FECD is a disorder influenced by multiple genes, leading to intricate pathophysiology. In this study, our goal is to discover the key biomarkers and pathways from the DEGs between a group of 6 patients affected with FECD and another group of 6 unaffected (control) micro array data (Accession no. GSE171830). Microarray is one of the most frequently utilized high-throughput methods for gene expression profiling (Liang et al. 2004). The volcano plot was plotted to visualise the expression pattern of the DEGs, from both the FECD affected and unaffected (control) samples. Through our analysis, we identified HLA-DRA, CSF1R, TNFRSF11B and COL4A1 as key DEGs with significant implications in the pathogenesis or potential therapeutic relevance to FECD. These genes were identified through the analysis of GO, KEGG and PPI. Hence, these DEGs can serve as potential biomarkers with functional significance in understanding the pathogenesis and progression of FECD.
We observed significant upregulation of certain genes with specific GO terms mainly associated with signal transduction, inflammatory response, and immune response within the realm of biological processes. Some significant enrichments were observed in the cellular components, particularly cell surface, exterior surface of the plasma membrane, the essential part of the plasma membrane, endoplasmic reticulum, and ECM. The prominant molecular functions that exhibits upregulation in the DEGs includes the ECM structural constituent, integrin binding, cytokine binding & cytokine activity. KEGG pathway of the upregulation was mostly associated with antigen processing and presentation, hematopoietic cell lineage, interactions between cytokines and their receptors, Phosphoinositide 3-kinase (PI3K)-Akt signaling pathway, and tumor necrosis factor-signaling pathway.
We also observed that significant downregulation of specific GO terms which are mainly associated with cellular response to hypoxia, actin cytoskeleton organization, mitochondrion organization, retinoid metabolic process etc. in the biological process. Significant enrichments were observed in the cellular components particularly the mitochondrial inner membrane, mitochondrial matrix, mitochondrial outer membrane etc. The major molecular function downregulated in the DEGs was the identical protein binding, GTPase activity, GTP binding etc. KEGG pathway of the downregulated was mostly associated with metabolic pathways, oxidative phosphorylation etc.
Literature studies show that the PI3-Akt signaling pathway exhibits significant importance in the biological process of corneal epithelial cells (CECs) and helps in the wound healing of corneal epithelium (CE) (Guo et al. 2019, Han et al. 2014, Li et al. 2020, Bettahi et al. 2014, Chen et al. 2022). Subsequent activation of the Phosphoinositide 3-kinase (PI3K)-Akt signaling pathway promotes inflammation and initiates the secretion of inflammatory cytokines such as IL-6, IL-1β, and TNF-α. TXNIP is a glucose-sensitive gene that holds a critical role in pro- IL-1β expression and exhibits significant induction in retinal cells (Sbai et al. 2010, Koenen et al. 2011, Perrone et al. 2009). Hence, genes primarily linked to the cytokine receptor interactions and Phosphoinositide 3-kinase (PI3)-Akt signaling pathway may also be important for maintaining the integrity of the patient’s cornea and its clinical application for the new drugs.
The GO chord plot reveals that TNFRSF11B is associated with the interaction between cytokines and cytokine receptors. The expression of TNFRSF11B was confirmed by immunohistochemistry in the eyes of patients with secondary glaucoma (Ehlken et al. 2015). The presence of the COL4A1 gene is a critical component of basement membranes found in various tissues, including the vascular and corneal epithelium as well as the conjunctiva of the eyes (Guey et al. 2022). Moreover, mutations in COL4A1 damage multiorgan particularly affecting the eyes, muscles, and kidneys (Vahedi et al. 2011). Immunohistochemistry on CE-DM complexes reveals the presence of HLA-DRA that cluster around the guttae (De et al. 2017). But the expression of TNFRSF11B, COL4A1, and HLA-DRA genes particularly related to the FECD has not been reported yet. Further research is warranted to uncover the precise role of HLA-DRA, CSF1R, TNFRSF11B, and COL4A1 to establish enhanced diagnostic and therapeutic strategies for FECD.
We performed virtual screening against FDA approved drugs to identify the possible drug candidates that can be repurposed against FECD. Drugs such as Naphazoline, Infigratinib, Lifitegrast, Netarsudil, Verteporfin, and Hyaluronic drugs show good binding affinity against the identified biomarkers (Fig. 9). These findings lays-out the initial theoretical groundwork for further experimental investigations. Further, experimental studies are warranted to identify the drugs that can possibly repurposed against FECD.