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Mouth Cells Coaxed to Repair Eye Damage
WEDNESDAY, Sept. 15 (HealthDayNews) -- Japanese researchers say they have turned cells from the mouth into eye cells that have successfully been implanted in four patients to repair damage to the delicate outer layer of the cornea. American ophthalmologists described the work as an impressive achievement in basic science, but one that needs much more investigation before it can be applied to treatment of patients when the outermost layer of the cornea is damaged by corrosive chemicals, fire or medical disorders. If there is damage to the entire cornea, it can be repaired by a complete transplant. About 40,000 such operations are done every year in the United States. The technique described in the Japanese report is designed to repair more limited damage -- confined to the epithelium, the outermost of the four layers of the cornea, which is the front part of the tough outer shell of the eyeball. When this epithelial layer is damaged, it can be repaired by taking corneal stem cells from the patient and growing a new epithelium. But for several thousand patients a year -- no exact number is available -- stem cells cannot be obtained. A transplant can repair the damage, but at a price, said Dr. Bennie H. Jeng, an associate staff member at the Cleveland Clinic Cole Eye Institute. "We have plenty of donors," Jeng said. "But then you require constant immune system suppression, because the rate of rejection of epithelial cells is high." Using stem cells from the mouth of a person requiring such a transplant could solve that problem, said Dr. Kohji Nishida, an associate professor of ophthalmology at Osaka University Medical School and lead author of a report on the advance in the Sept. 16 issue of the New England Journal of Medicine. The mouth cells used in the study were similar to those of the eye because both are epithelial stem cells, Nishida said. But, he said, using formal scientific language, "it is a significant finding that autologous stem cells in cultured mucosal epithelial cell sheets could regenerate corneal epithelium." But even though the results are "very impressive," caution is required, Jeng said. "We need to see bigger studies," he stressed. And Dr. Ivan R. Schwab, a professor of ophthalmology at the University of California at Davis who has done research on culturing corneal epithelial cells, is even more cautious. "I'd like to see it replicated, and I'd like to see it stand the test of time," Schwab said. Nishida said the transformed cells are working well a year after they were implanted. But Schwab said that cultured epithelial cells that his group implanted in patients four years ago "have gradually deteriorated, suggesting that these cells will not last forever. We need to learn more about the biology of these stem cells." "I'm still not convinced that the cells from the mouth are true corneal epithelial cells," Schwab said. Nevertheless, he said, the Japanese work "hold great promise for patients with these eye problems. What we learn about the way these cells grow and replicate is the more important aspect of this work." More information A primer on the cornea, its function, its problems and its treatment can be found at the National Eye Institute.
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