Purpose of ReviewThe cell surface-attached extracellular glycocalyx (GCX) layer is a major contributor to endothelial cell (EC) function and EC-dependent vascular health and is a first line of defense against vascular diseases including atherosclerosis. Here, we highlight our findings regarding three GCX-dependent EC functions, which are altered when GCX is shed and in atherosclerosis. We discuss why the GCX is a viable option for the prevention and treatment of atherosclerosis.Recent FindingsGCX regulated EC activities such as barrier and filtration function, active cell-to-cell communication, and vascular tone mediation contribute to function of the entire vascular wall. Atheroprone vessel regions, including bifurcation sites, exhibit breakdown in GCX. This GCX degradation allows increased lipid flux and thereby promotes lipid deposition in the vessel walls, a hallmark of atherosclerosis. GCX degradation also alters EC-to-EC communication while increasing EC-to-inflammatory cell interactions that enable inflammatory cells to migrate into the vessel wall. Inflammatory macrophages and foam cells, to be specific, appear in early stages of atherosclerosis. Furthermore, GCX degradation deregulates vascular tone, by causing ECs to reduce their expression of endothelial nitric oxide synthase (eNOS) which produces the vasodilator, nitric oxide. Loss of vasodilation supports vasoconstriction, which promotes the progression of atherosclerosis.SummaryCommon medicinal atherosclerosis therapies include lipid lowering and anti-platelet therapies. None of these treatments specifically target the endothelial GCX, although the GCX is at the front-line in atherosclerosis combat. This review demonstrates the viability of targeting the GCX therapeutically, to support proper EC functionality and prevent and/or treat atherosclerosis.

Background and aims: Endothelial surface glycocalyx shedding plays a role in endothelial dysfunction and increases vessel wall permeability, which can lead to inflammation and atherogenesis. We sought to elucidate whether a high fat diet (HFD) or disturbed blood flow conditions, both of which are atherogenic risk factors, would contribute more detrimentally to pre-atherosclerotic loss of endothelial glycocalyx integrity and vascular inflammation. Methods: Six to seven week-old C57BL/6-background apolipoprotein-E-knockout (ApoE-KO) male mice were either fed a chow diet, fed a modified Western HFD, and/or subjected to a partial left carotid artery (LCA) ligation procedure to induce disturbed blood flow patterns in the LCA. Mice were sacrificed after 1 week of experimental conditions. Both LCA and right carotid artery (RCA) vessels were dissected and preserved to compare glycocalyx coverage and thickness as well as macrophage accumulation in carotid arterial walls amongst and between cohorts. Results: Glycocalyx coverage of the endothelium was significantly reduced in the LCAs of HFD fed mice when compared to the control. More significant reduction in glycocalyx coverage occurred in the LCAs of mice exposed to disturbed flow by partial LCA ligation when compared to the control. No differences were found in glycocalyx coverage of RCAs from all cohorts. Regarding inflammation, no difference in macrophage accumulation in carotid arterial walls was observed when comparing the LCAs and RCAs of control and HFD fed mice. However, macrophage infiltration in vessel walls showed a 20-fold increase in the LCAs exposed to disturbed flow following ligation, when compared to control LCAs, while no such statistical difference was observed between the RCAs of the group. Conclusions: In our mouse model, endothelial glycocalyx integrity was compromised more by disturbed blood flow patterns than by exposure of the carotid vessel to HFD conditions. The pathophysiological implications include endothelial dysfunction, which correlates to macrophage infiltration in vessel walls and promotes atherogenesis.

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Introduction Endothelial glycocalyx (GCX) shedding plays a role in endothelial dysfunction and increases vessel wall permeability to inflammatory cells contributing to atherogenesis. We sought to determine whether a high fat diet (HFD) or disturbed blood flow conditions, both well‐known atherogenic risk factors, would more detrimentally contribute to pre‐atherosclerotic loss of GCX integrity and vascular inflammation. Materials and Methods C57BL/6‐background apolipoprotein E knockout (ApoE‐KO) mice were fed either a HFD or chow diet, and/or underwent a ligation of the left carotid artery (LCA), inducing disturbed flow conditions. After one week, mice were sacrificed and LCAs and right carotid arteries (RCAs) were preserved to compare GCX coverage and thickness and inflammatory macrophage accumulation in carotid arterial walls amongst and between cohorts. Results and Discussion Endothelial GCX damage occurred in LCAs of HFD fed mice when compared to the control. More significant GCX damage occurred in the LCAs of mice exposed to disturbed flow by partial LCA ligation, also compared to control. Flow simulations conducted through SimVascular adequately characterized flow patterns, pressure, and wall shear stresses in non‐ligated vs. ligated mice. They confirmed the notion that the LCA partial ligation surgery does indeed reduce wall shear stress and increase pressure, characteristics of disturbed flow. No difference in macrophage accumulation in carotid arterial walls was observed when comparing the LCAs of control mice to the LCAs of HFD fed mice. However, macrophage infiltration in vessel walls showed a 20‐fold increase in LCAs exposed to disturbed flow following ligation, when compared to control LCAs. Conclusions This study was the first to demonstrate that disturbed flow contributes more detrimentally to pre‐atherosclerotic loss of GCX integrity and vascular inflammation. The study concluded that disturbed flow conditions induced by partial ligation, compared to HFD conditions, compromised the integrity of the endothelial GCX to a greater extent. We anticipate more rapid atherogenesis as a consequence of the severity of this flow induced GCX damage. Support or Funding Information We are pleased to acknowledge that this work was funded by the National Institute of Health (NIH) K01‐ HL125499 awarded to E Ebong, NIH R21‐DA042583 awarded to S Sridhar, and Air Force Office of Scientific Research (AFOSR) FA2386‐17‐1‐4042 awarded to S Sridhar.