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John Yeong Se Han, Kathleen Boesze-Battaglia, Nancy J Philp; Metabolic Reprogramming of the Retinal Pigment Epithelium in Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4147.
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Retinitis Pigmentosa (RP) is a group of genetic diseases that results in progressive loss of vision. The majority of gene mutations associated with RP are rod specific genes, with the most common mutation in rhodopsin (Rho), specifically the P23H mutation that causes rod photoreceptor cell death. Over time rod photoreceptor cell death leads to a secondary wave of cone photoreceptor cell death, causing permanent blindness in patients. Photoreceptors and the retinal pigment epithelium (RPE) are metabolically coupled and are reliant on each other to maintain their structural and functional properties. Loss of rod photoreceptors has been shown to cause metabolic reprogramming of the RPE, but alterations to the RPE have not been extensively characterized. In this study, we show the loss of rod photoreceptors cause decrease in metabolic substrates for the RPE, leading to changes in RPE signature genes.
P23H knock-in mice were purchased from Jackson labs and crossed to B6/J mice to generate P23H knock in heterozygous mice (P23H+/-) that were used for the study. Live animal imaging with Confocal Scanning Laser Ophthalmoscopy (cSLO) and Spectral Domain Optical Coherence Tomography (SD-OCT) were done to monitor the rate of outer nuclear layer (ONL) degeneration. Ex-vivo metabolic studies were used to characterize the metabolic alterations in the outer retina. qPCR, immunoblotting and immunofluorescent were performed to identify any alterations to metabolic pathways, and RPE integrity.
P23H+/- showed progressive loss in ONL over time. Degeneration of ONL correlated with decrease in lactate produced by the neural retina. Flatmounts of the RPE showed morphological changes correlated with degeneration of the ONL. RPE exhibited decrease in expression of key metabolic transporters and enzymes and RPE differentiation markers with degeneration of ONL.
Rod photoreceptor death leads to a loss of two key substrates that support oxidative metabolism in the RPE, lactate and fatty acids. Dedifferentiation of the RPE as well as loss of RdCVF could contribute to cone photoreceptor cell death.
This is a 2020 ARVO Annual Meeting abstract.
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