In Vivo Functional Comparison of Polarized and Non-polarized hESC-RPE Cells Transplantation in RCS Rats

Abstract

Purpose: To evaluate the visual functional differences in dystrophic Royal College of Surgeons (RCS) rats after transplantation of retinal pigment epithelial cells derived from H9 human embryonic stem cells (hESC-RPE) delivered as a polarized monolayer cell sheet on a thin parylene membrane or non- polarized cell suspension.

Methods: For transplantation of polarized monolayer cell sheet, hESC-RPE cells were cultured for 3 weeks on parylene sheets; for transplantation of cell suspension, hESC-RPE cells were cultured for 3 weeks and digested into cell a suspension before implantation. Subretinal implantation of hESC-RPE /parylene (approximately 3000 cells/implant, n=6) and subretinal injection of hESC-RPE cells (10 ⁵/2µl, n=6) was performed in 27 to 29 day old RCS rats. Six non-implanted RCS rats served as controls. Prednisolone was administered through drinking water (0.002mg/liter) for the entire period of study. Post-surgical evaluation was performed using spectral-domain optical coherence tomography (SD-OCT). Optokinetic head tracking (OHT) testing and luminance threshold measurement from the superior colliculus (SC) were employed for visual functional assessments at 2 months post-surgery.

Results: Based on SD-OCT, preservation of the retinal layers in the transplant area was observed in both implant groups. In hESC-RPE/parylene implanted animals, the head tracking duration was higher (4.06±0.76 sec/min) compared to the suspension injection group (2.56±0.53 sec/min). SC recording demonstrated significantly lower (p=0.008) luminance threshold in the hESC-RPE/parylene implant group (-5.15±0.27 log cd/m²) compared to the subretinal injection group (-3.31±0.49 log cd/m²). SC luminance threshold map showed good correlation with the location of the hESC-RPE/parylene in the retina.

Conclusions: hESC-RPE when implanted as a monolayer or injected as cell suspension demonstrated preservation of the retina in RCS rats up to 2 months post-surgery. Better visual preservation was observed in the hESC-RPE/parylene implanted animals as evidenced by SC luminance threshold measurement and OHT testing. Our study suggests that implantation of hESC-RPE/parylene may be a more desirable therapeutic approach for disease conditions related to RPE dysfunction such as dry age-related macular degeneration.

Keywords: 701 retinal pigment epithelium • 687 regeneration • 412 age-related macular degeneration