Heparanase-Dependent Remodeling of Initial Lymphatic Glycocalyx Regulates Tissue-Fluid Drainage During Acute Inflammation in vivo

Abstract

The glycocalyx is a dense layer of carbohydrate chains involved in numerous and fundamental biological processes, such as cellular and tissue homeostasis, inflammation and disease development. Composed of membrane-bound glycoproteins, sulfated proteoglycans and glycosaminoglycan side-chains, this structure is particularly essential for blood vascular barrier functions and leukocyte diapedesis. Interestingly, whilst the glycocalyx of blood vascular endothelium has been extensively studied, little is known about the composition and function of this glycan layer present on tissue-associated lymphatic vessels (LVs). Here, we applied confocal microscopy to characterize the composition of endothelial glycocalyx of initial lymphatic capillaries in murine cremaster muscles during homeostatic and inflamed conditions using an anti-heparan sulfate (HS) antibody and a panel of lectins recognizing different glycan moieties of the glycocalyx. Our data show the presence of HS, α-D-galactosyl moieties, α2,3-linked sialic acids and, to a lesser extent, N-Acetylglucosamine moieties. A similar expression profile was also observed for LVs of mouse and human skins. Interestingly, inflammation of mouse cremaster tissues or ear skin as induced by TNF-stimulation induced a rapid (within 16 h) remodeling of the LV glycocalyx, as observed by reduced expression of HS and galactosyl moieties, whilst levels of α2,3-linked sialic acids remains unchanged. Furthermore, whilst this response was associated with neutrophil recruitment from the blood circulation and their migration into tissue-associated LVs, specific neutrophil depletion did not impact LV glycocalyx remodeling. Mechanistically, treatment with a non-anticoagulant heparanase inhibitor suppressed LV HS degradation without impacting neutrophil migration into LVs. Interestingly however, inhibition of glycocalyx degradation reduced the capacity of initial LVs to drain interstitial fluid during acute inflammation. Collectively, our data suggest that rapid remodeling of endothelial glycocalyx of tissue-associated LVs supports drainage of fluid and macromolecules but has no role in regulating neutrophil trafficking out of inflamed tissues via initial LVs.

Dendritic cell entry to lymphatic capillaries is orchestrated by CD44 and the hyaluronan glycocalyx

“…However, we have described a different role for CD44 in the exit of DCs via dermal lymphatic vessels in that the HA it engages is not sequestered on lymphatic endothelium but rather synthesized by the DC itself, and its function is to mediate intravasation and not extravasation. Indeed, lymphatic vessels do not possess an HA glycocalyx, neither in vitro nor in vivo (45,46), nor express CD44. Also, lymphatic endothelium does not use endogenously generated HA for DC adhesion (12).…”

Shape and Function of Interstitial Chemokine CCL21 Gradients Are Independent of Heparan Sulfates Produced by Lymphatic Endothelium

“…showed a dramatic reduction in HS coverage of lymphatic capillaries upon inflammatory stimulus ( 29 ). Interestingly, a decrease in the HS coverage of lymphatic capillaries was essential for efficient tissue fluid drainage, but, importantly, not CCL21 dependent migration and entrance of neutrophils to lymphatic capillaries ( 29 , 30 ). Together with our study, these results show that CCL21 dependent leukocyte migration cues are not affected by the changes in lymphatic endothelial HSs.…”

Rationale for the Role of Heparin and Related GAG Antithrombotics in COVID-19 Infection

“…Glycation with thickening of the vascular basement membrane, Increased expression of heparanase 78 resulting in cleavage and loss of HS from the glycocalyx and basement membrane, [79][80][81] Reduction of synthesis and sulphation of the heparan sulphate proteoglycans, Reduction in the luminal glycocalyx volume by shedding of negatively charges GAGs, Increased expression of adhesion molecules, Formation of cross-linked collagen with reduction in the elasticity of the vascular wall.…”