Verhaar, N. | bioRxiv Science

bioRxiv2020

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

BackgroundIschaemic postconditioning (IPoC) has been shown to ameliorate ischaemia reperfusion injury in different species and tissues. ObjectivesTo assess the feasibility of IPoC in equine small intestinal ischaemia and to assess its effect on histomorphology, electrophysiology and paracellular permeability. Study designrandomized controlled terminal in vivo experiment MethodsExperimental 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 3H-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). ResultsPostconditioning 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/cm2/h, p=0.007) compared to group C. There were no significant differences between the groups for the other tested variables. Main limitationssmall sample size, long term effects were not investigated. ConclusionsFollowing 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.

pathology↗

bioRxiv2019

Ischaemic preconditioning and pharmacological preconditioning with dexmedetomidine in an equine model of small intestinal ischaemia-reperfusion

Small intestinal strangulation associated with ischaemia-reperfusion injury (IRI) is common in horses. In laboratory animals IRI can be ameliorated by ischaemic preconditioning (IPC) and pharmacological preconditioning (PPC) with dexmedetomidine. The aim of this study was to determine the effect of PPC with dexmedetomidine or IPC in an equine model of small intestinal ischaemia-reperfusion (IR).\n\nIn a randomized controlled experimental trial, 15 horses were assigned to three groups: control (C), IPC, and PPC with dexmedetomidine (DEX). All horses were placed under general anaesthesia and 90% jejunal ischaemia was induced for 90 minutes, followed 30 minutes of reperfusion. In group IPC, three short bouts of ischaemia and reperfusion were implemented, and group DEX received a continuous rate infusion of dexmedetomidine prior to the main ischaemia. Jejunal biopsies were collected before ischaemia (P), and at the end of ischaemia (I) and reperfusion (R). Mucosal injury was assessed by the Chiu-Score, inflammatory cells were stained by cytosolic calprotectin. The degree of apoptosis and cell necrosis was assessed by cleaved-caspase-3 and TUNEL.\n\nParametric data were analyzed by two-way ANOVA for repeated measurements followed by Dunnetts t-test. Non parametric data were compared between groups at the different time points by a Kruskal-Wallis-Test and a Wilcoxon-2-Sample-test.\n\nThe mucosal injury score increased during I in all groups. After reperfusion, IRI further progressed in group C, but not in IPC and DEX. In all groups the number of cleaved caspase-3 and TUNEL positive cells increased from P to I. The number of TUNEL positive cells were lower in group DEX compared to group C after I and R. Infiltration with calprotectin positive cells was less pronounced in group DEX compared to group C, whereas in group IPC more calprotectin positive cells were seen.\n\nIn conclusion, IPC and DEX exert protective effects in experimental small intestinal ischaemia in horses.

physiology↗