ROBERT SIEGEL, HOST:
New research suggests that something in the blood of babies' umbilical cords could help fight aging - in mice, at least. But as NPR's Rae Ellen Bichell reports, scientists caution that they need to do a lot more research.
RAE ELLEN BICHELL, BYLINE: Decades ago, scientists found that old animals lived longer if they received blood from younger ones. Then just a few years ago, scientists again looked at the impact of young blood on aging liver and muscle...
JOE CASTELLANO: And found that aged muscle can look young again.
BICHELL: That's Joe Castellano, a neuroscientist at Stanford University's School of Medicine.
CASTELLANO: And then a variety of groups went on to show this for other aging tissues with young blood.
BICHELL: This kind of research is controversial but Castellano and his colleagues wondered if young human blood might have rejuvenating effects. So he and his colleagues collected plasma, which is the watery part of blood, from donors of different ages - some were in their 70s and 80s, some were in their 20s - and also from umbilical cords. Then they injected that human plasma into aging mice several times over the course of a few weeks.
And when they dissected the mouse brains, they found that one part - the hippocampus, which is important for memory and emotion - looked different in animals that had received plasma from young people or from umbilical cords. Certain genes were turned on, genes that are linked with making new memories.
CASTELLANO: So we had a hint early on that one of these donor groups, specifically the cord plasma, might be having an effect on the brain itself.
BICHELL: Then they injected more aging mice with human plasma and tested the animals' memories, like how long it took them to learn to escape from a maze. The researchers write in the journal "Nature" that on multiple tests, mice that had received plasma from human umbilical cords did better.
CASTELLANO: So at this stage, we're first of all surprised and excited that there was something in human plasma. And more specifically, there's something exciting about cord plasma.
BICHELL: After a series of other experiments, Castellano and his colleagues concluded that one protein in human umbilical cord blood might be responsible for the improvement, a protein called TIMP2. But Castellano is the first to say that no, this finding does not mean that everyone should start sprinkling TIMP2 protein on their cereal or signing up for transfusions of young blood. First off, there's no evidence that humans would experience the same effects as the mice in the study did. It's also unclear what the longer term effects might be on mice or humans. And...
CASTELLANO: Maybe there's a reason that older brains aren't exposed to certain proteins any longer.
BICHELL: In fact, other researchers found that this very protein is actually elevated in people with Alzheimer's disease, so it could end up being harmful for older brains. And some in the field are not convinced that the protein Castellano found in mouse brains actually came from the human plasma they injected. Maybe it was already there. Aubrey de Grey, a biologist studying aging with the SENS Research Foundation, has a goal of essentially keeping people healthy into old age.
AUBREY DE GREY: The desired outcome is overall whole body rejuvenation.
BICHELL: He thinks this study is an exciting starting point.
DE GREY: The only thing, of course, is that it's a mouse experiment. And mice - mouse experiments often doesn't actually translate faithfully into the human setting.
BICHELL: De Grey and Castellano both concede that however promising a single protein may look, it's highly likely that the biological fountain of youth - if it exists - is going to be much more complicated. Rae Ellen Bichell, NPR News.
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