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mei jiang, Marta Stevanovic, Vanda Lopes, Biju Thomas, David Russell, Mark S. Humayun, Dennis O Clegg; HLA-E-Expressing “Universal” Pluripotent Stem Cells as a Source of Retinal Pigment Epithelium to Treat Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2018;59(9):539.
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Identifying a suitable stem cell source for retinal pigmented epithelium (RPE) has been a challenge in creating a treatment for dry age-related macular degeneration (AMD). Using human embryonic stem cells (hESC), which express polymorphic human leukocyte antigens (HLA), may cause immune rejection. Creating induced pluripotent stem cells from a patient’s own tissue is costly and time-consuming. A solution may be to use “universal stem cells” (Ucells), which do not express polymorphic HLA proteins. We differentiated Ucells into RPE and tested the phenotype and function of RPE derived from U3 (lack HLA class I expression), U37 (lack HLA class I and II expression), and the controls U1 and H9 in vitro.
Quantitative PCR (Q-PCR) was used to analyze RPE gene expression and to test for genes of contaminating cell types. Morphology and epithelial polarity were assessed using light microscopy and immunohistochemistry. Differentiation efficiency was examined by flow cytometry using the Pmel17 antibody, which labels pigmented cells. Loss of Oct4, a pluripotency marker, was also determined by flow cytometry. Ucell-RPE function was analyzed by measuring secretion of the growth factor PEDF using ELISA assays and also by measuring the ability of Ucell-RPE to carry out phagocytosis of bovine photoreceptor outer segments. For all studies, hESC-derived (H9) RPE was a positive control.
Ucell and H9-RPE showed similar expression of RPE-specific genes, including visual cycle genes (RPE65, CRLBP), RPE membrane channel and transporter genes (BEST1), and pigment and melanin biosynthesis genes (TYRP1, tyrosinase, and MITF). The Pmel17 gene was expressed in 86.12±0.9248 % of U1-, 84.65±1.392 % of U3-, and 88.67±1.506 % of H9-RPE. There was no significant difference between U3- and U1-RPE (Mann-Whitney test, two-tailed, p=0.4) or U3- and H9-RPE (Mann-Whitney test, two-tailed, p=0.1) Pmel17 expression. Ucell-RPE morphology and phagocytosis ability were also similar to those of H9-RPE.
Our results show that Ucell-RPE is similar in form and function to H9-RPE. Deriving RPE from Ucells is a novel approach to bypass immune-mediated graft rejection without using immunosuppression. Using Ucells as progenitors may be also be applicable to transplantation of other cell types.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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