Inducible overexpression of sFlt-1 in podocytes ameliorates glomerulopathy in diabetic mice

Abstract

OBJECTIVE-Podocyte-specific, doxycycline (DOX)-inducible overexpression of soluble vascular endothelial growth factor (VEGF) receptor-1 (sFlt-1) in adult mice was used to investigate the role of the VEGF-A/VEGF receptor (VEGFR) system in diabetic glomerulopathy. RESEARCH DESIGN AND METHODS-We studied nondia-betic and diabetic transgenic mice and wild-type controls treated with vehicle (VEH) or DOX for 10 weeks. Glycemia was measured by a glucose-oxidase method and blood pressure by a noninvasive technique. sFlt-1, VEGF-A, VEGFR2, and nephrin protein expression in renal cortex were determined by Western immunoblotting; urine sFlt-1, urine free VEGF-A, and albumin-uria by enzyme-linked immunosorbent assay; glomerular ultra-structure by electron microscopy; and VEGFR1 and VEGFR2 cellular localization with Immunogold techniques. RESULTS-Nondiabetic DOX-treated transgenic mice showed a twofold increase in cortex sFlt-1 expression and a fourfold increase in sFlt-1 urine excretion (P < 0.001). Urine free VEGF-A was decreased by 50%, and cortex VEGF-A expression was upregulated by 30% (P < 0.04). VEGFR2 expression was unchanged, whereas its activation was reduced in DOX-treated transgenic mice (P < 0.02). Albuminuria and glomerular morphology were similar among groups. DOX-treated transgenic diabetic mice showed a 60% increase in 24-h urine sFlt-1 excretion and an ∼70% decrease in urine free VEGF-A compared with VEH-treated diabetic mice (P < 0.04) and had lower urine albumin excretion at 10 weeks than VEH-treated diabetic (D) mice: d-VEH vs. d-DOX, geometric mean (95% CI), 117.5 (69-199) vs. 43 (26.8-69) jxμg/24 h (P = 0.003). Diabetes-induced mesangial expansion, glomerular basement membrane thickening, podo- cyte foot-process fusion, and transforming growth factor-(31 expression were ameliorated in DOX-treated diabetic animals (P < 0.05). Diabetes-induced VEGF-A and nephrin expression were not affected in DOX-treated mice. CONCLUSIONS Podocyte-specific sFlt-1 overexpression ameliorates diabetic glomerular injury, implicating VEGF-A in the pathogenesis of this complication. © 2008 by the American Diabetes Association.