Allogeneic iPSC-Derived RPE Cell Graft Failure Following Transplantation Into the Subretinal Space in Nonhuman Primates

Abstract

PurposeTo characterize the intraocular immune response following transplantation of iPS-derived allogeneic RPE cells into the subretinal space of non–immune-suppressed rhesus macaques.MethodsGFP-labeled allogeneic iPS-derived RPE cells were transplanted into the subretinal space of one eye (n = 6), and into the contralateral eye 1 day to 4 weeks later, using a two-stage transretinal and transscleral approach. Retinas were examined pre- and post-surgery by color fundus photography, fundus autofluorescence, and optical coherence tomography (OCT) imaging. Animals were euthanized between 2 hours and 7 weeks following transplantation. T-cell (CD3), B-cell (CD20), and microglial (Iba1) responses were assessed immunohistochemically.ResultsCells were delivered into the subretinal space in all eyes without leakage into the vitreous. Transplanted RPE cells were clearly visible at 4 days after surgery but were no longer detectable by 3 weeks. In localized areas within the bleb containing transplanted cells, T- and B-cell infiltrates and microglia were observed in the subretinal space and underlying choroid. A T-cell response predominated at 4 days, but converted to a B-cell response at 3 weeks. By 7 weeks, few infiltrates or microglia remained. Host RPE and choroid were disrupted in the immediate vicinity of the graft, with fibrosis in the subretinal space.ConclusionsEngraftment of allogeneic RPE cells failed following transplantation into the subretinal space of rhesus macaques, likely due to rejection by the immune system. These data underscore the need for autologous cell sources and/or confirmation of adequate immune suppression to ensure survival of transplanted RPE cells.

Transplantation of Human Embryonic Stem Cell-Derived Retinal Tissue in the Subretinal Space of the Cat Eye

“…Other reported cases of graft rejection [70,121] can be related to the impact of innate immunity [122] and/or surgical complications, for example, bleeding [8], which are likely to be related. Although work in animal models places human grafts in a more challenging environment (as they are xenogeneic grafts) than would be expected in the actual clinical settings (where they will be allogeneic grafts), this preclinical work demonstrates potential pitfalls of cell therapies and will enable the development of fail-proof protocol and directions, which will ultimately robustly work in the subretinal space to restore vision.…”

“…On day 50-70, we consistently observed retinal progenitor/eye field marker PAX6 [82,83], OTX2, pan-neural retina progenitor marker CHX10 (VSX2) [84][85][86][87], photoreceptor progenitor marker CRX [88,89], photoreceptors and amacrine progenitor marker NEUROD1 [90][91][92][93][94][95], photoreceptor progenitor marker BLIMP1 [96][97][98], amacrine marker CALB2 (Calretinin) [99][100][101], and retinal ganglion marker BRN3A [102] in hESC-derived retinal tissue. The retinal pigment epithelial layer was detected by immunolabeling with tight junction protein zonula occludens (ZO)-1 [103] and pigmented RPE marker PMEL17 [70,104] (Fig. 1g-n and Supplementary Fig.…”

“…In addition, small eye size makes it challenging to evaluate the size of a patch needed for therapy in a human eye to restore useful vision. In contrast, large-eye animals with inherited RD mutations such as dogs [61,62], cats [63][64][65], and pigs [66][67][68], and primates with induced RD [69][70][71][72] provide better opportunity to translate in vivo findings to blind patients. Both dogs and cats have an area centralis [65,73,74], which is functionally similar to primate macula.…”

Physiologic constraints of using exosomes in vivo as systemic delivery vehicles

“…However, once exosomes are produced ex vivo and scaled up to reach the volume of systemic administration, they resemble the status of the monoclonal antibodies produced at industrial scale (35) in that they face the problems such as chemical engineering, mixing, separation and purification complying with good manufacturing practice or the differentiated retinal pigment epithelium (RPE) cells sheet made from induced pluripotent stem cell (iPSC). (36,37) Monoclonal antibodies might provoke innate and adaptive immune responses and thus blood clearance was short. The second (or even the first) administration did not meet the purpose of maintaining sufficiently long circulation time (38,39).…”

Optimizing Donor Cellular Dissociation and Subretinal Injection Parameters for Stem Cell-Based Treatments

“…Although extensive data exist to demonstrate that iPSC‐derived retinal cells have the ability to integrate with the remaining host retina , different strategies for retinal cell replacement have resulted in variable success. For instance, nonautologous iPSC‐derived RPE cell transplants can result in minimal clinical adverse effects, but elicit an immune response at the cellular level in various animal models . On the other hand, autologous RPE transplantation studies in humans have resulted in retinal detachment, ocular inflammation, proliferative vitreoretinopathy, and/or hemorrhage post‐transplantation .…”