Nature | Confocal laser endomicroscopy (pCLE) provides real-time histologic
imaging of human tissues at a depth of 60–70 μm during endoscopy. pCLE
of the extrahepatic bile duct after fluorescein injection demonstrated a
reticular pattern within fluorescein-filled sinuses that had no known
anatomical correlate. Freezing biopsy tissue before fixation preserved
the anatomy of this structure, demonstrating that it is part of the
submucosa and a previously unappreciated fluid-filled interstitial
space, draining to lymph nodes and supported by a complex network of
thick collagen bundles. These bundles are intermittently lined on one
side by fibroblast-like cells that stain with endothelial markers and
vimentin, although there is a highly unusual and extensive unlined
interface between the matrix proteins of the bundles and the surrounding
fluid. We observed similar structures in numerous tissues that are
subject to intermittent or rhythmic compression, including the
submucosae of the entire gastrointestinal tract and urinary bladder, the
dermis, the peri-bronchial and peri-arterial soft tissues, and fascia.
These anatomic structures may be important in cancer metastasis, edema,
fibrosis, and mechanical functioning of many or all tissues and organs.
In sum, we describe the anatomy and histology of a previously
unrecognized, though widespread, macroscopic, fluid-filled space within
and between tissues, a novel expansion and specification of the concept
of the human interstitium.
Independent | 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 while investigating a patient’s bile duct, searching for
signs of cancer.
They noticed cavities that did not match any previously
known human anatomy, and 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 because the “fixing” method for
assembling medical microscope slides involves draining away fluid –
therefore destroying the organ’s structure.
Instead of their true identity as bodywide, fluid-filled
shock absorbers, the squashed cells had been overlooked and 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.