Hierarchies of healing in gut mucosal injury.

The mucosal response to injury can best be understood as a complex layering of different responses that may be invoked depending upon the size and nature of the injury, the persistence of the injurious stimulus, and the availability of various trophic host factors that stimulate repair. There is a hierarchy of responses that ranges from small rapid resealing of acute apical membrane or single cell wounds through the long term attempt to heal a giant peptic ulcer or respond to inflammatory bowel disease. Although much previous attention has been paid to the local factors that regulate these pathways and responses, there is increasing interest in systemic factors that may act either by the production of cytokines and trophic factors or by the direct migration of bone marrow derived stem cells into the mucosal wound.