Looking Toward a Treatment for Blindness

Researchers have successfully preserved the eyesight of rats by transplanting cells into their diseased eyes. The result gives hope to the 25 million people worldwide afflicted with retinal degenerative diseases, the leading cause of blindness in industrialized countries.

Transfer of the promising technique to humans may take some time, however. Dr. Raymond Lund, one of the U researchers involved with the project, said he and the other researchers are partnering with Neurotech, a Paris-based biotechnology company, to verify the procedure’s safety on humans.

“This next step is much more complex,” Lund said. “It is not usually done at a university setting. [We] will find a whole new set of experiments to ensure it’s going right.”

A phase-one clinical trial (testing on a small group of patients for side effects) may begin as early as this year, Lund said, and phase two (further safety evaluation in a larger group) within three. The researchers will then conduct two more phases of testing, as required by the federal government.

“It’s not a life-threatening disease,” Lund said, “so the last thing we want is to endanger the remaining vision or the health of the patient,”

Retinal degenerative diseases, such as age-related macular degeneration and retinitis pigmentosa, cause blindness in humans as the eye’s photoreceptor cells die. These cells line the retina, which is at the back of the eye, and are essential to vision because they convert light into signals to the brain. A type of support cells called retinal pigmented epithelium (RPE) helps nourish the photoreceptor cells. Malfunctioning of RPE cells leads to the death of photoreceptor cells.

The researchers transplanted RPE cells into rats that have retinitis pigmentosa, an inheritable disease. After 10 weeks, comparison showed the transplanted rats’ ability to discern patterns of stripes was similar to that of the normal rats. Brain activity in the region responsible for vision also seemed normal in the transplanted rats.

Another encouraging aspect of the transplant procedure is the use of cultured RPE cells. Originally harvested from human donors, these cells can continue to grow and proliferate in the laboratory, and thus provide a continuous supply of cells for future transplants.

Because human donors are often the limiting resource in organ transplant procedures, not having to rely on donated tissue means many more patients can be treated. Also, the cultured cells elicit a smaller immune response than freshly donated cells, making rejection by the recipient less likely.

In a study published earlier this year, another team of researchers performed RPE transplants on humans with mixed results. The patients’ improved vision was not proven conclusively, according the Lund, and may have been a placebo effect.

“There wasn’t rigorous testing,” Lund said. “It was done in a rather rushed way. [Our study] goes back a few steps.”

Published last month in the journal Nature Neuroscience, the study is a collaboration of British and U researchers.

Lund worked on cell transplants for 25 years. He left London to join the Moran Eye Center three years ago so he can concentrate on finding a treatment for degenerative eye diseases.

“There was far too much administration and far too little research,” Lund said. “It’s more important to do things for [the patients].”

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