This photo, taken in October 2024 by the Oregon Health & Science University, is not dated. It shows Drs. Erin Yamamoto and Juan Piantino used special imaging to discover a previously unknown pathway that the brain uses to eliminate waste. (Christine Torres Hicks/OHSU via AP)
WASHINGTON, D.C. (AP) – A unique look inside the brain could help explain how it removes waste that can lead to Alzheimer’s.
Brain cells produce a large amount of waste because they use so many nutrients. Scientists believed for a long time that the brain had a special plumbing system to flush out cellular waste, especially during sleep. They could see this happening in mice. There was only circumstantial proof that a similar system existed in humans.
Researchers have now discovered the network of tiny waste-clearing canals in the brains and bodies of living people. This was made possible by a special type of imaging.
“I was sceptical,” said Dr. Juan Piantino, of Oregon Health & Science University. His team announced the findings on Monday. “We needed this article to show that this also happens in humans.”
The study was published by Proceedings of the National Academy of Sciences.
The brain is extremely active while sleeping. One reason is that it’s when it does a thorough cleaning. This has attracted attention because chronic sleep deprivation is also considered a risk for dementia.
How does the brain cleanse itself then?
Scientists at the University of Rochester reported the discovery of a network of channels that surround blood vessels. Cerebrospinal Fluid uses these channels to reach deep into tissue, and then move waste out of the brain. When mice were injected beta-amyloid — a major Alzheimer’s culprit — it cleared faster when they were sleeping.
Although it’s not known exactly how this network works, some research has shown that the pulsing blood vessels help move the waste-clearing liquid where it needs to go.
But it has been difficult to find this system in humans. Piantino said that regular MRI scans may show some of these fluid-filled channels, but they do not reveal their function.
His team in Oregon injected a tracer into five patients undergoing brain surgery who needed a more sophisticated form of MRI. The tracer “lit-up” under these scans, and sure enough, it was moving through the brain via those channels, just as previous research had found with mice.
Dr. Maiken Ndergaard, from Rochester, predicted that a small study but one of potential importance would increase interest in the connection between brain waste clearance and people’s health.
To test if better sleep, or other treatments, could really spur waste clearance, and improve health, Dr. Jeff Iliff of University of Washington who pioneered waste-clearance, said, “I need to be able measure glymphatic functions in people.” The question is if the new study could point to ways to measure.
Sleep isn’t all that matters. Iliff and Dr. Elaine Peskind, who are studying it with certain patients, will be examining animal studies that show a drug used to treat PTSD can improve glymphatic functions.
Piantino’s lab, which focuses on sleep, is looking for a noninvasive, easier test.
“We cannot study these questions by injecting humans,” he said.
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