By Rob Waters

June 18 (Bloomberg) — 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. The patients were followed for an average of
three years and some for as long as a decade, Pellegrini said.

“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.

‘Long-Term’ Effect

“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. Pellegrini estimated 1,000 to 2,000
patients in Europe suffer from burns with chemicals such as
bleach or industrial solvents and may benefit from the
procedure.

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.

Success Rate

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.

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.”

To contact the reporter on this story:
Rob Waters in San Francisco at
rwaters5@bloomberg.net.