Basic Study
Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. May 14, 2018; 24(18): 2009-2023
Published online May 14, 2018. doi: 10.3748/wjg.v24.i18.2009
Ischemia/reperfusion injury in porcine intestine - Viability assessment
Runar J Strand-Amundsen, Henrik M Reims, Finn P Reinholt, Tom E Ruud, Runkuan Yang, Jan O Høgetveit, Tor I Tønnessen
Runar J Strand-Amundsen, Jan O Høgetveit, Department of Clinical and Biomedical Engineering, Oslo University Hospital, Oslo 0424, Norway
Runar J Strand-Amundsen, Jan O Høgetveit, Department of Physics, University of Oslo, Oslo 0316, Norway
Henrik M Reims, Finn P Reinholt, Department of Pathology, Oslo University Hospital, Oslo 0424, Norway
Tom E Ruud, Institute for Surgical Research, Oslo University Hospital, Oslo 0424, Norway
Tom E Ruud, Department of Surgery, Baerum Hospital, Vestre Viken Hospital Trust, Drammen 3004, Norway
Runkuan Yang, Tor I Tønnessen, Department of Emergencies and Critical Care, Oslo University Hospital, Oslo 0424, Norway
Tor I Tønnessen, Institute of Clinical Medicine, University of Oslo, Oslo 0424, Norway
Author contributions: Strand-Amundsen RJ, Yang R and Tønnessen TI performed the experiments, collected the histological samples and analyzed the microdialysis data; Reims HM and Reinholt FP analyzed, described and graded the histological samples; Strand-Amundsen RJ, Tønnessen TI, Ruud TE and Høgetveit JO designed and coordinated the research; Strand-Amundsen RJ wrote the paper with assistance and input from all the co-authors.
Supported by the Norwegian Research Council through the Integrisc project number 219819, and by Sensocure AS, Langmyra 11, 3185 Skoppum, Norway.
Institutional review board statement: The study was reviewed and approved by the Research and Development section at the Department of Clinical and Biomedical Engineering at the Oslo University Hospital.
Institutional animal care and use committee statement: All procedures involving animals were reviewed and approved by the Animal Ethics and Welfare Committee of Oslo University Hospital, and the Norwegian Food Authority (FOTS ID 8304 and 12695). The experiment was conducted in accordance with Norwegian animal welfare guidelines (FOR-2015-06-18-761) and EU directive (2010/63/EU).
Conflict-of-interest statement: The authors declare that they have no competing interests.
Data sharing statement: Readers can request the data of this paper by contacting us via runar.strand-amundsen@fys.uio.no.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Runar J Strand-Amundsen, MSc, Research Scientist, Department of Physics, University of Oslo, Postboks 1048 Blindern, Oslo 0316, Norway. runar.strand-amundsen@fys.uio.no
Telephone: +47-40029762
Received: March 9, 2018
Peer-review started: March 10, 2018
First decision: April 11, 2018
Revised: April 20, 2018
Accepted: April 23, 2018
Article in press: April 23, 2018
Published online: May 14, 2018
Processing time: 63 Days and 1.9 Hours
ARTICLE HIGHLIGHTS
Research background

The clinical gold standard used on humans for assessment of intestinal viability is still based on palpation, visual inspection, bleeding from cut ends and the use of second look operations. The high mortality rates related to acute mesenteric ischemia have not been reduced drastically since the 1980’s.

Research motivation

We are investigating methods to improve the accuracy of intraoperative surgical decision making with respect to assessment of the viability of ischemic/reperfused intestine. To assess the accuracy of these methods we need a reference for the limits of intestinal tissue viability. As the pathophysiology of ischemia/reperfusion in the porcine model is similar to humans, and because the pig model has been suggested as a reference standard in intestinal transplantation research, we decided to investigate the jejunal viability limit in a pig model. Our hypothesis is that the results with a pig model can have translational relevance for humans.

Research objectives

We investigated viability assessment in a porcine model of warm ischemia on jejunum with mesenteric occlusion, followed by reperfusion. Our aim was to determine the time point of irreversible damage, to provide a reference for experimental approaches to intestinal viability assessment.

Research methods

We created parallel segmental models on the jejunum in 15 pigs, by clamping the mesenteric arteries and veins for 1 to 16 h. Reperfusion was initiated after different intervals of ischemia (1-8 h) and subsequently monitored for 5-15 h. We compared the results from visual inspection with histology (light microscopy and transmission electron microscopy) and intraluminal microdialysis. The intestinal injury was graded using Park/Chiu and modified Swerdlow grading.

Research results

Only jejunal segments that had been ischemic for ≤ 3 h appeared viable (following ≥ 1 h of reperfusion). The jejunal segments that had been ischemic for 4 h showed (following ≥ 1 h of reperfusion) a total loss of crypt epithelium, extensive shrinkage and loss of myocytes in the outer layer of the muscularis propria. Intraluminal microdialysis allowed us to closely monitor the onset and duration of ischemia and the onset of reperfusion. We observed return of color and peristalsis in intestine that histologically contained areas of probably irreversible damage. The sequence of ischemia/reperfusion injury using the SMO model does not follow the outwards direction from the mucosa to the outer muscular layer, as most current histological grading and classification system suggest.

Research conclusions

In the present porcine model with segmental occlusion of the jejunal mesentery, the intestinal tissue was judged to be probably irreversibly damaged when exposed to ≥ 4 h of ischemia and then reperfused. Three hours of ischemia followed by reperfusion appeared to be the upper limit for viability in this model. We were unable to find sufficient level of association between tissue viability and metabolic markers to conclude that microdialysis is clinically relevant for viability assessment. Evaluation of color and motility appears to be poor indicators of intestinal viability.

Research perspectives

Segmental mesenteric occlusion provides reproducible injury in porcine jejunum and appears to be a relevant model for studies on viability assessment. Future studies should consider viability assessment in settings where the various etiologic factors related to acute mesenteric ischemia (emboli, arterial and venous thrombus and nonocclusive ischemia) can be evaluated, as good reference models are needed for each etiology.