Use this URL to cite or link to this record in EThOS:
Title: Understanding the renal pathogenesis of diarrhoea associated haemolytic uraemic syndrome : the role of the podocyte
Author: Keir, Lindsay Susan
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2013
Availability of Full Text:
Access from EThOS:
Haemolytic uraemic syndrome (HUS) is the leading cause of childhood acute kidney injury. It often occurs after a diarrhoeal illness caused by Shiga toxin (Stx) producing bacteria. HUS has significant morbidity and mortality but no direct treatment. The pathogenesis is incompletely understood. Initially considered an endothelial cell disease because glomerular thrombotic microangiopathy (TMA) is the pathological hallmark, this was challenged when patients treated with anti-vascular endothelial growth factor (VEGF) agents and mice with a podocyte specific Vegf knockout developed TMA and HUS. Affected children's kidneys and Stx treated cultured human podocytes also showed reduced VEGF. The study of familial atypical HUS also added to our understanding of the pathogenesis. It identified over-activation of the alternative complement pathway, leading to treatments blocking the complement cascade. Based on these data a hypothesis was generated. In Stx HUS, the podocyte is the initial toxin target. Stx binds to podocyte Gb3 receptors reducing VEGF secretion which decreases glomerular endothelial cell (GEnC) expression of protective complement regulators, making these cells vulnerable to complement mediated injury causing TMA and HUS. Human glomerular cells were tested for Gb3 expression and Std sensitivity. Both podocytes and GEnC expressed Gb3 but podocytes were significantly more Std sensitive. Consistent with previous reports, mouse podocytes did not express Gb3 and were Stx insensitive. Transfection with Gb3 synthase did induce Gb3 expression. An inducible, podocyte specific Gb3 synthase expressing mouse was made to study the central hypothesis. The podocytes of these mice expressed Gb3 but showed no glomerular abnormalities. They are now being challenged with Stx. The effect of VEGF on GEnC expression of complement regulators was studied. VEGF regulated GEnC expression of CD46 and CDS9 in a dose dependent manner. Serum based regulator factor H (CFH) was also synthesized and secreted and was up regulated by VEG F. Functional relevance of these changes was shown using a complement challenge assay. Significantly fewer complement deposits were seen on VEGF treated cells suggesting protection from complement attack. Kidneys from inducible podocyte specific Vegf knockout mice with TMA showed reduced glomerular CFH with evidence of complement deposition. In conclusion, human podocytes are sensitive Stx targets. Reduced VEGF secretion occurs after Stx challenge. loss of VEGF reduces GEne expression of protective complement regulators in a functionally significant way leading to complement deposition in a model of TMA. This work supports the central hypothesis. An inducible podocyte specific Gb3 expressing mouse has been created to test this further in vivo. This mouse is being studied to see if it develops HUS. If this occurs, it will allow the in vivo study of the pathogenesis of Stx HUS. Hopefully this will help identify potential therapeutic targets.
Supervisor: Not available Sponsor: Medical Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available