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Fnu Ruchi, Aman George, Zoya Qureshy, Roba Dejene, Qin Wan, Justin Ren Yuan Chang, Kapil Bharti; Aging in iPSC-RPE helps understand AMD-initiating events. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2292.
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© ARVO (1962-2015); The Authors (2016-present)
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly population in the developed world. Dysfunction of retinal pigment epithelium (RPE) likely triggers early AMD stages, whereas RPE degeneration leads to an advanced AMD stage geographic atrophy, eventually leading to photoreceptor cell death and vision loss. RPE is a post-mitotic monolayer located between photoreceptors and the choroid and maintains the homeostasis of these two tissues. With aging, RPE cells are unable to perform some of their functions affecting homeostasis in the photoreceptors and the choroid, likely triggering the early stages of AMD. In order to understand the factors and processes causing RPE aging, we developed an in vitro induced pluripotent stem cell (iPSC)-derived RPE aging model.
Fibroblast derived from both healthy and AMD patients’ skin biopsies were reprogrammed to the pluripotent state using the “Yamanaka factors”. Fully-characterized iPS cells were differentiated to RPE using a developmentally guided differentiation protocol. iPSC-derived RPE were cultured on semi-permeable membranes for 8 weeks to obtain a functionally mature and polarized monolayer tissue. iPSC-derived RPE monolayer was stressed for 48 hours with complement competent human serum. The stressed cells were checked for RPE-specific functions like measurement of electric intactness, ability to digest photoreceptors outer segments, and the junctional integrity.
Complement competent human serum stressed RPE exhibited several features of “aged” RPE and AMD-like disease processes including reduced ability to digest photoreceptor outer segments, decreased trans epithelial resistance, and increased APOE deposition and intracellular basal protein aggregates. Complement competent human serum also decreased autophagy levels, increased IL-6 secretion, and caspase-1 activation in iPSC- derived RPE cells. This cellular-aging phenotype is associated with the activation of NK-kB pathway and STAT3 pathway inhibition.
We propose that this cell culture model of RPE-aging provides a basis to discover the mechanism of disease-related RPE dysfunction and atrophy, a tool to identify the role of AMD genetics in disease initiation and progression, and to discover potential therapeutic interventions for AMD.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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