Photoreceptor survival in transplantation of autologous iris pigment epithelial cells to the subretinal space

Purpose: To investigate photoreceptor survival in transplantation of non-cultured iris pigment epithelial (IPE) cells to the subretinal space in a prospective experimental study. Methods: Upper iridectomies were carried out in the right eyes of 37 pigmented rabbits. Suspensions of freshly harvested autologous IPE cells (without culturing) were prepared and injected into the subretinal space of the same eye. Follow-up examinations were carried out using ophthalmoscopy and colour fundus photography. The rabbits were killed at 1, 2, 3 and 6 months, respectively, and the eyes examined with light and electron microscopy. Results: On histological examination, the photoreceptor cells were found to be well-preserved in grafted areas at 1-3 months. At 6 months, the photoreceptors generally disclosed a normal nuclear layer and long outer segments when overlying areas with single cells or clusters of transplanted IPE cells. Multilayers of cells in abundance, including native RPE cells and macrophages (stained with RAM 11), particularly under microfolds of the neural retina, were occasionally associated with photoreceptor damage and nuclear drop out from the outer retinal layer. There was no inflammatory response in the choroid and the choriocapillaris remained patent. Conclusion: The experiments show that grafting freshly harvested autologous IPE cells to the subretinal space is feasible and that the photoreceptors generally survive for at least 6 months when overlying the transplanted areas. Multilayers of abundant cells in the subretinal space may induce adverse focal effects on adjacent photoreceptors.