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An experimental 'rescue' of retinas by treating eyes with certain stem cells has been shown to preserve visual function in mice that were genetically predisposed to degenerative diseases of the retina.
In the September 15 issue of the Journal of Clinical Investigation, a team of researchers at the Scripps Research Institute, headed by Martin Friedlander, M.D., Ph.D., reported that mouse eyes treated with adult bone-marrow-derived stem cells from mice or humans achieved normal blood circulation in the retina, had significantly improved retinal tissue, and responded to light, in contrast to no such improvements in untreated eyes. The work was funded primarily by the National Eye Institute (NEI), part of the National Institutes of Health.
The retina is the light-sensitive tissue at the back of the eye that instantly converts light, or an image, into electrical impulses. The retina rescue procedure holds promise for future preventive therapies to prolong vision in humans who may be on genetic paths to blindness due to retinitis pigmentosa (RP) or other degenerative retinal conditions. More than 100,000 Americans have RP, which is caused by more than 100 different genetic mutations. The retinal improvements were achieved after the Scripps team injected the stem cells from mice or humans into the mouse eyes. Further studies in animal models will next help determine dosage and possible toxicities of a treatment based on these new findings.
"The surprising findings establish a dramatically new paradigm for understanding and potentially treating retinal degenerative diseases using a cell-based approach," said Paul A. Sieving, M.D., Ph.D., director of the NEI. "Determining the precise mechanism of this cell-mediated rescue presents an exciting research challenge and is a high priority for the Institute."
In mice that were genetically predisposed to retinal eye disease, the outer layer of the retina would degenerate by programmed cell death, called apoptosis. To rescue the eye from such a fate, the Scripps team targeted the extensive blood vessels, the vasculature, in the retina. They selected a type of adult stem cells that has the capability of becoming endothelial cells that line blood vessels. Once injected into a mouse eye, the adult stem cells were guided by support cells called astrocytes to the vasculature in the back of the eye. As a result, they appeared to protect both the blood vessels and retinal neurons from death.