New investigative methods revealed an interstitium under our skin and mucous membranes, made of canals full of fluids. Now we need to know its usefulness.

Is it possible that, 500 years after Leonardo’s accurate drawings of the human body, there are still organs to be discovered? According to Neil Theise, professor of pathology at New York University, we had in fact overlooked one of our body’s largest organs. “We called it ‘interstitium’ and it is formed by our connective tissue, i.e. the layer that makes skin adhere to our muscles or mucous membrane to internal organs” he says. “We thought that the connective tissue was formed by a compact collagen matrix and other fibrous proteins generated by specialized cells. However we discovered that it is actually intersected by a dense network of vessels full of liquid, the function of which we still ignore”.

It is easy to understand why nobody noticed it until now. In order to examine tissues under a microscope, researchers dehidrate them for preservation, thus causing the collapse of the connective tissue’s vessels, about twenty thousandths of a millimiter, making them unrecognizable. “We have only just noticed them thanks to the laser confocal endomicroscopy, which makes it possible to examine working living tissues.” Applying this technique to find out the size of a tumour in a patient’s bile ducts, surgeons David Carr Locke and Petros Benias at Beth Israel Medical Centre were the first ones to notice the canals in the connective tissue, which were later found under every tissue lining the human body. The interstitium can therefore be considered one of our largest organs”.
So large that it also solved the mystery of the location of approximately 40 litres of water in our body, as our cells contain about half that amount, blood and lymph only another 15%: the missing 35% swells the interstitium.

“This liquid pillow’s main function is probably to cushion the impact on internal organs, but it could also convey nutrients or it could play a role in immune reactions as these canals are carpeted with mesenchymal cells forming scars when inflamed. It could even convey electric current, thus explaining the efficacy of acupuncture” concludes Thiese, who is very interested in traditional medicine.

This discovery can have a considerable medical spillover” confirms Giorgio Iervasi, head of the Institute of Clinical Physiology at Pisa’s CNR.
“This network of canals can explain, for example, why interstitial tumours are quite dangerous: maybe cancer cells move through them creating metastases. The interstitium could also play a part in skin diseases and aging. In order to understand it we must identify this new organ’s role and ascertain what flows in its canals. Only thus we shall be able to see how it changes in case of diseases and if it can be used as a diagnostic means and to administer therapies.”

This article was written by Alex Saragosa from “Il Venerdì” of the “La Repubblica” newspaper on the 20th of April 2018