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Pseudoxanthoma elasticum (PXE) is a rare metabolic disease with autosomal recessive inheritance. The manifestation in PXE is represented by retinal complications, pseudoxanthomas of the skin folding areas, and arterial calcification. The retinal complications are caused by the calcification of Bruch's membrane beneath retinal pigment epithelial cells (RPE) that can lead to retinal macular degeneration. The exact mechanism for the retinal pathophysiology is not known, and patients have variable symptoms and findings. Two induced pluripotent stem cell (hiPSC) lines from a patient carrying the common homozygous mutation c.3421C > T, p.Arg1141X in the ATP‐binding cassette transporter gene (ABCC6; OMIM264800) were established and fully characterized. Then, RPE cells were differentiated, and molecular and functional characterization was conducted as a comparison to healthy controls. Data demonstrated that PXE‐specific high‐quality hiPSC lines can be established from a skin biopsy regardless of the skin‐related disease phenotype and disease‐specific RPE differentiation is feasible. The molecular and functional assessment of the PXE‐specific RPE indicated increased pigmentation and reduced epithelial barrier functions as well as phagocytosis activity as compared to healthy controls. Although preliminary data, this indicates possible RPE‐dependent factors that might explain the individual vulnerability of the retinas for macular degeneration in PXE. Future validation of the novel findings with additional PXE patients will be important. [ABSTRACT FROM AUTHOR]

Background: Differentiation of functional limbal stem cells (LSCs) from human pluripotent stem cells (hPSCs) is an important objective which can provide novel treatment solutions for patients suffering from limbal stem cell deficiency (LSCD). Yet, further characterization is needed to better evaluate their immunogenicity and regenerative potential before clinical applications. Methods: Human PSCs were differentiated towards corneal fate and cryopreserved using a clinically applicable protocol. Resulting hPSC-LSC populations were examined at days 10–11 and 24–25 during differentiation as well as at passage 1 post-thaw. Expression of cornea-associated markers including PAX6, ABCG2, ∆Np63α, CK15, CK14, CK12 and ABCB5 as well as human leukocyte antigens (HLAs) was analyzed using immunofluorescence and flow cytometry. Wound healing properties of the post-thaw hPSC-LSCs were assessed via calcium imaging and scratch assay. Human and porcine tissue-derived cultured LSCs were used as controls for marker expression analysis and scratch assays at passage 1. Results: The day 24–25 and post-thaw hPSC-LSCs displayed a similar marker profile with the tissue-derived LSCs, showing abundant expression of PAX6, ∆Np63α, CK15, CK14 and ABCB5 and low expression of ABCG2. In contrast, day 10–11 hPSC-LSCs had lower expression of ABCB5 and ∆Np63α, but high expression of ABCG2. A small portion of the day 10–11 cells coexpressed ABCG2 and ABCB5. The expression of class I HLAs increased during hPSC-LSCs differentiation and was uniform in post-thaw hPSC-LSCs, however the intensity was lower in comparison to tissue-derived LSCs. The calcium imaging revealed that the post-thaw hPSC-LSCs generated a robust response towards epithelial wound healing signaling mediator ATP. Further, scratch assay revealed that post-thaw hPSC-LSCs had higher wound healing capacity in comparison to tissue-derived LSCs. Conclusions: Clinically relevant LSC-like cells can be efficiently differentiated from hPSCs. The post-thaw hPSC-LSCs possess functional potency in calcium responses towards injury associated signals and in wound closure. The developmental trajectory observed during hPSC-LSC differentiation, giving rise to ABCG2+ population and further to ABCB5+ and ∆Np63α+ cells with limbal characteristics, indicates hPSC-derived cells can be utilized as a valuable cell source for the treatment of patients afflicted corneal blindness due to LSCD. [ABSTRACT FROM AUTHOR]

Background: Human pluripotent stem cells (hPSCs) provide a promising cell source for retinal cell replacement therapy but often lack standardized cell production and live-cell shipment logistics as well as rigorous analyses of surgical procedures for cell transplantation in the delicate macula area. We have previously established a xeno- and feeder cell-free production system for hPSC differentiated retinal pigment epithelial (RPE) cells, and herein, a novel immunosuppressed non-human primate (NHP) model with a disrupted ocular immune privilege is presented for transplanting human embryonic stem cell (hESC)-derived RPE on a scaffold, and the safety and submacular graft integration are assessed. Furthermore, the feasibility of intercontinental shipment of live hESC-RPE is examined. Methods: Cynomolgus monkeys were systemically immunosuppressed and implanted with a hESC-RPE monolayer on a permeable polyester-terephthalate (PET) scaffold. Microscope-integrated intraoperative optical coherence tomography (miOCT)-guided surgery, postoperative follow-up incorporated scanning laser ophthalmoscopy, spectral domain (SD-) OCT, and full-field electroretinography (ERG) were used as outcome measures. In addition, histology was performed after a 28-day follow-up. Results: Intercontinental cell shipment, which took >30 h from the manufacturing to the transplantation site, did not alter the hESC-RPE quality. The submacular hESC-RPE xenotransplantation was performed in 11 macaques. The miOCT typically revealed foveal disruption. ERG showed amplitude and peak time preservation in cases with favorable surgical outcomes. Histology confirmed photoreceptor preservation above the grafts and in vivo phagocytosis by hESC-RPE, albeit evidence of cytoplasmic redistribution of opsin in photoreceptors and glia hypertrophy. The immunosuppression protocol efficiently suppressed retinal T cell infiltration and microglia activation. Conclusion: These results suggest both structural and functional submacular integrations of hESC-RPE xenografts. It is anticipated that surgical technique refinement will further improve the engraftment of macular cell therapeutics with significant translational relevance to improve future clinical trials. [ABSTRACT FROM AUTHOR]

Purpose: To study immunogenic properties of human embryonic stem cell–derived retinal pigment epithelium (hESC‐RPE) and to evaluate subretinal xenotransplantation of hESC‐RPE on porous polyethylene terephthalate (PET) in rabbits. Methods: Human ESC‐RPE cells were characterized by morphology, transepithelial electrical resistance (TER), protein expression and photoreceptor outer segment phagocytosis in vitro. Expression of major histocompatibility complex (MHC) proteins was assessed in conventionally or xeno‐free produced hESC‐RPE ± interferon‐gamma (IFN‐γ) stimulation (n = 1). Xeno‐free hESC‐RPE on PET with TER < 200 Ω·cm2 > or PET alone were transplanted into 18 rabbits with short‐term triamcinolone ± extended tacrolimus immunosuppression. Rabbits were monitored by spectral domain optical coherence tomography. After 4 weeks, the eyes were processed for histology and transmission electron microscopy. Results: Upon in vitro IFN‐γ stimulation, xeno‐free hESC‐RPE expressed lower level of MHC‐II proteins compared to the conventional cells. Outer nuclear layer (ONL) atrophy was observed over the graft in most cases 4 weeks post‐transplantation. In 3/4 animals with high TER hESC‐RPE, but only in 1/3 animals with low TER hESC‐RPE, ONL atrophy was observed already within 1 week. Retinal cell infiltrations were more frequent in animals with high TER hESC‐RPE. However, the difference was not statistically significant. In three animals, preservation of ONL was observed. Weekly intravitreal tacrolimus did not affect ONL preservation. In all animals, hESC‐RPE cells survived for 4 weeks, but without tacrolimus, enlarged vacuoles accumulated in hESC‐RPE (n = 1). Conclusions: Xenografted xeno‐free hESC‐RPE monolayers can survive and retain some functionality for 4 weeks following short‐term immunosuppression. The preliminary findings of this study suggest that further investigations to improve transplantation success of hESC‐RPE xenografts in rabbits should be addressed especially toward the roles of hESC‐RPE maturation stage and extended intravitreal immunosuppression. [ABSTRACT FROM AUTHOR]