Interstitium: the new human organ you didn’t know you had
Researchers at the University School of Medicine in New York identified a previously unknown component of the human body that they classify as a new organ.
The interstitium, as it is called, is a network of cavities filled with liquid that lies under the skin and covers many other organs.
Until now scientists believed there was an “interstitial space” between the cells, but not that it was an organ.
It went unnoticed because the ducts seem empty and flattened completely when fixing the anatomical samples in microscope slides, giving the impression of a dense and solid tissue.
Scientists suggest that the interstitium could act as a buffer, to prevent tearing tissue by the movement of muscles, viscera and blood vessels.
As described in the journal Scientific Reports, the cavities are formed by an external structure of collagen and elastin, two proteins that give it resistance and elasticity, respectively.
In addition, the fluid produced by the interstitial cells feeds the lymphatic system, responsible for generating the inflammatory response and maintaining the white blood cells of the immune system.
The interstitium is under the skin, between the muscles and in the lining of the lungs, blood vessels, the digestive system and the excretory system.
By connecting almost the entire body through cavities with fluid in motion, scientists believe that it can play an important role in the proliferation of cancer.
In addition, the authors of the study explain that, with age, the deterioration of the proteins that form the external structure of the cavities can contribute to the formation of wrinkles in the skin, rigidity of the extremities and the progression of fibrosis and sclerosing or inflammatory diseases.
The discovery has the potential to drive radical advances in medicine, including the possibility that taking samples of interstitial fluid becomes a powerful diagnostic tool.
Along with the skin, the interstitium is one of the largest organs in the body.
Doctors David Carr-Locke and Petros Benias observed the cavities of the interstitium for the first time in 2015, while examining the bile ducts of a cancer patient, at Mount Sinai Beth Israel Hospital.
They were able to see them thanks to a technique known as confocal laser endomicroscopy, in which a flexible tube equipped with a laser and sensors that detect fluorescent reflections from the tissues are inserted into the body.
In this way, they could appreciate the hollow spaces that disappear under the microscope.
Researchers repeated the laser endomicroscopy scan during 12 operations of the pancreas and bile ducts.
They also took biopsies of these tissues to learn how to identify the crushed cavities of the interstitium in microscope slides.
Thanks to these samples, they have been able to identify the presence of the interstitium throughout the body, where the tissues undergo compression or are subject to the movement of nearby organs.
Scientists have not yet been able to identify the cells lining the cavities, although they suggest that they might be necessary to create and maintain the collagen walls.
Scientists point out that they could also be mesenchymal stem cells, which contribute to the healing response.