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Min Jae Song, Russell Quinn, Roba Dejene, Kapil Bharti; 3D tissue engineered RPE/“choroid” to identify mechanism of AMD-disease initiation and progression. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3760.
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Retinal pigment epithelium and choroid form a homeostatic unit that maintains functionality of photoreceptors by regulating their micro-environment. Several diseases including age related macular degeneration (AMD) are related to dysfunction or atrophy of this homeostatic unit. The advanced AMD stage has two main sub-types the “wet” and “dry” AMD. In wet AMD, choroidal vessels breach through RPE tight junctions, leak fluid and blood in the retina causing vision loss. In dry AMD, RPE atrophy leads to photoreceptor cell death and choroidal atrophy. There is currently no effective disease model to study AMD in vitro. Here, we use engineered 3D RPE/ “choroid” tissue to develop an in vitro model for AMD.
Human iPSC-derived endothelial cells, pericytes, and fibroblasts together with hydrogels were used for bioprinting on a biodegradable scaffold. iPSC-derived RPE was seeded on the other side of the scaffold. Transepithelial resistance (TER) of the tissue was measured using Endohm (WPI). Immunostaining for RPE, vessel, and fenestration markers was performed on entire tissues and vibratome cut sections, and specimen was imaged using Leica two-photon microscope.
Endothelial cells organized with in a week into a vascularized tissue that resembles the native choroid. RPE cells seeded on the other of the scaffold formed a monolayer with in a month. The biodegradable scaffold provided the framework for RPE and endothelial cells to secrete ECM. Bioprinted RPE/choroid maintained 300-800 Ohms x cm2 TER after 4 weeks of culture and expressed plasmalemma vesicle associated protein (PLVAP), a marker of fenestrated capillaries. In the intact RPE/choroid tissue vessel proliferation & PLVAP expression was dependent on the presence of RPE monolayer.
We have successfully engineered a tissue mimicking the RPE/“choroid” . Vessel growth in this intact tissue was dependent on RPE cells providing direct evidence that communication between RPE and choroid is crucial to maintain choroid health. We are currently using engineered RPE/“choroid” developed with patient specific iPS cells to study AMD initiation and progression.
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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