iPSC-Derived Retinal Pigment Epithelium Allografts Do Not Elicit Detrimental Effects in Rats: A Follow-Up Study

Figure 2

Cells with features characteristic of RPE are readily distinguishable in old RCS rats using ultrastructural examinations. (a and b) Ultrastructural RPE-like features are seen in electron micrographs. Just beneath the choriocapillaris (CC) lies Bruch’s membrane (BM). Basal infoldings, melanosomes (marked with “”s; not to be confused with electron dense mitochondria (marked with “”s)), and long apical processes seen in normal RPE cells are apparent. (c) Immunohistochemistry performed on paraffin embedded sections was performed with anti-Tra-I-85 (which recognizes human cells) and anti-Iba1 (which recognizes activated microglia) antibodies. Membranes of pigmented cells in the RPE domain of the RCS retina are Tra-I-85 positive (red) and Iba1 negative (green). (d) Other pigmented cells outside of the subretinal space are probably macrophages based on Tra-I-85 negative (red) and Iba1 positive (green) signatures. (e) An electron micrograph of a melanin-laden macrophage. (f) Melanin in the macrophages accumulated in very dense aggregates in the phagolysosomes compared with the pigment distribution in RPE cells (b). Images are representative; evidence of proper integration and some unintegrated RPE (especially around the injection site) were seen in all iPS-RPE injected eyes examined. Scale bars: (a) = 5 μm, (b) = 2 μm, (c) = 10 μm, (d) = 10 μm, (e) = 5 μm, and (f) = 1 μm.

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