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Quantitative Measurement of Photoreceptor Outer Segment Phagocytosis by Retinal Pigment Epithelium Cells derived from Induced Pluripotent Stem Cells through Flow Cytometry

Friday, November 08, 2013 — Poster Session III

10:00 a.m. – 12:00 p.m.

FAES Academic Center (Upper-Level Terrace)




  • RS Villasmil
  • O Memon
  • J Laux
  • S Miller
  • K Bharti


The retina is susceptible to a variety of diseases, degenerative as well as inflammatory, that can lead to vision loss or complete blindness due to loss of critical cellular elements required for vision. Induced pluripotent stem cells (iPSCs) offer a great promise for generating different types of retinal cells. Functional characterization of iPSC-derived retinal pigment epithelium (RPE) is an important tool in the development of regenerative technologies. Phagocytosis of rod outer segments (OS) by pigment epithelium is a key function of retinal homeostasis. Here, we describe a method of measurement of photoreceptor cell outer segment phagocytosis by iPSC derived RPE using Flow Cytometry. This method measures RPE uptake of OS labeled with a pH dependent fluorescent probe. The probe changes its fluorescent properties when exposed to the low pH environment of the phagosome. This novel approach distinguishes OS bound to the outside of the RPE from the OS within the phagosome. Thus, flow cytometry allows quantification of OS phagocytosis and shows different levels of RPE phagocytic activity in RPE derived from iPSCs of different tissue sources, providing important information for development of iPSC derived RPE.

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