[RPE transplantation: the challenges and the future]

Transplantation of RPE cells represents a potential therapeutic intervention for various retinal degenerations including complex, multifactorial age-related macular degeneration (AMD). Prerequisite for a successful RPE transplantation is the isolation of suitable cells, which must establish themselves in the host eye to develop functionality similar to that of healthy RPE cells in vivo. Autologous cells can be harvested from the peripheral retina. Ex vivo gene manipulation offers the possibility that even a dysfunctional donor RPE cell can be restored to perform a required specific function in the retina which may in turn help prevent or slow down the degenerative process in the host eye. The problem of cultured RPE cells is that they lose many of their normal phenotypic characteristics, which also leads to a reduction of their functional capacity. Currently highly "stressed" RPE cells are transplanted, whether fresh or cultured, which may not establish their normal in vivo functions. The generation of a genetically engineered cell line with all the functions of a healthy RPE cell and the use of retinal stem cells represent alternative and promising approaches for the future.