Transplantation of human pluripotent stem cell-derived photoreceptors on a biocompatible scaffold in the S334ter rat

Abstract

Purpose : Disorganization of retinal grafts and reflux of donor cells during surgery can prevent optimal cell delivery in photoreceptor (PR) transplantation. For this study, we transplanted a novel biocompatible scaffold seeded with human pluripotent stem cell (hPSC)-derived PRs in the S334ter rat model of retinitis pigmentosa. To determine the impact of donor cell maturity on graft survival and cell differentiation in vivo, cells were transplanted at early- and mid-stages of differentiation.

Methods : An hPSC CRX^+/tdTomato reporter line was used to produce optic vesicle-like structures (OVs). Dissociated hPSC-OVs were seeded onto a micro-patterned polydimethylsiloxane (PDMS) scaffold at day 70 or day 115, which represent early and mid-stages of PR differentiation, respectively. After 1 month, punches from seeded PDMS scaffolds were transplanted into the subretinal space of adult immune-compromised S334ter rats. Eyes collected 2 or 6 months post-transplant (n=4 eyes each) were analyzed for PR survival, differentiation, and synaptic marker expression. Confocal images were quantified using Columbus image analysis software. Statistical analyses were performed with GraphPad Prism.

Results : Donor cells transplanted on PDMS scaffolds survived and were observed in the subretinal space at both 2 and 6 months post-transplantation. A large percentage of surviving donor cells differentiated into mature PRs during this period. In vivo, PR precursors mature to both rods and cones, which form outer segments and express key synaptic markers. Proliferation of residual retinal progenitor cells (RPCs) and ectopic cell migration was also noted in transplants with scaffolds seeded with day 70 hPSC-OVs. This was largely mitigated in transplants with scaffolds seeded with day 115 hPSC-OVs, where proliferation was low and high percentages of transplanted PRs were maintained out to 6 months, the latest time point examined.

Conclusions : This study demonstrates the use of a novel, biocompatible PDMS scaffold to successfully deliver hPSC-PRs in an organized manner into the subretinal space of degenerate rat retinas. hPSC-PRs survive and mature long-term in vivo. In addition, proliferation of residual RPCs was dramatically reduced when seeding scaffolds with more mature cultures prior to transplantation, thus maintaining a high percentage of PRs over time in vivo.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.