The role of microRNAs in corneal neovascularization and its relation to VEGF

Effect of topical motesanib in experimental corneal neovascularization model

PURPOSE

This study aimed to compare the efficacy of topical bevacizumab and motesanib in an experimental corneal neovascularization model, and find the most effective motesanib dose.

MATERIALS AND METHODS

In experiments, 42 Wistar Albino rats were randomly divided into six groups (n = 7). Corneal cauterization was applied to all groups except the group 1. Group 1 did not receive any treatment. Topical dimethylsulfoxide was applied to sham group three times a day(tid). Topical bevacizumab drops (5 mg/ml) were applied to Group 3 tid. Topical motesanib drops with a dose of 2.5, 5, and 7.5 mg/ml were respectively applied in Groups 4, 5, and 6 tid. On the 8th day, corneal photographs of all rats were taken under general anesthesia, and the percentage of corneal neovascular area was calculated. VEGF-A mRNA, VEGFR-2 mRNA, miRNA-21, miRNA-27a, miRNA-31, miRNA-126, miRNA-184, and miRNA-204 were evaluated by the qRT-PCR method in corneas taken after decapitation.

RESULTS

The percentage of corneal neovascularization areas and VEGF-A mRNA expression levels were decreased in all treatment groups compared to group 2 (p < 0.05). VEGFR-2 mRNA levels were found to be statistically significantly decreased in groups 4 and 6 compared to group 2 (p < 0.05). Statistically significant changes were detected in the expression levels of only miRNA-126 among all miRNAs.

CONCLUSION

Motesanib with a dose of 7.5 mg/ml statistically significantly suppressed the VEGFR-2 mRNA level compared with other treatment doses and may be more effective than bevacizumab. Further, miRNA-126 can be used as a proangiogenic marker.

Targeting HMGB1-NFκb Axis and miR-21 by Glycyrrhizin: Role in Amelioration of Corneal Injury in a Mouse Model of Alkali Burn

Corneal neovascularization (CNV) is a sight-threatening condition usually associated with various inflammatory settings including chemical injury. High mobility group box 1 (HMGB1) is identified as an inflammatory alarmin in diverse tissue damage. Here, we evaluate the expression of HMGB1 and the consequences of its inhibition through its selective inhibitor glycyrrhizin (GLY) in alkali burn-induced corneal inflammation and neovascularization. GLY effectively attenuated alkali burn-induced HMGB1 expression at both mRNA and protein levels. Furthermore, slit-lamp analysis, ink perfusion, H&amp;E staining, and CD31 histochemical staining showed that GLY relieved corneal neovascularization, while GLY attenuated VEGF expression via inhibiting HMGB1/NF-κB/HIF-1α signal pathway. In addition, GLY treatment decreased the cytokine expression of CCL2 and CXCL5, accompanied by the reduction of their receptors of CCR2 and CXCR2. GLY diminished the inflammatory cell infiltration of the cornea, as well as reduced the expression of IL-1β, IL-6, and TNF-α. Moreover, treatment with GLY reduced the degree of cornea opacity through inactivating extracellular HMGB1 function, which otherwise induces TGF-β1 release and myofibroblast differentiation. Furthermore, we found that GLY treatment attenuated the upregulation of miR-21 levels in alkali burned cornea; while inhibition of miR-21in keratocytes in vitro, significantly inhibited TGF-β1-induced myofibroblast differentiation. Collectively, our results suggested that targeting HMGB1-NFκb axis and miR-21 by GLY could introduce a therapeutic approach to counter CNV.