Forkhead Domain Inhibitor-6 Suppresses Corneal Neovascularization and Subsequent Fibrosis After Alkali Burn in Rats

PURPOSE: The purpose of this study was to investigate the effects of Forkhead Domain Inhibitor-6 (FDI-6) on regulating inflammatory corneal angiogenesis and subsequent fibrosis induced by alkali burn. METHODS: A corneal alkali burn model was established in Sprague Dawley rats using NaOH and the rat eyes were topically treated with FDI-6 (40 µM) or a control vehicle four times daily for 7 days. Corneal neovascularization, inflammation and epithelial defects were observed on days 1, 4, and 7 under a slit lamp microscope after corneal alkali burn. Analysis of angiogenesis-, inflammation-, and fibrosis-related indicators was conducted on day 7. Murine macrophages (RAW264.7 cells) and mouse retinal microvascular endothelial cells (MRMECs) were used to examine the effects of FDI-6 on inflammatory angiogenesis in vitro. RESULTS: Topical delivery of FDI-6 significantly attenuated alkali burn-induced corneal inflammation, neovascularization, and fibrosis. FDI-6 suppressed the expression of angiogenic factors (vascular epidermal growth factor, CD31, matrix metalloproteinase-9, and endothelial NO synthase), fibrotic factors (α-smooth muscle actin and fibronectin), and pro-inflammatory factor interleukin-6 in alkali-injured corneas. FDI-6 downregulated the expression of monocyte chemotactic protein-1, pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-alpha), nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3, and vascular endothelial growth factor in RAW264.7 cells and inhibited the proliferation, migration, and tube formation of MRMECs in vitro. CONCLUSIONS: FDI-6 can attenuate corneal neovascularization, inflammation, and fibrosis in alkali-injured corneas.