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See Inside Scientific American Mind Volume 24, Issue 2

Without Glia, the Brain Would Starve

Blood vessels break down if certain glial cells are not present
glia



FROM “NEUROSCIENCE: GLIA—MORE THAN JUST BRAIN GLUE,” BY NICOLA J. ALLEN AND BEN A. BARRES, IN NATURE, VOL. 457; FEBRUARY 5, 2009

The brain is voracious: compared with other organs, it consumes 10 times more oxygen and nutrients, receiving them by way of dense networks of blood vessels. Scientists know how these networks initially grow, but a surprising new study suggests that they are stabilized in early life by stem cells in the brain called radial glia. The finding could have significant implications for our understanding of Alzheimer's disease, a condition characterized in part by brainwide vascular problems.

Radial glia are stem cells that have been shown to help neurons grow and migrate throughout the brain. So when Zhen Huang, a neuroscientist at the University of Wisconsin–Madison, eliminated a gene in mice and thereby prevented radial glia from regenerating, he was “surprised to find [blood] vessels regress,” he says. The mice lacking this gene not only developed fewer radial glia, blood vessel density in their cortex also dropped by 83 percent.

Huang found that the loss of glial cells caused activity in a biochemical pathway called Wnt to increase. In additional experiments, he showed that ramping up Wnt in healthy mouse embryos caused their vascular brain networks to collapse, whereas turning Wnt down preserved them. Given that the brains of people with Alzheimer's are also plagued by blood vessel problems, the findings suggest that radial glia—and their careful control over Wnt—could be important for ensuring healthy brain energy metabolism and preventing neurodegeneration.

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