Giving old mice blood from their younger counterparts result in a three-fold increase in the number of brain cells critical to memory and learning, researchers from Stanford University School of Medicine have discovered.
They isolated the chemical eotaxin and discovered that injecting it into younger mice had the opposite effect, causing fewer brain cells to be produced.
The team are now testing eotaxin's role in memory loss associated with Alzheimer's disease and hope their research might also prove useful in treating dementia.
The findings raise the question of whether it might be possible to shield the brain from aging by eliminating or mitigating the effects of these apparently detrimental blood-borne substances, or perhaps by identifying other blood-borne substances that exert rejuvenating effects on the brain but whose levels decline with age, said associate professor of neurology and neurological sciences Tony Wyss-Coray, PhD, the study's senior author.
An early step in the Stanford team's study involved connecting the circulatory systems of pairs of old and young mice via a surgical procedure, so that blood from the two mice commingled.
"This way, we could examine the effects of old mice's blood on young mice's brains, and vice versa," said Saul Villeda, PhD, a postdoctoral researcher in Wyss-Coray's laboratory, who led the study en route to his doctoral thesis.
The mixing of old and young blood produced changes in both the young and the old mice's brains. For one thing, the older mouse in these pairs produced more new nerve cells in their dentate gyrus than solo older mice did.
"We saw a threefold increase in the number of new nerve cells being generated in old mice exposed to this 'younger' environment," said Wyss-Coray.
In contrast, the young members of old/young mouse pairs exhibited fewer new nerve cells than did young mice untethered to elders.
The study was recently published in the journal Nature.