Why a see-through mouse is a big deal for scientists


Science isn't always pretty. (Yang et al, Caltech)

Today in Cell, a group of Caltech researchers announced their success in making an entire organism transparent. Unfortunately, this isn’t any kind of “Invisible Man” scenario: The organism in question is a mouse, and the mouse in question is quite dead.

But a see-through rodent is exciting nonetheless. The mouse, researchers said, is an important proof-of-concept for a new scientific technique—one that will help scientists study organs and tissues in the lab, and could even help diagnose illnesses in humans.

A 3D visualization of intact kidney tissue, cleared and stained to show different cell types. (Yang et al, Caltech) A 3D visualization of intact kidney tissue, cleared and stained to show different cell types. (Yang et al, Caltech)

Senior study author Viviana Gradinaru, an assistant professor at Caltech, focuses on the neuroscience applications of such technology. When neuroscientists want to figure out what kinds of cells make up the human brain (a vital step in understanding how it works, and how to fix it when it’s broken) they usually have to slice and dice it.

Laboratory technicians will cut thin sections of the brain, label them, take high resolution images of them, and then reconstruct the whole brain with software. But the process is quite tedious, Gradinaru said, so people will often only sample every other slice. This can lead to errors.

This is a 3D visualization of intact intestine tissue, obtained through the whole-body clearing and staining method. (Yang et al, Caltech) This is a 3D visualization of intact intestine tissue, obtained through the whole-body clearing and staining method. (Yang et al, Caltech)

Any imaging technique that would allow researchers to see high resolution tissue imaging without slicing would be a boon to the field.

Gradinaru previously worked on a process to do just that: By removing the lipids in the brain with detergent, researchers could make them transparent. But the real trick was maintaining the structural integrity of the organ once those lipids were gone. Gradinaru and her colleagues found a way to replace the lipids with a transparent gel to support the tissue.

Researchers can inject markers—colorful liquids designed to seek out specific proteins— to create a 3D map of the cell types within the brain.

The new study shows that by pumping the detergent and gel through an animal’s circulatory system, you can very quickly make an entire body transparent and ready for research. In mice, most organs were cleared in two days, with the entire body clear in two weeks.

And even though it’s no invisibility cloak, the technique can already benefit humans: Labs have already begun using the lipid-clearing technique on tissue from human biopsies. Using the technique for finding cancerous cells, Gradinaru said, is a no-brainer.

Rachel Feltman runs The Post's Speaking of Science blog.
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Rachel Feltman · July 30, 2014