Growth of IPE and RPE Cells on Biological and Artificial Substrata

Abstract

Purpose: : Vision recovery in retinal degeneration at minimum requires the replacement of degenerated RPE cells. Since previous studies have shown that transplanted pigment epithelial cells in suspension do not form a monolayer on Bruch’s membrane, it may be necessary to transplant in vitro pre-formed pigment epithelial cell monolayers at the location of the exposed photoreceptors. Here we have analyzed four possible materials as substrates for pigment cell growth in vitro and their biocompatibility in vivo.

Methods: : Primary bovine retinal pigment epithelial (RPE) and iris pigment epithelial (IPE) cells were cultured on equine collagen type I, human amniotic membrane, silk and polylactic acid (PLA) electrospun nanofibers. Surface characteristics of the substrata were examined by SEM. Cell morphology, viability and proliferation were evaluated for each substratum as were transepithelial resistance of monolayers. Tight junction formation was evaluated by ZO-1 immunocytochemistry. Biocompatibility of materials was evaluated by subconjunctival transplantation in rabbits.

Results: : Of the four materials analyzed equine type I collagen was most similar to Bruch’s membrane in its surface topology. Primary RPE and IPE cells adhered and formed monolayers on all four materials. Once confluent all monolayers developed a transepithelial resistance with highest values for cells on collagen membranes of approximately 10 Ohm*cm². Except for PLA nanofibers the other materials show good stability in water and handling characteristics in vitro and during subconjunctival transplantation. Biocompatibility was best for collagen type I, followed by human amniotic membrane and PLA nanofibers. Silk caused a mild inflammatory reaction with encapsulation of the material and vessel ingrowth.

Conclusions: : Of the four materials evaluated collagen type I and amniotic membranes have the most suitable characteristics to be used as a scaffold for the growth and eventual subretinal transplantation of pigment epithelial cells.

Keywords: retinal pigment epithelium • transplantation • cell adhesions/cell junctions