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Mouse’s body turned transparent to reveal its central nervous system

Researchers at the Ludwig Maximilian University of Munich in Germany have demonstrated a new technique called “tissue clearing,” which can turn the entire body of an animal transparent so that it can be examined in previously unimaginable levels of detail.

“We wanted to find a method of converting biological tissue into a transparent structure for high-resolution deep tissue laser scanner,” Dr. Ali Ertürk, group leader at the university’s Acute Brain Injury Research Group, told Digital Trends.

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Unlike X-rays, the technique doesn’t just show the skeleton of a subject, but also its entire central nervous system. The treatment has the side effect of reducing the body to one-third of its size due to the dehydrating process, although this turned out to help the team since it made looking at it under a microscope easier.

“Normally, tissues are opaque because the light is scattered by the different components of the tissues which have different refractive indexes,” Ruiyao Cai, a doctoral student involved in the research, explained to Digital Trends. “What we did was to remove the main scattering agents: water and lipids by using alcohol and organic solvents. In the end, the animals were soaked in a chemical with a refractive index that matches the one of the residual components of the tissue. In this way, when the light tries to cross the tissue, it will not be scattered anymore.”

While right now the technique has only been tested on deceased rodents, Ertürk said that its creation came about as a result of his team’s desire to analyze brain injuries among humans.

“We started this project because there was a scientific need for it,” he said. “We’re studying traumatic brain injuries, and after brain injuries we believe that far more of the body is affected than just the brain. Because neurons in the brain are connected to the spinal cord, a head injury can affect the whole body. Unfortunately, this perspective isn’t always taken into consideration because there’s no good way to look into it. People just look at the brain, or part of the brain. I wanted to see the global effects of these injuries.”

Cai noted that this technique could help lead to breakthroughs in analysis of the body’s central nervous system. “In principle it will be possible to map the whole neuronal network of mouse nervous system and maybe in the future the entire human nervous system,” she said. “It could also be useful in the future for studying neurodegenerative diseases such as Alzheimer’s.”