ESPN 54th Annual Meeting

ESPN 2022


 
Podocyte-endothelial communication in WT1 childhood glomerular disease
JENNIFER C. CHANDLER 1 SAIF MALIK 1 DAVID A. LONG 1 AOIFE M. WATERS 2

1- DEVELOPMENTAL BIOLOGY AND CANCER PROGRAMME, UCL GREAT ORMOND STREET INSTITUTE OF CHILD HEALTH, LONDON, UK
2- DEPARTMENT OF NEPHROLOGY, GREAT ORMOND STREET HOSPITAL, LONDON UK
 
Introduction:

It is known that disruption of podocyte to endothelial communication is associated with albuminuria and glomerular damage in adult disease such as Diabetic Nephropathy.  The vascular growth factors, VEGF-A and angiopoietin-1, are secreted by podocytes and promote endothelial survival and stabilise endothelial cell-cell junctions. However, little is known about disrupted podocyte to endothelial signalling in childhood glomerular disease. As mutations in the transcription factor Wilms Tumour 1 (WT1) account for 8-13% of congenital nephrotic syndrome, we investigated a role for disrupted podocyte to endothelial communication in Wt1 glomerulopathy.

Material and methods:

We characterised a murine model (Wt1R394W/+) of Wt1 glomerulopathy, involving early-onset (<5 years) renal failure, consequence of diffuse mesangial sclerosis (DMS). We analysed biochemical markers, alongside histological features of the glomerulus from early to late disease (4 to 14 weeks of age). We next quantified podocyte (WT1+) and endothelial (CD31+) number via immunofluorescence at 2, 4 and 8 weeks and investigated the levels of vascular growth factors by RT-qPCR. 

Results:

We found Wt1R394W/+ mice to have severe albuminuria from 4 weeks of age, prior to histological features of DMS in the kidney, which were pronounced by 8 weeks. We next quantified podocyte number (WT1+) at 2, 4 and 8 weeks, highlighting a significant decline from 4 weeks of age, as well as a shift in WT1+ cells from inside the tuft to the parietal epithelial layer. Conversely, endothelial cell number (CD31+) was maintained in 2 and 4 week old glomeruli, but showed a significant reduction by 8 weeks; indicating podocyte loss precedes endothelial damage. We also found a significant downregulation in the podocyte secreted factors Angiopoietin-1 and Vegfa in primary Wt1R394W/+ podocytes at 4 and 8 weeks.

Conclusions:

Together this shows that podocyte loss and reduction in Angiopoietin-1 and Vegfa, drive endothelial damage in this model of Wt1 glomerulopathy. Targeting these signalling pathways may be a promising approach in the treatment of childhood glomerular disease.