Subretinal implantation of a monolayer of human embryonic stem cell-derived retinal pigment epithelium: a feasibility and safety study in Yucatán minipigs

Abstract

Purpose A subretinal implant termed CPCB-RPE1 is currently being developed to surgically replace dystrophic RPE in patients with dry age-related macular degeneration (AMD) and severe vision loss. CPCB-RPE1 is composed of a terminally differentiated, polarized human embryonic stem cell-derived RPE (hESC-RPE) monolayer pre-grown on a biocompatible, mesh-supported submicron parylene C membrane. The objective of the present delivery study was to assess the feasibility and 1-month safety of CPCB-RPE1 implantation in Yucatán minipigs, whose eyes are similar to human eyes in size and gross retinal anatomy. Methods This was a prospective, partially blinded, randomized study in 14 normal-sighted female Yucatán minipigs (aged 2 months, weighing 24-35 kg). Surgeons were blinded to the randomization codes and postoperative and post-mortem assessments were performed in a blinded manner. Eleven minipigs received CPCB-RPE1 while three control minipigs underwent sham surgery that generated subretinal blebs. All animals except two sham controls received combined local (Ozurdex™ dexamethasone intravitreal implant) and systemic (tacrolimus) immunosuppression or local immunosuppression alone. Correct placement of the CPCB-RPE1 implant was assessed by in vivo optical coherence tomography and postmortem histology. hESC-RPE cells were identified using immunohistochemistry staining for TRA-1-85 (a human marker) and RPE65 (an RPE marker). As the study results of primary interest were nonnumerical no statistical analysis or tests were conducted. Results CPCB-RPE1 implants were reliably placed, without implant breakage, in the subretinal space of the minipig eye using surgical techniques similar to those that would be used in humans. Histologically, hESC-RPE cells were found to survive as an intact monolayer for 1 month based on immunohistochemistry staining for TRA-1-85 and RPE65. Conclusions Although inconclusive regarding the necessity or benefit of systemic or local immunosuppression, our study demonstrates the feasibility and safety of CPCB-RPE1 subretinal implantation in a comparable animal model and provides an encouraging starting point for human studies.

A Systematic Review on Transplantation Studies of the Retinal Pigment Epithelium in Animal Models

“…In larger eyed animals, such as rabbits, pigs, and monkeys, the lens:vitreuscavity ratio is much smaller and more space is available to insert instruments. RPE sheets are usually placed using forceps or custom-made delivery tools [81][82][83]. Before placement of the graft, a complete vitrectomy is mostly performed, which is impossible in rodent eyes so far.…”

Cell-based therapeutic strategies for replacement and preservation in retinal degenerative diseases

“…Preclinical studies focused on the subretinal transplantation of CPCB-RPE1 into the Yucatan mini pig and analysis was performed at three months after implantation (Brant Fernandes et al, 2016). The CPCB-RPE1 implants survived, and the ESC-RPE cells still formed an intact monolayer (Brant Fernandes et al, 2016; Koss et al, 2016). No intraocular or systemic tumors were detected, but normal retinal lamination around injection site was disrupted.…”

Functional Voltage-Gated Calcium Channels Are Present in Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium

“…Stem cells provide potential for the development of transplantation therapies producing a limitless source of RPE cells for the treatment of AMD and other RPE‐originated retinal dystrophies . Remarkably, such therapies are already being subjected to clinical trials for AMD and Stargardt's macular dystrophy as well as to several preclinical trials . Stem cell‐derived RPE has been demonstrated to resemble native tissue in many respects: it has been shown to have a proteome closely similar to the native counterpart , phagocytose photoreceptor outer segment (POS) fragments , secrete vascular endothelial growth factor (VEGF) , and participate in the functional visual cycle .…”