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.
The findings were presented at Neuroscience 2009, the annual meeting of the Society for Neuroscience and the world's largest source of emerging news about brain science and health.
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 (four with age-related macular degeneration and six with retinitis pigmentosa), seven improved, one remained the same, and two 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 one and six 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.
Research was supported by an anonymous donor, the Foundation Fighting Blindness, the Kentucky Lions Eye Foundation, the Murray Foundation Inc., Research to Prevent Blindness, and the Vitreoretinal Research Foundation. Drs. Aramant and Seiler have a proprietary interest in the implantation instrument and procedure.
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