Vascular endothelial growth factor receptors in human mesangium in vitro and in glomerular disease

Mesangial tell proliferation and growth factor overexpression are character istic features of several glomerular diseases. Vascular endothelial growth factor (VEGF), a potent mitogen, is expressed in podocytes in the glomerulu s, and VEGF receptors (flt-1, KDR, and neuropilin-1) are present on endothe lial cells and other cell types. This study examined whether human mesangia l cells (HMC) express VEGF receptors in vitro and ex vivo and evaluated the effect of VEGF on HMC proliferation. All receptor types were detected in H MC in vitro by immunofluorescence and Western blotting. VEGF(165) induced a dose-responsive increase in H-3-thymidine incorporation (25 ng/ml VEGF(165 ): 2.3-fold increase; 50 ng/ml: 3.8-fold: 100 ng/ml: 4.8-fold; 200 ng/ml: 3 .4-fold; P = 0.016) and in cell number (50 ng/ml VEGF(165): 1.2-fold increa se; 100 ng/ml: 1.6-fold; 200 ng/ml: 1.4-fold; P = 0.005), effects prevented by an anti-VEGF(165) polyclonal neutralizing antibody (100 mu g/ml). The p roliferative effect was confirmed by a tetrazolium dye-based assay (100 ng/ ml VEGF(165): 1.4-fold increase). In ex vivo experiments, VEGF receptors in biopsy material from normal and diseased kidneys were detected by immunohi stochemistry. No mesangial flt-1 receptor staining was seen in normal renal cortical tissue samples, and only weak mesangial KDR staining was detected . In contrast, mesangial flt-1 and KDR receptor staining were both clearly seen in biopsy samples from proliferative renal diseases. Ln conclusion, fl t-1, KDR, and neuropilin-1 are present on cultured HMC, and VEGF(165) induc es HMC proliferation. In addition, the flt-1 and KDR receptors are expresse d in the mesangium in mesangioproliferative disease.