Abstract: BACKGROUND: Studies have shown that an elevation in miR-23b is closely related to the occurrence and development of rheumatoid arthritis; therefore, inhibiting the expression of miR-23b can be a new target for the treatment of the disease. 
OBJECTIVE: To explore the effect of miR-23b on the regulation of transforming growth factor-β1 in synovial tissue and the inhibition of osteoclast activity in rats with rheumatoid arthritis. 
METHODS: Sixty SPF male Sprague-Dawley rats were randomly divided into normal control group, model group, miR-NC group, and miR-23b inhibitor group (n=15 per group). Except for the normal control group, animal models of rheumatoid arthritis were prepared in the other three groups using Fredrin complete adjuvant method. After successful modeling, the miR-NC group was injected with 20 μL of 1×108/L miR-NC and the miR-23b inhibitor group was injected with 20 μL of 1×108/L miR-23b inhibitor. Normal control group and model group were injected with the same volume of normal saline at the same time. Twenty-one days later, hematoxylin-eosin staining was used to detect the pathological morphology of the articular tissue of rats, real-time PCR was used to detect the relative mRNA expression of miR-23b in rat serum, and immunohistochemical method was used to detect the protein expression of transforming growth factor-β1 in the synovial tissue of rats. The activity of osteoclasts was detected by tartrate-resistant acid phosphatase staining and phalloidin staining.
RESULTS AND CONCLUSION: In the normal control group, the structure of synovial cells was normal and neatly arranged. In the model and miR-NC groups, synovial cells proliferated obviously and arranged in disorder. At the same time, capillaries and fibrous connective tissue were obviously proliferated, accompanied by a large number of inflammatory cells infiltrated. In the miR-23b inhibitor group, mild hyperplasia of synovial cells and a small amount of inflammatory cell infiltration appeared, and edema and congestion were significantly improved. The relative expression of miR-23b in the serum was significantly increased in the model group compared with the normal control group (P < 0.05), while there was no significant difference between the model group and the miR-NC group (P > 0.05). The relative expression of miR-23b in the miR-23b inhibitor group was significantly lower than that in the miR-NC group 
(P < 0.05). Compared with the normal control group, the expression of transforming growth factor-β1 protein in the synovial tissue was significantly increased in the model group (P < 0.05), while there was no significant difference between the model and miR-NC groups (P > 0.05). The expression of transforming growth factor-β1 protein in the synovial tissue was significantly lower in the miR-23b inhibitor group than the miR-NC group (P < 0.05). Compared with the normal control group, a highly positive expression of typical multinucleated osteoclasts was found in the synovial fibroblasts of the model group by the tartrate-resistant acid phosphatase staining (P < 0.05). There was no significant difference between the model and the miR-NC groups (P > 0.05). The volume and number of osteoclasts in the miR-23b inhibitor group were significantly lower than those in the miR-NC group (P < 0.05). Compared with the normal control group, the phalloidin staining of osteoclasts significantly indicated the formation of rings composed of actin filaments in the model group (P < 0.05) and there was no significant difference between the model and miR-NC groups (P > 0.05), while the actin ring area was significantly reduced in the miR-23b inhibitor group compared with the miR-NC group (P < 0.05). The above results indicate that reducing the expression of miR-23b can play a therapeutic effect on rheumatoid arthritis, which can effectively inhibit the expression of transforming growth factor-β1 and reduce the activity of osteoclasts in rat synovial tissue.

Key words: miR-23b, rheumatoid arthritis, synovial tissue, transforming growth factor-β1, osteoclast activity