FOXM1 Promotes Intestinal Vascular Endothelial Cell Proliferation and Protects Neonatal Mice against Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a life-threatening gastrointestinal illness affecting mostly premature infants characterized by intestinal inflammation and necrosis. While several factors such as abnormal intestinal colonization and an immature immune response have been shown to play a role in NEC, we previously found that defective intestinal microvascular development promotes NEC development. FOXM1 is a protein expressed in cells undergoing proliferation and a member of the Forkhead box family, a master regulator of cell cycle progression. FoxM1 has been shown to mediate endothelial cell proliferation under stress conditions. Here we hypothesize that promoting FOXM1 expression protects neonatal mice against intestinal injury in an experimental NEC model by promoting endothelial cell proliferation. To test our hypothesis, we first examined FOXM1 mRNA expression during NEC development in a neonatal mouse model. Second, we investigated the role of FOXM1 in NEC development using FOXM1 transgenic and knockout animals. Finally, we examined in vitro whether FOXM1 can protect endothelial cell proliferation under stress condition. We found that FOXM1 expression was significantly decreased in the intestine of pups exposed to the NEC model for 24 and 48 hours compared to dam-fed littermate controls. Neonatal mice that lack of FOXM1 in endothelial cells showed higher mortality rate and more severe intestinal injury when exposed to the experimental NEC model. While their 3-day survival remained unchanged, pups with endothelial-cell specific overexpression of FOXM1 had decreased incidence of severe intestinal injury. Furthermore, when cultured in vitro, intestinal endothelial cells obtained from pups overexpressing FOXM1 showed increased proliferation, which was unaffected by VEGFR2 inhibition using VEGFR2 kinase inhibitor Ki-8751. In conclusion, FOXM1 protects against neonatal NEC by promoting endothelial cell proliferation.