Scientists have recently discovered a method to temporarily make mouse skin transparent, opening up the possibility of observing living mouse organs without surgical intervention.
According to a publication in the journal Science on September 6, a type of dye commonly used to color “Doritos” can render mouse tissues transparent. When applied to the skin of living mice, this dye allows scientists to see through the tissues and observe both blood vessels and internal organs. This is considered a significant breakthrough in the study of living animals used in medical research.
When dissolved in water, tartrazine causes the water to bend light like fat, making tissues containing fluids and lipids transparent. (Photo: Stanford University).
This technique works by altering how body tissues interact with light. Components such as fluids, fats, and proteins in tissues typically have different refractive indices, causing light to scatter and making the tissues appear opaque. By adding a strong light-absorbing substance, researchers narrowed the gap between these refractive indices, thereby rendering the tissues transparent.
The research team utilized theoretical physics to predict how certain molecules would change the interaction of mouse tissues with light. They focused on tartrazine, a dye commonly found in many processed foods. When dissolved in water, tartrazine causes the water to bend light like fat, making tissues containing fluids and lipids transparent.
Scientists tested the transparency-inducing capability of tartrazine on thin slices of raw chicken meat. They then applied the dye to various areas of living mouse skin. When applied to the head, they could clearly observe small blood vessels; when applied to the abdomen, they could see the mouse’s intestines contracting during digestion and movements related to respiration. When applied to the mouse’s legs, they could even distinguish the muscle fibers beneath the skin.
However, this technique can currently only render tissues transparent to a depth of about 3mm, which limits its application to thicker tissues and larger animals. On the other hand, since tartrazine is a food dye, it is safe to use on living mice, and the process is reversible – when the dye is washed off, the skin returns to its normal opaque state.
This is a significant advantage over existing tissue transparency methods, which often are unsuitable for live animals and usually involve using chemicals to alter or completely remove certain tissue components.
Experts believe this new method will be widely applied, especially in laboratory mice to study the nervous system and neurodegenerative diseases.
