Embryonic stem cells: potential source for ocular repair

Many ocular diseases, such as retinitis pigmentosa and age-related macular degeneration, reflect damage to specific cells that are not normally repaired or replaced. Preliminary results of animal studies suggest that these degenerative diseases may be treatable by transplantation of healthy fetal cells. However, obtaining a sufficient number of suitable donor cells remains a problem. The isolation of human embryonic stem (ES) cells has drawn much attention because of their potential clinical application for patients with these degenerative diseases. Because ES cells have the potential to generate all adult cell types, ocular diseases resulting from the failure of specific cell types would be potentially treatable through the transplantation of differentiated cells derived from ES cells. In addition, because ES cells can proliferate indefinitely in their undifferentiated state, they are expected to alleviate the problem of the shortage of donor cells for cell-replacement therapy. Recently, reproducible and efficient differentiation methods for the generation of lens cells, retinal neurons, and retinal pigment epithelial (RPE) cells from ES cells have been developed. This review focuses especially on these ocular cells differentiated from ES cells. We will also discuss the potential therapeutic uses of ES cells for the treatment of ocular diseases.