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Gene Therapy Eyed as Alzheimer's Treatment

Initial results of small study show slowed mental decline

MONDAY, April 25, 2005 (HealthDay News) -- New research suggests that gene therapy could slow the devastating mental decline of those with Alzheimer's disease by stopping brain cells from dying.

Seven Alzheimer's patients did better on cognition tests than would have been expected after protective proteins were implanted into their brains, says a team of U.S. researchers.

"Our hope is that these findings mean people can remain more functional in their home setting for a longer period of time, and have an improved quality of life," said Dr. Mark Tuszynski, a professor of neurosciences at the University of California, San Diego and co-author of the study.

The finding appears in the April 24 online issue of Nature Medicine.

The research is preliminary, however, and one Alzheimer's specialist cautioned that it's too early to raise hopes.

"There are major questions that have not been resolved," said researcher William J. Netzer, of the Fisher Center for Alzheimer's Research at Rockefeller University.

Alzheimer's disease affects an estimated 4.5 million Americans, and the number is expected to grow as baby boomers become senior citizens.

The disease begins when beta-amyloid plaques develop in the brain. Both the plaques and neuron "tangles" kill off brain cells, leading to the declines in mental ability that are the hallmarks of the disease.

Alzheimer's patients can take drugs to ward off symptoms, but the medications don't tend to work very well or for very long, making the disease extremely difficult to treat.

Enter gene therapy. Tuszynski and his colleagues hope they can stop brain cells from dying by inserting protective proteins into the brain.

The researchers took skin cells from eight volunteer patients and modified them to carry a protein known as nerve growth factor that appears to prevent cell death. Then the researchers implanted the cells into the brains of the patients in 2001 and 2002, and waited to see what happened.

One patient died after suffering bleeding in the brain during the surgery; the researchers later changed the procedure to prevent bleeding.

The other seven patients survived and are still alive today. Tests over the next two years suggested the procedures may have slowed their mental decline by 36 percent to 51 percent, and PET scans revealed that some of the patients' brains were using more energy-providing glucose, a possible sign of increased mental activity.

Meanwhile, an autopsy of the patient who died revealed that dying brain cells had begun to respond to the injected protein, the researchers said.

Previous studies in animals have suggested that the protein helps prevent cells from dying, Tuszynski said. "These effects are not subtle. They are strong," he said. "If we can create a safe and effective treatment for humans, this could really affect how we treat neurological diseases."

Rush University Medical Center in Chicago, in conjunction with a drug company founded by Tuszynski, recently began another study of the gene therapy approach. Six patients will undergo treatment using a gene that piggybacks on a deactivated germ, Tuszynski said.

After that study, researchers hope to expand to a larger group of patients and compare their responses to those of people who don't undergo the treatment.

Netzer cautioned that the researchers still need to understand possible side effects of the procedure: "There's always a danger when you put a cell into the brain of what's going to happen over the long term."

There's also the matter of the tiny number of patients in the study, he said, which makes it hard to determine if an apparent effect really exists. "There's a great deal of variability in the way people decline with Alzheimer's," he said. "At this point, we'll have to await much larger studies."

More information

To learn more about Alzheimer's disease, try the Alzheimer's Association.

SOURCES: Mark Tuszynski, M.D., Ph.D., professor, neurosciences, University of California, San Diego; William J. Netzer, Ph.D., research associate, Laboratory of Cellular and Molecular Neuroscience, The Rockefeller University, New York City; April 24, 2005, Nature Medicine online
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