Experimental transplantation of IPE to the subretinal space-morphology and photoreceptor survival

Abstract

Background: Age-related macular degeneration (AMD) is associated with degeneration and subsequent loss of the retinal pigment epithelium (RPE). Transplantation of allogeneic RPE cells seems to induce graft rejection. Therefore, autotransplantation was suggested. Iris pigment epithelial cells (IPE) are embryologically similar to RPE.

Methods: Suspensions of freshly harvested autologous IPE cells (without culturing) were transplanted to the subretinal space of 37 rabbits. The eyes were examined with light and electron microscopy after 1, 2, 3 and 6 months, respectively.

Results: On histological examination, the photoreceptor cells were preserved in grafted areas at 1–3 months and the transplanted IPE formed one or more contiguous layers on top of native RPE. There was no inflammatory response in the choroid and the choriocapillaris remained patent.

The grafted area retained the same configuration over 6 months but then appeared less pigmented and the photoreceptors disclosed a normal appearance. Only in circumscribed locations with multilayers of cells was there a focal photoreceptor damage.

Conclusion: When grafting freshly harvested autologous IPE cells to the subretinal space the photoreceptors generally survive for at least 6 months overlying the transplanted areas. Our observations suggest a scenario of remodeling of the cellular layers in the subretinal space over time where grafted IPE cells form a compound layer with the native RPE. Autologous IPE cells seem to have a potential of supporting photoreceptors, maybe also in diseases with RPE degeneration.