology of the disease are apparent apoptosis of cartilage cells in joints along with progressive degradation of the extracellular matrix. Some studies showed that NO and the expression levels of its products have a significant positive correlation with the number of apoptotic cells of articular cartilage as well as the severity of osteoarthritis. During the early stages of the disease, NO and its products can stimulate and induce apoptosis of articular cartilage cells, and then the combination of the two substances result in pathologic articular cartilage degradation. NG-monomethyl-arginine (L-NMMA) is an analogue of L-arginine that can compete with NOS L-arginine binding site showing inhibitive effect for three kinds of NOSwithout significant selectivity, progressively causing irreversible inactivation of iNOS. So, this study aims to explore the effects of L-NMMA on the apoptosis of articular cartilage cell in experimental osteoarthritis from rabbit kneesand its mechanism.Method30experimental rabbits were randomly divided into five groups:normal group (A), model group (B), L-NMMA low-dose treatment group (C group), L-NMMA middle-dose group (D group) and L-NMMA high-dose treatment group (E group). HE staining was used to detect the pathological changes; the NO expression levels of rabbit joint synovial fluid and serum were detected; situ apoptosis staining (TUNEL) and flow cytometry was applied to detect the chondrocyte apoptosis; ELISA method was used to detect the expression levels of rabbit serum BMP2and TGFβ1; western-bloting method was used to detect the expression of cartilage Caspases-3; immunohistochemistry was used to detect the expression of cartilage Bax and Bcl-2.Results1. HE staining of the normal group showed as followed:the surface is smooth and even; the cartilage cells were well distributed with intact tide lines and no cartilage cells clustered; HE stain evenly without any staining loss; HE staining of the model group showed as followed:the surface became thin with fissures down to subchondral bone; cells arranged in disorder together with a large number of clusters of cartilage cells and the tide lines disappeared; HE stain is uneven, there were significant staining loss throughout the whole layers; with the increasing treatment concentration of L-monomethyl-arginine, the degree of histological structure damage of the cartilage significantly alleviated.2. The expression levels of rabbits synovial fluid and serum NO in the model group were significantly higher than that in the normal group (P<0.01), and with the increasing treatment concentration of L-monomethyl-arginine, the expression levels of synovial fluid and serum NO decreased significantly in the modelgroup (P<0.05).3. The apoptosis rate and apoptotic index of rabbit articular chondrocytes in the model group were significantly higher than that in the normal group (P<0.01), and with the increasing treatment concentration of L-monomethyl-arginine, the rate of apoptosis and apoptosis index decreased significantly (P<0.05).4. The expression levels of rabbit serum BMP2and TGFβ1in the model group were significantly lower than that in the normal group (P<0.01), and with the increasing treatment concentration of L-monomethyl-arginine, the expression levels of rabbit serum BMP2and TGFβ1significantly increased (P<0.05).5The expression level of rabbit articular cartilage Caspases-3in the model group was significantly higher than that in the normal group (P<0.01), and with the increasing treatment concentration of L-monomethyl-arginine, the expression level of Caspases-3 significantly decreased (P<0.05).6. The expression level of rabbit articular cartilage Bax in model group was significantly higher than that in the normal group (P<0.01), and with the increasing treatment concentration of L-monomethyl-arginine, the expression level of Bax significantly decreased (P<0.05);The expression level of rabbit articular cartilage Bcl-2in the model group showed no significant difference compared with the normal group (P>0.05), and with the increasing treatment concentration of L-monomethyl-arginine, the Bcl-2expression levels significantly increased (P<0.05); and with the increasing treatment concentration of L-monomethyl-arginine, the numerical value of Bcl-2/Bax significantly increased (P<0.05).ConclusionsL-NG-monomethyl-arginine (L-NMMA) can significantly reduce the expression levels of synovial fluid and serum NO as well as the Caspases-3of articular cartilage, increase expression levels of serum BMP2, TGFβi; The apoptosis of articular cartilage could be inhibited through increased numerical value of Bcl-2/Bax; L-NMMA can be used in clinical practice for the treatment of osteoarthritis disease.
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