title: Damaging effects of ischemia/reperfusion on intestinal muscle.
abstract: Periods of ischemia followed by restoration of blood flow cause ischemia/reperfusion (I/R) injury. In the intestine, I/R damage to the mucosa and neurons is prominent. Functionally, abnormalities occur in motility, most conspicuously a slowing of transit, possibly as a consequence of damage to neurons and/or muscle. Here, we describe degenerative and regenerative changes that have not been previously reported in intestinal muscle. The mouse small intestine was made ischemic for 1 h, followed by re-perfusion for 1 h to 7 days. The tissues were examined histologically, after hematoxylin/eosin and Masson's trichrome staining, and by myeloperoxidase histochemistry to detect inflammatory reactions to I/R. Histological analysis revealed changes in the mucosa, muscle, and neurons. The mucosa was severely but transiently damaged. The mucosal surface was sloughed off at 1-3 h, but re-epithelialization occurred by 12 h, and the epithelium appeared healthy by 1-2 days. Longitudinal muscle degeneration was followed by regeneration, but little effect on the circular muscle was noted. The first signs of muscle change were apparent at 3-12 h, and by 1 and 2 days, extensive degeneration within the muscle was observed, which included clear cytoplasm, pyknotic nuclei, and apoptotic bodies. The muscle recovered quickly and appeared normal at 7 days. Histological evidence of neuronal damage was apparent at 1-7 days. Neutrophils were not present in the muscle layers and were infrequent in the mucosa. However, they were often seen in the longitudinal muscle at 1-3 days and were also present in the circular muscle. Neutrophil numbers increased in the mucosa in both I/R and sham-operated animals and remained elevated from 1 h to 7 days. We conclude that I/R causes severe longitudinal muscle damage, which might contribute to the long-term motility deficits observed after I/R injury to the intestine.
authors.affiliation: Department of Anatomy & Cell Biology, University of Melbourne, Parkville, VIC, 3010, Australia.
authors.forename: Louise
authors.initials: L
authors.lastname: Pontell
authors.forename: Purnima
authors.initials: P
authors.lastname: Sharma
authors.forename: Leni R
authors.initials: LR
authors.lastname: Rivera
authors.forename: Michelle
authors.initials: M
authors.lastname: Thacker
authors.forename: Yan Hong
authors.initials: YH
authors.lastname: Tan
authors.forename: James A
authors.initials: JA
authors.lastname: Brock
authors.forename: John B
authors.initials: JB
authors.lastname: Furness
mesh_terms: D000818:Animals; D006651:Histocytochemistry; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology; D007421:Intestine, Small / Q000098:blood supply / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009130:Muscle, Smooth / Q000473:pathology; D009504:Neutrophils / Q000473:pathology; D015427:Reperfusion Injury / Q000473:pathology*