Wednesday, September 15, 1999 Published at 11:14 GMT 12:14 UK
Genes help brain recapture youth
As the brain ages, many cells shrink but few die
Withered brain cells could bloom again using gene therapy techniques to restore them to their former glory, scientists have said.
The finding could help doctors develop new therapies for diseases such as Alzheimer's, which causes a breakdown in brain function.
It also reinforces scientists understanding of how the brain works and suggests that old brain cells do not die, they simply shrivel.
The technique has been shown to restore the brain cells in monkeys - although an ongoing study is examining whether it reinvigorates memory and thinking - and the researchers are seeking permission to test it on patients with Alzheimer's disease.
Dr Mark Tuszynski, of the University of California, San Diego, led the study and explained how his team sees the ageing process of the brain.
A count of cells in the cortex - a key area in the brain involved in thinking - showed that very few were lost with age, he said.
However, cells in the part known as the basal forebrain, were dramatically affected by age and had stopped producing certain chemicals - a change that affects thinking ability in the cortex.
"These cells are like the air traffic controllers of the brain," Dr Tuszynski said.
The cells were not dead, however, and when genes that make nerve growth factor (NGF) - an essential chemical found in the brain - were injected into the brain, they were revived.
Human tests next
The researchers used eight monkeys with an average age of 23 - the monkey equivalent of the late 60s to 70s in humans.
The researchers inserted the NGF gene into skin cells and then injected the modified cells into the front of the monkeys' brains. Four monkeys got injections of skin cells without the gene.
"We restored the number of cells we could detect to about 92% of normal for a young monkey and size of the cells was restored to within 3%," Dr Tuszynski said.
The application of this technique to Alzheimer's - which destroys chemical messengers used by the cells of the brain to communicate with each other - will need to be tested in humans, as animals do not suffer the disease in the same way.
The researchers have already applied to the US Food and Drug Administration for permission to run human trials, although it would be a number of years before they could tell if the treatment was effective.
The study was published in the Proceedings of the National Academy of Sciences journal.