Specialized cells host a hitherto unknown cleansing system

By Laura Sanders

Web edition: August 15, 2012
Print edition: September 22, 2012; Vol.182 #6 (p. 15)

The brain is a self-cleaning machine. A previously unknown plumbing system blasts out waste by flushing it with the brain’s cleaning solution — cerebrospinal fluid.

Jeffrey Iliff of the University of Rochester Medical Center in New York and his colleagues watched cerebrospinal fluid flowing through the brains of living mice using an advanced imaging technique called two-photon laser scanning microscopy. First, the fluid rushed into the brain by piggybacking on the outer surfaces of arteries. Once in the brain, the fluid swept away wastes such as the protein amyloid beta, which accumulates in the brains of people with Alzheimer’s disease. Finally, the brain expelled the liquid through large cellular drains.

Channels on specialized brain cells called astrocytes control the fluid flow, the team reports in the Aug. 15 Science Translational Medicine. Mice lacking these channels on their astrocytes had sluggish plumbing. Malfunctions of a similar plumbing system in humans could be behind brain conditions in which harmful proteins accumulate in the brain, such as Alzheimer’s, Parkinson’s and traumatic brain injury.