Optimizing a Biodegradable Scaffold for Clinical Applications of iPS Cell Derived RPE Tissue

Abstract

Purpose : Previous work suggests replacing diseased RPE with a healthy autologous RPE sheet can provide vision rescue for AMD patients. Here we evaluate biodegradable and non-biodegradable substrates for RPE sheet maturation, biocompatibility, and degradation in vivo and in vitro.

Methods : Induced pluripotent stem (iPS) cells are differentiated into RPE using a directed-differentiation protocol with three phases: neuroectoderm/RPE progenitor, committed and immature RPE. Immature RPE cells are seeded onto electrospun poly(lactic-co-glycolic acid) (PLGA) or non-biodegradable polyester scaffolds. RPE on these two scaffolds are evaluated in vitro using molecular and electrophysiological assays and in vivo for biodegradability, mechanical properties, and biocompatibility. Mature tissues are implanted in a laser-injured pig eye subretinal space and evaluated using optical coherence tomography, multifocal ERG, and histology.

Results : PLGA and polyester substrates produce functionally similar tissues in vitro. Electrophysiological and gene expression experiments show that RPE cells grown on PLGA scaffolds and polyester membranes form single cell layer, develop transepithelial resistance more than 200 ohms/cm², and show electrophysiological responses to [K+] and ATP changes that are similar to responses previously observed in native human RPE. In vitro evaluation of PLGA scaffolds showed complete degradation over 8-10 weeks, without affecting RPE monolayer integrity. Following transplantation into pig subretinal space, PLGA scaffold continued to degrade without causing toxicity to the RPE monolayer. RPE monolayer on biodegradable scaffold rescued laser-induced RPE and retina injury. These PLGA scaffolds showed comparable integration results to polyester implants.

Conclusions : We confirm that biodegradable substrates are suitable for RPE transplantation in degenerative eye diseases. RPE cells behave similar on biodegradable and non-biodegradable substrates, forming a tissue similar to native RPE in its molecular and functional properties. Biodegradability and biocompatibility data from a pig model demonstrates that PLGA scaffold is safe, with the added benefit of being resorbed by the surrounding tissue over time, leaving no foreign material in the eye.

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