Retinal proteome changes mirror brain pathology and reveal synaptic and cytoskeletal dysfunction in Alzheimer's disease.

Visual dysfunction is increasingly recognized as an important feature of Alzheimer's disease, and substantial retinal changes have been documented across multiple studies. Yet the molecular changes underlying retinal neurodegeneration and which retinal protein signatures best track cerebral pathology remain incompletely defined. Here, we performed comprehensive mass spectrometry-based proteomics on paired retinal and hippocampal tissue from the same postmortem donors (8 AD, 8 non-demented controls) to identify disease-associated molecular signatures and assess their overlap between these tissues. Using a sequential dual-extraction protocol, we identified 372 differentially abundant retinal proteins in AD, including established APP-processing regulators (SORL1, BACE1) and synaptic proteins. Retinal proteomes clearly separated AD from controls in principal component analysis, indicating robust AD-related molecular differences in the retina. Notably, 87% of proteins were detected in both retina and hippocampus, with 64 differentially abundant proteins shared between tissues, some of which showed strong cross-tissue correlation. Several retinal proteins also correlated with neuropathological disease stage. Functional enrichment analysis revealed convergent alterations in synaptic organization, cytoskeletal dynamics, mitochondrial function, cell adhesion, and APP metabolism in both tissues. Cell-type mapping using single-cell retinal reference data indicated that most proteomic changes were broadly distributed across cell types, though some proteins showed enrichment in specific populations, such as SORL1 in microglia and EYS in photoreceptors. The molecular changes identified here offer a potential basis for the retinal alterations previously documented through in vivo imaging and histological studies. Their similarities with brain pathology further support the retina as a promising window for assessing cerebral disease.