Interstitial Fluid and Multiple Sclerosis: Conductor of the Homeostatic Orchestra

As part of the continuing series on systemic homeostasis, I have decided to deliver a post that has both a global application as well as a focused and specific target audience.  Although seemingly contradictory, the main message to take away from this post is that the overall implications of the contribution of interstitial fluid are universal and can be applied to any condition (acute or chronic) or pathology.

The choice of the term "conductor" was made intentionally to convey a fundamental understanding that can be imported from our intuitive notion of conductor into the general "biological" perspective:  Despite the presence of finely tuned intruments and classically trained musicians, it is the conductor that mediates the activities of the orchestra with the end objective of achieving pleasant,  seemless, and integrated sound.  Therefore without the "physiological conductor", the biological orchestra is reduced to a conglomerate of subsystems that ultimately underperform and actually contribute to the overall deterioration of the architectural integrity of the Supersystem (human organism).  More importantly, the role of homeostatic "catalyst" indicates that strategic focus in improving the flow of interstitial fluid will have a significant impact on improving the intrinsic physiological environment and health. I will refer to specific non-invasive strategies for systemic enhancement through the promotion of interstitial fluid flow in the follow-up post...but in order to fully grasp the practical aspects, there needs to be a fundamental understanding of the theoretical and conceptual ideas.

Interstitial Fluid:
Interstitial fluid is defined as the fluid found in the intercellular spaces composed of water, amino acids, sugars, fatty acids, coenzymes, hormones, neurotransmitters, salts, and cellular products. It bathes and surrounds the cells of the body, and provides a means of delivering materials to the cells, intercellular communication, and removal of metabolic waste.  In addition to these essential systemic functions, the interstitial fluid also transports nutrients to all of the tissues in the body and has a critical role in tissue maintenance.  It has also been shown that interstitial fluid flows have a role in tissue morphogenesis, tissue remodelling, inflammation, morphoregulation, and immune cell trafficking (1). 

Interstitial flows and their corresponding microenvironments

As shown in the adjacent image, interstitial fluid is exists within a matrtix (extracellular matrix, or ECM) that is composed of specialized cells (fibroblasts, etc),  fibers (collagen, elastin), and other differentiated tissues.  The cells are attached to the ECM in a 3-dimensional manner by the specialized fibers and therefore compose a highly active and reactive environment (respond to mechanical stress).

Interstitial flow through the ECM

The flow of blood (within the red vessel) and the flow of lymph (green vessel) can be considered as luminal flow.  The green arrows  represent interstitial / intervascular flows which act upon the ECM through sheer stress and therefore, depending on flow rate and velocity, contribute to the establishment of mechanical stability through mechanotransduction and systemic competence.



Importance of Interstitial Flow Rate:

With the fundamental relevance of interstitial fluid well established, the efficiency of flow velocity and rate become quite obvious.  More specifically, the reduction of interstitial flow rate results in degeneration of the tissue environment (mechanical and systemic).  Further, the flow of interstitial fluid (convection) is typically generated by the pressure gradient that exists between blood and lymph capillaries (see image, red and green tubes respectively) (2), as well as by the mechanical stimulus generated by active muscular contraction.

Relevance to Multiple Sclerosis:
The individual with Multiple Sclerosis manifests a very diverse range of symptomatic challenges which ultimately stress the ability to establish and maintain systemic homeostasis.  Regardless of the specific neurological genesis, the biomechanical manifestations are significant and demonstrate progressive deterioration over time.  They can be demonstrated in the more intuitive fashion such as gait difficulties and dysfunction, postural dysfunction, and spasticity...however, the long-term consequences are more profound.  The select muscular dysfunction ultimately leads to fibrotic conditions brought on and exacerbated by irregular muscular activation, chronic overuse syndromes, and gradual deterioration of the entire extended fascial (connective tissue) system. This can also be described as a loss of the visco-elastic properties of the fascia, connective tissue, and ECM.  This loss of viscoelasticity in the ECM will ultimately reduce interstitial fluid flow similar to the way (to use an analogy) a hair mat would block the flow of water through a drain.  The denser the hair mat, the more resistance to flow is present.  This flow reduction will ultimately results in metabolic waste build-up and inefficient delivery of nutrients to the tissues.  When this is allowed to persist, it will inevitably accumulate and tax an already sensitive system which contribute to a degenerative "spiral" (reduced systemic competence---reduced muscular performance---irregular muscle activation and force transfer---increased fibrotic environments---further reduced systemic competence---further reduced muscular performance, etc...).  The profound muscular consequences are a result of the reduced viscolelastic properties of the deep fascia and the secretion hyaluronic fluid which permits the efficient "sliding" of muscle bundles (as well as capillaries) between each other.  When this is deficient, the result is poor muscle function and force transmission through the mechanical chain as well as to adjacent synergists.

In summary, when the accurate "biophysical" reality is examined and explored, it exposes some fundamental concerns regarding the "Big Pharma" philosophy of treatment of pathology.  Indeed, when a specific "diseased state" exists a mechanistic (disease fighting) strategy should be considered...however, the over-looked and under-appreciated reality is that there exists a profound organic (promotion of health) opportunity that shows equally (or greater) potential to contribute to a homeostatic state.

Practical Strategies:
The follow-up to this post will focus on the strategic implementation of practical (non-invasive) interventions designed to contribute to the improvement of interstitial fluid flow.  As a result, there will be a "flush" of stagnant interstitial fluid and a subsequent "drag" of fresh and nutrient rich fluid.  In addition, the mechanical stimulus will contribute to the healthy remodelling of weak and dysfunctional tissues and therefore reduce any muscular imbalances that exist.

Using the pre-established analogy:  this paradigm serves to contribute to the potential and performance of the "conductor" of the orchestra.  Even with sub-standard "instruments" and musicians, the overall effect on the "music" will be far greater.   

Cheers!
---Gavin---