Researchers at The Schepens Eye Research Institute, an affiliate of Harvard Medical School, have reported success transplanting stem cells into the diseased eye. More importantly, a percentage of these cells have actually taken on some of the characteristics of retinal cells and extended into the optic nerve.
Although in its infancy, stem cell research has tremendous potential for helping millions of people whose vision has been impaired by injuries and diseases including glaucoma.
Stem cells are what is known as “pluripotent.” These are cells that have not yet differentiated into the cell they are to become. Unlike mature cells, they hold the possibility of integrating into any organ of the body. Scientists experimenting with mice have introduced pluripotent mouse embryo stem cells into diseased organs. These stem cells have begun to take on certain characteristics of the organ cells.
The stem cells don’t actually develop into organs, but they do begin to resemble the organ cells. Stem cells introduced into a diseased kidney, for example, become much like ordinary kidney cells. The idea is that the other cells will “educate” and integrate the new cells until the organ is effectively regenerated.
Researchers at Schepens found that these cells not only migrated to the right place, appearing to take on the right characteristics, but also show early signs of connecting the retina to the brain. If sight is to be restored, this must happen.
Significant to these findings is that the transplants appeared to work best when the receiving retina was “sick.” In other words, states Michael Young, PhD, who led the study, “these cells somehow sense that they are needed and begin to differentiate into cells that could take on the job of retinal neurons.”
Researchers injected stem cells from adult rats into the eyes of two groups of rats with retinal degeneration. One group was four to ten weeks old; the other group was 18 weeks old. Results were slightly better with the younger group but the older group showed fairly good results as well. Young stated, “As the rat retina is fully developed before the end of the third postnatal week, the widespread incorporation seen at four to ten weeks indicates that developmental maturity is not a barrier to the acceptance of neuronal stem cells by the diseased mammalian retina.”
Dr. Young and his colleagues stress that there is much more work yet to be done before any of this research can be clinically applied. He adds, “We first need to show that this technique can actually restore sight in animals.”
Reviewed by George Cioffi, MD, Director of Glaucoma Service, Devers Eye Institute, Portland OR; Member, GRF Scientific Advisory Committee.
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