Human colon ischemia and reperfusion

Gastrointestinal ischemia-reperfusion (IR) remains a common, major clinical
problem. Colon ischemia is the most common form of intestinal ischemia and
carries high morbidity and mortality because of the high bacterial density in
the intraluminal milieu and ischemia-associated intestinal barrier loss,
bacterial translocation and subsequent systemic inflammatory responses. Next to
that, colon ischemia is a major risk factor for anastomotic dehiscence, a
serious complication with great impact on morbidity, mortality, length of
hospitalization and costs. At the same time there are no optimal diagnostic
tools or preventive and therapeutic strategies available, which also
contributes to the high morbidity and mortality rates in patients suffering
from this condition. In contradiction to the human small intestine, hardly
anything is known about colonic IR. Therefore we use a new human experimental
model for colonic IR, to gain insight in the pathophysiology of colonic IR in
man.

This study aims at revealing the pathophysiology of colonic IR in man, with a
specific interest for cellular and inflammatory changes, barrier function and
intestinal permeability, macroscopic mucosal changes, gene expression patterns
and identification of targets for diagnostic, preventive and therapeutic
strategies. The information and knowledge obtained after completion of this
study will be helpful in the improvement of diagnostic, preventive and
therapeutic strategies in patients suffering colonic IR.

During colonic surgery a small colonic segment, to be removed for surgical
reasons, is isolated and selectively subjected to 30 (30I), 45 (45I) or 60
minutes of ischemia (60I), followed by 30 (30R) and 60 minutes of reperfusion
(60R). The supplying small arterial branches and draining venous structures of
the specific colonic segment are identified in the mesentery and subsequently
clamped to halt circulation. Release of the clamps will allow for reperfusion.
In a subgroup of patients a sterile saccharide solution (sucralose and
erythritol) will be injected intraluminally just before initiation of ischemia.
Blood and tissue will be sampled at all time points for further analysis of
intestinal permeability, barrierfunction, cellular and inflammatory changes and
gene expression patterns. These analysis will be carried out by means of
different techniques such as High Performance Liquid Chromotography Mass
Spectrometry (HPLC-MS), immunohistochemistry, immunofluorescence, western blot,
qPCR, laser capture microdissection (LCM) and subsequent genome wide expression
analysis, electron microscopy and other techniques which seem to be useful
during the course of the study. In another subgroup of patients a sterile video
capsule will be inserted in the isolated colon segment, before applying
ischemia and reperfusion. The images can be used to visualize macroscopic
mucosal changes during IR.

The patients enrolled in this study will all undergo major abdominal surgery
with duration of about 2-3 hours. Because IR is applied on intestinal tissue
which will be resected anyway during the surgical procedure, this will not
interfere with standard surgical care. The only actions undertaken by the
surgeon solely related to this research proposal, are the isolation of 3-6 cm
of gut, application of the clamp (followed by 30, 45 or 60 minutes of
ischemia), administration of the saccharides or video capsule (just before de
start of ischemia) and blood sampling from the vein of the isolated gut
segment. These actions will not add substantially to the total duration of the
operation.

There are no specific benefits for the participating patients, however in the
future the results of our study will likely be useful for patients suffering
from intestinal ischemia and reperfusion. The additional risks for the patients
in this study are minimal and they will not increase the total risk of the
operation. Studies carried out in the human small intestine and colon according
to a similar design show no negative effects or increased risk for the
participating patients