How to Make a Transparent Mouse with a Few Simple Ingredients

By Veronique Greenwood | August 31, 2011 3:02 pm

embryos
On the left: A mouse embryo preserved in para-formaldehyde. On the right: A mouse embryo soaked in Scale for two weeks.

What’s the News: The trouble with brains, organs, and tissues in general, from a biologist’s perspective, is that they scatter light like nobody’s business. Shine a light into there to start snapping pictures of cells with your microscope, and bam, all those proteins and macromolecules bounce it around and turn everything to static before you’ve gotten more than a millimeter below the surface. Scientists at RIKEN in Japan, however, have just published a special recipe for a substance that makes tissue as transparent as Jell-O, making unprecedentedly deep imaging possible.

How the Heck:

  • Substances to make tissue more transparent are called clearing agents, and the ones we have now have varying degrees of penetration—in other words, they don’t always take you as deep as you’d like. To boot, they sometimes mess with the fluorescent tags that biologists splice into certain tissues to light up a particular set of blood vessels or neurons, for example.
  • This recipe clears out tissue so well that the only limitation on how deep you can see is the power of the lens of the microscope. And, as the researchers proved when they used it to image part of a mouse brain, it doesn’t diminish the glow of the fluorescent tags they’d engineered the mouse to express.
  • The clearing agent is called Scale, and, serendipitously, it’s made from odds and ends that any lab will have lying around. Urea, which most of us know as a compound in urine; Triton-X, a detergent biologists use to make cell membranes more permeable; and glycerol, which is used in antifreeze, are all it takes to whip up a batch.
  • Once the team figured out the correct proportions of each, they soaked mouse brains, mouse brain slices, and the above embryos in the stuff for two weeks and examined the results under the microscope. They were able to see at least several millimeters below the surface and, by activating fluorescent labels in neurons with a laser light, traced patterns neurons in the hippocampus and other areas of the brain.

brain
A mouse brain soaked in Scale looks like tiny glob of jello. Turn
off the lights and shine a laser through it, and the light shoots
right through.

What’s the Context:

  • The researchers suggest that the clearing agent could be useful for drawing connectivity maps of the brain, a field known as connectomics.
  • Tracing circuits in the brain is such delicate work that it is still done by hand, and some of the most exciting new imaging methods focus on making clearer and deeper pictures of neurons for use in such cartography.
  • Scale is unusual among these, however, because instead of using algorithms to cancel out fuzz in the image or bypassing light entirely by using certain types of fMRI, it alters the tissue itself to be more amendable to viewing.

The Future Holds: Though this time the team used it to study the brain, Scale can be used in any tissue. The downside is that, like other clearing agents and treatments, Scale only works with dead tissue, so don’t expect to see barrel-fish-like mice wandering around in labs just yet. But the team is working on a milder version that they hope could be used in living creatures in the future.

Reference: Hama, et al. Scale: a chemical approach for fluorescence imaging and reconstruction of transparent mouse brain. Nature Neuroscience (30 August 2011). doi:10.1038/nn.2928

Image courtesy of Nature Neuroscience and Hama, et al.

CATEGORIZED UNDER: Mind & Brain
  • Ed

    Invisible man, here I come!

  • http://www.johnz.realstew.com John M. Tax

    I’d sure like to know more about what causes the light to reflect vs shoot through and what needs to be done to cause the transparency.

  • http://faculty.alverno.edu/bowneps Pat Bowne

    Wow! Is it suitable for clearing and staining for osteology, or does it also clear the bones? I got good results with the old KOH/trypsin procedure, but it’s always fun to try something new. Is this compatible with cartilage or nerve staining, as well?

  • Chris

    So if I fill my bathtub up with that and soak for a few weeks will you be able to see through me? I’d like to sneak into the girl’s locker room :-P

  • http://iheardacouplethings.blogspot.com Listener 43

    While this is quite a discovery, there are many potential abuses, as I’ve written about here:
    http://iheardacouplethings.blogspot.com/2011/09/threat-of-transparency.html

  • Abizar

    So what is the recipe, how much urea, triton and glycerol?

  • Durant S.

    Is glycerol used in antifreeze ? I always thought that antifreeze was ethylene glycol.

  • Reasearcher

    @Listener 43- just read your blog dude.. You might wanna research things a little harder before you go posting BS on your blog . Even of they COULD do this with live tissue, there’s no way a semi-transparent man would make a great spy.. If anything he’d stick out like a sore thumb.. Look @ the pic above ^^ is the mouse invisible? I didn’t think so

  • Chris

    @Durant S.
    Antifreeze can be a couple of things. Ethylene glycol is used in automotive applications but is pretty toxic to living tissues. Glycerol (which is naturally occurring) is used to preserve tissues below 0 Celsius otherwise when frozen the ice crystals would make your biological sample into mush.

  • Jennifer Angela

    I was thinking the same myself, Ed. It looks like we are just one step away from creating the invisible man (like Chevy Chase in the movie). I wonder if there will be an invisible woman too. But all jokes aside. I´ve got to say this article is one of the most fascinating ones and one of the best of all articles I´ve read in a long time! An inspiring discovery has been described in a truly interesting way! Moments like these make me recommend discover to all (educated) people I know! Where else do you get to read fascinating things AND comment on them anytime you like?

  • Jennifer Angela

    In the name of the safety of teeenage girls, I hope Chris meant a women´s locker room.

  • Chris

    If we’re able to study and replicate every connection in the human brain, what is there to stop us creating a replacement? Transferring consciousness? Am I reading too much into the fantastic possibilities of understanding every connection.

  • John Sousthual

    Invisible spy? Haha, well it doesnt work like that.. it does makes the tissue transparent, but not a 100% as you can se.. but more importantly it doesnt stop the light from being refracted, wich means its not invissible… If you have ever seen a glass sculpture you see that its very very far from invisible, because light rays are always bent in a medium unless it has the exact same reftactory constant as the medium its in, in this case air… SO far no solid material can be made like this.. so invisible man is more likely gonna be produces by some kind of technology (suite) recording incoming light, calculating the angels etc, and then emmit light from correct points.

  • http://twitter.com/cancerclasses cancerclasses

    @Reasearcher Says, What mouse?

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