Old mice got stronger, exercised longer and performed better mentally after they were injected with blood from young mice, or even just with a substance that's more abundant in younger blood, researchers found as part of three separate studies published on Sunday.
In two papers in the journal Science, Professors Amy Wagers and Lee Rubin of Harvard's department of stem cell and regenerative biology, reported that injections of a protein known as GDF11, which is found in humans as well as mice, improved the exercise capability of mice equivalent in age to that of about a 70-year-old human.
Wagers and Rubin said the protein, which is more abundant in the blood of younger mice than old, also improved the function of the olfactory region of the brains of the older mice, allowing them to detect smells more like younger mice.
They also found that exposing older mice to the blood of younger mice produced more blood vessels and blood flow in the brain.
Previous studies had shown that giving young mice blood from old mice impaired their cognitive function. But these discoveries are the first to show the opposite: Young blood can reverse age-related impairments.
If the research continues to go well, the findings could lead to better treatment of some of the infirmities of old age in people, Rubin and Wagers said.
Rubin and Wagers say that, barring unforeseen developments, they expect to have GDF11 in initial human clinical trials within three to five years.
In another paper, published in the journal Nature Medicine, biologists led by Tony Wyss-Coray of Stanford University and Saul Villeda of the University of California San Francisco described two ways of exposing old mice to young blood.
They either injected plasma from 3-month-old mice into 18-month-olds, which are near the end of their lifespan, or surgically connected the circulatory system of a young mouse to that of an old one.
In that study, old mice exposed to young blood improved markedly on two standard tests of learning and memory.
Examining the brains of aged mice exposed to young blood, the scientists found structural and molecular differences from untreated old brains. Those that were exposed to young blood did better in learning and memory tests. They, for example, performed better at recalling where to find a submerged platform in a maze.
"We've shown that at least some age-related impairments in brain function are reversible," Villeda said in a statement to Reuters.