Back in 2013, Stanford scientists discovered a way to turn mice brains transparent with the aptly-named technique CLARITY. Last year, scientists used it to delve into the neuroscience behind pleasure and pain. Now, researchers at the University of Duisburg-Essen in Germany are employing the technique to study the damage that strokes cause to the brain's blood vessels. 

CLARITY involves bathing the brain in chemicals before subjecting it to a series of electric currents. This removes any opaque elements while keeping everything intact, turning the brain a ghostly transparent white. The creators hoped the technique would help revolutionize brain research by offering a simpler and more precise alternative to the usual method of cutting and slicing brains to make a series of 2D slides. 

Excitingly, CLARITY could lead to more effective treatment for strokes, the fifth most common cause of death in the US. Strokes occur when the blood supply to the brain is blocked, starving it of oxygen and nutrients. The findings have been published in the Journal of Cerebral Blood Flow and Metabolism. 

Most researchers use dyes, 2D slides, and brain scans to study the causes and effects of strokes in the brain. However CLARITY allowed Dirk Hermann, Chair of Vascular Neurology and Dementia at the University of Duisburg-Essen, and Matthias Gunzer, from the Center for Medical Biotechnology, and their team to examine mice brains in 3D. This gave them a clear view of what was happening in the blood vessels. 

First, the researchers injected mouse hearts with a fluorescent gel so that they could pump the solution around the body. Then they removed the brains of the mice and soaked them in chemicals. 

“You’re left with a brain that is clear like glass,” Hermann told New Scientist.

The researchers then placed the see-through brains under a microscope and used a laser to illuminate the gel. This, along with subsequent image processing, allowed them to look at the way a stroke interrupts the brain's blood supply in 3D for the first time.

“You could see which capillaries had died and how the surviving ones were reorganizing themselves,” Gunzer told New Scientist. 

Strokes are responsible for one in every 20 deaths in the US and are a leading cause of disability, according to Centers For Disease Control and Prevention (CDC). The researchers at Duisburg-Essen hope their work with mice brains will inform future research and pave the way for treatment in human stroke patients.