Morphological alterations and redox changes associated with hepatic warm ischemia-reperfusion injury

Abstract

Aim: To study the effects of warm ischemia-reperfusion (I/R) injury on hepatic morphology at the ultrastructural level and to analyze the expression of the thioredoxin (TRX) and glutaredoxin (GRX) systems.

Methods: Eleven patients undergoing liver resection were subjected to portal triad clamping (PTC). Liver biopsies were collected at three time points; first prior to PTC (baseline), 20 min after PTC (post-ischemia) and 20 min after reperfusion (post-reperfusion). Electron microscopy and morphometry were used to study and quantify ultrastructural changes, respectively. Additionally, gene expression analysis of TRX and GRX isoforms was performed by quantitative PCR. For further validation of redox protein status, immunogold staining was performed for the isoforms GRX1 and TRX1.

Results: Post-ischemia, a significant loss of the liver sinusoidal endothelial cell (LSEC) lining was observed (P = 0.0003) accompanied by a decrease of hepatocyte microvilli in the space of Disse. Hepatocellular morphology was well preserved apart from the appearance of crystalline mitochondrial inclusions in 7 out of 11 patients. Post-reperfusion biopsies had similar features as post-ischemia with the exception of signs of a reactivation of the LSECs. No changes in the expression of redox-regulatory genes could be observed at mRNA level of the isoforms of the TRX family but immunoelectron microscopy indicated a redistribution of TRX1 within the cell.

Conclusion: At the ultrastructural level, the major impact of hepatic warm I/R injury after PTC was borne by the LSECs with detachment and reactivation at ischemia and reperfusion, respectively. Hepatocytes morphology were well preserved. Crystalline inclusions in mitochondria were observed in the hepatocyte after ischemia.

Keywords: Electron microscopy; Glutaredoxins; Hepatic ischemia-reperfusion injury; Ischemia reperfusion injury; Oxidative stress; Portal triad clamping; Thioredoxins; Warm ischemia-reperfusion injury.

Figure 1

Morphological changes in liver before and after ischemia and reperfusion, transmission electron micrographs of representative images of liver sections from one patient. A: Baseline, before induction of ischemia, shows the normal state of liver morphology at a cellular level; B: Morphology of a sinusoid with neighbouring hepatocytes 20 min after ischemia; C: Representative image of sinusoid and haptocytes 20 min after reperfusion; D: Endothelial lining of a sinusoid with hepatocyte microvilli; E: Morphology of the Space of Disse post-ischemia; F: Morphology of the space of disse post-reperfusion. SD: Space of disse; H: Hepatocyte; EC: Endothelial cells; VL: Vessel lumen; K: Kupffer cell. Arrow shows the absence of hepatocyte microvilli.

Figure 2

Crystalline mitochondrial inclusions. A: Baseline, before induction of ischemia, shows hepatocyte mitochondria with normal appearance; B: Post-ischemia, showing mitochondria with the crystalline inclusions and a few dilated mitochondria; C: Mitochondrial inclusions, close-up of a single mega-mitochondrion showing the inclusions post-ischemia.

Figure 3

Morphometric analysis of endothelial lining. The percentage of attached endothelial lining along sinusoidal walls was quantified using network information services elements Basic Research Software. Statistical analysis was performed in Graphpad Prism, and differences were determined by the non-parametric Friedman test followed by Dunn’s post-hoc test (P < 0.01). Baseline: Before induction of ischemia; Ischemia: Twenty minutes of ischemia; Reperfusion: Twenty minutes after reperfusion.

Figure 4

Quantification of immunogold staining. Number of gold particles of 5 hepatocytes for each time point and patient were recorded. A-C: Values from the TRX immunogold staining where A: Quantification of TRX in the cytosol; B: Quantification of TRX in the nuclei; C: Total value from of TRX both in cytosol and nuclei; D-F: Values from the quantification of GRX immunogold staining where D: Quantification of GRX in the cytosol; E: Quantification of GRX in the nuclei; F: Total value of GRX both in cytosol and nuclei. Baseline: Before induction of ischemia; Ischemia: Twenty minute of ischemia; Reperfusion: Twenty minute after reperfusion.