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Soile Nymark, Kati Juuti-Uusitalo, Heli Skottman, Jari Hyttinen; Maturation of Stem Cell Derived Retinal Pigment Epithelium Changes Its Electrophysiological Properties. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2244.
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© ARVO (1962-2015); The Authors (2016-present)
Subretinal transplantations of retinal pigment epithelial (RPE) cells have therapeutic potential in treatments for many degenerative eye diseases. Potent origins for the transplants are human embryonic stem cells (hESC) and human induced pluripotent stem cells (hiPSC). However, if transplanted cells are too immature, they cannot functionally replace the diseased cells. Thus, more information about the functionality and maturation of stem cell derived RPE cells is needed to increase the efficacy of transplantation. In this study, we characterized the electrophysiological properties of hESC derived RPE cells in different stages of maturation.
The pluripotent hESC lines were maintained and RPE cells differentiated using existing protocols in our laboratory. Electrophysiological properties of hESC-RPE monolayers were characterized by whole-cell patch clamp recordings during different stages of hESC-RPE development. Recordings from immature RPE were made 2 weeks after replating at the stage when cells were lightly pigmented or depigmented and were forming small monolayer colonies. Recordings from mature RPE were made more than 20 weeks after replating when cells were pigmented, had typical cobblestone morphology and were forming a confluent monolayer.
Whole-cell current-clamp recordings demonstrated that mature hESC-RPE cells had resting membrane potential values typically between -40 and -50 mV, comparable to values previously reported in the literature for cultured human fetal RPE. However, immature hESC-RPE cells had slightly depolarized resting membrane potentials (typically -25 to -35 mV) compared to mature hESC-RPE. Whole-cell voltage-clamp recordings demonstrated that mature hESC-RPE cells had transient voltage-activated inward currents with kinetics and activation characteristic of voltage-gated sodium channels. In contrast, these currents were not observed in immature RPE cells. Finally, outward potassium currents were recorded in both immature and mature hESC-RPE, and they activated typically at potentials positive to -30 mV.
Our results indicate that the stage of maturation is critical for RPE cells in order to obtain the full capacity for transepithelial ion transport resembling that of the native RPE. A thorough electrophysiological characterisation of both hESC-RPE and hiPSC-RPE is important before these cells are used for cell transplantations.
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