Fuchs Endothelial Corneal Dystrophy Involves Decreased Expression of Genes for Fe-S Cluster Synthesis

Abstract

Purpose : Fuchs endothelial corneal dystrophy (FECD), the leading indication for corneal transplantation in the US, is a degenerative disease characterized by progressive loss of corneal endothelial cells (CECs). Cell dropout occurs secondary to impaired regulation of oxidative stress and features high levels of intracellular Fe²⁺ and iron-mediated lipid peroxidation, indicating cell death occurs via ferroptosis. To date, a mechanism for observed increases in intracellular Fe²⁺ has not been explored. Iron-sulfur clusters (ISCs) and their synthesis proteins have important regulatory roles regarding intracellular Fe²⁺ concentration. ISC dysfunction due to low levels of bioreactive Fe²⁺ is known to induce an iron starvation response resulting in a significant increase in the Fe²⁺ labile iron pool and an increased susceptibility to ferroptosis. ISC dysfunction, activation of iron regulatory proteins, and iron starvation response can also occur following cellular exposure to oxidative stress. We hypothesized that in FECD, genes responsible for ISC synthesis will display differences in expression compared to control samples.

Methods : We investigated the transcriptional expression of genes responsible for the regulation of intracellular iron levels and production of ISCs with close interactions according to STRING functional protein networks. Reverse transcription and real time PCR were performed to compare gene expression levels between FECD explanted endothelial tissue surgical samples (N=21, 3 pools of 7), non-FECD surgical samples (N=9, 3 pools of 3), and healthy donor tissue control samples (N=12, 3 pools of 4).

Results : We identified significant downregulation compared to controls of ten genes whose proteins function in cellular iron regulation and ISC synthesis in FECD tissue, including NCOA4, GSS, TXNRD1, NFS1, FDX1, GLRX, PCBP1, ISCA2, BOLA2, BOLA3 (fold change >0.40, fold change <0.56, (p<0.05).

Conclusions : Results reveal a potential role for ISC dysfunction and activation of the iron starvation response in FECD pathobiology. Further elucidation of the relationship between oxidative stress, ISC protein function, and increased intracellular Fe²⁺ in FECD will provide insight into mechanisms that trigger ferroptosis-mediated CEC death. Our results provide the basis for future investigations surrounding the effects of oxidative stress on ISC activity and iron regulatory proteins in FECD pathogenesis.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.