Retinal progenitor sheet transplants improve vision in a severe retinal degenerate (RD) rat

Abstract

Purpose : To test if retinal progenitor sheets can develop laminated photoreceptor layers and improve vision after transplantation to a severe retinal degeneration (RD) rat.

Methods : On day 19 of gestation (day of conception day 0), fetuses were removed by cesarean section from timed-pregnant rats. Dissected retinas were incubated in BDNF/GDNF microspheres overnight at 4°C, and then transplanted to the subretinal space of Rho S334ter-3 retinal degeneration (RD) rats. Development of transplants was monitored by high resolution optical coherence tomography (SD-OCT). Visual function was assessed by optokinetic test (OKT), light-dark box test (LDBT) and single-unit cortical recording using multi-electrode arrays, from higher visual areas (anterior lateral [AL] and lateral medial [LM] cortex). Sinusoidal gratings with optimized parameters and natural images were used to measure details of the receptive fields. Cryostat sections through transplants were stained with hematoxylin & eosin (H&E); or processed for immunohistochemistry (IHC) to label donor cells, retinal cell types and synaptic markers.

Results : After transplantation, the fetal retinal sheets developed and matured into various retinal cells and integrated with the degenerating host retina. Transplanted eyes showed vision improvement by OKT and LDBT. Furthermore, we recorded more than 200 cells from higher visual cortical areas of RD, transplanted RD and normal rats. Based on our findings only 10 percent of light-responsive cells showed selectivity in RD rats while this number was 24 and 50 percent for transplanted and control animals respectively. Transplants developed mostly into rosetted structures, but some were laminated similar to normal retina. Photoreceptors in the transplants were positive for photoreceptor markers, and apparently developed outer segments.

Conclusions : Our data shows that after transplantation into the RD rats, retinal sheets can mature into retinal cells, integrate with the host retina, and improve visual function, including the tuning parameters and selectivity of V2 neurons.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.