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Janmeet S Saini, Barbara Corneo, Jeffrey Stern, Sally Temple; Modeling Age-related Macular Degeneration (AMD) using Patient-Specific induced Pluripotent Stem Cells. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2346.
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Age-related Macular Degeneration (AMD) is the leading cause of visual impairment and irreversible blindness in the elderly people in the developed world. AMD affects the retinal pigment epithelium (RPE), a pigmented cellular monolayer lying beneath and supporting the neural retina. AMD is characterized by the presence of extracellular deposits termed drusen that accumulate sub-retinally in the macular region, leading to focal degeneration of the photoreceptors. In some cases dry AMD can progress to more devastating forms such as geographic atrophy or wet/neovascular AMD. Considerable progress has been made to elucidate the molecular composition of drusen. Drusen include Amyloid β (Aβ) deposits, also found in amyloid plaques in Alzheimer’s. Aβ accumulation in drusen is associated with disease progression and stimulation of the complement cascade, which plays a role in the generation of a pro-angiogenic environment including upregulation of VEGF-A. VEGF-A is a potent angiogenic factor preferentially secreted basolaterally by RPE and its basal expression is increased in AMD, resulting in ocular neovascularization.<br /> Induced pluripotent stem cells (iPSCs) reprogrammed from somatic cells can be used to generate patient-specific differentiated cells in vitro. We hypothesized that iPSC-derived RPE from AMD eyes can be used for modeling AMD pathogenesis.
RPE cells isolated from AMD cadaver donor eyes as well as from healthy control donors, were reprogrammed using Sendai virus to generate transgene-free iPSCs that were then differentiated into functional monolayers of RPE.
Gene expression analysis of iPSC-derived RPE revealed significantly higher expression of Aβ precursor transcripts (APP, BACE-1 and PS-1) and other drusen-associated transcripts such as VEGF-A and αA Crystallin in AMD iPSC-derived RPE cells. When compared to healthy controls using ELISA, a significantly higher secretion of Aβ42 and Aβ40 was detected in AMD iPSC-derived RPE cells. Aβ42 is a cytotoxic form of Aβ and is capable of rapid oligomerization and aggregation. VEGF-A, involved in triggering neo-vascularization, was also secreted at a significantly higher concentration by AMD iPSC-derived RPE cells when compared to controls.
Our results indicate that iPSCs derived from AMD patients can be used to create a disease-relevant in vitro model to shed light on the disease mechanism and for drug screening.
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