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.
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.
A major hallmark of aging is that regenerative properties significantly decline in most tissues. In 2005, Dr. Thomas Rando’s laboratory at Stanford University used heterochronic parabiosis, the connection of the circulatory systems of a young and an old animal, to demonstrate that factors derived from a young animal are able to activate molecular signaling pathways of an old animal, leading to increased tissue regeneration. These findings demonstrated for the first time that the age-associated impairment of cell function is induced to a significant extent by the molecular composition of the surrounding milieu rather than by cell specific changes alone.
Dr. Tony Wyss-Coray and Dr. Saul Villeda, in collaboration with Dr. Rando, subsequently reported that the old systemic environment negatively affects adult neurogenesis in brains of young heterochronic parabiont animals, and conversely, a young environment can increase neurogenesis in the old brain. This led to the discovery that soluble factors – rather than cells – in old blood are responsible for the decrease in synaptic plasticity and impair learning and memory. They discovered certain protein factors that impair adult neurogenesis and cognition in mice. Other groups demonstrated rejuvenating effects in a wide range of tissues and organs in old heterochronic parabionts.
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.
SOURCES - New Scientist, Alkahest