Several studies are showing success at using stem cell transplantation to treat retinal degeneration.

According to an August 14, 2006 press release from the University of Washington ("Stem-cell procedure promising" by Warren King, Seattle Times), Tom Reh, UW professor of biological structure and leader of the research, said that if the stem-cell research at the UW and other institutions (see "Other Research" below) continues to be successful, the first human tests of the technique could begin by 2009.

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.

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.

Reh said his team now has begun injecting the new cells into the eyes of retina-damaged mice, measuring nerve reactions to see whether there is actual vision improvement.

Reh, along with Deepak Lamba, the lead author of the research report, and the UW team reported their findings in the August 2006 online version of the Proceedings of the National Academy of Sciences.

Other Research

On September 21, 2006, Raymond D. Lund, (University of Utah's John A. Moran Eye Center in Salt Lake City) and Robert Lanza (Advanced Cell Technology Inc. in Worcester, Mass.) reported that cells grown from human embryonic stem cells slowed vision loss when injected into the eyes of rats with a disease similar to macular degeneration.

According to a September 21, 2006 press release ("Stem Cell Experiments Slow Vision Loss in Rats" by Rick Weiss, Washington Post) the researchers achieved the transformation in all 18 stem cell lines they worked with, proving that their approach can consistently produce the crucial pigment cells. Then they injected the cells, about 20,000 per eye, into the retinas of 14 rats with a genetic disease similar to macular degeneration. Eight control rats received eye injections without any cells.

Forty days after treatment, the team measured retinal electrical activity in response to flashes of light, and it found that the treated rats were twice as responsive as the untreated ones, which by then were going blind. A separate test -- which tracks eye and head movements in response to a moving display, a measure of an animal's ability to discern fine details -- showed that the treated rats had twice the visual acuity of the untreated rats nearly three months after treatment.

Microscopic examination of the retinas at autopsy showed that the treated eyes had healthy photoreceptor layers five to seven cells thick, while the untreated eyes had an average thickness of just one cell. (Healthy rats have layers 10 to 12 cells thick.) None of the cells divided abnormally or grew into tumors, the team reported in the September 2006 issue of the journal Cloning and Stem Cells.

In June 2007, Advanced Cell Technology announced successful production of a human embryonic stem cell line (hESC) without destroying an embryo. In 2006, ACT announced the development of the technique for harmlessly removing a single cell (a blastomere) from an eight-cell human embryo, and now they have succeeded in reality.

On January 7, 2007, researchers at the Institute for Regenerative Medicine at Wake Forest University School of Medicine discovered another potential source of embryonic stem cells in the amniotic fluid that protects babies in the womb. These cells appear to be almost as malleable as those in the embryo itself, and the advantage would be that harvesting them would not harm the embryo. Several more years of study are needed to assess their application in humans.

Other research is taking place in the United Kingdom at the University College London, Moorfields Eye Hospital and Sheffield University, in a cooperative effort called the London Project to Cure Blindness. Doctors at Moorfields have had some success with human subjects using adult stem cells from the patients' own eyes. Embryonic cells, however, have been shown to be more malleable and easier to transplant than adult stem cells. Laboratory-grown cells from the blastocyst of a 5-day old embryo require only one injection (a 45-minute procedure), whereas the Moorfields experiments have taken two hours and two surgical procedures. This protocol would be very expensive and impractical in general practice, so the researchers at the University of Sheffield are using embryos, which will take a little longer to get into human trials.

It is important to remember that stem cell transplantation is a treatment, not a cure. It is definitely promising, but if the cause of the disease is not eliminated, even replacement cells can eventually be affected. The cure will likely come from gene replacement, and that is a few more years down the road.

To read reports on earlier stem cell research, follow these links (each will open a separate window):

www.mdsupport.org/library/stemcell.html

www.mdsupport.org/library/stemcell2.html

www.mdsupport.org/library/stemcell3.html

www.mdsupport.org/library/stemcell4.html