By Warren King,
Seattle Times medical reporter.
Tuesday, August 15, 2006.
Procedures using stem cells derived from human embryos could be utilized in a few years to repair disease-damaged retinas, new research by University of Washington scientists indicates.
UW scientists reported Monday that they have successfully used the stem cells to treat diseased tissue in mouse retinas, a key portion of the eye.
"This is a very promising development for cell replacement in the retina," said Tom Reh, UW professor of biological structure and leader of the research.
Reh said that if the stem-cell research at the UW and other institutions continues to be successful, the first human tests of the technique could begin in about two years.
The UW team used a mix of "growth factors" — natural proteins that encourage cell growth — to coax the embryonic cells into becoming retinal cells. It was the first use of human stem cells using the technique for the retina; previous research has been conducted with mouse stem cells.
The embryonic cells used in the research were from a cell line existing before August 2001, when President Bush, citing ethical reasons, prohibited federal funding of research on future lines.
The retina, at the back of the eye, receives images and sends them to the brain through the optic nerve.
Macular degeneration, deterioration of the center of the retina, affects 10 million people in the United States and is the leading cause of blindness in the elderly, according to the National Eye Institute. Diabetic retinopathy, which damages retinal blood vessels, affects 5.3 million adults, according to the American Academy of Ophthalmology. And retinitis pigmentosa, a genetic disease, affects about 75,000 people.
The UW researchers, who have done extensive previous research on the retina, spent about two years working on their stem-cell research. Finding the right combination of growth factors to develop the retina cells was the key.
"The idea was that we already have these proteins [growth factors] that already control development naturally," said Reh.
After growing the embryonic cells in the lab for several weeks, the researchers first placed them in growth factors important to head development in humans and mice. They then added another factor that other scientists have found leads to large eye development in frogs.
That combination stimulated the embryonic cells to become retinal "progenitor" cells, sort of the parents of retina cells. The development occurred in two weeks, about twice as fast as during normal development in the uterus.
Finally, when the scientists mixed the new cells with damaged mouse retina, the cells replaced key cells: cones, responsible for color perception; rods, which enable night vision; and amacrine cells, which form the other layer of the retina.
Jason Meyer, a University of Wisconsin scientist who has used mouse embryonic cells for similar research, praised the "highly efficient" technique of the University of Washington team. "The results have profound implications for the future use of such cells in cell-replacement strategies to counteract [retinal] degeneration," Meyer said.
Reh said his team now have begun injecting the new cells into the eyes of retina-damaged mice, measuring nerve reactions to see whether there is actual vision improvement. He said the scientists also will be watching the work of a California company using the same cell line to generate cells for repair of spinal-cord injuries.
"If things continue to look [good] over the next six months and other research moves ahead, we should be in a position to use this for eye diseases," he said.
Reh, along with Deepak Lamba, the lead author of the research report, and the UW team reported their findings in the week's online version of the Proceedings of the National Academy of Sciences.
Other University of Washington researchers also have been using stem cells to make important advances. In June, UW scientists reported that they had put human-liver stem cells into mice, where they replaced dead liver cells. The research could lead to treatments for livers damaged by hepatitis, alcoholism and drug overdoses.
Warren King: 206-464-2247 or firstname.lastname@example.org
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