Our Hidden Vascular Coral Reef: Understanding the Glycocalyx’s Ecosystem Within Our Blood Vessels

Just as in our precious ocean waters, which have coral reefs to provide a healthy ecosystem, we have a very similar process in the lining of our blood vessels.  In 1966, a discovery was made by electron microscopy that revealed a dark layer lining every blood vessel. In 2009, with better technology, this dark thickness inside the blood vessels showed a dynamic moving layer that was called the glycocalyx. By 2017, advanced techniques quantified the glycocalyx structure, showing that it had an ecosystem of its own, like the coral reefs.  Today, we know that the health of the vascular glycocalyx is involved in aging and disease, and this raises the question of how we protect this critical barrier. The endothelial glycocalyx (EG) lines each artery, vein, and capillary and is a significant factor for the health of our blood-brain barrier.

Just in the last 5 years, scientists have figured out what this structure is doing inside each blood vessel.  There are three main ways the EG provides health to our blood vessels: Selective permeability, sensing mechanical forces, and acting as a bridge for immune surveillance.

The EG has a jelly substance made from hyaluronic acid, heparin sulfate, and chondroitin sulfate, which are carbohydrate molecules with an electric negative charge provided by the sulfate molecules. These negative charges prevent any other negative charged molecules or cells from entering while attracting positive charged molecules. The hairs within the EG provide sensors for blood pressure changes.  The shearing forces from elevated blood pressure will cause the specific cells to release nitric oxide within the vessels, thus dilating arteries to normalize blood pressure. Our blood vessels carry hormones, proteins, inflammatory cells, and, of course, our red blood cells, to name a few.  The EG prevents the inflammatory cells from binding to our blood vessel walls, thereby supporting an environment free from blood clots. 

Calcified plaques inside our arteries develop from oxidized LDL particles, activating an inflammatory response within the EG.  This injures the EG and permits immune cells and LDL particles to pass through our vessel walls.

There are many factors responsible for the destruction of the Endothelial Glycocalyx. Chronic inflammation releases reactive oxygen species (ROS) which will go on to damage the EG. Certain cytokines, due to inflammation and metabolic disorders, such as tumor necrosis factor alpha (TNF alpha) degrade the hyaluronic acid component, which acts as the protective jelly layer. Also, uncontrolled hypertension (high blood pressure) will eventually destroy the EG via sheer forces. High glucose or lipid levels in the blood will damage the EG sometimes in just hours. Finally, microplastics in the blood can damage the EG, leading to vascular permeability and more ROS.

There are no symptoms to correspond to the damage of our Endothelial Glycocalyx until it is too late and then we present with coronary artery disease, strokes, or vascular dementia.  Scientists are now looking into therapies to restore the health of this very important ecosystem.   However, at the present time, given that we know what damages it, we have modalities to prevent further damage.

It’s essential to understand the importance of maintaining an ecosystem for the health of the organism. We spend a great deal of time making efforts to protect our environment and the unique ecosystems on our planet. But maybe …it’s time to take this same focus inwards and start with ourselves?