Glycome Atlas
concept
Also known as glycocalyx, endothelial surface layer, vascular glycocalyx
Plain-language answer
The endothelial glycocalyx is a soft, gel-like coating of sugars and sugar-linked proteins that lines the inside of every blood vessel. It sits between flowing blood and the endothelial cells that form the vessel wall, forming a protective, slippery layer that is normally invisible on a standard blood test.12
A healthy glycocalyx keeps vessels from leaking, helps blood flow smoothly, and prevents clotting and inflammation from switching on at the wrong time. When it thins or sheds, fluid and immune cells cross the vessel wall more easily, which is a feature of sepsis, diabetes, and many post-viral and cardiovascular conditions.1
Technical detail
The endothelial glycocalyx is a negatively charged, hydrated mesh of membrane-bound proteoglycans, glycoproteins, and associated glycosaminoglycans lining the luminal endothelial surface, integrating endothelium- and plasma-derived molecules into the endothelial surface layer that regulates permeability, mechanotransduction, and blood-cell interactions.1
The core scaffold consists of membrane-bound proteoglycans, principally the syndecans and glypicans, whose protein cores carry sulfated glycosaminoglycan chains, most abundantly heparan sulfate along with chondroitin and dermatan sulfate. The non-sulfated polysaccharide hyaluronan is enmeshed within this layer, and glycoproteins bearing sialylated oligosaccharides contribute additional negative charge.12
In vivo the proteoglycan and glycoprotein scaffold binds plasma proteins and soluble glycosaminoglycans to form a thicker, dynamic endothelial surface layer whose measured dimensions depend heavily on the visualization method used.1
The layer acts as a molecular sieve that sets vascular permeability to water and macromolecules, transmits shear stress to the endothelium as a mechanosensor, and shields adhesion molecules so that leukocytes and platelets do not engage the endothelium under healthy flow.1
Inflammatory mediators, hyperglycemia, oxidized lipids, and enzymes such as heparanase, hyaluronidase, and matrix metalloproteinases degrade the layer, releasing fragments such as syndecan-1 and heparan sulfate into plasma. Glycocalyx damage is described in sepsis, diabetes, ischemia-reperfusion, and atherosclerosis and contributes to edema, coagulation, and inflammation.1
Human relevance
Glycocalyx shedding is mechanistically linked to increased vascular permeability, and circulating shedding markers such as syndecan-1 rise in sepsis and critical illness.1
A reduced or degraded glycocalyx is associated with hyperglycemia, microvascular dysfunction, and atherosclerosis-prone endothelial phenotypes.1
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References