Transplantation of Human Amniotic Membrane and ex vivo Expanded Homologous Retinal Pigment Epithelial Cells on Human Amniotic Membrane into Subretinal Space of New Zealand White Rabbits

Abstract

Abstract: : Purpose: To evaluate the feasibility of using amniotic membrane (AM) as a basement membrane (BM) substitute for Bruch’s membrane reconstruction and RPE sheet transplantation. Methods: 12 New Zealand white rabbits underwent 3–port vitrectomy with subretinal bleb detachment. Six received subretinal implantation of epithelial denuded AM (dAM), while another 6 received subretinal implantation of dAM on which RPE had been expanded from homologous Dutch belted rabbits in culture. We performed slit lamp examination, ophthalmoscopy and fundus color photography. The animals were euthanized 6 weeks after surgery. Samples of transplanted area were evaluated by conventional histology, immunohistochemistry and transmission electron microscopy. Results: The post–operative ophthalmoscopic and biomicroscopic examinations revealed no signs of inflammation in both groups. All transplants kept the form and transparency over the entire period of observation. Histology disclosed retinal glial cell activation in all transplanted eyes, mild inflammation in eyes with dAM, and occasionally moderate inflammatory signs in eyes with dAM–RPE. We observed good tolerance and integration of denuded AM in subretinal space with moderate retinal changes. Host RPE cells formed a monolayer on the basement membrane of dAM, especially at the edges of transplants, where photoreceptor outer segments were detectable. Destruction of the overlaying retina and disorganization of homologous RPEs were observed in AM–RPE transplants. Conclusions: Epithelially denuded AM may be useful for treating defects in Bruch's membrane to serve as a BM to allow the repopulation of the host’s RPE. The less favorable results of homologous AM–RPE transplantation could be explained by either immune rejection or related to technique–dependent, intraoperative damage of RPE, or both. This may be solved by the use of an autologous source of RPE.

Keywords: transplantation • retinal pigment epithelium • retina