Objective To observe the changes that occur as a rule in microRNA-21 （miR-21） expression in a mouse corneal neovascularization （CorNV） model induced by alkali burn and its relationship with vascular endothelial growth factor-A （VEGF-A）. Methods This was an experimental study. All right eyes of sixty-eight BALB/c mice were used to create models of CorNV induced by alkali burn and were included as the experimental group； the untreated left eyes were included as the control group. Biomicroscopic neovascularization was observed and photographed on days 4， 7， 14， 21 and 28. The areas of CorNV were then calculated. On days 4， 7， 14， 28 after alkali-induced injury， 3 mice were randomly euthanized and six eye balls were embedded in paraffin. Sections were cut for hematoxylin-eosin （HE） staining and immunohistochemical （IHC） staining to observe the corneal histopathological changes and to detect the protein expression of VEGF-A. Fourteen mice were randomly sacrificed for testing the expression of miR-21 and VEGF-A mRNA in corneal tissues by quantitative real-time polymerase chain reaction （real-time PCR）. The results were analyzed statistically with an analysis of variance of repeated measurement data. Linear correlation analysis was used for correlation analysis. Results After alkali-induced injury， slit lamp biomicroscopy was used to detect CorNV. It was first detected on day 4， peaked on day 14， and started to regress after day 21. The maximum area of CorNV appeared on day 14. HE staining showed that CorNV was most obvious on day 14 after alkali injury and less obvious on day 28. IHC showed that expression of VEGF-A positive staining was higher than in the control group （t=19.47， 61.8， 44.18， P<0.05） on days 4， 7， 14. Positive staining of VEGF-A was obvious on day 7 and started to decrease after day 14. The difference was statistically significant （F=649.4， P<0.05）. Real-time PCR analysis showed that on days 4， 7， 14， 28 after injury， the relative expression of miR-21 increased in the alkali-burn group compared to the control group （t=4.60， 14.74， 9.78， 5.69， P<0.01） and VEGF-A mRNA levels were higher than levels in the control group on days 4， 7， 14 after injury （t=5.82， 14.11， 3.41， P<0.05）. Their expression levels both reached a maximum on day 7 （F=62.1， 64.5， P<0.05）. There were positive correlations in miR-21 expression with VEGF-A mRNA and VEGF protein at each investigative time point （r=0.62 and r=0.66， respectively， P<0.05）. Conclusion miR-21 and VEGF-A were upregulated during the CorNV course in a mouse model induced by alkali burn. The peak expression of miR-21， VEGF-A mRNA and protein preceded CorNV formation. miR-21 may play a potential role through the VEGF signal pathway in the course of CorNV formation.
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