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Several studies have implicated the angiogenic cytokine vascular endothelial growth factor (VEGF) in the development of diabetic nephropathy, but no data are available about its local activity during human disease. Glomeruli from 52 archival biopsies from type II diabetics were evaluated and compared to 10 renal biopsies without kidney disease (controls). Glomerulosclerosis, capillary rarefaction, glomerular and endothelial cell proliferation, apoptosis, VEGF expression, as well as receptor-bound VEGF indicating local VEGF activity, and phosphorylation of the signal transduction molecule Akt were investigated. Owing to substantial heterogeneity of glomerular lesions in individual biopsies, these parameters were correlated with the degree of injury in individual glomeruli rather than biopsies. Severe glomerular capillary rarefaction was linked to the degree of glomerulosclerosis. While cellular apoptosis was detected independent of the stage of injury, endothelial cell proliferation indicating capillary repair was markedly increased only in mildly/moderately injured glomeruli. In controls, VEGF was predominantly expressed in podocytes, whereas receptor-bound VEGF was confined to the glomerular endothelium. VEGF expression was increased in all diabetic glomeruli by many different cell types. In contrast, VEGF receptor activation was increased predominantly in the endothelium of only mildly injured glomeruli, but significantly decreased in more severely injured glomeruli. Diabetic nephropathy is associated with glomerular capillary rarefaction. Despite overall increased glomerular VEGF, the decreased receptor-bound VEGF on the endothelium may be an indicator of an insufficient capillary repair reaction.Kidney International (2006) 69, 1654–1661. doi:10.1038/sj.ki.5000294; published online 15 March 2006 [ABSTRACT FROM AUTHOR]

Objective: Previous in vitro and in vivo studies demonstrated a relevant role of vascular endothelial growth factor (VEGF) in experimental diabetic renal disease, whereas inhibition of VEGF ameliorated development of experimental diabetic nephropathy. Nevertheless, little information exists about the relevance of VEGF, VEGF receptor 2 (VEGF-R2), and VEGF mediated VEGF-receptor activation during diabetic nephropathy in man. Methods: In this study, we investigated expression profiles of VEGF and VEGF-R2, the receptor thought to be responsible for VEGFinduced angiogenesis, using specific antibodies in renal biopsies of 52 patients with type 2 diabetic nephropathy. Ten renal biopsies without evidence of kidney disease served as controls. VEGF-receptor bound VEGF (representing endothelial cells actively undergoing VEGFinduced angiogenesis) was detected using a monoclonal antibody specifically/exclusively recognizing the VEGF-VEGF-R complex. Glomerular expression of VEGF, VEGF-R2, and VEGF-receptor bound VEGF was quantified using computer assisted image analysis of the immunostaining. Due to the heterogeneity of the diabetic lesions, individual glomeruli were classified as mildly (a), moderately (b), or severely (c) injured according to cellularity, capillarisation and sclerosis. Immunostaining was compared between these three groups and to controls. Results: Control biopsies demonstrated glomerular expression of VEGF in a typical podocytic pattern (2.6 ± 2.2). Glomeruli of diabetic kidneys (n = 575 glomeruli) with mild, moderate and severe injury showed increased expression of VEGF (a = 8.7 ± 5; b = 10.4 ± 6; c = 10.1 ± 6.9; all P < 0.001), but no differentiation according to the degree of injury could be done. Surprisingly, VEGF-R2 was predominantly detected in podocytes of controls as well as diabetic kidneys. During diabetic nephropathy, VEGF-R2 was also found in different cell types including glomerular endothelial cells. Overall expression of VEGF-R2 was unchanged in glomeruli with mild injury compared to controls (3.3 ± 3.4 vs. 5 ± 2.7), but was significantly increased in moderately (8.1 ± 5.8; P < 0.05) and almost significantly increased in severely injured glomeruli (7.6 ± 7.1; P = 0.06). VEGF-receptor bound VEGF was exclusively distributed in a typical endothelial pattern (by immunostaining) in glomeruli of control and diabetic kidneys (n = 575). Expression of VEGF-receptor bound VEGF was significantly increased in glomeruli with mild injury (16.4 ± 6.9) compared to controls (12.7 ± 5.8; P < 0.01). In contrast, VEGF-receptor bound VEGF significantly decreased in moderately (b = 10.9 ± 5.8) and severely (c = 10.7 ± 6.9) injured glomeruli compared to controls (P ≤ 0.05) and to glomeruli with mild injury (P < 0.001). Conclusions: The VEGF and VEGF-receptor system is differentially regulated during diabetic glomerulopathy. VEGF-receptor bound VEGF representing endothelial cells actively undergoing VEGFinduced angiogenesis is markedly increased in early stages of diabetic glomerulopathy, while later stages are associated with a decreased activity of VEGF-mediated angiogenesis. [ABSTRACT FROM AUTHOR]

Objective: Increased renal nitric oxide production and/or activity has been associated with glomerular hyperfiltration, vascular permeability and modulation of glomerulosclerosis and tubulointerstitial fibrosis. Several studies demonstrated regulated expression of nitric oxide synthases (NOSes) in experimental diabetic nephropathy. However, the regulation of NOSes and its clinical relationship in diabetic nephropathy in man is still not yet specified. Methods: We investigated renal biopsies and clinical data of 36 patients with diabetic nephropathy, 10 renal biopsies without evidence of renal disease served as controls. Glomerular and cortical eNOS and iNOS expression were assessed by immunhistochemical staining and correlated with clinical data such as the duration of diabetes, creatinine clearance, duration of arterial hypertension, albuminuria/ proteinuria, HbA1c, duration of insulin therapy, presence of vascular complications or diabetic retinopathy and smoking. Results: Mean age of patients at biopsy was 59 years, mean duration of diabetes 13.6 years. Compared to normal biopsies, expression of cortical (14.2 ± 8 vs. 10.7 ± 5.5; P = 0.05) and glomerular (16.4 ± 8 vs. 4.6 ± 3.3; P < 0.001) eNOS was increased in type 2 diabetics, whereas no significant differences could be detected for iNOS. Expression of cortical eNOS related with duration of arterial hypertension (r = 0.55) and that of glomerular eNOS with the degree of microvascular complications (r = 0.43). Interestingly expression of glomerular iNOS was linked to the duration of insulin therapy (r = 0.65). In addition, patients treated with insulin for less than 1 year had significantly lower iNOS levels (same levels as healthy controls) compared to patients with insulin therapy for more than one year (1.4 ± 0.8 vs 3.3 ± 2.1; P < 0.05). No correlations could be detected for all other clinical parameters as mentioned above. Conclusions: This study demonstrates significantly increased eNOS expression in kidney biopsies from patients with histologically proven diabetic nephropathy. Expression of eNOS as well as iNOS were in addition related to clinical risk factors of disease progression. [ABSTRACT FROM AUTHOR]