Figure 2.

Illustration showing the phases of intestinal epithelial barrier repair. Restoration of barrier function after damage to the epithelium is well characterized to occur in 3 phases. (1) Contraction of villus occurs by smooth muscle fibroblasts in the lamina propria to reduce denuded surface area. (2) Depolarization and migration of wound-associated epithelial cells occurs across the denuded basement membrane to cover the wounded surface. (3) Repolarization and reformation of tight junction structure to seal the paracellular spaces occurs, effectively restoring barrier function. (A) Transmission electron microscopy showing open paracellular space between 2 intestinal epithelial cells with a leaky tight junction (white arrows). (B) TEM showing closed paracellular space and tight junction (white arrows) coinciding with restoration of intestinal barrier function.

Panels A and B were used with permission from Little D, et al. PI3K signaling is required for prostaglandin-induced mucosal recovery in ischemia-injured porcine ileum. Am J Physiol Gastrointest Liver Physiol 2003;284:G46–G56.