The Interstitium

     On March 27th, 2018, Scientific Report published a study titled, “Structure and Distribution of an Unrecognized Interstitium in Human Tissues.” It’s kind of crazy to think scientists are still discovering new structures in the body. The authors described the “interstitium” as “a novel, interstitial space defined by a complex lattice of thick, collagen bundles,” and “dynamically compressible, and distensible sinuses through which fluid flows around the body.” Evidently, the structure was previously missed in microscope studies secondary to the compression placed upon the fluid filled space from preparing slides. The researchers were able to visualize this new structure in and around the dermis, arteries, gastrointestinal tract, urinary bladder, bronchial tree of the lungs, and the fascial planes of the musculo-skeletal system. This discovery could have implications for the way cancer, lymphedema, renal and cardiac failure are treated. Furthermore, this could impact the way we view any system in the body that undergoes cyclical compression and distension phases, including the musculoskeletal, respiratory and digestive systems.

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Schematic of the fluid-filled space supported by a network of collagen bundles lined on one side with cells. Illustration by Jill Gregory.

            The results of this discovery should be far-reaching for rehab and fitness professionals. Indeed, these research findings promote the idea of the inter-connectedness of structures in the body vs. the perspective that organs and organ systems within the body function in an isolated and independent way. It seems that clinical practitioners have been treating the interstitium from a bio-mechanical viewpoint for years. As a physical therapist, I have some questions about what this discovery means for clinical practice: How does a scar, bruise or inflammation affect this space? Is fluid in this space stagnant or is it pumped throughout the body like blood and cerebrospinal fluid? Can nutrition affect it? Can it become inflamed and affect surrounding structures? Do the modalities we use such as manual therapy, dry needling, and neuro-muscular re-education affect this structure? Do prolonged postures or function change the structure of this organ?

            Some practitioners have been studying and treating this structure for years. Thomas Meyers, the Father of Fascia (although he claims to dislike the term ‘fascia’), believes the interstitium is “part of the continuous bio-mechanical auto-regulatory system that runs in a continuous mechanical linkage from the DNA through the nuclear membrane via the microtubules to the cellular membrane, out through the transmembranous proteins to the glycocalyx (the first mucousy layer outside the cell) to this interstitium and on up to the more gross and dissectible fascial structures.” That is one complex sentence, and it should be; the human movement system is terribly complicated. The discovery of the interstitium is just another component of this bio-mechanical regulatory system. Going on all day about the complexity of the system is something I will hold off on. The real question is what this discovery means for you and your everyday life.

MOVEMENT

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Image taken from the book, Anatomy Trains by Thomas Meyers. Originally from Dr. J. C. Guimberteau. A diagram of the microvacuole sliding system between the skin and the underlying tendons.

            I believe this finding is another reminder that we need to move, with intention, every day. The interstitium is a three-dimension structure found all over our body. If we never move out of prolonged postures and positions, perhaps the fluid within the interstitium becomes stagnant. I took a course called “Mobilization of the Neuro-immune System” a few years ago, and a point they emphasized was the nervous system loves movement. Nerves live in fluid filled tunnels which rely on movement to change pressure gradients. This makes me wonder if movement helps to pump the fluid of the interstitium around- another reason to get moving!

SOFT TISSUE MOBILIZATION

            Massages feel great and can be very therapeutic. I use massage or soft tissue mobilization (a term for the insurance companies out there) with a goal to relax a muscle, increase blood flow and move lymph. The interstitium can be another reason why a massage feels so good. Perhaps getting a massage improves fluid dynamics within the interstitium, stimulates collagen and gets tissue surfaces to better glide across each other.

PAIN

            Can pain be a result of a restriction or dysfunction within the interstitium? Some people are suggesting the interstitium is a shock absorber, like a built-in padding for other structures. When this compartment is damaged from surgery, injury, poor posture, or disease, can the body’s ability to withstand forces be altered? Could this subsequently lead to pain?

            This finding is an indication that there is so much more for us to learn. I think this is encouraging for the fields of medicine, health and wellness. As a physical therapist, I am constantly evaluating clients during treatment sessions. Technically, the first appointment is an examination and evaluation, but the body is constantly changing minute to minute and day to day. The interstitium could be another component of the body that we, as physical therapists, could evaluate and treat. If you’d like to learn more about the interstitium, click on the links below.

Sources

https://www.anatomytrains.com/blog/2018/03/29/interstitium-statement-tom-myers/

https://www.nature.com/articles/s41598-018-23062-6.pdf

https://www.scientificamerican.com/article/meet-your-interstitium-a-newfound-organ/

Strolling Under The Skin: https://www.youtube.com/watch?v=eW0lvOVKDxE