STORY HIGHLIGHTS
- A team of doctors have identified a previously unrecognized characteristic of the human body that they have classified as a new organ.
- The “Interstitium” refers to a network of fluid-filled cavities surrounding tissues and organs that may act as shock absorbers and mass transit system throughout the body.
- The discovery promises to redefine concepts of how the human body functions and may provide new understanding of how cancer and other diseases are spread throughout the body.
Pathologist Neil Theise, MD of New York University and endoscopy experts David Carr-Locke, MD and Petros Benias, MD of New York’s Mount Sinai Beth Israel recently announced the results of a study in which they discovered a previously unrecognized “organ” of the human body, and they say it might be the biggest one of them all.1
Dubbed “the Interstitia,” the structure the scientists identified is a network of fluid-filled collagen and connective tissue that is present throughout the body. They described it as “the anatomy and histology of a previously unrecognized, though widespread, macroscopic, fluid-filled space within and between tissues.”1
Knowledge that the interstitium exists is not new, but its interconnectedness and potential for transporting harmful substances like cancer cells throughout the human body is a new discovery.
The word interstitial means “Pertaining to being between things, especially between things that are normally closely spaced.”2 In non-medical terms, it can refer for example to a sub-ceiling that houses the mechanical structures for a building. In medicine, it is used to describe the cells, fluids and spaces between tissues and parts of organs in the body.
Interstitial cells and fluid are found in the spaces around cells of a given organ (like the spaces between the air sacs of the lungs) and help transport oxygen and nutrients and waste products into or out of the cells. It drains into the lymph system, which plays an important role in immunity. Previously, the interstitiumit was thought to be specific to a particular tissue or area of the body rather than functioning as a system-wide superhighway that connects all parts of the body.
A Novel Idea About Interstitial Space
The revolutionary change in understanding of the interstitium was made possible because of a new technology called “probe-based confocal laser endomicroscopy,” which allows researchers to examine living tissue instead of relying on traditional prepared microscope slides.3 It was during such an examination of a patient’s bile duct to check for cancer spread that the doctors noticed a series of “interconnected cavities in this submucosal tissue level that [did] not match any known anatomy.”4
Drs. Theise, Carr-Locke, and Benias suspected that the “densely-packed barrier-like walls of collagen,” as the interstitial space was previously understood, only looked that way because tissue-sampling techniques involved removing all of the fluid from the slide samples, forcing the collagen framework to collapse and stick together into what seemed like a dense layer. They hypothesized that the interstitium, instead, is a complex of fluid-filled interstitial spaces held by a lattice-like network of collagen. Thus, the whole is flexible and can be compressed and distended, acting as a sort of shock absorber that “keep tissues from tearing as organs, muscles, and vessels squeeze, pump, and pulse as part of daily function.”5 It is also subject to directional flow caused by the alternating contraction and relaxation of the body.6
First observed in the human extra-hepatic (liver) bile duct, similar structures were subsequently confirmed in many other parts of the body, including the skin, gastrointestinal tract, urinary tract, lungs, musculoskeletal system, blood vessels and fat tissue… anywhere “tissues moved or were compressed by force.”
Drs. Theise, Carr-Locke and Benias explained that the interstitial space may actually comprise a system of “dynamically compressible and distensible sinuses through which interstitial fluid flows around the body,” potentially acting as a “conduit for movement of injurious agents, pro-fibrogenic signaling molecules, and tumor cells.”7 It was previously recognized that permeation of the interstitial space is a necessary first step in the spread of cancer metastasis.
It’s Important, But is It a New Organ?
Its status as a new organ is not being embraced universally. The study’s authors contend that it should be considered an organ, as the skin is, because it has both a “unitary structure” and a “unitary function.” According to co-senior investigator Theise, “This has both…This structure is the same wherever you look at it, and so are the functions that we’re starting to elucidate.”8
Michael Nathanson, MD, professor of medicine and cell biology and chief of the section of digestive diseases at Yale University School of Medicine, however, disagrees. He says, “I would think of this as a new component that is common among a variety of organs, rather than a new organ in and of itself… It would be analogous to discovering blood vessels for the first time, in that they are in every organ but they aren’t an organ themselves.”9
What there seems to be a consensus on is that Theise, Carr-Locke and Beniashave have “identified a previously unknown feature of human anatomy with implications for the function of all organs, most tissues, and the mechanisms of most major diseases.”10
