Stem cells: a source for neuron repair in retinal disease.

Several features of the eye make it an excellent candidate for cell-based therapy to treat corneal and retinal degenerative disease. Corneal and retinal stem cells have been identified in the adult human eye. Advances in the stem cell field, including methods for cell purification, culture, and molecular characterization, have made it easier to manipulate eye stem cells. Moreover, delivery, sequestration, tracking, and measurement of outcomes of transplanted cells are both feasible and easier for the eye than for other tissues. These factors, together with our understanding of the molecular pathways that regulate eye development, have resulted in promising results in transplantation of cells to the cornea and retina. While there is certainly reason for cautious optimism, several obstacles remain before this will ever be a clinical reality, including identification of the most appropriate source of stem cells, the long-term efficacy of cell transplantation in the context of ongoing disease, and the potential of transplanted cells to give rise to tumours.