Researchers have come up with a method that not only turns mice, rats and other mammals transparent but also shrinks them, making them easier to study.

Every year, some 25 million animals are used in labs for the sake of research. Cheap and simple to use, animal models have been utilized mostly to create powerful drugs and assess treatment options for humans. Unfortunately, they are not without their limitations.

Ali Erturk and colleagues hoped to address these limitations by developing a lab process known as uDISCO, or ultimate 3D imaging of solvent-cleared organs, which can turn lab animals — skin, muscles, bones and all — almost entirely clear.

This isn't the first time lab animals have been turned transparent to make them easier to study, but uDISCO is the first to also shrink animal models to make it possible to 3D-scan small specimens.

By essentially creating high-resolution digital maps of lab animals, detailed enough down to the cellular level, uDISCO is making the most of a lab animal's sacrifice by allowing more researchers access to the specimen.

"One would just need to go to [the] website, choose the organ of their interest and visualize various cellular systems within the individual organ or in the entire organism if desired," said Erturk.

Additionally, uDISCO doesn't interfere with fluorescent proteins that light up to identify certain tissues within transgenic animals.

Critical to the method is diphenyl ether (DPE), a fat-dissolving chemical, and tert-butyl alcohol, which is used to push out water gently from animal cells and replace it. Both DPE and tert-butyl alcohol are flushed through the to-be-turned-transparent lab animal, achieving transparency over a few days.

Turning a lab animal transparent and shrinking it makes specimen not only easier to handle but also allows an overview that makes it possible to see how different systems work together. This makes it easier to understand what goes wrong when a disease manifests itself.

According to Erturk, uDISCO can someday make it possible to map the human brain, acting as a compromise between brain-scanning machines that only show anatomy on a larger scale and microscopes that are unable to show connections between neurons.

Aside from facilitating studies into various human processes, the researchers are also looking at uDISCO to reduce the amount of lab animals killed every year. They have not determined just how many lab animals will be saved by uDISCO but even just a 5-percent drop would mean hundreds of thousands of animals every year could be saved around the world.

Erturk and colleagues' work is published in the journal Nature Methods.

Photo: Rene Schwietzke | Flickr