30 March 2022

Dry cleaning for fabrics

Scientists have figured out how to make living tissues transparent

Alexandra Medvedeva, Naked Science

Scientists from the organization Scripps Research (USA) have proposed a new method of cleaning tissues that makes biological samples transparent. The technology will simplify the visualization of the body and investigate diseases of various organ systems. The method, called HYBRiD, was described in the journal Nature Methods (Nudell et al., HYBRiD: hydrogel-reinforced DISCO for clearing mammalian bodies). It combines elements of the two main previous approaches to cleaning fabrics, but is more practical than either of them. In addition, the scalable technology can be easily used in almost any laboratory.


HYBRiD-visualization of the chest of a mouse infected with SARS-CoV-2/ © Scripps Research.

Traditional tissue cleaning involves the use of solvents that allow you to remove opacity-providing molecules (such as fat) from it, while preserving most proteins and structures for further study. For example, with the help of genetic engineering, scientists attach fluorescent labels to certain proteins of organisms or use fluorescent antibodies to visualize specific molecules inside the body. Cleaning the tissues allows you to see these glowing marks all over the body at once.

For the first time, scientists thought about cleaning tissues about 15 years ago. Basically, they used these technologies to study neural connections all over the brain at once. The existing methods worked well for him, but were not suitable for other parts of the body that contain difficult-to-dissolve components. Organic or aqueous solvents have been used in the cleaning process so far. The former, as a rule, allowed to clean the tissue faster and more efficiently, but could weaken the fluorescent signals. The latter retained fluorescence better, but turned out to be practically useless for cleaning any tissues other than the brain. Moreover, both types of methods required long time-consuming procedures and often required the use of toxic chemicals. Therefore, an ordinary laboratory could not afford the large-scale and regular use of such methods.

HYBRiD technology includes the consistent use of organic and polymer solvents. In addition, the scientists treated the samples with a water-based hydrogel for three-dimensional visualization of solvent-purified organs (DISCO) in order to protect those molecules in the tissue that needed to be examined. HYBRiD does not require pumping solvents through the sample: it can simply be immersed in a container with reagents, it is extremely convenient and safe for everyday use.

Scientists have demonstrated the effectiveness of the method for imaging cells infected with SARS-CoV-2 in the lungs of mice. The thorax cells of infected rodents were treated with antibodies with fluorescent tags. The new method of tissue purification revealed macroscopic and microscopic signs of pathology in the samples.

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