To investigate the effect of microRNA-155(miR-155) on transforming growth factor β2 (TGF-β2)-induced epithelial-mesenchymal transition of human retinal pigment epithelial cells and its mechanism.

The retinal pigment epithelial cell ARPE-19 cell line was used as the research object.The cells cultured with DMEM medium were served as the control group and the cells cultured with DMEM medium containing 10 ng/ml TGF-β2 were served as the TGF-β2 group.The ARPE-19 cells transfected with miR-155 inhibitor were set as the miR-155 inhibitor group and the ARPE-19 cells transfected with miR-155 negative control were set as the miR-155 negative control group, and the cells in the two groups were cultured in DMEM medium containing 10 ng/ml TGF-β2.After 48 hours cell culture, reverse transcription-PCR was used to detect the expression of miR-155 in each group, and scratch migration test and Transwell chamber test were used to detect cell migration and invasion ability, and Western blot was used to detect the expressions of phosphate and tension homology deleted on chromosome ten gene (PTEN), phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt), p-Akt and epithelial mesenchymal markers E-cadherin (E-cad), zonula occludens protein 1 (ZO-1), F-actin, α-smooth muscle actin (α-SMA), fibronectin 1 (FN-l) vimentin, proteins.The target gene prediction library predicted miR-155 target gene and fluorescein enzyme reporter vectors were used to identify target genes.

After 48 hours of culture, the cells in the control group were in good condition with tight adherence and regular shape.The cells in the TGF-β2 group showed more obvious spindle shape with loose arrangement, and most of the cells were fibrous.The relative expression level of miR-155 in the cells of TGF-β2 group was 0.92±0.14, which was significantly higher than 0.35±0.06 of the control group (t=7.242, P=0.003). The relative expression level of miR-155 in the cells of miR-155 inhibitor group was 0.21±0.03, which was significantly lower than 0.98±0.09 of the miR-155 negative control group (t=12.421, P<0.01). The migration rate was higher and the number of cells passing through basement membrane was more in the TGF-β2 group than those of the control group, and the migration rate was higher and the number of cells passing through basement membrane of miR-155 was more in the miR-155 negative control group than those of the miR-155 inhibitor group, and the differences were statistically significant (all atP<0.01). Compared with the control group, the relative expression levels of PTEN, E-cad, ZO-1, F-actin protein were decreased, while the relative expression levels of PI3K and the p-Akt/Akt ratio were increased, and the relative expression levels of α-SMA, FN-1, vimentin proteins were increased in the TGF-β2 group, and the differences were statistically significant (all atP<0.01). Compared with the miR-155 negative control group, the relative expression levels of E-cad, ZO-1, F-actin and PTEN proteins were increased, while the relative expression levels of α-SMA, FN-l, vimentin, PI3K and the p-Akt/Akt ratio were decreased in the miR-155 inhibitor group, and the differences were statistically significant (all atP<0.01). Target gene prediction library prediction and luciferase reporter vector identification confirmed that PTEN was a downstream target gene of miR-155.

miR-155 can promote the TGF-β2-induced epithelial-mesenchymal transition progress in human retinal pigment epithelial cells, and its mechanism may be related to inhibiting the expression of the target gene PTEN and stimulating the activation of the PI3K/Akt signaling pathway.

MicroRNA-155; Human retinal pigment epithelium; Epithelial-mesenchymal transition; PTEN