Patient induced pluripotent stem cells identify specificities of a reticular pseudodrusen phenotype in age-related macular degeneration.

BACKGROUND: Age-related macular degeneration (AMD) is a leading cause of vision loss. Reticular pseudodrusen (RPD), deposits on the apical side of the retinal pigment epithelium (RPE), signify a distinctive and critical AMD phenotype. Yet, their molecular basis and relationship to the conventional drusen seen in AMD remain unclear. METHODS: We generated induced pluripotent stem cell-derived RPE cells from a clinically phenotyped cohort comprising only individuals with conventional drusen (AMD/RPD-) or with drusen coexisting with RPD (AMD/RPD +). To identify differences between the two cohorts, we performed single-cell transcriptomic, proteomic, quantitative trait locus (QTL) and transcriptome-wide association (TWAS) analyses, together with functional assays. RESULTS: AMD/RPD + RPE cells exhibited enrichment of extracellular matrix (ECM) and hypoxia-responsive pathways, and a relative underrepresentation of mitochondrial and oxidative phosphorylation processes, when compared with AMD/RPD- cells. Genetic analyses supported shared modulation of mitochondrial pathways across AMD, with additional regulatory signals associated with RPD risk. Functionally, all RPE cohorts formed drusen-like deposits in vitro. AMD/RPD- lines generated more basal deposits, whereas AMD/RPD + cells exhibited increased susceptibility to monolayer disruption. CONCLUSIONS: These findings indicate that AMD with and without RPD represent mechanistically distinct entities and provide novel insight into the molecular mechanisms underlying disease heterogeneity in AMD.