A clinical study is the first to show that advanced stages of incurable retinal diseases can be stopped and improved by a cell replacement technique. The researchers transplanted intact “sheets” of fetal retinal cells that develop into light-sensitive nerve cells, along with a supporting layer of tissue, into damaged human eyes.
To date, most clinical studies have targeted the early stages of retinal disease in attempts to rescue photoreceptors, the light-sensitive nerve cells. But once photoreceptors have died, they cannot be regenerated. Animal studies have shown that transplanted donor cells and nearby sustaining tissue grow into healthy cells and integrate with the recipient’s own damaged retina. The researchers created a special instrument to transplant these extremely fragile sheets of young retinal cells.
Of the 10 patients who received the transplants (4 with age-related macular degeneration and 6 with retinitis pigmentosa), 7 improved, 1 remained the same, and 2 continued to deteriorate. The individuals were assessed using different methods. The main test was to read letters on a chart to check visual acuity, and follow-up time was between 1 and 6 years.
Although most tissue donors and recipients were tested for compatibility, no immunological match was seen. “Despite this limitation, it was encouraging that no rejection was seen clinically and the surgery had no negative side effects,” said Robert Aramant, PhD, visiting scientist at the University of California, Irvine, and lead author.
The authors suggest that these results — along with previous positive results in animal retinal degeneration studies — are evidence of the safety and benefits of retinal transplantation in humans. Widespread application, however, would be limited by the restricted access to donor tissue. “These results indicate that this is a viable technique, but more patients are needed to confirm these results,” Aramant said. The clinical study was performed in Louisville, KY.
“Basic neuroscience research has formed the basis for significant progress in treating eye disease,” said press conference moderator Rachel O. L. Wong, PhD, of the University of Washington, an expert on visual system development. “These studies would not be possible without technological advances and basic science research that continues to explain the normal function and development of the visual system,” Wong said.
Retinitis pigmentosa and age-related macular degeneration destroy the light-sensitive nerve cells in the retina, leading to blindness. In all, vision loss and eye disease affect 3.6 million Americans and cost the United States $68 billion each year.
Illustration: Microsoft clipart.
Society for Neuroscience Press Release (10/20/09)
Science Daily (10/21/09)
e! Science News (10/21/09)
Abstract (Presented at Neuroscience 2009, the annual meeting of the Society for Neuroscience. Scientific Presentation: Wednesday, Oct. 21, 4–5 p.m., South Hall A)