September 24, 2003.
Seeing is believing: Stem cells have regenerated blood vessels in mouse eyes
Blood stem cells have spurred the development of human blood vessels in mouse eyes, confirming their value for treating such diseases as diabetes-related blindness.
The approach could help researchers develop safe and more efficient methods for testing stem cell-based therapies for diseases involving blood vessel growth, including retinal disorders and cancer.
"This approach makes it faster for us to test therapies, find which ones work and try to improve them, so we can get them to clinical trial status faster," says Edward Scott, an associate professor of molecular genetics at the University of Florida Shands Cancer Center and director of the university's stem cell biology program.
"Unfortunately, there have been a number of times where mice can do things but people can't," says Scott. "We wanted to make sure that human cells can do these same things. Now we know that the things we're studying in the mouse are going to be applicable in humans."
In the study, researchers transplanted human blood stem cells derived from umbilical cord blood into the eyes of mice lacking an immune system.
The mice were models for a diabetes-related complication called retinopathy, the leading cause of blindness in the US.
Retinopathy involves destruction of the capillaries that provide blood to the retina, the light-sensitive nerve tissue that sends visual images to the brain.
Four to six weeks after the transplantation, human blood vessels started to grow in the animals' eyes.
"What this study is demonstrating is the remarkable ability of stem cells that are derived from blood to reconstitute tissues in other organs," says John Wingard, a UF professor of medicine and the associate director of clinical and translational research at Shands.
"We are gaining increasing information about the potential of these cells to restore function in brain, heart, liver and other tissues," Wingard says. "The more we learn about this, the more horizons are expanding as to clinical applications."
Transferable to humans
The next step for the researchers will be to test ways of preventing retinopathy and blood vessel formation in solid tumors.
The latter will involve the use of human pancreatic and breast cancer cells.
"Once again we'll be using the mouse-human system to confirm that what works in a mouse works on human cells before trying to take it to a clinical trial," Scott says. "We're excited about having both systems to work with, so at every step along the way we can confirm that things we find in mice hold true for humans."
The research could prove valuable in the treatment and prevention of diseases involving excessive blood vessel growth, diseased arteries and other circulatory problems, as stem cells can block or prompt blood vessel growth.
"We now know a number of proteins and factors that are required to get the stem cell to make blood vessels," says Scott. "Those give us targets to try to stop their activity and keep them from working, thereby preventing the vessels from forming. Now that we know where these repair cells come from, we have a lot of different things we can try now, and animal models to show whether or not they're effective."
The study is published in the journal Blood (read abstract).
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