Transplantation of retinal pigment epithelium and photoreceptors generated concomitantly via small molecule-mediated differentiation rescues visual function in rodent models of retinal degeneration

Abstract

Background Age-related macular degeneration (AMD) is a result of degeneration/damage of the retinal pigment epithelium (RPE) while retinitis pigmentosa (RP), an inherited early-onset disease, results from premature loss of photoreceptors. A promising therapeutic approach for both is the replacement of lost/damaged cells with human induced pluripotent stem cell (hiPSC)-derived retinal cells. Methods The aim of this study was to investigate the in vivo functionality of RPE and photoreceptor progenitor (PRP) cells derived from a clinical-grade hiPSC line through a unified protocol. De novo-generated RPE and PRP were characterized extensively to validate their identity, purity, and potency. Results RPE expressed tight junction proteins, showed pigmentation and ciliation, and secreted polarization-related factors vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF). PRP expressed neural retina proteins and cone and rod markers, and responded to KCl-induced polarization. Transcriptomic analysis demonstrated an increase in the expression of mature retinal tissue-specific genes coupled with concomitant downregulation of genes from undesired lineages. RPE transplantation rescued visual function in RCS rats shown via optokinetic tracking and photoreceptor rescue. PRP transplantation improved light perception in NOD.SCID-rd1 mice, and positive electroretinography signals indicated functional photoreceptor activity in the host’s outer nuclear layer. Graft survival and integration were confirmed using immunohistochemistry, and no animals showed teratoma formation or any kind of ectopic growth in the eye. Conclusions To our knowledge, this is the first demonstration of a unified, scalable, and GMP-adaptable protocol indicating strong animal efficacy and safety data with hiPSC-derived RPE and PRP cells. These findings provide robust proof-of-principle results for IND-enabling studies to test these potential regenerative cell therapies in patients.

Cell Ferroptosis: New Mechanism and New Hope for Retinitis Pigmentosa

“…Induced pluripotent stem cell (iPSC) can differentiate to RPE and photoreceptor cells. Transplantation of these derived cells has been shown to rescue light perception and visual function in RCS rats and NOD.SCID-rd1 mice [83]. Another study also demonstrated that the long-term treatment of iPSC-derived RPE and photoreceptor cells effectively protected Pde6b knockout rats [93].…”

“…For people with impaired vision, a typoscope can be worn to improve their vision for reading. Meanwhile, RPE [83], retinal photoreceptor cell [84], retinal progenitor cell [85], and iris pigment epithelial cell (IPE) [86], have been selected as candidates for cell transplantation, with varying results. Some studies have successfully established the cultivation of photoreceptor cells.…”

Stem Cell Therapy for Retinal Degeneration: The Evidence to Date

“…None of the animals showed abnormal proliferation or teratoma formation; however, the graft was compromised in two animals due to inflammatory response. 15 Interestingly, co-transplantation of RPCs and RPE cells derived from iPSCs was superior to transplanting individual cell types, it resulted in better visual response and preservation of ONL in a rat model of retinal degeneration. 16 Further, in an animal model of RP, subretinally transplanted iPSC-derived CRX-expressing photoreceptor precursors engrafted at the inner nuclear layer (INL).…”

“…Some of them required surgical interventions to facilitate retinal attachment. Other adverse effects include inflammatory response due to the injections of the cells 15 or its factors. 42 These adverse effects might be due to the invasive nature of intravitreal transplantation, and thus further research on the optimal delivery route for each disease type is required.…”

A defined subset of clonal retinal stem cell spheres is biased to RPE differentiation

“…Loss of RPE cells will consequently result in loss of photoreceptors and subsequently blindness ( Hollyfield and Witkovsky, 1974 ; Miller et al., 2017 ; Mitrousis et al., 2020 ). Replacement of dead or dysfunctional RPE with stem cell-derived RPE along with photoreceptors is a promising alternative to treat age related macular degeneration (AMD) and some forms of retinitis pigmentosa (RP) ( Surendran et al., 2021 ). We suggest that the highly proliferative early RPE progenitor population in the CP spheres will provide an enriched and safe source to replace lost RPE in retinal degenerative diseases.…”