Patients blinded in one or both eyes by chemical burns regained their vision after healthy stem cells were extracted from their eyes and reimplanted, according to a report by Italian researchers at a scientific meeting.
The tissue was drawn from the limbus, an area at the junction of the cornea and white part of the eye. It was grown on a fibrous tissue, then layered onto the damaged eyes. The cells grew into healthy corneal tissue, transforming disfigured, opaque eyes into functioning ones with normal appearance and color, said researchers led by Graziella Pellegrini of the University of Modena’s Center for Regenerative Medicine.
The stem-cell treatment restored sight to more than three- quarters of the 112 patients treated, Pellegrini said yesterday in a presentation at the International Society for Stem Cell Research meeting. She estimated the work may benefit 1,000 to 2,000 patients in Europe whose eyes have been damaged by chemical burns and many more in developing countries where the use of chemicals is less regulated. Her patients were followed for an average of three years and some for as long as a decade.
“The patients, they are happy, even the partial successes,” she said in an interview at the meeting in San Francisco. “We have a couple of patients who were blind in both eyes. Can you imagine for these patients the change in their quality of life?”
The work was praised by Ivan Schwab, an ophthalmology professor and stem cell researcher at the University of California, Davis, who has treated patients in clinical trials with a procedure based on Pellegrini’s work. While his patients improved for a time, the benefits didn’t endure, he said in a June 15 telephone interview. Pellegrini’s patients appear to have long-term improvement, he said.
“The powerful part of her work is she has such long-term follow-up,” Schwab said.
Many of the patients she treated had been blind for years as result of tissue and blood vessels growing over damaged parts of the eye. Some had been through failed surgeries and alternative treatments.
The key to success is to be certain that when the stem cells extracted from the limbus are grown in culture they have the right mix of stem cells and the differentiated cells that form the corneal tissue, Pellegrini said. If there are too few stem cells in the transplant, the improvement won’t last because there will be no reservoir to form the new corneal cells needed with the normal recycling of cells over time, she said.
The procedure succeeded after a single transplant in 69 percent of cases. A second procedure was performed on some patients, boosting the success rate to 77 percent, she said. The procedure was deemed a partial success in 13 percent of cases and a failure in 10 percent, she said.
Depending on the depth of the injury, some patients regained sight in as little as two months, Pellegrini said. Others with deeper injuries needed a second procedure and waited a year before sight was restored, she said.
At least one hospital in India, Prasad Eye Hospital in Hyperabad is doing limbus-derived stem cell transplants.
The applications of the work may extend to other organs, Schwab said.
“This is bigger than just the surface of the eye,” he said. “She may be making a model for how to regenerate livers or other organs.”