August 16, 2012
Cleansing System Inside Brain Drains Waste Products
Connie K. Ho for redOrbit.com — Your Universe Online
Researchers recently discovered a cleansing system in the brain with a new imaging technique.
Neuroscientists at the University of Rochester Medical Center found a system that can drain the waste from the brain; it was previously unrecognized by scientists. The system is highly organized and is designed with a series of pipes that depend on the brain´s blood vessels, providing the same function in the brain as the lymphomatic system does for the rest of the body by moving away waste products. The results were recently published in Science Translational Medicine.
“Waste clearance is of central importance to every organ, and there have been long-standing questions about how the brain gets rid of its waste,” commented senior author Dr. Maiken Nedergaard, co-director of the University´s Center for Translational Neuromedicine, in a prepared statement. “This work shows that the brain is cleansing itself in a more organized way and on a much larger scale than has been realized previously."
The team of scientists call the new system “the glymphatic system” as it is works like the lymphatic system but is controlled by glial cells, a type of brain cell. They discovered the system from studying mice, whose brains are similar to human brains.
“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,” continued Nedergaard in the statement.
Based on past research, the investigators identified that cerebrospinal fluid (CSF) could help cleanse brain tissue by moving waste products and bring nutrients to brain tissue through diffusion. The system moves CSF to all parts of the brain in an efficient manner. The scientists describe it as “bulk flow” or “convection,” with the new system under pressure to push large amount of CSF through the brain each day to move waste.
“It´s as if the brain has two garbage haulers — a slow one that we´ve known about, and a fast one that we´ve just met,” explained Nedergaard in the statement. “Given the high rate of metabolism in the brain, and its exquisite sensitivity, it´s not surprising that its mechanisms to rid itself of waste are more specialized and extensive than previously realized.”
As stated before, the scientists did not see the new system before as the system worked only when it was intact and functioning in a living brain. In addition, it was difficult for scientists to examine it in a live animal and they only had the opportunity to study sections of brain tissue that were no longer alive. Eventually, the researchers used a two-photo microscopy to study the flow of blood, CSF, and other substance in a living animal´s brain.
“It´s a hydraulic system,” noted Nedergaard in the statement. “Once you open it, you break the connections, and it cannot be studied. We are lucky enough to have technology now that allows us to study the system intact, to see it in operation.”
Researchers found that the glymphatic system can remove amyloid beta, a protein that increases in the brain of Alzheimer´s disease patients.
“Understanding how the brain copes with waste is critical. In every organ, waste clearance is as basic an issue as how nutrients are delivered. In the brain, it´s an especially interesting subject, because in essentially all neurodegenerative diseases, including Alzheimer´s disease, protein waste accumulates and eventually suffocates and kills the neuronal network of the brain,” remarked Jeffrey Iliff, a research assistant professor in Nedergaard´s lab, in the statement.
The study allows scientists to better understand how the newly discovered system could aid in the development of treatments for Alzheimer´s disease.
“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. This may be what is happening with amyloid deposits in Alzheimer´s disease,” concluded Iliff in the statement. “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.”