The effect of ischaemic postconditioning on mucosal integrity and function in equine jejunal ischaemia

Summary Background Ischaemic postconditioning (IPoC) has been shown to ameliorate ischaemia reperfusion injury in different species and tissues. Objectives To assess the feasibility of IPoC in equine small intestinal ischaemia and to assess its effect on histomorphology, electrophysiology and paracellular permeability. Study design randomized controlled terminal in vivo experiment Methods Experimental jejunal ischaemia was induced for 90 min in horses under general anaesthesia. In the control group (C; n=7), the jejunum was reperfused without further intervention. In the postconditioning group (P; n=7), IPoC was implemented by clamping the mesenterial vessels after ischaemia. This was followed by 120 minutes of reperfusion in both groups. Intestinal microperfusion and oxygenation was measured during IPoC using spectrophotometry and Doppler fluxmetry. Histomorphology and histomorphometry of the intestinal mucosa were assessed. Furthermore, electrophysiological variables and unidirectional fluxrates of 3 H-mannitol were determined in Ussing chambers. Western Blot analysis was performed to determine the tight junction protein levels of Claudin-1, Claudin-2 and Occludin in the intestinal mucosa. Comparisons between the groups and time points were performed using a two-way repeated measures ANOVA or non-parametric statistical tests for the ordinal and not normally distributed data (significance p<0.05). Results Postconditioning significantly reduced intestinal microperfusion during all clamping cycles, yet affected tissue oxygenation only during the first cycle. After reperfusion, group IPoC showed significantly less mucosal villus denudation (mean difference 21.5 %, p=0.02) and decreased mucosal-to-serosal fluxrates (mean difference 15.2 nM/cm 2 /h, p=0.007) compared to group C. There were no significant differences between the groups for the other tested variables. Main limitations small sample size, long term effects were not investigated. Conclusions Following ischaemic postconditioning, the intestinal mucosa demonstrated significantly less villus denudation and paracellular permeability compared to the untreated control group, possibly indicating a protective effect of IPoC on ischaemia reperfusion injury.