Food Dye Makes Live Mice Transparent

Researchers at Stanford University have found that applying a common food dye to the skin of mice enables biologists to see through to the animals’ internal organs and structures, enhancing their research capabilities.

Scientists have methods to examine tissues and bodies of humans and animals, but these often involve biopsies or are limited to postmortem studies.

The ability to observe inside a living organism provides researchers with a valuable tool to study biological processes in real time, advancing their work. This approach is also more humane, as it avoids causing pain or death to animal subjects.

Overcoming Light Scattering in Living Animals

A major challenge in viewing the internal structures of living animals is that the protein and fat in their skin efficiently scatter light, making it opaque. However, Stanford researchers found that applying tartrazine, commonly known as FD&C Yellow 5, reduced this scattering.

The dye absorbs light in the near-ultraviolet and blue spectrum, allowing red and orange light to penetrate deeper into the tissue, effectively making the mice’s skin transparent. The transparency was easily reversed when the dye was washed off.

By applying the dye to the abdomens of mice, the researchers were able to observe neurons tagged with fluorescent markers in real time, revealing gut motility. This technique could improve understanding of digestive conditions like IBS. They also applied the dye to the mice’s skulls and hindlimbs, allowing them to see cerebral blood vessels and muscle activity.

“Our approach … offers opportunities to visualize the structure, activity, and functions of deep-seated tissues and organs without needing surgical removal or replacing overlying tissues with transparent windows,” the researchers explain.

New Dye Method Enables Transparency in a Wider Range of Animals

This discovery could broaden the range of animals used in research. In a commentary published in Science, Christopher J. Rowlands and Jon Gorecki, who were not involved in the study, note that species like zebrafish and nematodes are often chosen because of their naturally transparent skin, which allows for easy observation of internal processes.

However, with this new dye-based method, nearly any animal could temporarily become transparent, giving researchers an inside view.

Rowlands and Gorecki also highlight the importance of this breakthrough.

“Based on these findings,” they write, “it is plausible to anticipate a tenfold improvement in imaging depth with sufficient dye penetration. This could enable advances like multiphoton imaging of an entire mouse brain or detecting tumors around blood vessels located beneath tissues several centimeters thick using optical coherence tomography catheters.”

Read the original article on: New Atlas

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