Ity assayBovine rod outer segments (POSs) were purified with discontinuous sucrose density gradient centrifugation as described previously [40]. The POS pellet was labeled with FITC using the established protocol [41]. Fluorescent POS (5 ?106) were added in 40 l of RPE media containing 2.5 sucrose to the apical surface of differentiated iPSC-RPE cells cultured on transwells; 40 l/well for 4 h. The reaction was then placed on ice and rinsed four times with PBS containing 1 mM MgCl2 and 0.2 mM CaCl2 (PBS-CM). Samples were incubated in 0.2 Trypan blue in PBS-CM for 10 min to quench the reaction. Cells were fixed according to the protocol [41] and nuclei were labeled with DAPI. Images were collected on confocal microscopy (Olympus Fluoview).Electron microscopyCultured iPSC-RPE cells were first washed with Dulbecco PBS and then fixed 2.5 glutaraldehyde in PBS (pH 7.4) and 0.5 osmium tetroxide in PBS. The cells were then embedded in epoxy resin. 90 nm sections were collected on 200 M copper mesh grids and left to dry for 24 h. The cells were then stained for uranyl acetate and lead citrate. JEOL JM-1010 electron microscope was used to view and image the cells.ATP levels were used to assay the mitochondrial activities. Samples were incubated for 2 h with 10uM of bromopyruvate analogue (3-BrPA) (EMD Millipore, cat# 376817), an inhibitor of glycolytic hexokinase II enzyme. Measurements were collected with Mitochondrial ToxGlo Assay that is based on the differential measurement of biomarkers associated with changes in cellular ATP PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/28854080 levels relative to vehicle-treated controls. The results are collected with bioluminescent readouts. Bioluminescent signal is proportional to ATP concentration (EPZ004777 solubility Promega, cat# G8000).Golestaneh et al. J Transl Med (2016) 14:Page 6 ofCytoplasmic glycogen concentration assayCytoplasmic glycogen levels were assayed using the Glycogen Assay Kit (Sigma, cat# MAK016) on iPSC-RPE monolayers grown in 96-well plates. Six wells were used for each sample. Glycogen concentration was determined by a coupled enzyme assay, which produces a colorimetric (570 nm)/fluorometric (535/587 nm) product, proportional to the glycogen present.G-band karyotyping of iPSC-RPEG-band karyotyping of the iPSCs was performed according to the established protocol [42]. The iPSC-RPE were cultured in 25 cm2 dishes and prepared for karyotyping.ResultsGeneration of functional iPSC-derived RPETo investigate the molecular and cellular mechanisms of AMD, we generated iPSCs from RPE of AMD and agematched normal donor eyes (RPE-iPSCs) and from skin fibroblasts of a dry AMD patient (Skin-iPSCs) (Table 1). While primary RPE could be used to study the disease phenotypes in AMD, they can quickly become depleted due to passaging and undergo senescence, whereas, iPSCs can serve as an inexhaustible source that could continuously be differentiated to the RPE for maintenance of the disease model. We purified and cultured the RPE isolated from the macular region of the human eyes according to the established protocol [38] and performed the genetic study of the single nucleotide polymorphisms (SNPs) for the known AMD susceptibility loci. Table 1 summarizes the age, gender, and genetic characteristics of the cultured RPE from donors and the skin fibroblasts of an AMD patient. As shown in Table 1, the control RPE #010 exhibits SNPs for known AMD susceptibility loci, however the donor did not present AMD at 80 years old. Moreover, the AMD RPE #009 with a history o.
