NEUTROPHIL MIGRATION ACROSS MODEL INTESTINAL EPITHELIA - MONOLAYER DISRUPTION AND SUBSEQUENT EVENTS IN EPITHELIAL REPAIR

Background & Aims: Acute inflammation of the intestine is associated w ith transepithelial migration of polymorphonuclear leukocytes (PMNs) a nd epithelial wounds that rapidly reseal. The aim of this study was to determine mechanisms by which such PMN-induced epithelial wounds rese al. Methods: Epithelial wound closure was modeled in vitro using T84 i ntestinal epithelial cells and PMNs. Wound closure was analyzed by con focal microscopy and by determination of barrier function, Wounds were highlighted by apical labeling with antibody to a basolaterally restr icted ligand, beta(1)-integrin. Results: High-density PMN transepithel ial migration for 70-110 minutes produced multifocal epithelial wounds that were 1-120 mu m in diameter and markedly diminished epithelial b arrier function that returned to baseline within 12-20 hours. Large wo und closure was initiated by cell flattening and extension of F-actin/ vinculin/paxillin-enriched lamellipodia at the leading edge. As wounds became small (similar to<30 mu m), epithelial cells at the wound edge s assumed columnar phenotype with poorly formed or absent lamellipodia . Apical localized circumferential, dense F-actin/myosin II rings were found to encircle such wounds, suggesting final closure by a sphincte r-like contraction. Conclusions: These data model mucosal repair in ac ute inflammatory conditions and, for the first time, show sequential e arly and late mechanisms by which epithelial discontinuities repair.