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Abstract: TH-PO782

Proteoglycans Play a Major Role in the Charge Selectivity of the Glomerular Barrier

Session Information

Category: Glomerular Diseases

  • 1201 Glomerular Diseases: Fibrosis and Extracellular Matrix

Authors

  • Khramova, Alina, University of Gothenburg, Göteborg, Sweden
  • Haraldsson, Boerje, Novartis, BASEL, Switzerland
  • Ebefors, Kerstin, University of Gothenburg, Göteborg, Sweden
  • Nystrom, Jenny C., University of Gothenburg, Göteborg, Sweden
Background

The loss of ability to retain macromolecules is a critical step during kidney disease progression. The luminal surface layer of the glomerular capillary endothelium (ESL) is an understudied part of the filtration barrier. The ESL consist of a glycocalyx and an endothelial cell coat, which together form a stagnant mucosal layer – an additional barrier to prevent a leakage of high molecular weight proteins such as albumin.

Methods

In this study, we were guided by basic principles of ion exchange chromatography. In order to elute highly negatively charged proteoglycans of the ESL, we used 1 M NaCl solution (HS). 1 M mannitol (HO) was included to evaluate osmotic effects. A control fraction was eluted with normal saline solution (0,15 M NaCl) (NS). Solutions were introduced intraarterially to rat kidneys under anesthesia in vivo. Venous effluent was collected and analyzed using proteomics and mass spectrometry. Immunohistochemistry was used to confirm the presence of identified PGs and the thickness of the glomerular ESL was evaluated using intralipid droplets.

Results

We identified 9 PGs in ESL, for their contribution to the glomerular barrier function (presented in the order of high to low abundance): lumican, glypican-1, syndecan-4, perlecan, podocan, decorin, serglycan, agrin and biglycan. In general, PGs were more abundant in HS samples compare to NS and HO. TEM demonstrated that the glomerular ESL thickness was significantly reduced in HS perfused rats – 28% (p<0.05) compared to rats perfused with NS.

Conclusion

ESL itself is formed by PGs, glycosaminoglycans, glycoproteins and soluble proteins and represents a dynamic structure with significant molecular turnover. As a part of molecular sieving system, PGs support the characteristic permselective properties in kidneys by balancing the level of mentioned molecules. Thus molecular composition of the ESL may have a significant impact on local charge alterations which can lead to severe interruptions of the filtration system and, as a result, macromolecular leakage. These findings might be essential for understanding kidney pathology development and protein leakage at a molecular level as well as result in new possible targets for treatment of proteinuria.

Funding

  • Private Foundation Support