The transcription factor NFAT5 is a crucial regulator of corneal edema resolution after injury

Abstract

Purpose : The cornea is physiologically free of blood and lymphatic vessels ([lymph]angiogenic privilege). However, injury or inflammation may lead to an ingrowth of these vessels. Recently, corneal lymphangiogenesis (LA) has been implicated to play a role in the regulation of corneal edema and inflammation resolution. Nuclear factor of activated T-cells 5 (NFAT5/TonEBP) has recently been identified as an important transcription factor that regulates LA and fluid homeostasis in skin. Here, NFAT5 enhances the expression of pro-lymphangiogenic vascular endothelial growth factor C (VEGF-C) in skin macrophages (MΦ), resulting in increased LA. So far, it has not been investigated whether NFAT5 is expressed in the cornea and which role it plays in the inflammatory response after corneal injury.

Methods : The corneal expression pattern of NFAT5 was investigated by immunofluorescence staining (IF) and qPCR in naïve and injured mouse corneas using a perforating corneal injury model to induce inflammation, LA and edema. The role of NFAT5 in corneal inflammation and the resolution of corneal edema was investigated using a tamoxifen-inducible NFAT5 knockout (KO) (Ubc-Cre/NFAT5^fl/fl) mouse model. Corneal thickness and resolution of corneal edema was measured by optical coherence tomography (OCT). Inflammation and LA were analyzed using IF.

Results : In naive corneas, NFAT5 was mainly expressed in corneal fibroblasts. After injury, NFAT5 expression in fibroblasts was downregulated and mainly expressed by MΦ (Correlation coefficient of TonEBP⁺/Vimentin⁺: 0.446±0.111 in naive corneas vs 0.153±0.024 after injury [p<0.0001]); TonEBP⁺/F480⁺: 0.113±0.032 in naive cornea vs. 0.446±0.018 after injury [p<0.0001]). In uninjured corneas, NFAT5 KO did not lead to changes in corneal thickness, however, the number of MΦ was significantly increased (24.76±3.54% in KO vs. 16.14±0.36%; p=0.0094 of corneal area covered by F480⁺ cells). After injury, the resolution of corneal edema was enhanced in NFAT5 KO mice (corneal thickness: 97.1±10.0 µm in KO vs. 137.1±28.8 µm [p=0.002]).

Conclusions : Our results demonstrate that NFAT5 is highly expressed in the cornea and its expression shows considerable changes after injury. Furthermore, our data indicate that the loss of NFAT5 leads to a faster resolution of corneal edema. The suppression of NFAT5 might be a promising strategy for the treatment of diseases associated with corneal edema.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.