Immunohistochemical expression of VEGF in normal human renal parenchyma

In the normal kidney, VEGF is constitutively expressed in podocytes and tubular epithelial cells of the renal cortex and medulla. The aim of this study was to determine distribution of VEGF in normal renal parenchyma using immunohistochemical methods. The study was retrospective, using normal kidneys samples taken from 28 patients with nephroureterectomy for different types of renal cell carcinomas. Sections were stained with routine Hematoxylin-Eosin method and immunohistochemically with anti-VEGF polyclonal antibody. All cases presented an intense immunoreaction in the cells lining the nephron tubular system, the higher immunoreaction intensity in the collecting and distal tubules, but weak or moderate in the proximal tubules. The Henle loop cells showed a negative immunoreaction. The immunoreaction was absent in most cells of the renal corpuscle. The cells lining the same tubule presented some variation of intensity, with large polygonal epithelial cells, bulging in the tubular lumen showing an intense cytoplasmic immunoreaction for VEGF. In the renal parenchyma adjacent to the tumor, we observed the same pattern of positive reaction distribution as in the nephron's epithelial tubular cells situated far from the tumor. Adjacent to the tumor proliferation front and in those cases with massive invasive features, we observed a partial depletion of VEGF in distal tubules, while the majority of collecting ducts remained intense positive. The VEGF immunostaining was significantly higher in the renal cortex than in the outer and respectively the inner medulla.