It may be possible to treat Alzheimer's by inserting genetically modified tissue directly into the brains of patients, research suggests.
Cells were implanted into the brain
A team from the University of California, San Diego, used the technique to boost activity in the brains of volunteers.
Brain cells appeared to respond to the introduction of grafts designed to trigger production of growth factors.
The research was presented at an American Academy of Neurology meeting.
The scientists stress that their work is still at a very early stage.
So far they have only worked on a small number of patients, and the tests have been designed to find out whether the technique is safe, rather than effective.
However, the early indications suggest that it might help to slow the advancement of disease.
Lead researcher Professor Mark Tuszynski said: "These results are intriguing. If these effects are borne out in larger, controlled trials, this could be a significant advance over existing therapies for Alzheimer's disease."
Eight patients with early-stage Alzheimer's disease received a transplant of their own skin cells which had been genetically modified to produce Nerve Growth Factor (NGF).
NGF is a naturally occurring protein that prevents cell death and stimulates cell function.
The cells were implanted into an area of the brain which controls memory and other aspects of thought, and where cells are known to die in Alzheimer's patients.
Similar experiments previously carried out on monkeys have produced promising results, restoring withered cells to near-normal size and quantity, and restoring crucial connections between cells.
A year after the surgery, the human volunteers were showing no signs of adverse effects, and their rate of mental decline appeared to have slowed, on one measure by 50%.
In addition, high tech imaging showed increased metabolic activity in the areas of the brains of patients who underwent the NGF treatment compared with Alzheimer's patients who did not undergo surgery.
Professor Clive Ballard, director of research at the Alzheimer's Society, said: "This is one of a number of innovative treatment approaches involving grafts of growth factors, stem cells or delivering genes that can modify key processes in nerve cells.
"Although many of these lines of investigation are at a relatively preliminary stage at the moment, there has been enormous development of the techniques over the last few years, and such approaches hold huge promise for the development of effective treatments.
"Many of these studies are being undertaken in cells cultured in the laboratory or in animals.
"It is therefore also very encouraging that Professor Tuszynski's study suggested that this could be a safe and viable treatment approach for people with Alzheimer's disease."