Human retinal organoid model of disease-relevant photoreceptor cell death amenable to drug screening

Dry age-related macular degeneration (AMD) is characterized by the progressive loss of retinal pigment epithelium cells in the macula, leading to photoreceptor degeneration and loss of central vision. Current treatments only modestly delay disease progression, but once photoreceptors are damaged, vision loss becomes irreversible. Therefore, there is an urgent need to develop therapies that prevent photoreceptor cell death and that may complement current and emerging treatment strategies. A critical step toward this goal is establishing pathophysiologically relevant human disease models for therapeutic testing. In this study, we developed a human induced pluripotent stem cell-derived retinal organoid (RO) model that recapitulates key aspects of AMD-associated photoreceptor degeneration. To mimic environmental stressors relevant to AMD, we treated mature ROs with cigarette smoke extract (CSE), a known oxidative agent and major modifiable risk factor for the disease. CSE exposure induced oxidative stress, mitochondrial membrane depolarization, and cell death primarily in the outer nuclear layer. Photoreceptor degeneration in this model involves the activation of the intrinsic apoptotic pathway and ferroptosis, which is accompanied by lipid peroxidation and dysregulation of the glutathione system. Proteomic profiling confirmed alterations in metabolic, redox, and cell death pathways consistent with AMD pathophysiology, and offered further insight into the mechanistic interplay among these pathways. Furthermore, we integrated this model with robust, quantitative outcome measures in live ROs, offering a powerful platform for preclinical therapeutic screening in dry AMD.