AILSA CHANG, HOST:
Next up, scientists are trying a new approach to reversing memory loss. NPR's Jon Hamilton reports on a study of forgetful mice treated with a substance found in spinal fluid.
JON HAMILTON, BYLINE: Mice, like people, tend to develop memory problems as they age. Tony Wyss-Coray of Stanford University says when mice are young, they will remember a painful experience for weeks.
TONY WYSS-CORAY: When they're old, they keep forgetting about this. A few days later, they can't remember that they were in a bad environment.
HAMILTON: Wyss-Coray thought one reason might involve the fluid that bathes the brain and spinal cord. After all, brain cells depend on this fluid, and its composition changes dramatically as an animal gets older. So Wyss-Coray had a researcher named Tal Iram try an experiment.
WYSS-CORAY: She collected spinal fluid from young mice and then infuse it into the brains of old mice.
HAMILTON: The idea was simple.
WYSS-CORAY: We were hoping that by mimicking a young environment that the brain would respond to that with better function.
HAMILTON: And it worked. The old mice began to remember as well as young ones. But why? Genetic tests showed that something in spinal fluid was rejuvenating specialized cells in the hippocampus, an area that's important to memory. These cells make the myelin sheath that insulates wiring in the brain. More tests revealed that the cells were responding to a growth factor called FGF17, which dwindles with age. So Wyss-Coray's team injected some FGF17 directly into the brains of old mice.
WYSS-CORAY: When we put the factor in the mice, they actually are better able to perform a memory task where they have to remember something that happened to them.
HAMILTON: Wyss-Coray says FGF17 is probably just one of many substances involved in brain aging. But the study, which appears in the journal Nature, suggests that restoring just one of these substances can make a difference. Wyss-Coray says an aging brain with memory loss is a bit like an old car that has broken down.
WYSS-CORAY: But similar to repairing a car, you don't necessarily have to fix all parts to make it still run. You have to find the key parts.
HAMILTON: Wyss-Coray says the approach could offer a new way to tackle problems like Alzheimer's disease. So far, he says, most treatments have focused on eliminating the disease's hallmarks, an accumulation of toxic plaques and tangles in the brain.
WYSS-CORAY: What we are seeing is that there's much more going on and that aging seems to produce a lot of abnormalities that contribute to the cognitive decline and dementia.
HAMILTON: And many of these abnormalities involve substances found in spinal fluid. Maria Lehtinen of Harvard University is excited but not entirely surprised by the result. Her lab has been studying the role of cerebrospinal fluid, or CSF, in young mouse brains.
MARIA LEHTINEN: We found that the CSF delivers these important health- and growth-promoting factors and essentially, in mouse models, can modulate brain growth.
HAMILTON: Lehtinen, who co-authored a piece accompanying the new study, says scientists are beginning to identify those factors.
LEHTINEN: What's been lacking so far is the next step, you know, of testing whether these CSF factors can confer benefits to adult functions.
HAMILTON: Like memory - Lehtinen says the new study suggests the answer to that question is yes.
Jon Hamilton, NPR News.
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