Exploring RPE as a source of photoreceptors: differentiation and integration of transdifferentiating cells grafted into embryonic chick eyes.
OBJECTIVE
To study the possibility of generating photoreceptors through programming RPE transdifferentiation by examining cell differentiation after transplantation into the developing chick eye.


METHODS
RPE was isolated, and the cells were dissociated, cultured, and guided to transdifferentiate by infection with retrovirus expressing neuroD (RCAS-neuroD), using RCAS-green fluorescence protein (GFP) as a control. The cells were then harvested and microinjected into the developing eyes of day 5 to day 7 chick embryos, and their development and integration were analyzed.


RESULTS
Cells from the control culture integrated into the host RPE. When grafted cells were present in large number, multilayered RPE-like tissues were formed, and the extra tissues consisted of 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 depigmented. A large number of them expressed photoreceptor-specific genes, such as visinin and opsins. Antibodies against red opsin decorated the apical tips and the cell bodies of the grafted, transdifferentiating cells. In the subretinal space, visinin(+) cells aligned along the RPE or an RPE-like structure. When integrated into the host outer nuclear layer, grafted cells emanated elaborate, axonal arborization into the outer plexiform layer of the host retina.


CONCLUSIONS
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. These data suggest that, through genetic programming, RPE cells could be a potential source of photoreceptor cells.
Liang
Lina
L
Department of Ophthalmology, University of Alabama at Birmingham, 700 South 18th Street, Birmingham, AL 35233, USA.
Yan
Run-Tao
RT
Ma
Wenxin
W
Zhang
Huanmin
H
Wang
Shu-Zhen
SZ
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000494:pharmacology; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002642:Chick Embryo; D053595:Embryonic Stem Cells / Q000166:cytology / Q000637:transplantation*; D019084:Fluorescent Antibody Technique, Indirect; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000494:pharmacology; D010786:Photoreceptor Cells / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000601:surgery*; D017299:Rod Opsins / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D009419:Nerve Tissue Proteins; D017299:Rod Opsins; C045140:visinin; C093564:Neurogenic differentiation factor 1