Mesenteric artery reactivity and small intestine morphology in a chicken model of hypoxia-induced fetal growth restriction.

Infants with intrauterine growth retardation are prone to intestinal disorders. The morphological and molecular mechanisms that lead to these complications are not completely understood and suitable experimental models are necessary. The aim of this study was to characterize mesenteric artery (MA) reactivity, small intestine morphometry and intestinal expression of vascular endothelial growth factor (VEGF) in a chicken model of hypoxia-induced fetal growth restriction. Chicken embryos (15 and 19 incubation days) and hatchlings (<3-h-old and 1-d-old) were incubated under hypoxic (15% O₂ from day 0 to day 19 of incubation) or normoxic conditions. Vascular reactivity was studied using wire miography. Intestinal morphometry was assessed in hematoxyline-eosine-stained sections. VEGF mRNA expression was determined by RT-PCR analysis. Hypoxia increased the responsiveness of chicken embryo MAs to the adrenergic agonist norepinephrine, the polypeptide endothelin (ET)-1, and the nitric oxide donor sodium nitroprusside and decreased the responsiveness to the endothelium-dependent relaxant agonist acetylcholine. However, the majority of these alterations, with the exception of the hyperresponsiveness to ET-1, were not present in the hypoxic hatchlings. When intestinal histology was analyzed, subtle hypoxia-induced changes were noted in the villi and the muscularis propria from the hatchlings. Hypoxic incubation also diminished the expression of VEGF mRNA in the terminal ileum of the hatchlings. In conclusion, chronic moderate hypoxia during incubation results in subtle but significant alterations in chicken MA reactivity, small intestine morphology and VEGF expression. Whether these alterations may have a direct effect on the functional status of the intestine remains to be investigated.