A close look at an artery in the brain of a mouse. The green and yellow are cerebrospinal fluid traveling outside of the artery. The red indicates cells within the artery. At the artery's edge, the blue coloration corresponds to special glial water channels that mediate the fluid's flow.
Image: Jeffrey Iliff, University of Rochester
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The brain can be a messy place. Thankfully, it has good plumbing: Scientists have just discovered a cleansing river inside the brain, a fluid stream that might be enlisted to flush away the buildup of proteins associated with Alzheimer's, Huntington's and other neurodegenerative disorders.
The researchers, based at the University of Rochester (U.R.), University of Oslo and Stony Brook University, describe this new system in the journal Science Translational Medicine today. The study adds to the evidence that the star-shaped cells called astrocytes play a leading role in keeping the nervous system in good working order.
In most of the body, a network of vessels carry lymph, a fluid that removes excess plasma, dead blood cells, debris and other waste. But the brain is different. Instead of lymph, the brain is bathed in cerebrospinal fluid. For decades, however, neuroscientists have assumed that this fluid simply carries soluble waste by slowly diffusing through tissues, then shipping its cargo out of the nervous system and eventually into the body's bloodstream. Determining what's really going on has been impossible until recently.
In this study, researchers led by U.R. neuroscientist Maiken Nedergaard have identified a second, faster brain-cleansing system. Nedergaard an expert in non-neuronal brain cells called glia, has long suspected that these cells might play a role in brain cleansing.
Nedergaard and colleagues studied live mice with holes drilled into their skulls to gain an unobstructed view. To see how waste is carried by cerebrospinal fluid in a living mouse, they injected the mice with radioactive molecules that could be traced using laser-scanning technology.
The molecules' journey began after being injected into the subarachnoid space, a cavity between membranes covering the brain and spinal cord. The researchers observed that, like a river, cerebrospinal fluid carried these molecules rapidly along specific channels. Glial cells along the outside of arteries form these channels, creating a flume for cerebrospinal fluid that follows the brain's blood vessels. In addition, the researchers found that these glial cells mediate the channel's activity, assisting the flow of fluid through the channel.
From channels alongside arteries, the tracer-bearing fluid then passes through brain tissues. At the other end of tissues, it flows into similar channels along veins. The fluid follows these veins then either returns to the subarachnoid space, enters the bloodstream or eventually drains into the body's lymphatic system. The researchers christened the network the "glymphatic" system, a nod to both glial cells and its functional similarity to the lymphatic system.
U.R. neuroscientist and lead author Jeff Iliff notes several surprises in the study: "I didn't think we would see these jets of fluid going through the brain," Iliff says. In addition, he explains that previous conception of cerebrospinal fluid's role in waste removal suggested that the process was one-way, sending particle-carrying fluid from the brain into the body. Instead, they observed a recycling, as much as 40 percent of the fluid returned to the brain.
As a test of their work, the researchers injected proteins called amyloid beta into mice's brains. In Alzheimer's, this protein—present in all healthy brains—can accumulate and clump, developing into cell-damaging plaque. The researchers compared mice with a normal glymphatic system to those with a disabled gene that prevented glial cells from assisting in the fluid flow. They found that in the normal mice, the protein rapidly cleared from the brain along these channels, but amyloid removal diminished in the gene-altered animals.
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7 Comments
Add CommentHow soon do they test on a higher life form such as chimps or humans?
Reply | Report Abuse | Link to thisYou are assuming chimps and humans are a higher form of life.
Reply | Report Abuse | Link to thisAll kidding aside, this study demonstrates that neurodegenerative disorders are treatable with gene therapy. I always understood these degenerative diseases were caused by a slow destruction of brain cells which could not regenerate as quickly as they failed. This sheds a whole new light on the problem. It is more like a slow acting pollution problem for the individual cells. It should be merely a matter of time before a discovery that would reverse the build up of this brain plaque in the first place.
Fascinating!
Reply | Report Abuse | Link to thisSince the pollutant seems to be excess protein perhaps we should decrease the amount and or types of protein we eat?
Reply | Report Abuse | Link to thisDoes anyone know what kind of<a href="http://www.storkpickerservices.ca/en/">waste </a>this would produce.
Reply | Report Abuse | Link to thisI sincerely believe that by following this article which refers on “how our brain clean itself” will help you to prevent diseases such Alzheimer’s and Parkinson’s disease. You can also see “http://selfhelptechniques.com/self-help-techniques/can-chakra-balancing-tapping-technique-clean-your-body-and-brain-space" This site can also help you.
Reply | Report Abuse | Link to thisThis is fascinating to me. I am still in the process of diagnosis but my father was diagnosed w/ ALS and then nine months later they re-diagnosed him w/ Multi-focal Motor Neuropathy. His father had early-onset alzheimer's. His sisters have lymphoma and amyloidosis. In light of the above article, this is very interesting to me as I've always wondered the connection between the "blood cancers" and the "neuro" issues in my family - I currently have nerve issues going on but have often wondered if it's lymphoma too... and I had a large "clump" on the top of my left hand... been having nerve issues in my left side. Anyway, I'm going to forward this on to my family as the connection between the two systems is fascinating in light of my family's genetic makeup and current health issues.
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