Abstract
Purpose :
Age-related macular degeneration (AMD) is a major cause of vision impairment worldwide. Characterized by the dysfunction and loss of retinal pigment epithelium (RPE) and photoreceptors, cell replacement has emerged as a potential therapeutic strategy for AMD, yet it is still unclear which donor cell characteristics are required to yield the best transplantation outcome. Here, we thus compared the influence of RPE passage age in culture and RPE cell numbers on graft monolayer formation and potential photoreceptor rescue after transplantation of hiPSC-derived RPE suspensions.
Methods :
Tail vein injection of 30 mg/kg NaIO3 was used to deplete endogenous RPE in adult female C57Bl/6Jrj mice. One week later, hiPSC-derived RPE was transplanted subretinally as a single cell suspension with vitreal immune suppression, using 50,000 or 100,000 cells of P1 or P2 RPE. Three weeks later, eyes were collected and analysed by EM and IHC.
Results :
Both P1 and P2 RPE showed the capacity for monolayer formation, pigmentation and proper polarization in culture and in vivo. However, P1 RPE proved superior for transplantation: it covered roughly 30% of the total retinal area, and the vast majority of the cells presented in the form of a well polarized monolayer positioned on the Bruch’s membrane with basal nuclei and collagen IV deposition, while melanin pigment, ATPase and F-actin was enriched apically. RPE flatmounts confirmed the presence of an organized, ZO-1+ cobblestone morphology in human monolayer regions. P2 RPE however covered only 15% of the retinal area and showed a low monolayer proportion, with the majority of cells instead forming disorganized clusters. Interestingly, P2 but not P1 RPE induced an intense immune reaction in the host.
Importantly, human monolayer formation was associated with an improved neuroretinal structure and monolayer formation was further increased by using 50,000 instead of 100,000 P1 RPE cells (90% and 70% of the retinal area covered, respectively).
Conclusions :
The capacity for monolayer formation and hence the potential for photoreceptor rescue via hiPSC-derived RPE transplantations is greatly influenced by the cell age in culture and the transplanted cell number in the NaIO3 mouse model of RPE loss. A detailed understanding of the differences leading to such variation in outcome will be essential to improve RPE cell suspension transplantations also in a clinical setting.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.