Inhibitory effect of miR-497 on corneal neovascularization and its regulation mechanism targeting STAT3

Objective

To investigate the role of microRNA (miR)-497 in the formation of corneal neovascularization (CNV) induced by alkali burn and its mechanism.

Methods

Forty-two wild type (WT) C57BL/6 mice aged 6 to 8 weeks, 42 CRISPR/Cas9 mediated miR-497 knockout (KO) and 42 CRISPR/Cas9 mediated overexpression transgenic (TG) C57BL/6 mice were selected and assigned as WT group, KO group and TG group, respectively.The corneal alkali burn model was established.At 3, 7, 14 and 21 days after modeling, corneal epithelium damage and stromal turbidity were scored according to slit lamp microscopy.The area of neovascularization was measured.Corneal structural changes and expression of inflammatory cells were observed by histopathological staining.The expression of CD31 in corneal tissues was detected by immunohistochemistry staining.The targeted binding relationship between miR-497 and signal transducer and activator of transcription 3 (STAT3) was detected by luciferase reporter assay.The relative expressions of miR-497, vascular endothelial growth factor A (VEGFA), tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β and macrophage inflammatory protein (MCP)-1 mRNA were detected by real-time quantitative PCR.At 14 days following modeling, the expression of STAT3 and p-STAT3 proteins in mice corneal tissues was detected by Western blot.The use and care of animals complied with the ARVO statement.The study protocol was approved by the Ethics Committee of Renmin Hospital of Wuhan University (No.2019K-K010).

Results

Corneal injury, inflammatory cell infiltration and CNV occurred in mice cornea after alkali burn.Corneal epithelial injury score, corneal stromal turbidity score and CNV area increased first and reached the peak on the 14th day after modeling, and then decreased.There were significant differences in corneal epithelial injury score, corneal stromal turbidity score, CNV area and number of CD31-positive cells among various time points after alkali burn (F_group=49.19, 34.56, 44.56, 77.56; all at P<0.01; F_time=51.62, 65.62, 71.32, 46.12; all at P<0.01). Corneal epithelial injury score, corneal stromal turbidity score, CNV area and the number of CD31-positive cells were greater in KO group at various time points than in WT and TG groups, and those in WT group were greater than in TG group (all at P<0.05). In WT STAT3 co-transfected cells, the luciferase activity of the miR-497 group was significantly lower than that of the miR-negative control group and normal control group (both at P<0.05). In mutant STAT3-transfected cells, there was no significant difference in luciferase activity among all groups (F=0.69, P=0.56). On the 14th day after modeling, the relative expression levels of miR-497 in corneal tissue of WT, KO and TG groups were 0.68±0.11, 0.41±0.06 and 1.05±0.14, respectively, which were significantly lower than 1.00±0.04, 0.56±0.07 and 1.34±0.11 before modeling (all at P<0.01). The relative expressions of STAT3 and p-STAT3 were higher in KO group than in WT and TG groups, and were lower in TG group than in WT group, and the differences were statistically significant (all at P<0.05). The expressions of VEGFA, TNF-α, IL-6, IL-1β and MCP-1 mRNA at various time points after modeling in various groups were significantly higher than before modeling, which were higher in KO group than in WT and TG groups and were lower in TG group than in WT group, and the differences were statistically significant (all at P<0.01).

Conclusions

MiR-497 inhibits corneal inflammation and CNV formation induced by alkali burn.It might inhibit the activation of the inflammation signal pathway via targeting STAT3.

Corneal neovascularization; MicroRNAs; Inflammatory cytokines; STAT3; Alkali burn