Chronic VEGF Blockade Worsens Glomerular Injury in the Remnant Kidney Model

VEGF inhibition can promote renal vascular and parenchymal injury, causing proteinuria, hypertension and thrombotic microangiopathy. The mechanisms underlying these side effects are unclear. We investigated the renal effects of the administration, during 45 days, of sunitinib (Su), a VEGF receptor inhibitor, to rats with 5/6 renal ablation (Nx). Adult male Munich-Wistar rats were distributed among groups S+V, sham-operated rats receiving vehicle only; S+Su, S rats given Su, 4 mg/kg/day; Nx+V, Nx rats receiving V; and Nx+Su, Nx rats receiving Su. Su caused no change in Group S. Seven and 45 days after renal ablation, renal cortical interstitium was expanded, in association with rarefaction of peritubular capillaries. Su did not worsen hypertension, proteinuria or interstitial expansion, nor did it affect capillary rarefaction, suggesting little angiogenic activity in this model. Nx animals exhibited glomerulosclerosis (GS), which was aggravated by Su. This effect could not be explained by podocyte damage, nor could it be ascribed to tuft hypertrophy or hyperplasia. GS may have derived from organization of capillary microthrombi, frequently observed in Group Nx+Su. Treatment with Su did not reduce the fractional glomerular endothelial area, suggesting functional rather than structural cell injury. Chronic VEGF inhibition has little effect on normal rats, but can affect glomerular endothelium when renal damage is already present

RT-PCR analysis of the expression of VEGF (A) and of its receptors, VEGFR1 (B), VEGFR2 (C), and VEGFR3 (D).

<p>^ap<0.05 vs. respective S; ^bp<0.05 vs. respective untreated; ^cp<0.05 vs. respective value on Day 7.</p

Evaluation of tubulointerstitial changes.

<p>A) Fractional cortical interstitial area; B) Cortical interstitial infiltration by macrophages; C) Tubular cells in proliferation (PCNA⁺); D) Interstitial cells in proliferation (PCNA⁺);^ap<0.05 vs. respective S; ^bp<0.05 vs. respective untreated; ^cp<0.05 vs. respective value on Day 7.</p

Renal and systemic parameters 7 and 45 days after renal ablation.

<p>Mean ±1 SE; BW: body weight, grams; TCP: tail-cuff pressure, mmHg; U_albV: daily urinary albumin excretion rate, mg/24 h; Ht, arterial hematocrit, %; S_Cr: serum creatinine concentration, mg/dL. ^ap<0.05 vs. respective S; ^bp<0.05 vs. respective untreated; ^cp<0.05 vs. respective value on Day 7.</p

Vascular endothelial evaluation.

<p>A) % glomerular area occupied by endothelium; B) Number of peritubular capillary profiles. ^ap<0.05 vs. respective S; ^bp<0.05 vs. respective untreated; ^cp<0.05 vs. respective value on Day 7.</p

Histologic and histomorphometric analysis of glomerular injury (Masson Trichrome).

<p>A) and B) normal glomeruli found in Group S+V and S+Su, respectively; C) and D) representative glomerular sclerotic lesions found in Group Nx+V and Nx+ Su. E) glomerular intracapillary microthrombi observed in Group Nx+Su, some of which appear partially organized. F) PTAH staining showing the presence of fibrin (in dark purple) in glomerular capillary lumina of Nx+Su rats. G) distribution of glomerular lesions among “microthrombi” (red) and “sclerosis” (blue). Normal glomeruli are represented in gray. ^ap<0.05 vs. respective S; ^bp<0.05 vs. respective untreated; ^cp<0.05 vs. respective value on Day 7.</p

A) Glomerular volume; B) glomerular cell proliferation assessed by the number of PCNA⁺ cells; C) Percentage of glomerular area staining positively for ZO-1; D) Number of podocytes per glomerulus.

<p>^ap<0.05 vs. respective S; ^bp<0.05 vs. respective untreated; ^cp<0.05 vs. respective value on Day 7.</p