Guido F Meert

Properties of interstitial water

The structure of water is not completely understood. Formed from tiny molecules, water is very versatile. Szent-Györgyi (1975) called water the “matrix of life” and it interacts with cells and molecules in complex, subtle and essential ways.

In the human body, and therefore also in connective tissue, we are dealing with interfacial and bulk water, and the interfacial water seems to interact with the protein function (Bellissent-Funel 2005). Water molecules seem to build “icosahedrons”, cubes with 20 surfaces, by their strong hydrogen bonds. But water is not static: hydrogen bonds are constantly forming and breaking in a period of some femtoseconds to picoseconds. Rearrangements of water molecules are ultrafast (Fayer et al. 2009). Simplified, the icosahedrons are presented in two states; a low-density expanded water-icosahedron and a high-density collapsed water-icosahedron. Water molecules are able to convert between the expanded and the collapsed version, without breaking the hydrogen bonds (Chaplin 2004).

Water is also able to form large regions of so called “structured water” or “liquid crystalline water”. In structured water, water molecules move together, like a shoal of fish, without losing mobility. Liquid crystalline water has special features; namely a greater molecular stability, a negative electrical charge, a greater viscosity, molecular stringing together and the ability to absorb certain spectra of light (Pollack 2002).

Water in bulk seems to behave differently from water in confined spaces, but more research is needed into this (Ye et al. 2004). Water seems to have a fourth phase, beside gas, liquid and solid and that occurs at interfaces (Pollack 2002). It is surprising that the presence of an interface is more important for the dynamics of the hydrogen bonds than the chemical nature of the interface (Fenn et al. 2009). In the human body, fascial sheets, fibers, cell membranes, molecules and so on are building bigger and smaller interfaces with a hydrophobic or hydrophilic character for the interstitial fluids. Research reveals that water inside nanotubes appears to build “water cylinders” which allow protons to jump ultrafast. Biochemical reactions take place in confined spaces with interfacial water, comparable to nanotubes, at the surface of proteins, membranes, etc.

There is a great affinity between the polymers and the water molecules of the cell, which condenses the gel into a compact structure and enables the cell to move or to open ion-channels without breaking down. The extracellular matrix (ECM) builds also a gelatinous fiber network and “binds” the containing water.

There are three “populations” of water molecules in contact with collagen fibers (Peto & Gillis 1990):

I would like to emphasize that flowing of this interstitial water happens in all directions between the cell–matrix interface. I will refer to the interstitial flow later.

Morphologic quality of interstitial fluids

The molecules and fibers of the ECM determine the properties of the interstitial gel. Furthermore fibroblasts, matrix molecules, enzymes and enzyme-inhibitors regulate the composition of the gelatinous ground substance of the connective tissue. This is important, while the composition of this interstitial matrix determines the transport for nutrients and waste materials between capillaries and parenchymal cells, as well as the mechanical properties of the connective tissue.

The German anatomist and embryologist Blechschmidt (2004) found that the movement of microscopic particles ocurs in an ordered manner and has a kinetic aspect, which he called “metabolic movements”. The flow of water, nutrients and waste materials lead to a canalization in the inner embryologic tissue and helps to form blood vessels. By stowing and condensing catabolites build the ground substance of the inner embryologic tissue. In “dilatation fields”, by condensation of catabolites, water tends to flow toward this tissue and pushes cells apart. On the other hand, when water is pushed out of the embryologic tissue, a “densation field” develops and the cells pack closely together. The flow of fluids develops creative morphologic forces to help in forming the embryologic tissues It seems that the flow of water plays even some role in the folding of proteins and there seems to be interaction between the shell of water surrounding the proteins and the shape and characteristics of those proteins; therefore water “tunes” the way proteins, the building blocks of life, are functioning (Ball 2008).

Proteins have to fluctuate in order to work and there are two types of fluctuation. The α-fluctuations proceed in the bulk of water, surrounding the protein and β-fluctuations take place in the shell of water (two layers) around the protein (Frauenfelder et al. 2009). Biochemistry has to deal with the interactions between the molecule and its environment. The environment for molecules (cytokines, neurotransmitter, hormones, growth-factors…) released by cells is made up of interstitial fluids and the ECM.