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Abstract: TH-OR086

Endothelial Glycocalyx Hyaluronan Is Required for Glomerular Integrity and Is Determined by Shear Stress-Regulated Glucobiosynthesis

Session Information

Category: Glomerular Diseases

  • 1201 Glomerular Diseases: Fibrosis and Extracellular Matrix

Authors

  • van den Berg, Bernard, Leiden University Medical Center, Leiden, Netherlands
  • Wang, Gangqi, LUMC, Leiden, Netherlands
  • Van der vlag, Johan, Radboud University Nijmegen Medical Centre; Dept of Nephrology, Nijmegen, Gelderland, Netherlands
  • Rabelink, Ton J., LUMC, Leiden, Netherlands

Group or Team Name

  • Division of Nephrology
Background

Endothelial cells are covered by a glycocalyx envelop, both luminal and abluminal, which predominantly consists of proteoglycans and adhering proteins. Conditional EC loss of glomerular hyaluronan (HA) resulted in mesangiolysis and capillary ballooning and albuminuria. Over time this process develops into glomerular capillary rarefaction and glomerulosclerosis. Laminar shear stress is required to preserve glycocalyx expression, but how downstream cellular regulation of production and maintenance of glycocalyx hyaluronan occurs is unknown.

Methods

EC-HA production and expression were tested in vitro and in vivo using primary glomerular derived EC or conditional EC HAS2-KO mice by fluorescent staining for HA, CRISPR-CAS9 editing of the HAS2 gene and NMR of 13C labelled glucose to determine cellular glucose metabolite concentrations.

Results

Here, we show how biosynthesis of the major structural component of EC glycocalyx, hyaluronan (HA), is regulated by shear. Both in vitro as well as in in vivo, HA expression on the endothelial surface is increased upon laminar shear and reduced when exposed to oscillatory flow, which is regulated by KLF2. We demonstrate increased expression and translocation of HAS2 to the endothelial cell membrane during laminar shear. HA production by HAS2 was shown to be further driven by availability of the HA 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. In addition, we found that HA harbours a specific binding site for the key regulator of endothelial quiescence and maintenance in glomerular endothelial barrier function, angiopoietin 1 (Ang1), and show that endothelial loss of HA resulted in disturbed Tie-2 kinase dependent glomerular endothelial stabilization.

Conclusion

These data demonstrate how endothelial glycocalyx function and functional adaptation to shear is coupled to KLF2 mediated regulation of endothelial glycolysis and HAS2 expression and HA is a critical growth factor signaling platform enabling effective Ang1/Tie2 signaling. As such, glomerular endothelial hyaluronan is a hitherto unrecognised key ECM component required for glomerular structure and function, which is lost in diabetic nephropathy.