MiR-34 promotes apoptosis of lens epithelial cells in cataract rats via the TGF-β/Smads signaling pathway.

OBJECTIVE: To discuss the effect of micro ribonucleic acid (miR)-34 on the lens epithelial cell functions in the cataract rats. MATERIALS AND METHODS: Differentially expressed miRNAs in the lens epithelial cells of the cataract rats were screened out by analyzing microarrays. The lens epithelial cells of the cataract rats transfected with miR-34 mimics were set as transfection group. Cells with silenced transforming growth factor-beta (TGF-beta) using RepSox were regarded as the transfection + inhibitor group, and the cells transfected with NC constituted control group. Relative expressions of miR-34, key genes in the TGF-beta/Smads signaling pathway and apoptosis-related proteins [B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax), Bcl-2 associated K protein (Bak), caspase-9 and surviving] in the control group, transfection group, and transfection + inhibitor group were detected. The proportions of apoptotic cells in the three groups were determined via flow cytometry. RESULTS: The differentially expressed miRNAs in the lens epithelial cells of the cataract rats included miR-5, miR-128, etc. Among the tested miRNAs, miR-34 presented remarkably downregulated expression [log(2) fold change (FC)=-2.11, p=0.000]. After the lens epithelial cells of the cataract rats were transfected with miR-34 mimics, the expression of miR-34 was evidently elevated (p=0.000), while the expressions of TGF-beta. Smad1, and Smad3 were significantly up-regulated. Following the treatment with the TGF-beta inhibitor RepSox, the expressions of TGF-beta, Smad1, and Smad3 were downregulated. After transfection of miR-34 mimics in lens epithelial cells of the cataract rats, upregulated Box and Bak, downregulated Bcl-2 and surviving, and elevated apoptosis rate were observed. After the TGF-beta inhibitor Rep-Sox was added, the expressions of Bax and Bak declined prominently, while those of Bcl-2 and survivin were on the contrary, manifesting a declining cell apoptosis rate. The expression of caspase-9 had no significant change among the three groups. The proportion of apoptotic cells in control group, transfection group, and transfection + inhibitor group was 2.33%, 38.14%, and 16.88%, respectively, displaying differences among the three groups (p=0.002). CONCLUSIONS: MiR-34 can promote the apoptosis in lens epithelial cells of cataract rats via the TGF-beta/Smads signaling pathway.