A Porcine Model of Retinal Pigment Epithelium (RPE) Injury to Test the Efficacy of Human Induced Pluripotent Stem Cell– derived RPE (hiPSC-RPE) Transplants.

Abstract

Purpose : RPE replacement therapy has potential for the treatment of retinal degenerative diseases. Autologous hiPSC-RPE transplantation avoids immune rejection and the complications of long-term immunosuppression. We have developed a porcine model of localized retinal degeneration and a surgical procedure to test the ability of hiPSC-RPE cell transplants to protect RPE injury induced retinal degeneration.

Methods : A micropulse laser with a 3% duty cycle and power between 600-750 mW was used to create a 5.4 mm²confluent grid lesion in 3 months old pigs. Histologic evaluation (n=15) was done on days 0, 2, and weeks 1, 2, 3 and 6 after laser. In selected cases, (n=14) 2 days after laser a standard 25G 4 port pars plana vitrectomy was done and a localized retinal detachment (RD) was created with a 38G cannula. Using a custom made injection tool, hiPSC-RPE cells on a PLGA biodegradable scaffold were introduced into the subretinal space. The retina was attached using fluid air exchange (FAX) without retinopexy.

Results : Laser treatment leads to an immediate RPE detachment with edema. Bruch’s membrane and choriocapillaries are not damaged. By day 2 there is extensive RPE and photoreceptor damage but the photoreceptor nuclear layer (ONL) is still present. Over the next 3 weeks the ONL shrinks in the areas not transplanted by the hiPSC-RPE scaffold with slow recovery after 5 - 6 weeks. During surgery a localized RD is induced in the laser treated area. The injector is introduced into the subretinal space through a retinotomy and the RPE scaffold is released. FAX is used to attach the RD and to close the enlarged sclerotomy via surface tension. Major complications include hemorrhage, proliferative vitreous retinopathy, and immune reaction against human cells. The overall success rate of the procedure is more than 50%.

Conclusions : We have developed a porcine laser model for RPE ablation with selective outer retina damage. Our model and surgical techniques are suitable for in- vivo functional evaluation of hiPSC-RPE transplants and their ability to rescue laser-damaged outer retina.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.