Submitted to: Investigative Ophthalmology and Visual Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2006
Publication Date: 10/26/2006
Citation: Liang, L., Yan, R., Ma, W., Zhang, H., Wang, S. 2006. Exploring RPE as a source of photoreceptors: differentiation and integration of transdifferentiating cells grafted into embryonic chick eyes. Investigative Ophthalmology and Visual Science. 47(11):5066-5076. Interpretive Summary: Degeneration of photoreceptor cells in the eye is one of the main causes of human and chicken blindness. Retina Pigment Epithelium, commonly known as RPE, is a pigmented layer of non-neural cells under the retina of the eyes. RPE performs many functions necessary for the normal function of retina. Chicken embryos from a special genetic line and a commercial breeder company were used to study the properties of the RPE cells in relation to the photoreceptor cells. Our results suggested that RPE cells under proper genetic treatment could be a vital source of cells in rescuing or replacing impaired photoreceptor cells.
Technical Abstract: The possibility of generating photoreceptors through programming retina pigment epithelium (RPE) transdifferentiation by examining cell differentiation after transplantation into the developing chicken eye was examined. RPE cells were dissociated, cultured, and guided to transdifferentiate by infecting them with retrovirus expressing neuroD (RCAS-neuroD), using RCAS-GFP as a control. The cells were then harvested and microinjected into the developing eyes of day 5-7 chicken embryos, and their development and integration were analyzed. When grafted cells were present in a large number, multi-layered RPE-like tissues were formed, and the extra tissues were comprised of both grafted cells and host cells. None of the cells from the control culture expressed photoreceptor-specific genes. In contrast, most cells from RCAS-neuroD-infected culture remained de-pigmented. A large number of them expressed photoreceptor-specific genes, such as visinin and opsins. Antibodies against red opsin decorated the apical tips, as well as the cell bodies, of the grafted, transdifferentiating cells. In the subretinal space, Visinin+ cells aligned along the RPE or a RPE-like structure. When integrated into the host outer nuclear layer, grafted cells emanated elaborate axonal arboration into the outer plexiform layer of the host retina. The cultured RPE cells retained their remarkable regenerative capabilities. Cells guided to transdifferentiate along the photoreceptor pathway by neuroD developed a highly ordered cellular structure and could integrate into the outer nuclear layer. Our data suggest that through genetic programming RPE cells could be a potential source of photoreceptor cells.