Influences of miR-320a on proliferation and apoptosis of fibroblast-like synoviocytes in rheumatoid arthritis through targeting MAPK-ERK1/2.

OBJECTIVE: To study the expression of micro ribonucleic acid (miR)-320a in synovial tissues of patients with rheumatoid arthritis (RA) and explore the influences of miR-320a on the proliferation and apoptosis of fibroblast-like synoviocytes (FLSs) in RA and its mechanism. PATIENTS AND METHODS: The expression level of miR-320a in synovial tissues of 40 healthy people and 32 RA patients was detected via reverse transcription-polymerase chain reaction (RT-PCR). The FLSs were isolated from RA patients, cultured in vitro and divided into Control group and miR-320a mimic group. The proliferation and apoptosis of FLSs in each group were observed. Finally, the expression level of mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK) 1/2 in each group was detected via Western blotting. RESULTS: The expression level of miR-320a in synovial tissues of RA patients was significantly lower than that in healthy people (p < 0.05). After miR-320a mimic was transfected into FLSs cultured in vitro, EdU staining and flow cytometry analysis were performed. The results revealed that the proportion of EdU-positive cells significantly declined in miR-320a mimic group, the proportion of cells in G0/G1 phase was increased, while the cells in G2/M and S phases were significantly decreased (p < 0.05). Above data indicated that the cell proliferation ability was significantly inhibited. In addition, the results of flow cytometry also showed that the apoptosis rate of FLSs in miR-320a mimic group was significantly higher than that in Control group (p < 0.05). The results of Western blotting manifested that the Bcl-2 associated X protein (Bax)/Bcl-2 ratio in miR-320a mimic group was also obviously increased (p < 0.05). According to further studies, the phosphorylation level of ERK1/2 in miR-320a mimic group was remarkably inhibited (p < 0.05). CONCLUSIONS: The expression level of miR-320a significantly declined in synovial tissues of RA patients. MiR-320a attenuated proliferation and promoted apoptosis of FLSs through inhibiting the activation of the MAPK-ERK1/2 signaling pathway.