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Nerve stem cell transplants may help slow the progression of macular degeneration, the most common cause of blindness in the developed world, U.S. researchers said on Monday.
They said putting nerve stem cells from StemCells Inc near the retinas of rats with a form of macular degeneration helped keep the disease from advancing to blindness for several months.
"These cells improve the chemical environment in the back of the eye," said Ray Lund of the Casey Eye Institute at Oregon Health and Science University in Portland, whose findings were presented at the Society for Neuroscience meeting in Chicago.
Lund said the mechanism is not clear, but he suspects that when immature nerve cells are placed near the retina, they produce growth factors that protect the cells from damage by the disease.
"It's basically a chemical pump that is sitting in the right place and producing the right things," Lund said in a telephone interview.
Where normally animals with eye disease lost their vision by three months old, rats that got the transplants kept their vision for at least seven months, he said.
"There is no evidence that they (the transplanted cells) do any damage," Lund said, adding that the animals do not develop tumours, a key worry for stem cell transplants.
Hope for treatment in humans
The findings raise hope for use of the treatment in humans with a range of diseases in which the retina become damaged, including age-related macular degeneration or AMD, which affects nearly 30 million people worldwide, including 15 million Americans.
People with AMD lose central vision when delicate light-sensing cells of the macula, a region at the center of the retina, become damaged.
In the rats, the researchers transplanted immature nerve cells into the space near the retina. Lund said the same could be done in people with retinal disease.
Dr. Stephen Huhn, head of the Central Nervous System research program at StemCells Inc, said the cells are adult neural stem cells. He said they are multipotent, meaning they can morph into different types of nerve cells.
Treatment tested in patients with Batten's disease
The company has already tested the treatment in a study of six patients with Batten's disease, a fatal inherited disorder of the nervous system.
"Having a cell that has already entered clinical testing that has been well tolerated at very high doses in the brain gives us a lot of confidence about exploring the same type of strategy in the eye," Huhn said.
Huhn said he thinks the cells may be especially well suited for use in the retina, brain and spinal cord, which are less likely to reject the cells than other parts of the body.
Ultimately, he said the hope is to develop a treatment for the dry form of macular degeneration, which affects around 90 percent of patients diagnosed with AMD. No treatments are available for this form of the disease.
Huhn said treating this form of the disease may prevent some people from developing wet AMD, in which tiny new blood vessels grow between the retina and the back of the eye. – (Julie Steenhuysen/Reuters Health, October 2009)
