Vascular endothelial growth factor (VEGF164) ameliorates intestinal epithelial injury in vitro in IEC-18 and Caco-2 monolayers via induction of TGF-β release from epithelial cells

Abstract

Objective. VEGF is a glycoprotein with various (e.g. angiogenic) activities. So far, research has focused on its angiogenic properties. VEGF receptors are localized on epithelial cells of patients with inflammatory bowel disease (IBD) and also on Caco-2 and IEC-18 cells. Our aim was to evaluate the role of VEGF on intestinal epithelial cell (IEC) migration and proliferation by utilizing an established in vitro model. Methods. IEC-18 and Caco-2 monolayers were wounded with a razor blade as described previously. Cells were incubated in medium w/o rat VEGF164. After 24 h, migration was assessed by counting cells across the wound edge. Migration was blocked with neutralizing TGF-β1 antibodies. IEC proliferation was assessed using the MTT (3-[4, 5-Dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide) test. Semi-quantitative changes of the TGF-β1 mRNA expression were evaluated before and after stimulation of the cells with VEGF164 by RT-PCR. Statistical analysis was performed with ANOVA and the Wilcoxon test. Results. VEGF164 significantly induced epithelial cell migration in Caco-2 and IEC-18 cells compared to control. TGF-β1 antibodies completely abolished this VEGF-induced cell migration. TGF-β1 mRNA significantly increased in IEC-18 and Caco-2 cells after stimulation with VEGF. VEGF significantly inhibited epithelial cell proliferation in IEC-18 and in Caco-2 cells, indicating that the observed effects on cell migration were not due to any proliferate effects. Conclusion. VEGF effects on epithelial cell migration play an important part in epithelial cell restitution by maintaining mucosal homeostasis after mucosal injury. This effect is mediated by TGF-β1. Our results obtain another possible role for increased VEGF levels in the intestinal mucosa of patients with IBD as reported recently by others.