Life and death at the mucosal-luminal interface: New perspectives on human intestinal ischemia-reperfusion

Intestinal ischemia is a frequently observed phenomenon. Morbidity and mortality rates are extraordinarily high and did not improve over the past decades. This is in part attributable to limited knowledge on the pathophysiology of intestinal ischemia-reperfusion(IR) in man, the paucity in preventive and/or therapeutic options and the lack of early diagnostic markers for intestinal ischemia. To improve our knowledge and solve clinically important questions regarding intestinal IR, we developed a human experimental intestinal IR model. With this model, we were able to gain insight into the mechanisms that allow the human gut to withstand short periods of IR without the development of severe inflammatory responses. The purpose of this review is to overview the most relevant recent advances in our understanding of the pathophysiology of human intestinal IR, as well as the(potential) future clinical implications.

Human small intestine is capable of restoring barrier function after short ischemic periods

AIM To assess intestinal barrier function during human intestinal ischemia and reperfusion(IR).METHODS In a human experimental model,6 cm of jejunum was selectively exposed to 30 min of ischemia(I) followed by 30 and 120 min of reperfusion(R). A sham procedure was also performed. Blood and tissue was sampled at all-time points. Functional barrier function was assessed using dual-sugar absorption tests with lactulose(L) and rhamnose(R). Plasma concentrations of citrulline,an amino acid described as marker for enterocyte function were measured as marker of metabolic enterocytes restoration. Damage to the epithelial lining was assessed by immunohistochemistry for tight junctions( TJs),by plasma marker for enterocytes damage(I-FABP) and analyzed by electron microscopy(EM) using lanthanum nitrate as an electrondense marker.RESULTS Plasma L/R ratio's were significantly increased after 30 min of ischemia(30 I) followed by 30 min of reperfusion(30 R) compared to control(0.75 ± 0.10 vs 0.20 ± 0.09,P < 0.05). At 120 min of reperfusion(120 R),ratio's normalized(0.17 ± 0.06) and were not significantly different from control. Plasma levels of I-FABP correlated with plasma L/R ratios measured at the same time points(correlation: 0.467,P < 0.01). TJs staining shows distortion of staining at 30 I. An intact lining of TJs was again observed at 30 I120 R. Electron microscopy analysis revealed disrupted TJs after 30 I with paracellular leakage of lanthanum nitrate,which restored after 30 I120 R. Furthermore,citrulline concentrations closely paralleled the histological perturbations during intestinal IR.CONCLUSION This study directly correlates histological data with intestinal permeability tests,revealing that the human gut has the ability of to withstand short episodes of ischemia,with morphological and functional recovery of the intestinal barrier within 120 min of reperfusion.