Image copyright Bin Yang & Viviana Gradinaru Image caption Scientists were able to take a closer look at organs such as the kidney

A way to turn an entire body transparent has been developed by scientists studying rodents.

Reporting in the journal Cell, they describe a technique that keeps tissues intact but allows key body parts and connections to be seen.

They say it could help visualise how separate organs interact and pave the way for a new generation of treatments.

The method may also be used to detect the spread of viruses and cancers in human tissues.

For almost a century scientists have attempted to turn opaque organs see-through, but most techniques have damaged tissues, putting a stop to further medical tests.

'Biologists' dream'

The fatty lipid molecules present in cells can distort light rays, rendering tissues opaque. But processes used to dissolve them have deprived organs of this key element of structural support, resulting in a shapeless mass of material.

Now researchers from the California Institute of Technology say they have achieved the "biologists' dream".

Building on previous work the team have developed a three-stage technique:

A soft plastic-like mesh provides support to tissues

Then a molecular detergent is continually infused via the bloodstream, dissolving away lipids and making organs transparent

Specific tracing dyes and tagging molecules can be added to the infusion to flag up the most important connections.

Using this method in rodents, researchers were able to clear whole kidneys, hearts, lungs and intestines within three days and the entire body within two weeks.

Image copyright Bin Yang & Viviana Gradinaru Image caption Using this method researchers could see details of intestinal tissues

And testing the procedure on samples from cancer patients allowed them to see how far the disease had spread.

The research has been carried out on euthanased rats and human tissue samples taken during operations but not yet in living organisms.

'Important advance'

Scientists say the technique could have many future uses, from mapping the journeys of long nerve fibres from the brain to the rest of the body to tracing exactly where different viruses hide in tissues.

The team are now collaborating with other scientists to examine brain tissue from people with dementia. They say comparing these with healthy samples will allow them to see potential differences in cell patterns and numbers in a way that has never been possible before.

Commenting on the processes this method was built upon, Thomas Insel, director of the US National Institute of Mental Health in the US said: "This is probably one of the most important advances for doing neuroanatomy in decades."

Dr Viviana Gradinaru, a lead author on the paper, told the BBC: "This is the realisation of the biologists' dream.

"Though scanning techniques already help doctors visualise the body they cannot show what each tissue or cell does.

"Adding tags and tracers in our method, we get crucial information on the exact identity and function of the parts of the body we want to know more about."