Making an eye
doi:10.1038/nindia.2013.5 Published online 17 January 2013
In an animal study that may someday help treat blindness, researchers in India have shown that a complete eye with lens, retina and other parts can be created from the ocular tissue.
Om Prakash Jangir and his colleagues at the life sciences department of the Institute of Advanced Studies in Education in Rajasthan have reported this remarkable fact in their experiment on tadpoles of the frog Euphlyctis cyanophlyctis1.
The researchers' have shown that even somatic cells can reprogramme and differentiate into separate cell lines under experimental conditions. "The most spectacular result we obtained was the formation of a complete eye from ectopic transplantation of ocular tissues," Jangir told Nature India.
All cell types in the mammalian body, other than the sperm and ova, are somatic. Most external and internal organs such as skin, bones, blood and connective tissues are all made up of somatic cells. "It is clear from our research that adult stem cells (somatic differentiated cells) are more versatile than previously thought," the researchers said.
In their study, they removed the eye lens of a few 'donor' tadpoles and excised the eye ball tissues surrounding the lens. These tissues from the donor tadpoles were then implanted into the tail of recipient tadpoles that were treated with vitamin-A. Histological examination revealed that in a few days the implanted ocular tissue, in the presence of vitamin-A, had developed into a complete eye with lens and retina.
"The present study has shown that differentiated ocular cells loose their definitive characteristics and acquire the feature of another specialized cell type under the influence of vitamin A," Jangir said. In other words, the findings indicate that differentiated ocular cells might be reprogrammed by exposure to new environment (vitamin A) to become another cell type."
Cells differentiate to specialize for different functions. "Understanding the cell interactions and signals which drive the organogenesis process is the central problem of developmental biology," Jangir explained adding that the present findings give evidence of plasticity of differentiated ocular tissue cells in the presence of vitamin A. Cell plasticity refers to the ability of cells to take on the characteristics of cells elsewhere in the body.
Jangir said that although several workers have earlier demonstrated that eye lens in frogs can be regenerated from cornea, "we have for the first time obtained clear evidence of plasticity and reprogramming of terminally differentiated ocular tissue into lens, retina and even complete eye." They said it was not clear how the complete eye developed.
In conclusion the researchers said their work "has introduced fundamentally new research areas, and offers exciting new opportunities to implement new therapies designated to repair the visual function when conventional treatments are not efficacious."
- Jangir, O. P. et. al. Plasticity and reprogramming of differentiated ocular tissue of tadpoles of the frog Euphlyctis cyanophlyctis under the influence of vitamin-A. Indian J. Exp. Biol. 51, 23-28 (2012)