Severe neonatal anemia increases intestinal permeability by disrupting epithelial adherens junctions

Abstract

Background: Anemia is a frequent diagnosis in critically-ill infants, but the clinical implications of severe anemia in these patients remain unclear. In this study, we examined pre-weaned mice to investigate the effects of severe anemia during early infancy on gut mucosal permeability. Methods: C57BL/6 mice were subjected to timed phlebotomy between postnatal days (P) 2-10 to induce severe anemia (hematocrits 20-24%), and intestinal permeability was tracked longitudinally between P10-20 as intestine-to-plasma translocation of enteral macromolecules and bacterial translocation. Epithelial junctions were evaluated by electron microscopy, polymerase chain reactions, immunohistochemistry, and/or enzyme immunoassays on intestinal tissues, Caco-2 intestinal epithelial-like cells, and colonic organoids. Results: Pre-weaned mouse pups showed an age-related susceptibility to severe anemia with increased intestinal permeability to enteral macromolecules (dextran, ovalbumin, β-lactoglobulin) and luminal bacteria. Electron micrographs showed increased paracellular permeability and ultrastructural abnormalities of the adherens junctions. These findings were explained by the loss of E-cadherin in epithelial cells, which was caused by destabilization of the Cdh1 mRNA due to microRNA let-7e-5p binding to the 3'-untranslated region. Conclusions: Severe anemia resulted in a disproportionate and persistent increase in intestinal permeability in pre-weaned mice due to the disruption of epithelial adherens junctions. These changes are mediated via microRNA let-7e-mediated depletion of Cdh1 mRNA.