Dementia patients have been offered hope that their memory could be repaired after scientists showed that injecting blood from the umbilical cords of human babies restores brain function.
Researchers at Stanford University School of Medicine in the US discovered that cord blood contains an important protein which vanishes as humans get older. It is believed the protein encourages neuroplasticity in the brain, allowing neurons to adapt and communicate more effectively.
When human cord blood was injected into elderly mice they performed far better in learning and memory tests and even started nesting again, gathering up cotton wads to make beds, an instinctive behaviour that is largely forgotten in old age.
Alzheimer's Society head of research Dr James Pickett said: "Everyone experiences some decline in memory as they get older.
The possibility that this process can be reversed by an infusion of young blood sounds like the stuff of science fiction, but this is what the study is beginning to show."
"This study finds that a factor in human umbilical cord blood can enter the brain and restore some of the processes that are essential for forming new memories."
The researchers think the cord blood repairs the hippocampus, a part of the brain which in both mice and humans is critical for converting experiences into long-term memories.
In particular, the hippocampus is essential for helping people remember spatial information, such as how to find your way back to your car or information about autobiographical events, such as what you ate for breakfast.
The new study marks the first demonstration that human blood can aid older mice's memory and learning, which the authors say increases the likelihood that it could have a similar beneficial effect in people.
"Neuroscientists have ignored it and are still ignoring it, but to me it's remarkable that something in your blood can influence the way you think," said the study's senior author, Dr Tony Wyss-Coray, PhD, professor of neurology and neurological sciences at Stanford.
"For largely unknown reasons, the hippocampus is especially vulnerable to normal aging. With advancing age, the hippocampus degenerates, loses nerve cells and shrinks. Hippocampal deterioration is also an early manifestation of Alzheimer's disease.
"Our results argue that systemic factors present early in life may be beneficial for revitalisation of aged tissue and that (the protein) represents such a restorative factor for the aged hippocampus."
The Stanford team had already proved that young blood can reverse some of the signs of ageing in mice but have never shown it could restore learning and memory.
For the new experiment, they injected either cord blood plasma, or the blood from people aged between 19 and 24, or 61 and 82.
When the older mice received human umbilical-cord blood plasma every fourth day for two weeks, their memory, learning and hippocampal function improved notably, as well as their ability to navigate through a complex maze. Plasma from older people, on the other hand, was no help at all, while young-adult plasma only induced an intermediate effect.
After realising that something in the umbilical cord blood was making the old brains act younger, the scientists set about trying to work out what it was, and discovered a protein called TIMP2
Injecting TIMP2 by itself into elderly mice largely duplicated the beneficial effects of umbilical-cord blood.
"TIMP2's effects in the brain have been studied a little, but not much and not in aging," added study author Dr Joseph Castellano, an instructor of neurology and neurological sciences at Stanford.
"In our study, it mimicked the memory and learning effects we were getting with cord plasma. And it appeared to do that by improving hippocampal function.
"In the current study, we have focused on age-related cognitive decline, but future studies will probe the extent to which TIMP2 might be beneficial in the context of more severe synaptic and neuronal dysfunction, for example, in Alzheimer's disease."
Experts in Britain said the research was interesting but called for more work on whether TIMP2 could also influence the brain activity in humans.
Dr David Reynolds, Chief Scientific Officer at Alzheimer's Research UK, said: "This study has zeroed in on a protein found in umbilical cord plasma that could play a role in keeping the brain healthy into older age.
"Although the treatments tested here boosted some aspects of learning and memory in mice, we don't know how relevant the findings might be to people.
"This research, while interesting, only looked at memory and thinking changes caused by ageing, and not those involved in dementia."
Dr Pickett added: "As we age, cells in the brain's memory centre - the hippocampus - become less able to form strong connections with one another. This study finds that a factor in human umbilical cord blood can enter the brain and restore some of the processes that are essential for forming new memories.
"The results offer a potential mechanism to explain why young mouse blood can rejuvenate some aspects of memory when injected into older mice. These findings are interesting, but do not shed any light on whether the blood factor could help in dementia, which is caused by diseases of the brain is not a normal part of the ageing process."
The study was published in the journal Nature.