From our community:
Say hello to the Interstitium. It’s a previously unrecognized network of spaces and tubules that extend throughout body tissues at the microscopic level. Traditional methods of tissue study that involve fixing and slicing tissue into thin slices failed to reveal it, because the slicing and dicing caused the spaces to drain and collapse. The use of new microscopic techniques — such as Confocal laser endomicroscopy — allows tissues to be studied while still intact.
From the study abstract:
...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...
emphasis added
An NBC News report by Alex Johnson, via AOL news, gets into some of the implications of this discovery. (The videos at the link seem to be completely unrelated to the discovery, other than involving cancer.) From Johnson’s write-up:
...Understanding the interstitium could be particularly significant in diagnosing and tracking the spread of cancers and other diseases that spread throughout throughout the body. Interstitial fluid is the source of lymph, which dispatches white blood cells, the body's immune system infection fighters, to wherever they're needed.
...In 2015, doctors called endoscopists, who peer inside the body using long, flexible tubes with cameras on them, found something strange when they were using a new technology that adds a laser and a tiny microscope to light up living tissues inside a patient's bile duct. Such examination is described as "in vivo," meaning it takes place inside a living organism, rather than on dead tissue on a slide.
...Once the researchers recognized the real nature of the structures, they quickly found them throughout the body, in any place where tissues move or are compressed by external forces. (One of their functions, in fact, may be to act like shock absorbers to keep organs, muscles and blood vessels from tearing apart as they and the body move, the paper proposes.)
The heart and circulatory system, the brain and the nervous system, the skeletal system, the digestive tract — these have been recognized because they are relatively large and visible to the naked eye. They are discrete structures. The interstitium is microscopic and organized on what sounds like an ad hoc basis. The initial studies suggest it’s important structurally for the body, and also as a means of access for lymphocytes and other components of the body’s immune system to get around within tissues.
It’s roughly comparable to looking at a city and discovering that the obvious networks of things like streets, telephone wires, etc. are also backed up by an underground system of pipes and drains.
What this means still needs to be worked out; years of study lie ahead. The initial findings will have to be confirmed by other researchers, now that they know what to look for and have the tools to start looking. Determining what is actually in the interstitial fluid, how it moves through the body, and what it actually does will be even more challenging.
Researchers will be looking at other species to see where else these structures occur, and trying to work out the evolutionary patterns involved. They’ll also be a target for diagnostic techniques and drug delivery.
This also means the field of histology is going to be turned upside-down.
Interesting times!