ET(B) receptor protects the tubulointerstitium in experimental thrombotic microangiopathy

BACKGROUND: The characteristic features of thrombotic microangiopathy (TMA) include glomerular and peritubular capillary endothelial cell injury with thrombus formation and subsequent ischemic tubulointerstitial damage. The endothelin ET(B) receptor has been shown to mediate both endothelial cell proliferation and vasodilation, and we therefore hypothesized that blockade of this receptor might promote more severe injury in this model. METHODS: TMA was induced in recently established transgenic rats that lack expression of ET(B) receptor in the kidney; these animals were compared to control rats with TMA both in the short-term (days 1 and 3) when acute glomerular injury was most manifest, and the long-term (day 17) when glomeruli have recovered but tubulointerstitial injury is still present. Renal damage was assessed by histological analysis and blood urea nitrogen (BUN) measurements. RESULTS: No difference in the TMA model was observed between rats with and without ET(B) receptor on days 1 or 3. At day 17, however, rats without the ET(B) receptor showed more severe tubulointerstitial injury compared with those with ET(B) receptor, which was associated with higher BUN levels. The tubulointerstitial damage was associated with a more severe loss of peritubular capillaries. CONCLUSIONS: These findings suggest that the ET(B) receptor may protect peritubular capillaries under the ischemic insult, and serve a defensive role in the tubulointerstitium induced by renal microvascular injury.     

The role of vascular endothelial growth factor (VEGF) in renal pathophysiology

Vascular endothelial growth factor (VEGF) is an endothelial-specific growth factor that promotes endothelial cell proliferation, differentiation and survival, mediates endothelium-dependent vasodilatation, induces microvascular hyperpermeability and participates in interstitial matrix remodeling. In the kidney, VEGF expression is most prominent in glomerular podocytes and in tubular epithelial cells, while VEGF receptors are mainly found on preglomerular, glomerular, and peritubular endothelial cells. The role of VEGF in normal renal physiology is essentially unknown. The absence of prominent effects of VEGF blockade in normal experimental animals suggests a limited function during homeostasis, although a role in the formation and maintenance of glomerular capillary endothelial fenestrations has been suggested. VEGF and its receptors are up-regulated in experimental animals and humans with type 1 and type 2 diabetes. Inhibition of VEGF has beneficial effects on diabetes-induced functional and structural alterations, suggesting a deleterious role for VEGF in the pathophysiology of diabetic nephropathy. VEGF is required for glomerular and tubular hypertrophy and proliferation in response to nephron reduction, and loss of VEGF is associated with the development of glomerulosclerosis and tubulointerstitial fibrosis in the remnant kidney. No firm conclusions on the role of VEGF in minimal change or membranous glomerulonephritis can be drawn. VEGF may be an essential mediator of glomerular recovery in proliferative glomerulonephritis. Glomerular and tubulointerstitial repair in thrombotic microangiopathy and cyclosporin nephrotoxicity may also be VEGF-dependent. In conclusion, VEGF is required for growth and proliferation of glomerular and peritubular endothelial cells. While deleterious in some, it may contribute to recovery in other forms of renal diseases.     

Protection of endothelial cells by dextran sulfate in rats with thrombotic microangiopathy

The characteristic features of thrombotic microangiopathy (TMA) include glomerular and peritubular capillary endothelial cell injury in association with loss of heparan sulfate proteoglycans on the cell surface and thrombus formation, followed by subsequent ischemic tubulointerstitial damage. It therefore was hypothesized that dextran sulfate (DXS) may protect the kidney against endothelial damage in a model of TMA. TMA was induced in rats by renal artery perfusion of an antiglomerular endothelial antibody, followed by the administration of DXS or vehicle. Renal damage was assessed by histologic analysis and measurements of blood urea nitrogen and creatinine. Whereas control rats developed severe renal failure with extensive glomerular and tubular injury, administration of DXS significantly protected renal function and preserved the glomerular endothelium and peritubular capillaries. The beneficial effect of DXS could be attributed to the ability of DXS to protect endothelial cells from coagulation and complement activation, as demonstrated by the histologic analysis. In addition, binding of the administered DXS to the surface of the glomerular endothelium was confirmed in TMA rats, suggesting that DXS acts as a "repair coat" of injured glomerular endothelium. In conclusion, DXS protects the kidney from experimental TMA. This protection may be mediated by DXS's binding directly to the surface of glomerular endothelium and amelioration of coagulation, complement activation, and cellular matrix loss.     

Renal Microvascular Disease in an Aging Population: A Reversible Process?

Renal microvascular disease and tubulointerstitial fibrosis are usually demonstrated in aging in humans and animals. It has recently been proposed that renal microvascular disease is the crucial determinant of tubulointerstitial disease or fibrosis. Enhanced circulating endothelial cell loss is a biomarker that reflects glomerular endothelial injury or renal microvascular disease, and fractional excretion of magnesium (FE Mg) is a sensitive biomarker that reflects an early stage of tubulointerstitial fibrosis. In aging in humans, both of these biomarkers are abnormally elevated. In addition, a glomerular endothelial dysfunction determined by altered hemodynamics associated with peritubular capillary flow reduction is substantiated. A correction of such hemodynamic alteration with vasodilators can effectively improve renal perfusion and restore renal function. Thus, anti-aging therapy can reverse the renal microvascular disease and dysfunction associated with the aging process.     

Renal microvascular disease in an aging population: a reversible process?

Renal microvascular disease and tubulointerstitial fibrosis are usually demonstrated in aging in humans and animals. It has recently been proposed that renal microvascular disease is the crucial determinant of tubulointerstitial disease or fibrosis. Enhanced circulating endothelial cell loss is a biomarker that reflects glomerular endothelial injury or renal microvascular disease, and fractional excretion of magnesium (FE Mg) is a sensitive biomarker that reflects an early stage of tubulointerstitial fibrosis. In aging in humans, both of these biomarkers are abnormally elevated. In addition, a glomerular endothelial dysfunction determined by altered hemodynamics associated with peritubular capillary flow reduction is substantiated. A correction of such hemodynamic alteration with vasodilators can effectively improve renal perfusion and restore renal function. Thus, anti-aging therapy can reverse the renal microvascular disease and dysfunction associated with the aging process.     

Vascular endothelial growth factor (VEGF121) protects rats from renal infarction in thrombotic microangiopathy

BACKGROUND: Renal thrombotic microangiopathy, typified by the hemolytic uremic syndrome, is associated with endothelial cell injury in which the presence of cortical necrosis, extensive glomerular involvement, and arterial occlusive lesions correlates with a poor clinical outcome. We hypothesized that the endothelial survival factor vascular endothelial growth factor (VEGF) may provide protection. METHOD: Severe, necrotizing, thrombotic microangiopathy was induced in rats by the renal artery perfusion of antiglomerular endothelial antibody, followed by the administration of VEGF or vehicle, and renal injury was evaluated. RESULTS: Control rats developed severe glomerular and tubulointerstitial injury with extensive renal necrosis. The administration of VEGF significantly reduced the necrosis, preserved the glomerular endothelium and arterioles, and reduced the number of apoptotic cells in glomeruli (at 4 hours) and in the tubulointerstitium (at 4 days). The prosurvival effect of VEGF for endothelium may relate in part to the ability of VEGF to protect endothelial cells from factor-induced apoptosis, as demonstrated for tumor necrosis factor-alpha (TNF-alpha), which was shown to be up-regulated through the course of this model of renal microangiopathy. Endothelial nitric oxide synthase expression was preserved in VEGF-treated rats compared with its marked decrease in the surviving glomeruli and interstitium of the antibody-treated rats that did not receive VEGF. CONCLUSIONS: VEGF protects against renal necrosis in this model of thrombotic microangiopathy. This protection may be mediated by maintaining endothelial nitric oxide production and/or preventing endothelial cell death.     

Vascular endothelial growth factor165 resolves glomerular inflammation and accelerates glomerular capillary repair in rat anti-glomerular basement membrane glomerulonephritis

Vascular endothelial growth factor (VEGF) is essential for maintenance of the glomerular capillary network. The present study investigated the effects of VEGF in rats with progressive crescentic glomerulonephritis (GN). Necrotizing and crescentic GN was induced in rats by injection of anti-rat glomerular basement membrane (GBM) antibody. The alterations of glomerular capillaries and glomerular VEGF expression were assessed. In addition, the effects of continuous VEGF165 administration (10 microg/100 g per d) on glomerular capillaries, glomerular inflammation, and the course of crescentic GN were examined. The appropriate timing of VEGF administration in progressive GN also was evaluated. In anti-GBM GN, necrotizing and crescentic glomerular lesions occurred by day 7, and newly formed necrotizing lesions reoccurred by week 3. Expression of VEGF was markedly reduced in necrotizing and crescentic lesions. Capillary repair was impaired after capillary destruction in necrotizing and crescentic glomeruli, which rapidly progressed to sclerotic glomeruli with chronic renal failure. In contrast, in the rats that received VEGF165 administration from day 7, the necrotizing and crescentic lesions recovered and renal function significantly improved in week 4. This was evident by proliferating endothelial cells and glomerular capillary repair. In addition, VEGF administration decreased intercellular adhesion molecule-1 and monocyte chemoattractant protein-1 expression in glomeruli (particularly on endothelial cells), reduced glomerular infiltrating CD8-postive and ED-1-positive cells, and inhibited the newly formed necrotizing lesions. VEGF administration was apparently effective against both the inflammatory and necrotizing glomerular lesions. These results suggest that VEGF administration resolves glomerular inflammation and accelerates glomerular recovery in the progressive necrotizing and crescentic GN. The therapeutic application of VEGF may be clinically useful for severe GN accompanied by extensive glomerular inflammation and endothelial injury.     

Local VEGF activity but not VEGF expression is tightly regulated during diabetic nephropathy in man

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.     

Blockade of VEGF accelerates proteinuria, via decrease in nephrin expression in rat crescentic glomerulonephritis

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor that maintains the glomerular and peritubular capillary (PTC) network in the kidney. The soluble form of the VEGF receptor-1 (soluble fms-like tyrosine kinase 1 (sFlt-1)) is known to regulate VEGF activity by binding VEGF in the circulation. We hypothesized that VEGF may be beneficial for maintaining glomerular filtration barrier and vascular network in rats with progressive glomerulonephritis (GN). For blockade of VEGF activity in vivo, rats were transfected twice with plasmid DNA encoding the murine sFlt-1 gene into femoral muscle 3 days before and 2 weeks after the induction of antiglomerular basement membrane antibody-induced GN. Inhibition of VEGF with sFlt-1 resulted in massive urinary protein excretion, concomitantly with downregulated expression of nephrin in nephritic rats. Further, blockade of VEGF induced mild proteinuria in normal rats. Administration of sFlt-1 affected neither the infiltration of macrophages nor crescentic formation. In contrast, treatment of sFlt-1 accelerated the progression of glomerulosclerosis and interstitial fibrosis accompanied with renal dysfunction and PTC loss at day 56. VEGF may play a role in maintaining the podocyte function as well as renal vasculature, thereby protecting glomeruli and interstitium from progressive renal insults.     

Everolimus inhibits glomerular endothelial cell proliferation and VEGF, but not long-term recovery in experimental thrombotic microangiopathy.

BACKGROUND: Everolimus is a potent immunosuppressant used in renal transplant therapy, but its effects on renal endothelial cell regeneration after injury are unknown. The effects of an everolimus therapy were investigated in a model of renal thrombotic microangiopathy (TMA) with specific endothelial cell (EC) injury in the rat in vivo as well as in glomerular ECs in vitro. METHODS: During the early regenerative phase (day 3) of the renal microvascular injury model in vivo, everolimus inhibited glomerular EC proliferation by up to 60% compared with vehicle-treated rats, whereas apoptosis was not different in these groups. This decreased EC proliferation was associated with an enhanced deposition of fibrin in everolimus treated animals on day 3. In cultured glomerular endothelial cells, everolimus effectively and dose dependently inhibited cellular proliferation. This anti-proliferative effect was associated with a reduced phosphorylation of the p70S6 kinase and reduction of the pro-angiogenic factor VEGF in glomeruli in vivo and in cultured podocytes in vitro. RESULTS: Despite the prolonged EC repair and in contrast to the anti-Thy1 nephritis model, everolimus therapy did not disturb the long-term repair reaction in this thrombotic microangiopathy model. CONCLUSION: Everolimus is anti-proliferative for glomerular EC in vitro and in vivo and does not seem to have detrimental long-term effects in experimental renal TMA, when only the glomerular endothelium, but not the mesangium is severely injured.     

Infusion of angiotensin II reduces loss of glomerular capillary area in the early phase of anti-Thy-1.1 nephritis possibly via regulating angiogenesis-associated factors

BACKGROUND: Although angiotensin II (Ang II) is involved in the progression of renal diseases, infusion of Ang II was reported to surprisingly ameliorate the early phase of anti-Thy-1.1 nephritis. Considering the known proangiogenic effect of Ang II and that angiogenic glomerular capillary repair is required for the recovery of damaged glomeruli in rat anti-Thy-1.1 nephritis, we hypothesized that Ang II infusion starting prior to the initiation of nephritis may induce the expression of angiogenic growth factors such as vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1), resulting in the increased glomerular capillary area in the early phase. METHODS: Ang II was infused (170 ng/min) in rats, and 5 days later, nephritis was induced by the administration of monoclonal 1-22-3 antibodies. Ang II type 1 or type 2 receptor antagonist (AT(1)R or AT(2)R, respectively) (losartan or PD123319, respectively) was coadministered. RESULTS: Ang II infusion affected on neither the deposition of Ig nor mesangiolysis in the initial phase, and resulted in the aggravation of creatinine clearance at day 14 and 35 after initiating anti-Thy-1.1 nephritis. Histologic alterations were ameliorated accompanied by reduced loss in rat endothelial cell antigen (RECA)-1(+) endothelial area in Ang II-infused nephritic rats on day 6 and 14 as compared to control nephritic group, and nephritic alterations were mostly resolved on day 35 in both groups. At the early stage (day 6), glomerular expression of VEGF and receptors flk-1 and flt-1 as well as Ang-1, and receptor Tie2 were increased, and glomerular monocyte infiltration and the expression of angiopoietin-2 (Ang-2), a natural antagonist of Ang-1, were reduced. Both Ang II receptors were involved in the regulation of angiogenic factors and receptors. CONCLUSION: These results demonstrate that infusion of exogenous Ang II starting prior to the induction of nephritis activates VEGF and Ang-1 signaling regulated via both Ang II receptors, potentially leading to the accelerated recovery of injured glomerular endothelial cells in the early phase of anti-Thy-1.1 nephritis. Increased expression of VEGF and Ang-1 on podocytes further suggests the crucial association of endothelial cells and podocytes in maintaining proper glomerular capillary structures.     

Thrombotic microangiopathy associated with the hypereosinophilic syndrome

BACKGROUND: Hypereosinophilic syndrome (HES), defined as persistent marked eosinophilia of unknown origin complicated by end organ damage, is thought to be due to activation of eosinophils and release of substances that are toxic to various cells and tissues. An association between hypereosinophilia and kidney damage is not well documented. METHODS: We describe two patients with the HES, acute renal failure, and thrombocytopenic hemolytic anemia. Renal biopsy pathology and immunohistochemistry for activated eosinophils were performed. RESULTS: Renal biopsy revealed glomerular thrombosis, proliferative arteritis, and glomerular and tubulointerstitial eosinophil infiltrates. Ultrastructurally, subendothelial glomerular fibrin deposits and numerous luminal platelets characteristic of thrombotic microangiopathy (TMA) were present. Abundant degranulated eosinophils were localized in glomeruli and the interstitium. Immunofluorescence with specific antibody to eosinophil granule major basic protein (MBP) showed striking extracellular MBP deposition within glomeruli, a marker of eosinophil degranulation. Both patients developed TMA. High-dose glucocorticoids achieved sustained decrease of blood eosinophils and improvement of renal function. CONCLUSION: To our knowledge these are the first documented cases of TMA associated with HES. We propose that products released from degranulated eosinophils caused endothelial injury and microvascular thrombosis. Recognition of this serious renal complication associated with blood eosinophilia should prompt early diagnosis and treatment.     

Protective role of nitric oxide in a model of thrombotic microangiopathy in rats

Anew model of thrombotic microangiopathy (TMA) was previously developed, and it was demonstrated that endothelial nitric oxide (NO) synthase (NOS) is upregulated in glomeruli in this model. It was hypothesized that the synthesis of NO, a potent vasodilator and platelet inhibitory factor, is induced as a defense mechanism. The goal of this study was to clarify the role of NO in this model. Ex vivo experiments using Western blotting and functional assays demonstrated upregulation of endothelial NOS in isolated glomeruli from TMA rats. In in vivo experiments, five groups of rats were studied, including rats with TMA treated with vehicle, N(G)-nitro-L-arginine methyl ester (L-NAME) (a NOS inhibitor), or L-N(6)-(1-iminoethyl)lysine (L-NIL) (a specific inducible NOS inhibitor) and normal control rats treated with vehicle or L-NAME. Blood urea nitrogen levels, BP, urinary nitrate/nitrite excretion, and proteinuria were measured. Histologic assessments using periodic acid-Schiff staining and immunohistologic studies with markers for endothelium, platelets, fibrin, cell proliferation, and apoptosis were also performed. L-NAME inhibition of NO synthesis in rats with TMA resulted in more severe glomerular and tubulointerstitial injury, which was accompanied by thrombus formation and a marked loss of endothelial cells, with more apoptotic cells. These changes were associated with severe renal function deterioration. In contrast, these features were less pronounced in the vehicle- or L-NIL-treated rats with TMA and were absent in the control animals. In conclusion, inhibition of NO production in this model of TMA markedly exacerbated renal injury. The absence of effects with L-NIL treatment suggests a minor role for inducible NOS in this model. These results suggest that production of NO, most likely by endothelial cells, is an important protective mechanism in TMA.     

Impaired angiogenesis in the remnant kidney model: II. Vascular endothelial growth factor administration reduces renal fibrosis and stabilizes renal function.

Impaired angiogenesis and decreased vascular endothelial growth factor (VEGF) expression were recently documented in the remnant kidney (RK) model of progressive renal failure. VEGF (50 microg/kg, twice daily) was administered to RK rats between weeks 4 and 8 after surgery, and rats were euthanized at week 8 for histologic study. During the administration of VEGF (n = 7) or vehicle (n = 6), systemic BP was comparable in the two groups. VEGF treatment resulted in improved renal function and lower mortality rates, compared with the vehicle-treated group. Renal histologic analyses confirmed a 3.5-fold increase in glomerular endothelial cell proliferation (0.14 +/- 0.03 versus 0.04 +/- 0.02 proliferating endothelial cells/glomerulus, VEGF versus vehicle, P < 0.05), a twofold increase in peritubular capillary endothelial cell proliferation (1.60 +/- 0.30 versus 0.78 +/- 0.17 cells/mm(2), VEGF versus vehicle, P < 0.01), a threefold decrease in peritubular capillary rarefaction (P < 0.01), and a twofold increase in endothelial nitrix oxide synthase expression (P < 0.05) in the VEGF-treated group; an eightfold increase in urinary nitrate/nitrite levels (P < 0.05) was also noted. Although the difference in glomerulosclerosis scores did not reach statistical significance (0.67 +/- 0.42 versus 1.22 +/- 0.63, VEGF versus vehicle; range, 0 to 4; P = NS), VEGF-treated rats exhibited less interstitial collagen type III deposition (9.32 +/- 3.26 versus 17.45 +/- 7.50%, VEGF versus vehicle, P < 0.01) and reduced tubular epithelial cell injury, as manifested by osteopontin expression (5.57 +/- 1.60 versus 9.58 +/- 3.45%, VEGF versus vehicle, P < 0.01). In conclusion, VEGF treatment reduces fibrosis and stabilizes renal function in the RK model. The use of angiogenic factors may represent a new approach to the treatment of kidney disease.     

Improvement of renal function in type 2 diabetic nephropathy

BACKGROUND: Therapeutic failure in preventing renal disease progression in type 2 diabetic nephropathy (DN) is due to a failure in the early detection of DN by microalbuminuria and the inappropriate correction of renal hemodynamic maladjustment secondary to glomerular endothelial dysfunction. METHODS: Thirty patients associated with normoalbuminuric type 2 DN were subject to the following studies: tubular function by means of fractional excretion of magnesium (FE Mg), vascular function by means of determining the circulating endothelial cell, VEGF, VEGF/TGF B ratio, and intrarenal hemodynamic studies. RESULTS: FE Mg, circulating endothelial cells, and TGF B were abnormally elevated, and VEGF/TGF B ratio was decreased in these normoalbuminuric patients. The intrarenal hemodynamic study revealed a hemodynamic maladjustment characterized by a preferential constriction at the efferent arteriole and a reduction in peritubular capillary flow. Following treatment with vasodilators, a decrease in efferent arteriolar resistance and increase in peritubular capillary flow as well as glomerular clearance were observed. CONCLUSION: FE Mg appears to be a more sensitive marker than microalbuminuria for the early detection of DN. Increased endothelial cell injury is reflected by enhanced circulating endothelial cell loss in conjunction with the increased TGF B and the decreased ratio between VEGF and TGF B. This is further supported by the dysfunctioning glomerular endothelium, which is characterized by hemodynamic maladjustment and a reduction in the peritubular capillary flow. A correction of such hemodynamic maladjustment by multidrug vasodilators effectively improves renal perfusion and restores renal function in type 2 DN.     

Antibodies against vascular endothelial growth factor improve early renal dysfunction in experimental diabetes

Vascular endothelial growth factor (VEGF) is a cytokine that potently stimulates angiogenesis, microvascular hyperpermeability, and endothelium-dependent vasodilation, effects that are largely mediated by endothelial nitric oxide synthase (eNOS). The expression of VEGF is pronounced in glomerular visceral epithelial cells, but its function in renal physiology and pathophysiology is unknown. VEGF expression is upregulated by high ambient glucose concentrations in several cell types in vitro and in glomeruli of diabetic rats. To assess the role of VEGF in the pathophysiology of early renal dysfunction in diabetes, monoclonal anti-VEGF antibodies (Ab) were administered to control and streptozotocin-induced diabetic rats for 6 wk after induction of diabetes. Based on in vitro binding studies, an adequate serum VEGF inhibitory activity was achieved during the entire course of anti-VEGF Ab administration. Anti-VEGF Ab treatment but not administration of isotype-matched control Ab decreased hyperfiltration, albuminuria, and glomerular hypertrophy in diabetic rats. VEGF blockade also prevented the upregulation of eNOS expression in glomerular capillary endothelial cells of diabetic rats. Antagonism of VEGF had no effect on GFR and glomerular volume in control rats. These results identify VEGF as a pathogenetic link between hyperglycemia and early renal dysfunction in diabetes. Targeting VEGF may prove useful as a therapeutic strategy for the treatment of early diabetic nephropathy.     

Improvement of Renal Function in Type 2 Diabetic Nephropathy

Background. Therapeutic failure in preventing renal disease progression in type 2 diabetic nephropathy (DN) is due to a failure in the early detection of DN by microalbuminuria and the inappropriate correction of renal hemodynamic maladjustment secondary to glomerular endothelial dysfunction. Methods. Thirty patients associated with normoalbuminuric type 2 DN were subject to the following studies: tubular function by means of fractional excretion of magnesium (FE Mg), vascular function by means of determining the circulating endothelial cell, VEGF, VEGF/TGF B ratio, and intrarenal hemodynamic studies. Results. FE Mg, circulating endothelial cells, and TGF B were abnormally elevated, and VEGF/TGF B ratio was decreased in these normoalbuminuric patients. The intrarenal hemodynamic study revealed a hemodynamic maladjustment characterized by a preferential constriction at the efferent arteriole and a reduction in peritubular capillary flow. Following treatment with vasodilators, a decrease in efferent arteriolar resistance and increase in peritubular capillary flow as well as glomerular clearance were observed. Conclusion. FE Mg appears to be a more sensitive marker than microalbuminuria for the early detection of DN. Increased endothelial cell injury is reflected by enhanced circulating endothelial cell loss in conjunction with the increased TGF B and the decreased ratio between VEGF and TGF B. This is further supported by the dysfunctioning glomerular endothelium, which is characterized by hemodynamic maladjustment and a reduction in the peritubular capillary flow. A correction of such hemodynamic maladjustment by multidrug vasodilators effectively improves renal perfusion and restores renal function in type 2 DN.     

Vascular endothelial growth factor expression and glomerular endothelial cell loss in the remnant kidney model.

BACKGROUND: Vascular endothelial growth factor (VEGF) is constitutively expressed in the glomerulus where it may have a role in the maintenance of capillary endothelial cell integrity. The present study sought to examine changes in VEGF expression in a model of progressive renal disease and to assess the effects of angiotensin converting enzyme (ACE) inhibition. METHODS: Subtotal nephrectomized (STNx) rats were randomly assigned to receive vehicle (n=10) or the ACE inhibitor perindopril (8 mg/l drinking water) for 12 weeks duration (n=10). Sham-operated rats were used as controls (n=10). Glomerular capillary endothelial cell density was evaluated by immunostaining for the pan-endothelial cell marker RECA-1 and VEGF expression was assessed by quantitative in situ hybridization. RESULTS: In STNx rats glomerular capillary endothelial cell density was reduced to 19% that of sham rats (P<0.01) with a concomitant reduction in glomerular VEGF expression, also to 19% of sham rats (P<0.01). Perindopril treatment was associated with normalization of both capillary endothelial cell density and glomerular VEGF mRNA. CONCLUSIONS: Reduction in glomerular VEGF expression is a feature of the renal pathology that follows subtotal nephrectomy. In the context of the known functions of this growth factor, these findings suggest that diminution in VEGF may contribute to the demonstrated loss of glomerular endothelium that develops in this model of progressive renal disease.