Stem cell success could help more than cornea
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The cure was so dramatic it surprised even the researchers.
They had injected human adult stem cells into the corneas of mice and, in due time, the scarring and cloudiness that cause corneal blindness completely disappeared.
But the results were more than met the eye.
Repairing corneas with adult stem cells, which already exist in the human eye, signals an advance in stem-cell research that could apply bodywide.
As such, research led by James Funderburgh, an associate professor in the University of Pittsburgh School of Medicine's Department of Ophthalmology, is clarifying more than mice corneas. It also points to a day when one's own stem cells can be used to repair one's injuries and cure one's diseases.
"This set of investigators is world class. They are primo leaders in the field, and what they are doing is revolutionary stuff," said Dr. Ivan Schwab, professor of ophthalmology at the University of California, Davis, who's not involved with the research. "What they have shown is dramatic in terms of biology."
Dr. Funderburgh and first author Yiqin Du of Pitt, along with researchers from Pitt, Case Western Reserve University, the universities of South Florida and Cincinnati, published results of their research today in Stem Cells journal.
"This proves that these stem cells can be used to treat scars and abnormal corneas," Dr. Schwab said. "This also has implications for other disease.
"For my money, it isn't what they've done for the cornea. There's another ray of hope with implications for biology across the body," he said. "This is a key step in tissue engineering. I applaud them for their spectacular work."
According to the study, Dr. Funderburgh and his team used stem cells -- basic cells that can turn into specialized cell types -- that already exist in the stroma, or fibrous part of the eye. These cells were cloned, then injected en masse into damaged cornea of mice.
In the cornea, the cells activated to transform into corneal cells that reorganized the tissue fibers and produced a smooth, transparent cornea.
The process was more difficult than it might appear. It required a method to inject cells into the thin corneas of mice and track the progress with dyes. It also required documenting eye improvements in mice. As Dr. Funderburgh noted, "It's hard to have a mouse read an eye chart."
But rodent corneas were restored to perfection. Dr. Funderburgh said it shows potential to cure corneal blindness "with a simple injection."
The success with mice, he said, "is a start, but we have a ways to go."
Repeating the process in humans remains years away. The human cornea is thicker and more complex than mouse corneas. But tests done on human eyes from an eye bank that couldn't be used for transplantation show that the technique could be used on human eyes.
As Dr. Schwab predicted, "It will pan out."
Dr. Funderburgh said the stem cells stored in niches in the stroma of the eye do not naturally become activated to repair the cornea, probably because the faster process of scarring supersedes stem-cell repair. Nature, he said, apparently seeks the quicker rather than better fix.
It's analogous to how we repair highways by patching potholes rather than rebuilding the entire roadway, he said.
Because stem cells are "immune privileged," which means they're not destroyed by the immune system of the host, immune suppression or tissue matching may not be necessary with the procedure.
In a laboratory, millions of the stem cells could be produced from one original donor cornea and used in hundreds and even thousands of cornea repairs.
In the United States, cornea transplantation is the primary treatment for damaged corneas that cause vision problems and blindness. About 40,000 cornea transplants are done annually in the United States.
But transplants require donated corneas and delicate surgery not available in many parts of the world. Transplants also can lead to rejection. Even good transplants can result in less-than-perfect vision.
"There are 10 million people in the developing world with corneal blindness, and they cannot afford transplants, and they don't have transplant systems in place," Dr. Schwab said.
So the stem-cell procedure could offer a cheaper procedure with superior results. "The stem-cell therapy would be much simpler and could be an outpatient therapy -- if it works," Dr. Funderburgh said.
Next comes a series of research steps leading to human clinical trials, which will require new funding and laboratory space that meets Food and Drug Administration guidelines.
"We have to demonstrate that it is safe for humans before we can conduct human trials," said Dr. Funderburgh said, anticipating "stem-cell therapies for lots of parts of the body in the next 15 to 20 years."
Advancing the research "will be a challenge," he said, but worth the effort in light of current accomplishments.
As the study states, "The results suggest that cell-based therapy can be an effective approach to treatment of human corneal blindness."
First Published April 9, 2009 12:00 am