A. Clarke4, P. Matheson1,2, E. Stamper4, J. Smith2, R. N. Garrison1,2, C. D. Downard3 1Robley Rex Veterans Affairs Medical Center,Surgery,Louisville, KY, USA 2University Of Louisville,Surgery,Louisville, KY, USA 3University Of Louisville,Pediatric Surgery,Louisville, KY, USA 4University Of Louisville,School Of Medicine,Louisville, KY, USA
Introduction: Necrotizing enterocolitis (NEC) is an intestinal disease which primarily affects premature infants. Relaxin (RLXN), a hormone of pregnancy, dilates intestinal microvasculature and increases angiogenesis, possibly via the vascular endothelial growth factor (VEGF) family. VEGF-A/VEGF-R2 is the most studied angiogenic ligand/receptor interaction, while the other factors and receptors have been vastly less scrutinized. However, it has been shown that VEGF-R1 plays a mediating role for VEGF-A/R2 while also interacting with VEGF-B, an important factor in vascular survival. Oral relaxin supplementation has been shown to lessen the severity of NEC in rat models, and we hypothesize that this is due at least partially to the upregulation of VEGF and its receptors.
Methods: NEC was induced in Sprague-Dawley rats by premature delivery, formula feeds, oral LPS, and episodic hypoxia/hypothermia. Time-matched Controls (n=12) were vaginally delivered and dam fed. NEC groups were randomized by litter (n=12/group): 1) NEC only, 2) NEC + 1x oral RLXN supplement (at 44 hours), and 3) NEC + oral RLXN supplement in All Feeds. At 48 hours, ileum was recovered, mounted in paraffin, and either stained with H&E or left for Immunohistochemistry (IHC). IHC staining was performed using rabbit anti-rodent polyclonal antibodies for VEGF-A, VEGF-B, and VEGF receptors 1 and 2.
Results: IHC staining indicated varying intensity and location of VEGF-A, VEGF-B, VEGF-R1 and VEGF-R2 in ileum sections. RLXN feed treatments diminished the histologic severity of NEC. VEGF factors increased in staining intensity and both VEGF receptors decreased in staining intensity in response to the RLXN treatments, but VEGF-B and VEGF-R1 had the most appreciable responses.
Conclusion: RLXN supplementation increases VEGF-B production while decreasing the histologic severity of NEC. Thus some of the therapeutic benefits of RLXN supplementation might be due to VEGF-B mediated maintenance of intestinal microvasculature. This interaction may provide further mechanistic direction for therapeutic interventions in NEC.
