Duration 5min, Q&A 3min
Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium Implant Is Safe and Effective in Rescuing Degenerating Photoreceptors
Retinal pigment epithelium (RPE) loss is the key event in atrophic age-related macular degeneration (AMD). Human embryonic stem cell-derived RPE (hESC-RPE) is a potential source to replace lost RPE in macular degeneration. Here, we present structural and functional consequences of polarized hESC-RPE implantation in an animal model of retinal degeneration.
hESC RPE cells were derived from H9 human embryonic stem cell line and seeded on a permeable parylene substrate to attain polarization. Royal college of Surgeon (RCS) rats were used as an animal model of retinal degeneration.
hESC-RPE implants were implanted in the subretinal space through a trans-scleral approach in 28- to 30-day-old RCS rats. Implantation of parylene without hESC-RPE and injection of hESC-RPE suspension were performed in control groups. The animals were kept under an immunosuppressive regimen. To evaluate tumor formation, subretinal injection of hESC-RPE suspension and undifferentiated human stem cells were compared. Visual behavior testing by optokinetic head tracking (OKN) and luminescence threshold mapping from the superior colliculus were performed to evaluate functional outcomes. In eye sections, the photoreceptor outer segment and outer nuclear layer (ONL) were quantified as anatomic evidence of retinal rescue. Phagocytic function of hESC-RPE was confirmed by immunostaining for rhodopsin.
Results and Conclusion
ONL preservation was significantly better in hESC-RPE-implanted animals compared to parylene-only and non-treated eyes 60 days after implantation. ONL thickness correlated with OKN response and light stimulus detection threshold. Implanted eyes showed higher ONL nuclei numbers (183±16 cells) than non-treated eyes (15±6 cells) at 120 days after the surgery. hESC-RPE-implanted RCS rats showed significantly better visual acuity and contrast sensitivity compared to non-implanted eyes 60 days after implantation. Rhodopsin was detected within the implanted RPE cells 2 and 6 months after implantation, showing phagocytosis of rat photoreceptor outer segments by the implanted hESC-RPE. Neither cell migration beyond the parylene membrane nor tumor formation was detected in hESC-RPE-implanted eyes, whereas four of fourteen rats injected with undifferentiated stem cell suspension developed intraocular tumors. Significantly more CD68-positive macrophages were observed in parylene-implanted compared to hESC-RPE-implanted animals. In conclusion, subretinal implantation of polarized hESC-RPE is a safe and effective approach for preserving outer retina in an animal model of macular degeneration. These data provide preclinical proof-of-concept for applying the same approach for the treatment of human atrophic AMD.
[ Keyword ]
Stem cell / Retinal pigment epithelium / Macular degeneration
[ Conflict of Interest ]