An Innovative Surgical Technique for Subretinal Transplantation of Human Embryonic Stem Cell-Derived Retinal Pigmented Epithelium in Yucatan Mini Pigs: Preliminary Results

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.

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

“…In the United States, Regenerative Patch Technologies has a Phase I/IIa clinical trial for dry AMD on the safety and efficacy of subretinal transplantation of ESC-RPE seeded on an ultrathin polymeric parylene-C scaffold, termed CPCB-RPE1 (NCT02590692). 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).…”

“…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.…”

“…Delivery of an RPE sheet or scaffold close to the macula is an invasive procedure and carries an added risk of compromising remaining macular vision. If the cells are attached to a scaffold, then RPE cells will not need to migrate from the injection site or find availability on the Bruch’s membrane; however, synthetic scaffold materials may cause structural differences in RPE cells, physically separate the RPE from the underlying choroid, and cause inflammation (Bhatt et al, 1994; Brant Fernandes et al, 2016; Diniz et al, 2013; Lee et al., 2002; Sorkio et al, 2014; Tezel and Del Priore, 1998). The caveat to single cell RPE suspensions is the distribution, polarity, and attachment to the Bruch’s membrane, as non-integrating RPE cells are at risk for ingestion by macrophages (Westenskow et al., 2016).…”

Controllable Immunosuppression in Pigs as a Basis for Preclinical Studies on Human Cell Therapy

“…Controllable Immunosuppression in Pigs as a Basis for Preclinical Studies on Human Cell Therapy DOI: http://dx.doi.org /10.5772/intechopen.89521 Transplantation of human embryonic stem cell-derived retinal pigmented epithelium was also performed in pigs [19]. Although immunosuppression was precarious, cyclosporine was added in the feed and their blood level 2 h after administration was only 1 pg/ml, and the graft tissue was detectable after 3 months.…”

Subretinal Injection: A Review on the Novel Route of Therapeutic Delivery for Vitreoretinal Diseases

“…It have been reported to be feasible and safe after subretinal implantation, with neither cell migration from the scaffold nor development of ocular or systemic tumors [77] . It therefore constitutes a promising start for human studies [78] .…”