The writer of Leviticus once wrote, “For the life of the flesh is in the blood… (Lev 17:11)” Now three new studies reveal that the blood from young animals may partially reverse the effects of aging in older animals. The three independent reports, two published this week in Science and one in Nature, all show reversal of muscular and nervous system aging after circulating the blood of young mice through the old mice tissues.

In one of the Science articles, Manisha Sinha and colleagues at Harvard University identified a role for growth differentiation factor 11 (GDF11), a protein that circulates in the blood, in skeletal muscle rejuvenation. The researchers determined that infusions of young-mouse blood and supplementation with synthetic GDF11 resulted in similar outcomes in older mice, including reversal of functional impairments and restored genomic acitivy in muscle stem cells. Also observed were increased strength and endurance exercise capacity with GDF11 supplementation.

“It’s really exciting,” said Amy Wagers of the Harvard Stem Cell Institute, senior author of this report. “It says there’s a coordination of signals through the blood system that’s affecting aging in many different organs.”

In a second report also published in the same issue of Science, Lida Katsimpardi, Wagers, and coworkers found similar rejuvenating effects of GDF11 and young blood in the aged mouse central nervous system. They showed that factors in young blood induced repair of brain blood vessels that ultimately allowed the old mice to exhibit neurogenesis and improved odor discrimination. They showed that GDF11 alone can exert these effects. The researchers are hopeful that the ground-breaking findings will ultimately lead to new therapies for treating age-related neurological disorders.

In a third study published this week in the journal Nature, Saul Villeda and fellow scientists at Stanford University and the University of California-San Francisco examined the effects of supplementing the blood of old mice with young mouse plasma, the liquid, non-cellular portion of blood, in a specific brain region called the hippocampus. The hippocampus is important in learning and memory and is the site of extensive studies on the ability of the brain to form new connections, or “neuroplasticity.”

Villeda and colleagues observed both structural and cognitive enhancements in the hippocampus of old mice given young mouse plasma. They determined that the effects are at least partially mediated by a protein called cyclic AMP response element binding protein, a protein important in gene transcription.

“It was as if these old brains were recharged by young blood,” said senior author Tony Wyss-Coray, neurology professor at Stanford University School of Medicine.

Efforts are underway to study whether similar benefits may be achievable in humans.