(22) Serum Flt-1 is Increased During the Development of Experimental Necrotizing Enterocolitis

Background: Necrotizing enterocolitis (NEC) is a disease affecting premature infants characterized by intestinal inflammation and necrosis that commonly evolves into overwhelming sepsis and death. There is growing evidence that impaired intestinal VEGF/VEGFR2 signaling and resulting microvasculature maldevelopment contributes to NEC. We previously found that recruited monocytes and pro-inflammatory macrophages inhibit endothelial cell proliferation and promote intestinal injury in experimental NEC. Our preliminary data has shown that monocytes and pro-inflammatory macrophages express VEGFR1/Flt-1 in both mouse and human NEC tissues. Flt-1 can be release in the plasma and is known to trap VEGF, reducing its availability to bind VEGFR2, thus preventing angiogenesis. Whether Flt-1 is increased in the serum prior to NEC in mice and humans remains unknown.

Objectives: Determine if serum flt-1 levels are increased in the development of NEC.

Design/Methods: Neonatal mouse were subjected to our established NEC model (adult commensal bacteria inoculation, hypoxic and cold stresses twice a day and formula feeding) or left with the dams to be dam fed (controls). Mice were euthanized after 48 or 72 hours and serum Flt-1 was assessed by ELISA. To assess Flt-1 stability, 3 NEC serum samples were divided into 4 aliquots that were either left at room temperature for 2, 8 or 24 hours or immediately frozen at -80oC. Flt-1 concentration was compared amongst aliquots.

Results: In mice subjected to our NEC protocol, serum Flt-1 concentration (ng/ml) was higher at 48 hours (25.05 ± 3.008 vs 14.81 p< 0.05) and 72 hours (mean 36.77 ± 2.906 vs 20.47 p< 0.001) when compared to control or dam fed (DF) littermates. Additionally, serum flt-1 levels were not different when samples were left at room temperature for up to 24h, compared to when immediately frozen.

Conclusions: In neonatal mice, soluble Flt-1 is increased in the serum during NEC development. Whether serum Flt-1 could predict NEC development in neonates remains unknown. To correlate our findings to humans and determine whether serum Flt-1 (obtained from blood left at room temperature in the lab for a few hours) can help predict evolving NEC, soluble flt-1 will be assessed by ELISA in leftover blood samples that were collected from premature infants who did or did not develop NEC through an approved IRB (2025).