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Young Blood Restores Old Mice

Blood from young mice boosted the memory and muscles of old mice, scientists report.
Image: A young and an old mouse
A young and an old mouse. New research shows blood from young mice can rejuvenate old mice.Wyss-Coray lab at Stanford University

Blood from young mice boosted the memory and muscles of old mice, scientists reported in a series of experiments that give new meaning to the phrase “young blood.”

The experiments, done by teams at Stanford and Harvard Universities, point to possible new ways to treat diseases of aging, from Alzheimer’s to heart disease. And they’re hoping they can find what it is in the blood so that people won’t have to resort to blood transfusions to do it.

Image: Blood from young mice boosted the memory and muscles of old mice
Blood from young mice boosted the memory and muscles of old mice.Joseph Castellano / Stanford University

The studies, published in the journals Nature Medicine and Science, suggest that whatever it is that rejuvenates muscles, brain cells and perhaps other functions in the body circulates in the blood when animals are young, and stops circulating as they age.

Both teams started with very simple approaches — they transfused blood from young mice into older mice.

“You just give an old mouse young blood and see if the animal is smarter than before."

“You just give an old mouse young blood and see if the animal is smarter than before,” said Tony Wyss-Coray, a professor of neurology at Stanford who led one of the studies.

They were. The old mice could navigate mazes as quickly as young mice could. “It was as if these old brains were recharged by young blood,” Wyss-Coray added.

“We’ve shown that at least some age-related impairments in brain function are reversible. They’re not final,” added Saul Villeda, who is now at the University of California, San Francisco.

Closer checks showed the new blood was acting on the hippocampus, the part of the brain used in navigating and orienting. “This brain region is very important not only for rodents, who use it to find their way around in their burrow, but for humans. It is also very important to make spatial maps, when you park your car somewhere you go shopping and you remember where it is.”

Wyss-Coray admits the experiments might evoke images of Dracula and even of Frankenstein. “You can’t drink the blood,” he points out. “But seriously, if you wanted to try that in humans you’d have to get a transfusion. And you can’t just do that at home.”

What you can do is set up an experiment with blood transfusions in Alzheimer’s patients, and Wyss-Coray is seeking federal government permission to do just that. You can also look to see just what it is in the blood that’s having the effect, and that’s what Amy Wagers and Lee Rubin of Harvard’s Department of Stem Cell and Regenerative Biology did.

They not only transfused mice with young blood, but surgically connected two-month-old mice to 15-month-old mice for five weeks. (This strain of mice usually lives just over 2 years). The young mice didn’t seem to suffer from sharing blood with the older mice. But when they hooked up the young mice to 21-month-old mice, production of new brain cells slowed.

Other studies have shown this, also -- something in the blood of older mice can impair young ones.

The researchers know that as animals age, they lose blood flow in the brain. The young blood restored some of this lost blood flow in the older mice. More tests showed the young blood was making the existing blood vessels healthier.

“This should give us all hope for a healthier future."

Other research had shown that a protein called GDF11 strengthened the hearts of elderly mice. When the Harvard team injected older mice with GDF11, they exercised better and smelled things better, also.

“This should give us all hope for a healthier future,” said Dr. Doug Melton, who helps head the department at Harvard. “We all wonder why we were stronger and mentally more agile when young, and these two unusually exciting papers actually point to a possible answer: the higher levels of the protein GDF11 we have when young. There seems to be little question that, at least in animals, GDF11 has an amazing capacity to restore aging muscle and brain function.”

The next step is to see how much of this applies in humans.

“It isn’t out of question that GDF11 … might be worthwhile in Alzheimer’s Disease,” Rubin said. His team is working with venture capitalists to raise the money to go forward. Wyss-Coray has co-founded a biotechnology company called Alkahest to move ahead.

Wyss-Coray believes there could be other factors besides GDF11 at work. And it will also be important to find out where they are made. It might not be the blood that is key — some other organ may be producing these rejuvenating factors, and the blood’s just carrying them around.

“What I think this opens is (the possibility that) we will be able to delay aging of your body,” Wyss-Coray said. “If you could do that and translate it to humans, you could delay a lot of diseases simply because your body would be younger.”