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Blood plasma from young people has been found to rejuvenate old mice, improving their memory, cognition, and physical activity. The method has the potential to be developed into a treatment for people, says Sakura Minami of , the company behind the work.

Previous research has found that stitching old and young mice together has an interesting effect. While sharing a blood system works out well for the older mouse, the younger one isn’t so lucky. The young animals started to show signs of brain ageing, while the brains of the older mice started to look younger. “We see a rejuvenation effect,” says Minami.

The key to youth appears to be in the blood plasma – the liquid part of blood. Several studies have found that injecting plasma from young mice into old mice can help rejuvenate the brain and other organs, including the liver, heart, and muscle.

Could blood plasma from young people have the same benefits? To find out, Minami and her colleagues took blood samples from 18-year-olds, and injected them into 12-month-old mice. At this age, the equivalent of around age 50 for people, the mice start to show signs of ageing – they move more slowly, and perform badly on memory tests.

The mice were given twice-weekly injections of the human plasma. After three weeks of injections, they were submitted to a range of tests. The treated mice’s performance was compared to young, 3-month-old mice, as well as old mice who had not received injections.

New neurons

They found that human plasma does have the power to rejuvenate. Treated mice ran around an open space like young mice. Their memories also seemed to improve, and they were much better at remembering their way around a maze than untreated mice.

“Young human plasma improves cognition,” says Minami, who presented her findings at the annual meeting in San Diego, California, on Monday. “Their memory was preserved.”

“It’s more or less what we would expect,” says , at Boston University in Massachusetts. “The blood of young people must have something in it that’s important for keeping them young,” she says.

The team then examined the brains of the treated and untreated mice. They looked for clues on the birth of new neurons in the hippocampus – a process called neurogenesis, which is thought to be important for memory and learning. Sure enough, the treated mice appeared to have created more new cells in their brain. “Young human plasma treatment can increase neurogenesis,” says Minami.

Minami says she has identified some factors in young blood that might be responsible for these benefits, but that she won’t reveal what they are yet. Some of them seem to be crossing into the brain, while others may be acting remotely, elsewhere in the body, she says.

She hopes to one day translate the findings into an anti-ageing treatment for people – one that might help those who start to experience the effects of an ageing brain. “There’s anecdotal evidence that people experience benefits after blood transfusions,” she says.

The company she works for, Alkahest, has already started a trial of young blood in people with Alzheimer’s disease.

Read more: Young blood to be used in ultimate rejuvenation trial