Far more research is needed to see if the experimental treatment, which requires a form of brain surgery, really helps.
But if the approach pans out, researchers say delivering protective substances, called growth factors, into a diseased brain holds the potential to rescue some dying brain cells.
In one patient, the brain tissue showed new growth, which was a first, according to a study published in Sunday's edition of the journal Nature Medicine.
"It won't cure the disease," said the lead researcher, Dr. Mark Tuszynski of the University of California, San Diego. That is because Alzheimer's destroys different types of cells in different areas of the brain; the new gene therapy targets just one of those.
The preliminary success indicates that similar approaches might help other neurodegenerative diseases, such as Parkinson's, Tuszynski said. "This is in a sense proof of principle for the potential use of growth factors," he said.
Doctors at Chicago's Rush University Medical Center have begun a second small study of the approach in Alzheimer's patients. Tuszynski, who co-founded a biotechnology company that is funding the Chicago work, hopes larger studies will begin within another year.
Tuszynski and colleagues took skin cells from eight patients in the early stages of Alzheimer's and modified the genes to secrete a protein found in healthy brains called nerve growth factor, or NGF.
Earlier studies had shown that injecting NGF-producing tissue into the brains of aging monkeys could reverse deterioration. Simply injecting NGF into people would not work. If it goes into the wrong part of the brain, it can cause serious side effects.
So, doctors drilled holes into the patients' skulls and implanted the NGF-producing skin cells directly onto Alzheimer's-injured spots.