MiR-7 regulates the PI3K/AKT/VEGF pathway of retinal capillary endothelial cell and retinal pericytes in diabetic rat model through IRS-1 and inhibits cell proliferation

OBJECTIVE: To investigate the role of miR-7 in diabetic retinopathy and the underlying mechanism.

MATERIALS AND METHODS: The rat model of diabetic retinopathy (DR) was established. After that, the endothelial cell (EC) and retinal pericyte (RP) were isolated. QRT-PCR was used to detect the expression of miR-7 and insulin receptor substrate-1 (IRS-1) in ECs and RPs cells while the protein level of IRS1 was detected by Western blot. miR-7 mimic and miR-7 inhibitor were transfected to achieve miR-7 overexpression or knockdown. Cell viability was detected by Cell Counting Kit-8 (CCK-8) assay after miR-7 overexpression or knockdown. Besides, the expression levels of PI3K, AKT, and VEGF were detected by Western Blot. The luciferase reporter assay was performed to investigate whether miR-7 could be combined with IRS-1. Conversely, whether miR-7 could affect IRS-1 was also verified.

RESULTS: miR-7 expression was significantly decreased in ECs and RPs of the experimental group compared with the control group, while the mRNA and protein levels of IRS-1 were increased. The CCK-8 assay showed that overexpression of miR-7 decreased the cell activity in ECs and RPs. In contrast, knock-down of miR-7 could increase the cell viability. Besides, Western blot showed that after overexpression of miR-7, the expressions of PI3K, AKT, and VEGF in ECs and RPs cells were down-regulated. Meanwhile, miR-7 knockdown upregulated the protein levels of PI3K, AKT, and VEGF. The luciferase reporter assay suggested that the 3'UTR region of IRS-1 could be combined with miR-7, which may be the downstream target gene for miR-7. Moreover, knockdown of IRS-1 could reverse the effect of the miR-7 inhibitor on cell proliferation in the diabetic model.

CONCLUSIONS: MiR-7 was lowly expressed in ECs and RPs cells. Overexpression of miR-7 can down-regulate the expression levels of PI3K, AKT, and VEGF by down-regulating its downstream target gene IRS-1, and ultimately inhibit the proliferation of retinal cells.

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