Scientists have identified a new human organ hiding in plain sight. They hope the discovery could help them understand the spread of cancer within the body.
Layers long thought to be dense, connective tissue are a series of fluid-filled compartments researchers have termed the “interstitium”.
These compartments are found beneath the skin, as well as lining the gut, lungs, blood vessels and muscles. They join to form a network supported by a mesh of strong, flexible proteins.
New analysis published in the journal Scientific Reports is the first to identify these spaces collectively as a new organ. The publication tries to understand their function.
Remarkably, the interstitium had previously gone unnoticed despite being one of the largest organs in the human body.
The team behind the discovery suggest the compartments may act as “shock absorbers” that protect body tissues from damage.
Mount Sinai Beth Israel Medical Center medics Dr David Carr-Locke and Dr Petros Benias came across the interstitium. It was whilst investigating a patient’s bile duct, searching for signs of cancer.
They noticed cavities that did not match any previously known human anatomy. They then approached New York University pathologist Dr Neil Theise to ask for his expertise.
The researchers realised traditional methods for examining body tissues had missed the interstitium. This was because the “fixing” method for assembling medical microscope slides involves draining away fluid – therefore destroying the organ’s structure.
Instead of their identity as body-wide, fluid-filled shock absorbers, the squashed cells had been overlooked. They had been considered a simple layer of connective tissue.
Having arrived at this conclusion, the scientists realised this structure was found not only in the bile duct but surrounding many crucial internal organs.
“This fixation artefact of collapse has made a fluid-filled tissue type throughout the body appear solid in biopsy slides for decades, and our results correct for this to expand the anatomy of most tissues,” said Dr Theise.
The researchers also found evidence that cancer cells from tumours could make their way via the interstitium into the lymphatic system.