The Anatomic Sites of Disruption of the Mucus Layer Directly Correlate With Areas of Trauma/Hemorrhagic Shock-Induced Gut Injury

Background: The intestinal mucus layer is an important but understudied component of the intestinal barrier. Consequently, we tested the hypothesis that the anatomic sites of loss of the mucus layer would directly correlate with sites of intestinal villous injury after trauma-hemorrhagic shock (T/HS) and may, therefore, serve as loci of gut barrier failure. Consequently, to investigate this hypothesis, we used Carnoy's fixative solution to prepare fixed tissue blocks where both the gut morphology and the mucus layer could be assessed on the same tissues slides. Methods: Male Sprague-Dawley rats were subjected to a laparotomy (trauma) and 90 minutes of sham shock (T/SS) or 35 mm Hg x 90 minutes of actual shock (T/HS). Three hours after resuscitation, the rats were killed, and samples of the terminal ileum were processed by fixation in Carnoy's solution. Gut injury was evaluated by determining the percentage of villi injured. The status of the intestinal mucus layer was quantified by determining the percentage of the villi covered by the mucus and the mucus thickness. Results: Histologic analysis of gut injury showed that the incidence of gut injury was similar to 10-fold higher in the T/HS than the T/SS rats (T/SS = 2.5% +/- 0.5% vs. T/HS = 22.4% +/- 0.5% of injured villi; p < 0.01). The T/SS rats had 98% of their ileal mucosa covered with a mucus layer, and this was decreased after T/HS to 63% +/- 3% (T/HS vs. T/SS; p < 0.001). Furthermore, loss of the mucus layer was found to directly correlate with villous injury with a regression coefficient of r(2) = 0.94 (p < 0.001). Conclusion: This study shows that T/HS significantly reduces the intestinal mucus layer and causes villous injury and that a correlation exists between specific anatomic sites of T/HS-induced loss of the mucus layer and gut injury.