Podocyte vascular endothelial growth factor (Vegf 164 ) overexpression causes severe nodular glomerulosclerosis in a mouse model of type 1 diabetes

Abstract

Aims/hypothesis The pathogenic role of excessive vascular endothelial growth factor (VEGF)-A in diabetic nephropathy has not been defined. We sought to test whether increased podocyte VEGF-A signalling determines the severity of diabetic glomerulopathy. Methods Podocyte-specific, doxycycline-inducible Vegf164 (the most abundant Vegfa isoform) overexpressing adult transgenic mice were made diabetic with low doses of streptozotocin and examined 12 weeks after onset of diabetes. We studied diabetic and non-diabetic transgenic mice fed a standard or doxycycline-containing diet. VEGF-A and albuminuria were measured by ELISA, creatinine was measured by HPLC, renal morphology was examined by light and electron microscopy, and gene expression was assessed by quantitative PCR, immunoblotting and immunohistochemistry. Results Podocyte Vegf164 overexpression in our mouse model of diabetes resulted in advanced diabetic glomerulopathy, characterised by Kimmelstiel–Wilson-like nodular glomerulosclerosis, microaneurysms, mesangiolysis, glomerular basement membrane thickening, podocyte effacement and massive proteinuria associated with hyperfiltration. It also led to increased VEGF receptor 2 and semaphorin3a levels, as well as nephrin and matrix metalloproteinase-2 downregulation, whereas circulating VEGF-A levels were similar to those in control diabetic mice. Conclusions/interpretation Collectively, these data demonstrate that increased podocyte Vegf164 signalling dramatically worsens diabetic nephropathy in a streptozotocin-induced mouse model of diabetes, resulting in nodular glomerulosclerosis and massive proteinuria. This suggests that local rather than systemic VEGF-A levels determine the severity of diabetic nephropathy and that semaphorin3a signalling and matrix metalloproteinase-2 dysregulation are mechanistically involved in severe diabetic glomerulopathy.

Podocyte-Specific VEGF-A Gain of Function Induces Nodular Glomerulosclerosis in eNOS Null Mice

“…We previously reported that podocyte VEGF 164 gain of function during 12 weeks in diabetic mice induces nodular glomerulosclerosis and advanced glomerulopathy. 6 Here, we immunostained kidney sections from those mice and detected both laminin and collagen IV colocalized mainly in diabetic nodules ( Figure 5A), a pattern similar to that observed in eNOS KO mice with podocyte VEGF 164 gain of function (Figure 5B). Collectively, these findings suggest that in mice with insufficient eNOS function, induced by diabetes mellitus or by eNOS deletion, increased glomerular VEGF-A causes laminin and collagen IV accumulation in glomerular nodules.…”

“…[1][2][3][4] Glomerular VEGF-A plays a critical role in the pathogenesis of diabetic nephropathy. [5][6][7] Transgenic mice with podocyte VEGF 164 gain of function develop a glomerular phenotype indistinguishable from early diabetic nephropathy, in the context of normal blood glucose and normal systemic VEGF-A. 5 In the setting of type 1 diabetes, plasma VEGF-A increases but nodular glomerulosclerosis develops only in mice with podocyte VEGF 164 gain of function, demonstrating that local rather than systemic VEGF excess is critical for the progression of diabetic glomerulopathy to advanced disease.…”

“…5 In the setting of type 1 diabetes, plasma VEGF-A increases but nodular glomerulosclerosis develops only in mice with podocyte VEGF 164 gain of function, demonstrating that local rather than systemic VEGF excess is critical for the progression of diabetic glomerulopathy to advanced disease. 6 Nitric oxide (NO) is a product of arginine oxidation: L arginine+O 2 → citrulline+NO, catalyzed by NO synthase (NOS). The major source of endogenous NO, NOS isoforms (neuronal NOS, inducible NOS, and endothelial NOS), [8][9][10] are expressed in the kidney.…”

Adenosine A2B receptor-mediated VEGF induction promotes diabetic glomerulopathy

“…6 Further, overproduction of VEGF in transgenic animals is sufficient to resemble the glomerular alterations seen in DN. 7,8 Moreover, biopsies from type 1 and type 2 diabetic patients with early renal damage show an increased glomerular VEGF. [9][10][11][12][13] Therefore, identification of upstream mediators of VEGF overproduction is critical for identifying the pathogenesis of this disease.…”

The Vasculature in Diabetic Nephropathy

“…For example, VEGF-A has been reported to be upregulated 12 or downregulated 13 in human DN biopsies. Deletion of VEGF from podocytes has been shown to exacerbate DN in the streptozotocin (STZ) model of type 1 diabetes by Sivaskandarajah et al, 14 whereas Veron et al 15 reported that inducible overexpression of VEGF in the podocyte causes severe nodular glomerulosclerosis in the STZ model. Similar to the results of Veron et al, the Gnudi laboratory showed that podocyte overexpression of a naturally occurring VEGF inhibitor called sFlt-1 improves DN.…”