Shear Stress Regulation of Endothelial Glycocalyx Structure Is Determined by Glucobiosynthesis

Abstract

Objective: Endothelial cells exposed to laminar shear stress express a thick glycocalyx on their surface that plays an important role in reducing vascular permeability and endothelial anti-inflammatory, antithrombotic, and antiangiogenic properties. Production and maintenance of this glycocalyx layer is dependent on cellular carbohydrate synthesis, but its regulation is still unknown. Approach and Results: Here, we show that biosynthesis of the major structural component of the endothelial glycocalyx, hyaluronan, is regulated by shear. Both in vitro as well as in in vivo, hyaluronan expression on the endothelial surface is increased on laminar shear and reduced when exposed to oscillatory flow, which is regulated by KLF2 (Krüppel-like Factor 2). Using a CRISPR-CAS9 edited small tetracysteine tag to endogenous HAS2 (hyaluronan synthase 2), we demonstrated increased translocation of HAS2 to the endothelial cell membrane during laminar shear. Hyaluronan production by HAS2 was shown to be further driven by availability of the hyaluronan substrates UDP-glucosamine and UDP-glucuronic acid. KLF2 inhibits endothelial glycolysis and allows for glucose intermediates to shuttle into the hexosamine- and glucuronic acid biosynthesis pathways, as measured using nuclear magnetic resonance analysis in combination with 13 C-labeled glucose. Conclusions: These data demonstrate how endothelial glycocalyx function and functional adaptation to shear is coupled to KLF2-mediated regulation of endothelial glycolysis.

Increased capillary stalling is associated with endothelial glycocalyx loss in subcortical vascular dementia

“…In the SVaD model used in this study, the gradual decrease in arterial flow speed and pulsatility index, which is influenced by artery inflow and vessel resistance, was followed by impaired microcirculation ( Supplementary Figure 2) 31,32 . Since the production and maintenance of the EG closely correlates with fluid shear stress, it is plausible that the decreased capillary flow speed may be a primary factor affecting the EG loss 25,33,34 . Furthermore, this correlation could explain why, even in the normal brain, the EG of some capillaries appeared to have a smaller extent.…”

The role of endothelial shear stress on haemodynamics, inflammation, coagulation and glycocalyx during sepsis

“…Hyaluronan synthesis is induced by laminar SS and reduced when EC are exposed to oscillatory (non‐laminar) blood flow 26 . EC need hyaluronan to maintain their integrity and its synthesis is determined by EC metabolic status 26 . Laminar SS controls hyaluronan synthesis via the shear‐responsive transcription factor KLF‐2, 78 through a mechanism involving EC glycolysis 26 .…”

Loss of Endothelial Glycocalyx Hyaluronan Impairs Endothelial Stability and Adaptive Vascular Remodeling after Arterial Ischemia

“…In this respect, it is of interest that addition of HA can enhance endothelial angiogenic cell therapy in the model of hindlimb ischemia [28]. In addition, biosynthesis of HA which is regulated by shear through the transcription factor Krüppel-like Factor 2 (KLF2), directly via increasing HAS2 protein expression and translocation of the enzyme to the cell membrane, and modulating endothelial glycolysis rate, through its activator 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 3 (PFKFB3) enzyme, influencing the rate limiting HA substrates UDP-glucosamine and UDP-glucuronic acid [29]. Thus, impaired perfusion can aggravate the process through reduced HA biosynthesis also.…”