1. Three-month survival was 31% in the untreated, 67% in the D and 100% in the P group respectively (p<0.05) Survival Rate delayed Rx prophylactic Rx untreated control untreated prophylactic Rx control untreated delayed Rx week 4 week 8 The research leading to these results has received funding from the European Community’s Seventh Framework Programme under grant agreement n° 2012-305608 “European Consortium for High-Throughput Research in Rare Kidney Diseases (EURenOmics)” NPHS2 mutations cause hereditary nephrotic syndrome and progressive renal failure. We recently generated an inducible knock-in mouse model carrying R140Q, the analogue of the most common human mutation R138Q. These mice develop focal-segmental glomerulosclerosis with nephrotic syndrome and progressive renal failure. Here we tested the efficacy of early and delayed RAS blockade in this model of hereditary podocyte disease. Background Podocin protein abundance was almost totally lost in both untreated and treated animals, despite preserved or even increased mRNA expression. In the P animals, RAS blockade persistently inhibited proteinuria (13% of untreated animals at 4 wks). In the D group, proteinuria sharply decreased upon RAS blockade. Proteinuria Model In C57BL/6 mice with Nphs2 Flox/R140Q/Cre+ genotype, hemizygosity for mutant podocin was induced by tamoxifen injection (i.p. 33 mg/kg/day). Pharmacological treatment Animals received combined high-dose ACE inhibition and AT1 receptor blockade (ramipril+candesartan 10 mg/kg each, R+C) or remained untreated. Treatment was started either prophylactically (P) at time of induction or with a 4-week delay (D). Animals were either sacrificed after 5 wks (9 wks in D) or observed open-end and the glomerular filtration rate, biochemical parameters and histopathological changes were examined (glomerulosclerosis, tubulointerstitial changes, podocyte loss). Proteinuria and blood pressure were monitored weekly. Results Conclusion Sclerosis within the glomerular tuft examined by PAS staining of 3µm paraffin sections (glomerular sclerosis index – GSI, 50 glomeruli/animal. *p<0.05 **p<0.01) Helga Denc 1,Tanja Wlodkowski 1, Mansoureh Tabatabaeifar 1, Ivana Simic 1, Geraldine Mollet 2, Corinne Antignac 2, Franz Schaefer 1 1 Pediatric Nephrology, Center for Pediatrics and Adolescent Medicine, University of Heidelberg, Germany 2 Inserm U983 and Dept. of Genetics, Hopital Necker, France WT1 immunostaining of glomerular cross-sections (4µm & 10 µm). Number of podocytes per glomerulus was preserved in P animals (***p<0.001). Quantification was done with ImageJ according to Animal Models of Diabetic Complications Consortium protocol. Tubulointerstitial fibrosis determined by Sirus Red staining. A slight, non-significant reduction was noted in treated animals. Quantification was done with Image ProPremier Software. p>0.05 Podocin protein & gene expression Plasma was obtained via cardiac puncture at the time of sacrificing. (***p<0.001 vs. untreated, Student´s t-Test) RAS Blockade Preserves / Restitutes Normoalbuminemia *** Nephroprotective Efficacy of RAS Blockade in Mice Carrying R140Q Podocin Mutation Controluntreated week 4 Week 4 prophylactic RxWeek 8 delayed Rx ControlWk 4 untreated Wk 4 prophylactic RxWk 8 delayed RxWk 8 untreated Control Wk 4 untreated Wk 4 prophylactic Rx Wk 8 delayed Rx Wk 8 untreated In mice carrying the most common human podocin mutation, RAS blockade attenatues proteinuria, podocyte loss and glomerulosclerosis despite persistently increased degradation of mutant podocin protein. Renal failure is delayed and survival prolonged. Treatment is more effective when applied prophylactically than when started in established nephropathy. Our findings indicate that early RAS blockade may provide effective nephroprotection in this hereditary podocytopathy. Number of podocytes per glomerulus Glomerular sclerosis Tubulointerstitial fibrosis Methods