Have scientists discovered a new organ?
The short answer is no, the interstitium is not an "undiscovered organ," but scientists are now reporting important and unrecognized roles for a network of connective tissue and fluid known as interstitium.
This "interstitial lining" has been included in medical textbooks for years, but the tissue that surrounds the lungs, GI tract, bladder, skin, and blood vessels has previously been considered a passive reservoir of fluid and body support system for important organs. With the new technology that allows researchers to microscopically examine tissue in living subjects, researchers will explore the interstitium more closely than ever before.
Interstitial areas, previously interpreted as either inconspicuous "spaces" between adjacent tissues or as densely packed walls of fibrous tissue, appeared to be networks of connective tissue that was primarily filled with fluid. As a result, these areas can act as "shock absorbers" for nearby organs that routinely stretch and compress in daily function ̵
Based on a unique structure in which the surrounding tissues directly touch this fluid-rich space (rather than encountering a barrier of dense connective tissue or cells), scientists suggested that the interstitium facilitate the early spread of cancer through the body's lymphatic system could be a process that is currently not well understood.
This mechanism could solve the mystery of cases in which the cancer has spread to a nearby lymph node – without ever penetrating into the adjacent lymphatics on the way there. Further research will help researchers to understand why some types of cancer (especially melanoma, breast, lung and gastrointestinal tumors) are more likely to spread in the lymphatic system than in the bloodstream, how to recognize this spread early and how to do it in the first Phase prevents location.
The cells that line the fluid and fibers of the interstice are also unique – they are most similar to collagen-producing cells. Researchers hypothesize that these cells are likely to respond to mechanical forces surrounding a surgical wound or injury, and act in wound healing and scarring. Of particular interest is whether these cells contribute to the development of autoimmune conditions that cause scarring (or "fibrosis") of affected organs, such as scleroderma or inflammatory bowel disease. They also have a potential role in the formation of keloids or exaggerated scars that form below the surface of the skin.
These discoveries highlight the possibilities of further investigating the function of the interstitium in cancerous and scarring diseases – and we can bet that this tissue will receive more than its usual mention in the next generation of medical textbooks.
Kell Arps, MD, is a medical resident and works in the ABC News Medical Unit.