Abstract
Introduction: Diabetes mellitus (DM) causes life altering microvascular complications,such as diabetic nephropathy and retinopathy (DR and DN). The endothelial glycocalyx
(eGlx), containing proteoglycans (core proteins with glycosaminoglycan (GAG) sidechains),
lines all blood vessels and helps to maintain vascular permeability barriers. Heparan
sulfate (HS) is the most abundant GAG in the eGlx. In DM, heparanase, an HS degrading
enzyme, is upregulated. The aim of this PhD was to show that eGlx HS is important in
glomerular and retinal microvascular barriers and that preventing its shedding, using a
novel heparanase inhibitor, OVZ/HS-1638, is protective in DM.
Methods: EGlx HS was removed in mice by i.v. of heparinase III, or by an Ext1 (an HS
biosynthesis enzyme) endothelial-specific conditional knock-out mouse (Ext1CKO). Type
2 diabetic mice (db/db) were treated with OVZ/HS-1638 or vehicle for two weeks, with a
9-week and 11-week old endpoint. Fluorescein angiography analysis was used as a
measure of retinal apparent solute flux, and albumin staining to measure vascular leak.
Mice were Ringer or Alcian blue/glutaraldehyde perfused for apparent glomerular
permeability (Ps’alb) studies and electron microscopy (EM), respectively. EGlx depth and
coverage was measured by EM. Urine albumin creatinine ratios (uACRs) were measured
at endpoint.
Results: A reduction of eGlx, using heparinase III or in Ext1CKO mice, was associated with
increased retinal solute flux and Ps’alb. Ext1CKO mice also had increased uACR when
tubular absorption was blocked. In 9-week-old db/db, OVZ/HS-1638 increased retinal eGlx
depth and reduced retinal albumin leak. In 11-week-old db/db mice, OVZ/HS-1638
restored glomerular eGlx depth and restored Ps’alb. uACR was no longer significantly
increased.
Conclusions: Together, this work shows that eGlx HS is structurally and functionally
important in two spatially and functionally distinct vessel beds and suggests that HS is
amenable to therapeutic intervention in DM, using a clinically relevant heparanase
inhibitor.
| Date of Award | 29 Sept 2020 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Rebecca Foster (Supervisor), Simon C Satchell (Supervisor) & Gavin I Welsh (Supervisor) |