Scientists Discover Previously Unknown Cleaning System in Brain
Newer Imaging Technique Brings 'Glymphatic System' to Light

A previously unrecognized system that drains waste from the brain at a rapid clip has been discovered by neuroscientists at the University of Rochester Medical Center. The findings were published online August 15 in Science Translational Medicine.

The highly organized system acts like a series of pipes that piggyback on the brain's blood vessels, sort of a shadow plumbing system that seems to serve much the same function in the brain as the lymph system does in the rest of the body to drain away waste products.

"Waste clearance is central to every organ, and there have been longstanding questions about how the brain gets rid of its waste," said Maiken Nedergaard, M.D., D.M.Sc., senior author of the paper and codirector of the University's Center for Translational Neuromedicine. "This work shows that the brain is cleansing itself on a much larger scale than has been realized previously.

"We're hopeful that these findings have implications for many conditions that involve the brain, such as traumatic brain injury, Alzheimer's disease, stroke, and Parkinson's disease," she added.

Nedergaard's team has dubbed the new system "the glymphatic system," since it acts much like the lymphatic system but is managed by brain cells known as glial cells. The team made the findings in mice, whose brains are remarkably similar to the human brain.

First author Jeffrey Iliff, Ph.D., research assistant professor in the Nedergaard lab, took an indepth look at amyloid beta, the protein that accumulates in the brain of patients with Alzheimer's disease. He found that more than half the amyloid removed from the brain of a mouse under normal conditions is removed via the glymphatic system.

"Understanding how the brain copes with its own waste is of great importance, because in essentially all neurodegenerative diseases, including Alzheimer's disease, protein waste accumulates and eventually suffocates and kills the neuronal network of the brain," said Iliff.

"If the glymphatic system fails to cleanse the brain as it is meant to, either as a consequence of normal aging, or in response to brain injury, waste may begin to accumulate in the brain, as seen with amyloid deposits in Alzheimer's disease," said Iliff. "Perhaps increasing the activity of the glymphatic system might help prevent amyloid deposition from building up or could offer a new way to clean out buildups of the material in established Alzheimer's disease," he added.