Inhibitory effect of miR-497 on the repair of diabetic mice corneal epithelial damage by targeting wnt3a

Objective

To investigate the inhibitory effect of miR-497 on the corneal epithelial healing in diabetic mice and its possible mechanism.

Methods

Forty healthy clean-grade wild-type C57BL/J6 mice were randomly divided into a blank control group and a model control group, with 20 mice in each group.Another 20 CRISPR/Cas9-mediated miR-497 knockout mice and miR-497 overexpression mice were taken as miR-497 knockout and miR-497 overexpression groups, respectively.The diabetes model was constructed by continuous intraperitoneal injection of streptozotocin (STZ) to the mice in model control, miR-497 knockout and miR-497 overexpression groups, and the mice in blank control group were injected with an equal amount of citrate buffer, followed by 8-week normal feeding.After the establishment of diabetes model, the corneal epithelial injury model was further constructed by scraping off part of the corneal epithelium with a central diameter of 2 mm.The corneal epithelial defect area of mice in 0, 12, 24 and 36 hours after corneal epithelial injury was observed by corneal fluorescein sodium staining.The expression of Wnt3a and β-catenin proteins in mice corneal tissues was detected by Western blot.The expression of miR-497 as well as the mRNA expression levels of cell proliferation-associated factor genes CyclinD1, c-Myc, and Ki-67 mRNA was detected by real-time quantitative fluorescence PCR.The targeting relationship between miR-497 and wnt3a was detected by a dual luciferase reporter gene assay.Human corneal epithelial cells (HCEC) were cultured in vitro and transfected with miR-497 mimics, miR-497 mimics negative control, miR-497 inhibitor, and miR-497 inhibitor negative control by Lipo8000 as miR-497 mimics group, mimics negative control group, miR-497 inhibitor group, andmiR-497 inhibitor negative control group, respectively, all of which were cultured in high glucose medium containing 25% glucose.Another two groups of HCEC were taken and cultured in medium containing 5% and 25% glucose as control and high glucose groups, respectively.The cell proliferation viability was determined by CCK8 method.The use and care of animals complied ith the ARVO statement.The study protocol was approved by the Ethics Committee of Renmin Hospital of Wuhan University (2019K-K010).

Results

Eight weeks after STZ injection, the blood glucose of mice was significantly higher and the weight was significantly lower in each diabetic model group than those of blank control group (all at P<0.05). At 12, 24 and 36 hours after the corneal epithelial injury, the percentages of corneal epithelial defect area observed by slit-lamp microscopy in model control group were significantly higher than those in blank control group and miR-497 knockout group and lower than those in miR-497 overexpression group, and the differences were statistically significant (all at P<0.05). The relative expressions of wnt3a and β-catenin proteins in the corneal tissues of model control group were significantly lower than those of blank control group and miR-497 knockout group, but higher than those of miR-497 overexpression group, and the differences were statistically significant (all at P<0.05). The relative expressions of CyclinD1, c-Myc and Ki-67 mRNA in model control group were lower than those in miR-497 knockout group, but higher than those in miR-497 overexpression group, and the differences were statistically significant (all at P<0.05). The relative expression of miR-497 in model control group, miR-497 knockout group and miR-497 overexpression group was 1.00±0.02, 0.63±0.06 and 1.48±0.03, respectively, with a statistically significant difference (F=19.62, P<0.01). The luciferase activity of miR-497-5p mimics group in wild-type wnt3a transfected cells was lower than that of miR-497-5p negative control group and empty vector group, and the differences were statistically significant (all at P<0.05). In the mutant wnt3a transfected cells, there was no significant difference in the luciferase activity among various groups (F=0.73, P=0.59). The cell proliferation A value of high glucose group was 0.59±0.03, which was significantly lower than 0.59±0.03 of normal control group and 0.88±0.08 of miR-497 inhibitor group, but significantly higher than 0.48±0.11 of miR-497 mimics group (all at P<0.05).

Conclusions

The silencing of miR-497 may promote the repair of diabetic corneal epithelial defects by targeting wnt/β-catenin pathway.

MicroRNA; Wnt3a; Diabetes mellitus; Corneal epithelium; Corneal injuries