Autologous retinal pigment epithelium (RPE) grafts derived from induced pluripotent stem cells (iPSCs) may be used to cure blinding diseases in which RPE dysfunction results in photoreceptor degeneration. Four, two, and one factor-derived iPS (4F-, 2F-, and 1F-iPSCs, respectively) were differentiated into fully functional cuboidal shaped pigmented cells in polarized monolayers that express RPE-specific markers. 1F-iPS-RPE strongly resemble primary human fetal RPE (hfRPE) based on proteomic and untargeted metabolomic analyses, and, utilizing novel in vivo imaging technology coupled with electroretinography, we demonstrate that 1F-iPS-RPE mediate anatomical and functional rescue of photoreceptors after transplantation in an animal model of RPE-mediated retinal degeneration. 1F-iPS-RPE cells were injected subretinally as a suspension and formed a monolayer dispersed between host RPE cells. Furthermore, 1F-iPS-RPE do not simply provide trophic support to rescue photoreceptors as previously speculated, but actually phagocytose photoreceptor outer segments in vivo and restore visual cycling (based on high-resolution mass spectrometry based detection of recycled photoreceptor protein and lipid end products and electron microscopic analysis). Thus, 1F-iPS-RPE grafts may be superior to conventional iPS-RPE for clinical use since 1F-iPS-RPE closely resemble hfRPE, mediate anatomical and functional photoreceptor rescue in vivo and are generated using a reduced number of potentially oncogenic reprogramming factors.

Diabetic retinopathy is the leading cause of visual loss in individuals under the age of 55. Umbilical cord blood (UCB)–derived myeloid progenitor cells have been shown to decrease neuronal damage associated with ischemia in the central nervous system. In this study we show that UCB-derived CD14+ progenitor cells provide rescue effects in a mouse model of ischemic retinopathy by promoting physiological angiogenesis and reducing associated inflammation. We use confocal microscopy to trace the fate of injected human UCB-derived CD14+ cells and PCR with species-specific probes to investigate their gene expression profile before and after injection. Metabolomic analysis measures changes induced by CD14+ cells. Our results demonstrate that human cells differentiate in vivo into M2 macrophages and induce the polarization of resident M2 macrophages. This leads to stabilization of the ischemia-injured retinal vasculature by modulating the inflammatory response, reducing oxidative stress and apoptosis and promoting tissue repair.

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