Proteome alterations in the aqueous humor reflect structural and functional phenotypes in patients with advanced normal-tension glaucoma

Previous reports have shown possible association between altered protein levels in aqueous humor (AH) and normal-tension glaucoma (NTG), but the underlying pathogenetic mechanism as well as specific molecular biomarkers for NTG remains still elusive. Here, we aimed to identify novel biomarkers for advanced NTG by analyzing the proteome of patient-derived AH and their correlation with various functional and structural parameters from the visual field test (VF), optical coherence tomography (OCT), and OCT angiography (OCTA). We determined differentially expressed proteins (DEPs) of the AH of patients with advanced NTG (n = 20) using label-free quantitative (LFQ) proteomics with pooled samples and data-independent acquisition (DIA) analysis with individual samples, and the roles of AH DEPs in biological pathways were evaluated using bioinformatics. We identified 603 proteins in the AH of patients with advanced NTG, and 61 of them were selected as DEPs via global proteome LFQ profiling. Individual DIA analyses identified a total of 12 DEPs as biomarker candidates, seven of which were upregulated, and five were downregulated. Gene ontology enrichment analysis revealed that those DEPs were mainly involved in the immune response. Moreover, IGFBP2, ENO1, C7, B2M, AMBP, DSP, and DCD showed a significant correlation with the mean deviation of VF and with peripapillary and macular parameters from OCT and OCTA. The present study provides possible molecular biomarkers for the diagnosis of advanced NTG.