Mechanisms of mucosal injury and repair in intestinal transplantation

Abstract

Intestinal transplantation faces challenges due to high risk of life-threatening complications following transplantation. Ischemia-reperfusion injury is a major cause of early morbidity and complications. By introducing a luminal polyethylene glycol-based (PEG) solution, ischemic injury can be alleviated, therefore our research investigates the effects of luminal preservation during cold storage and the effects of reperfusion injury after transplantation. We also investigated whether additional air insufflation during luminal preservation can improve intestinal morphology. In addition, we studied the effects of preservation injury on the human colon. Intestinal tissue from human brain-dead organ donors were perfused and stored in IGL-1, with and without luminal PEG-3350 solution with sampling after 4h, 8h, 14h and 24h of cold storage (Paper I). During Paper II rat intestines were perfused and stored in saline for 3h, then transplanted and graft segments were obtained after 20min, 6, 12 and 24h after reperfusion. In Paper III we studied the effects of air insufflation using rat intestines, Group 1 received IGL-1 preservation, Group 2 received a PEG and amino acid-based luminal solution, and Group 3 received luminal PEG and amino acids with air insufflation. In Paper IV we observed the effects of cold storage with IGL-1 solution on human colonic tissue. Assessment was done by histology, IHC, PCR and western blot. In Paper I, histology showed lower grade injury in the luminal PEG group compared to control, while preserving tight junction proteins and exhibiting lower apoptotic activity. Paper II showed that reperfusion worsened tissue injury and led to several molecular changes, however, gradual recovery was noted over the first 24 hours. Paper III revealed that luminal PEG is protective compared to cold storage, however the addition of air appeared to have limited effects. In Paper IV colonic tissue showed resistance to cold ischemia with low grade injury during all observed time points. Current data suggest that mucosal injury and molecular alterations occur within the first 14h of cold ischemia, preservation with PEG 3350 solution seem to be protective compared to standard cold storage solutions. Reperfusion injury is seen up to 6h post-transplantation, but near-complete morphologic recovery can be seen after 24h, however molecular alterations persist. Additional air insufflation currently showed limited additional protective properties to luminal preservation. And the colon appears more resilient towards cold ischemia than the small intestine.