The glycocalyx as a permeability barrier: basic science and clinical evidence

Area of Science:

• Vascular biology and endothelial function.

Background:

• The endothelial glycocalyx is a proposed barrier regulating vascular permeability.
• Its role in transendothelial passage of water and proteins is debated.
• Breakdown products in plasma may not accurately reflect glycocalyx integrity.

Purpose of the Study:

• To evaluate the clinical significance of the endothelial glycocalyx as a permeability barrier.
• To assess the correlation between glycocalyx breakdown products and vascular leakage.

Main Methods:

• Analysis of preclinical animal studies and human clinical trials.
• Comparison of plasma glycocalyx fragment concentrations with in vivo imaging and hydraulic conductivity measurements.
• Evaluation of correlations between degradation products and capillary leakage in humans.

Main Results:

• Glycocalyx breakdown products originate primarily from non-barrier regions of the endothelium.
• Plasma fragment concentrations show poor correlation with glycocalyx thickness and hydraulic conductivity.
• Increased breakdown products in rats did not correlate with vascular permeability; human studies showed inverse correlations with capillary leakage.

Conclusions:

• The endothelial glycocalyx layer's role as a clinically significant permeability barrier is questionable.
• Plasma levels of glycocalyx degradation products may not be reliable indicators of vascular permeability.
• Further research is needed to clarify the glycocalyx's function in vascular health and disease.