Background & aims: Acute inflammation of the intestine is associated with transepithelial migration of polymorphonuclear leukocytes (PMNs) and epithelial wounds that rapidly reseal. The aim of this study was to determine mechanisms by which such PMN-induced epithelial wounds reseal.
Methods: Epithelial wound closure was modeled in vitro using T84 intestinal epithelial cells and PMNs. Wound closure was analyzed by confocal microscopy and by determination of barrier function. Wounds were highlighted by apical labeling with antibody to a basolaterally restricted ligand, beta1-integrin.
Results: High-density PMN transepithelial migration for 70-110 minutes produced multifocal epithelial wounds that were 1-120 microm in diameter and markedly diminished epithelial barrier function that returned to baseline within 12-20 hours. Large wound closure was initiated by cell flattening and extension of F-actin/vinculin/paxillin-enriched lamellipodia at the leading edge. As wounds became small (approximately <30 microm), epithelial cells at the wound edges 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 sphincter-like contraction.
Conclusions: These data model mucosal repair in acute inflammatory conditions and, for the first time, show sequential early and late mechanisms by which epithelial discontinuities repair.