The rejuvenating effect of young blood could be largely due to certain packages of RNA and proteins that bud off from some cells and travel via the blood to other cells. When researchers injected these cell buds into old mice, it reversed several signs of ageing, including boosting muscle strength and hair growth and improving coordination and endurance.
“What we saw was that the physical performance of the animals was better,” says Consuelo Borrás at the University of Valencia in Spain.
Several animal studies over the past decade have shown that transfusions of young blood can have rejuvenating effects, and there are signs it might work in people, too. Borrás thinks that the particular make-up of the extracellular vesicles – in the bodies of animals – in young blood are largely responsible.
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“I don’t know if all the effect is due to the extracellular vesicles, but I’m sure that extracellular vesicles are important,” she says.
“Yes, I think that is possible,” says at Stanford University in California, whose team first demonstrated the effect of young blood in 2012 in experiments that involved linking the blood supplies of young and old mice.
Wyss-Coray’s team hasn’t looked at extracellular vesicles. However, last year, a separate study by at the University of Pittsburgh, Pennsylvania, found that in mice.
“Our work does indeed suggest that extracellular vesicles may play a role in the beneficial effect of young blood on aged skeletal muscle regenerative capacity,” says Ambrosio. Her team hasn’t looked at tissues other than muscle yet, she says.
Some extracellular vesicles form when the membrane of a cell pinches in and tiny parts of the cell bud off. They can travel through the blood and fuse with distant cells, releasing their contents. The proteins and RNA that extracellular vesicles carry can switch genes on or off, and thus alter the behaviour of the cells. In other words, they are a form of cell-to-cell communication.
Recent studies have suggested that in good and bad ways. While those from stem cells can boost healing, the contents of extracellular vesicles change as cells age. Those from senescent cells – older cells that can no longer replicate – may accelerate ageing.
Now, Borrás and her colleagues have produced the best evidence yet that extracellular vesicles can have anti-ageing effects. The researchers first obtained fat stem cells from young mice, then derived extracellular vesicles from these stem cells. They injected old mice with two doses, spaced a week apart, of either extracellular vesicles or a saline solution.
A month later, the grip strength and motor coordination of the mice had improved, and they could exercise for longer. Those mice given only saline injections showed no improvements, and neither did mice injected with extracellular vesicles from old mice.
The team also plucked the fur from a small patch of skin just before the first injection. After two weeks, it had completely regrown in the mice given the extracellular vesicles, but only partially in the controls.
However, two months after the injections, the effects had faded. Borrás and her colleagues are now giving mice monthly injections to see if this extends lifespan.
Because of the safety issues involved in injecting extracellular vesicles into the blood, the team is planning a human trial that will instead involve applying them to the skin, to see if they can help heal pressure sores in elderly people. Borrás thinks skin application could also have cosmetic benefits.
Her team is also trying to pinpoint the specific components responsible for the beneficial effects. There are likely to be several elements at least. “Ageing is a very complex process,” says Borrás. “I don’t think you can do something for ageing with only one molecule or only one thing.”
Reference: bioRxiv, DOI:
