Determination of Apparent Diffusion Coefficient to Quantitatively Study Partial Hepatic Ischemia Reperfusion Injury in a Rabbit Model

Multimodal modulation of hepatic ischemia/reperfusion-induced injury by phytochemical agents: A mechanistic evaluation of hepatoprotective potential and safety profiles

BACKGROUND

Hepatic ischemia-reperfusion (I/R) injury is a clinically fundamental phenomenon that occurs through liver resection surgery, trauma, shock, and transplantation.

AIMS OF THE REVIEW

This review article affords an expanded and comprehensive overview of various natural herbal ingredients that have demonstrated hepatoprotective effects against I/R injury through preclinical studies in animal models.

MATERIALS AND METHODS

For the objective of this investigation, an extensive examination was carried out utilizing diverse scientific databases involving PubMed, Google Scholar, Science Direct, Egyptian Knowledge Bank (EKB), and Research Gate. The investigation was conducted based on specific identifiable terms, such as hepatic ischemia/reperfusion injury, liver resection and transplantation, cytokines, inflammation, NF-kB, interleukins, herbs, plants, natural ingredients, phenolic extract, and aqueous extract.

RESULTS

Bioactive ingredients derived from ginseng, curcumin, resveratrol, epigallocatechin gallate, quercetin, lycopene, punicalagin, crocin, celastrol, andrographolide, silymarin, and others and their effects on hepatic IRI were discussed. The specific mechanisms of action, signaling pathways, and clinical relevance for attenuation of liver enzymes, cytokine production, immune cell infiltration, oxidative damage, and cell death signaling in rodent studies are analyzed in depth. Their complex molecular actions involve modulation of pathways like TLR4, NF-κB, Nrf2, Bcl-2 family proteins, and others.

CONCLUSION

The natural ingredients have promising values in the protection and treatment of various chronic aggressive clinical conditions, and that need to be evaluated on humans by clinical studies.

Combined administration of membrane-permeable and impermeable iron-chelating drugs attenuates ischemia/reperfusion-induced hepatic injury

BACKGROUND

The underlying pathophysiological mechanisms of hepatic ischemia-reperfusion (I/R) injury have not been completely elucidated. However, it is well known that oxidative stress, caused by a burst of reactive oxygen species (ROS) production during the reperfusion phase, plays a crucial role. A growing body of evidence indicates that the intracellular availability of free iron represents a requirement for ROS-induced adverse effects, as iron catalyzes the generation of highly reactive free radicals. The aim of this study was to examine whether a combination of iron chelators with varying lipophilicity could offer enhanced protection against I/R by diminishing the conversion of weak oxidants, like H₂O₂, to extremely reactive ones such as hydroxyl radicals (HO^.).

METHODS

HepG2 cells (hepatocellular carcinoma cell line) were exposed to oxidative stress conditions after pre-treatment with the iron chelators desferrioxamine (DFO) and deferiprone (DFP) alone or in combination. Labile iron pool was estimated using the calcein-acetoxymethyl ester (calcein-AM) method and DNA damage with the comet assay. We subsequently used a rabbit model (male New Zealand white rabbits) of hepatic I/R-induced injury to investigate, by measuring biochemical (ALT, ALT, ALP, γGT) and histological parameters, whether this may be true for in vivo conditions.

RESULTS

The combination of a membrane-permeable iron chelator (DFP) with a strong membrane-impermeable one (DFO) raises the level of protection in both hepatic cell lines exposed to oxidative stress conditions and hepatic I/R rabbit model.

CONCLUSIONS

Our results show that combinations of iron chelators with selected lipophilicity and iron-binding properties may represent a valuable strategy to protect against tissue damage during reperfusion after a period of ischemia.

Assessment of liver ischemia reperfusion injury in mice using hepatic T2 mapping: Comparison with histopathology

BACKGROUND

Liver ischemia reperfusion injury (IRI) occurs during liver surgery or transplantation resulting in an inflammatory response, tissue damage, and functional impairment of the organ.

PURPOSE

To assess the feasibility of T₂ mapping for noninvasive quantification of liver edema after partial liver IRI in mice.

STUDY TYPE

Prospective, experimental study.

ANIMAL MODEL

Partial liver IRI was induced in C57BL/6-mice by transient clamping of the left lateral and median liver lobes for 35 (n = 8), 45 (n = 6), 60 (n = 17), or 90 minutes (n = 5). For comparison, healthy C57BL/6-mice were examined as controls (n = 9).

FIELD STRENGTH/SEQUENCE

Functional liver MRI was performed on a 7T scanner using a respiratory-triggered multiecho spin-echo sequence.

ASSESSMENT

Healthy control mice and mice with partial liver IRI on day 1 after surgery, and additionally on day 7 in a subgroup with 60 minutes IRI (n = 8) were examined. Maps of T₂ relaxation time of liver tissue were used to assess distribution, severity of tissue edema (mean T₂ time), and the percentage of edematous liver tissue.

STATISTICAL TEST

One-way analysis of variance (ANOVA) with Tukey's honest significant difference (HSD), paired t-tests, Pearson's test for correlation of MRI parameters with levels of liver enzymes, and histopathology, receiver operating characteristic (ROC) analysis.

RESULTS

Significant tissue edema induced by liver IRI as compared to the control group was detected by increased mean T₂ times in groups with 60 minutes (P < 0.001) and 90 minutes IRI (P < 0.001). The percentage of edematous liver tissue significantly increased with longer ischemia times (controls 3.4 ± 0.4%, 35 minutes 5.3 ± 0.6%, 45 minutes 23.3 ± 7.6%, 60 minutes 39.7 ± 3.6%, 90 minutes 51.3 ± 4.5%). Mean T₂ times and the percentage of edematous liver tissue significantly correlated with elevation of liver enzymes (P < 0.001), histological evidence of liver injury (r = 0.80 and r = 0.82, P < 0.001), and neutrophil infiltration (r = 0.70 and r = 0.74, P < 0.001). In the subgroup with follow-up, the severity (P < 0.01) and extent of liver edema decreased significantly over time (P < 0.01).

DATA CONCLUSION

T₂ mapping allows quantification and follow-up of liver injury in mice.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1586-1594.

Multiparametric functional magnetic resonance imaging for evaluation of hepatic warm ischemia-reperfusion injury in a rabbit model

BACKGROUND

To assess the feasibility of noninvasive and quantitative evaluation of hepatic pathophysiological changes in rabbit hepatic warm ischemia-reperfusion injury (WIRI) models by using intravoxel incoherent motion (IVIM), diffusion tensor imaging (DTI) and blood oxygen level dependent (BOLD) MRI.

METHODS

Twenty rabbits were randomly divided into hepatic WIRI model group and sham-operation group (n = 10 for each group). Hepatic WIRI was induced in rabbit by occluding hepatic inflow for 30 min and reperfusion for 6 h. The control group only underwent laparotomy and liver ligament dissection. IVIM with 11 b values (0 to 800 s/mm²), DTI with 2 b values (0 and 500 s/mm²) on 12 diffusion directions, and BOLD MRI with 9 TE (2.57 to 24.25 ms) were performed at 3 T clinical MR scanner. Rabbits were sacrificed for biochemical and histopathological analysis after MR scanning. All of functional MR, biochemical and histopathological parameters were analyzed by independent sample t test, Mann-Whitney U test, Pearson and Spearman correlation methods.

RESULTS

All of MR parameters showed moderate to excellent interobserver reproducibility. True diffusion (Dslow), pseudodiffusion (Dfast), perfusion fraction (PF), and mean diffusitivity (MD) were lower in WIRI models than in control rabbits (P < 0.01), R2* was higher in WIRI models than in control rabbits (P < 0.001), while fractional anisotropy (FA) showed no statistical difference. There were significant differences in I score and all of biochemical parameters between the two groups (P < 0.01). Functional MR parameters corresponded well with all of biochemical parameters and some of histopathological parameters (P < 0.05). Histopathological analysis showed the structure and morphology of hepatic lobule was normal and clear in control rabbits, while diffuse hepatocyte swelling, central vein and sinusoids congestion, and inflammatory cell infiltration in WIRI models.

CONCLUSIONS

IVIM, DTI, and BOLD MRI are noninvasive and useful techniques for assessing the microenvironment changes of hepatic WIRI in rabbit models.

Quantitative Analysis of Hepatic Microcirculation in Rabbits After Liver Ischemia-Reperfusion Injury Using Contrast-Enhanced Ultrasound

Previous studies have shown that contrast-enhanced ultrasound (CEUS) can be used quantitatively to analyze microcirculation blood perfusion in hepatocellular carcinoma patients. However, limited data have described the application of CEUS in hepatic microcirculation after liver ischemic-reperfusion injury (IRI). The purpose of this study was to explore the use of CEUS quantitatively to assess liver microcirculation after liver IRI. We randomly sorted 45 New Zealand rabbits into 3 groups (15 in each). Group A was a control group in which the rabbits underwent laparotomy alone. In groups B and C, hepatic blood was blocked for 30 min. Simultaneously, rabbits in group C underwent left lateral lobe resection. After 30 min of ischemia, CEUS was conducted after 0 h, 1 h, 6 h and 24 h of reperfusion in the 3 groups. Time-intensity curves (TICs) for CEUS were constructed and quantitative parameters (maximum intensity [IMAX], rise time [RT], time to peak [TTP] and mean transit time [mTT]) were obtained. In addition, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were computed to estimate liver function before the operation and at 0 h, 1 h, 6 h and 24 h after reperfusion, respectively. Pathologic changes in the liver after reperfusion were also observed. Simultaneously, the correlations between serum transaminase and a variety of quantitative analysis parameters were analyzed. In groups B and C, the IMAX value decreased; whereas RT, TTP, mTT and serum ALT and AST levels increased significantly in comparison with those in group A after 0 h and 1 h of reperfusion. The pathology revealed that erythrocytes were destroyed and microcirculation was disturbed. Then, at 6 h of reperfusion, the IMAX continued to decrease. Additionally, the levels of RT, TTP, mTT and serum ALT and AST increased in comparison with those at 1 h of reperfusion. The pathologic analysis revealed inflammatory cell aggregation and leukocyte infiltration. After 24 h of reperfusion, the IMAX was reduced in comparison with that of the 6-h group. The levels of RT, TTP, mTT and serum ALT and serum AST were increased in comparison with that of the 6-h group. These findings were in accordance with the pathologic analysis. In addition, serum transaminase had a negative correlation with IMAX (p < 0.001) and a positive correlation with RT, TTP and mTT (all p < 0.001). So, in conclusion, the quantitative analysis of CEUS can be used to assess hepatic microcirculation after liver IRI.

A Novel and Sensitive Approach for the Evaluation of Liver Ischemia-Reperfusion Injury After Liver Transplantation

OBJECTIVES

The purpose of our study was to evaluate the potential of x-ray propagation-based phase-contrast imaging (PCI) computed tomography (CT) for the detection and characterization of early changes after ischemia-reperfusion (IR) in a standardized rat liver transplantation (LTx) model.

MATERIALS AND METHODS

Syngeneic orthotopic liver transplantation was performed in male Lewis rats. Ischemia-reperfusion injury (IRI)-induced changes of liver parenchyma were investigated in a time-dependent manner (2, 16, 24, and 32 hours). X-ray phase-contrast images of formalin-fixated liver specimens were acquired in CT mode by using a voxel size of 8 × 8 × 8 μm. Necrapoptotic cell death was visualized with the TdT-mediated dUTP-biotin nick end labeling technique, and alterations of liver graft microhemodynamics, that is, acinar and sinusoidal perfusion failure, were evaluated by in vivo fluorescence microscopy.

RESULTS

Acquired and reconstructed PCI-CT images showed an increase in necrotic liver parenchyma dependent on cold storage time, measuring 5.7% ± 1.6% after 2 hours (comparable to 2.6% ± 0.4% for sham livers), 11.5% ± 2.1% (16 hours; P < 0.05 vs control), 23.0% ± 0.5% (24 hours; P < 0.001 vs control), and 31.3% ± 2.2% (32 hours; P < 0.001 vs control). There were a significant lower number of perfused acini in dependence on increasing cold storage time. The acinar perfusion index reached 0.970 ± 0.006 after 2 hours of cold ischemia (comparable to 0.960 ± 0.009 for sham livers) and declined continuously after 16, 24, and 32 hours cold ischemia (0.58 ± 0.03, 0.49 ± 0.02, 0.41 ± 0.03, each P < 0.0001 vs controls). Comparable results were found for sinusoidal perfusion, reaching 1.8% ± 0.4% of nonperfused sinusoids for 2 hours of cold ischemia and 8.2% ± 0.8% after 16 hours, 18.8% ± 1.4% after 24 hours, and 39.0% ± 2.4% after 32 hours (each P < 0.0001 vs controls). Prolonged cold ischemia was associated with an increasing number of TdT-mediated dUTP-biotin nick end labeling-positive cells (hepatocytes and sinusoidal lining cells), reaching 0.4 ± 0.1 (sham), 0.7 ± 0.4 (2 hours), 6.4 ± 1.1 (16 hours), 2.1 ± 0.3 (24 hours), and 14.7 ± 3.5 (32 hours; P = 0.002) for hepatocytes.

CONCLUSIONS

X-ray PCI of histological liver specimens can detect IR-induced tissue necrosis and can provide detailed complementary 3-dimensional information to standard histopathologic findings.

Can intravoxel incoherent motion diffusion-weighted imaging characterize the cellular injury and microcirculation alteration in hepatic ischemia-reperfusion injury? An animal study

PURPOSE

To investigate whether intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) can be used to quantitatively analyze the cellular injury and microcirculation alterations in hepatic ischemia-reperfusion injury (HIRI).

MATERIALS AND METHODS

Thirty-two New Zealand white rabbits were randomly and equally assigned to the sham group, 1-hour, 4-hour, and 12-hour groups according to the reperfusion time after 1 hour of ischemia using a 70% liver ischemia-reperfusion injury model. All the animals underwent IVIM-DWI with 12 b values at 1.5T. The imaging parameters (IVIM parameters and apparent diffusion coefficient [ADC]) among different groups were compared. The correlations between imaging parameters and histological scores, and the ratio of serum aspartate aminotransferase to serum alanine aminotransferase (serum AST/ALT) were analyzed.

RESULTS

During the first hour of HIRI, true diffusion coefficient (D) and ADC significantly decreased (P < 0.05), while there was no significant decrease in perfusion fraction (f) (P = 0.708). There was fair to good correlation between histological scores and f (rs  = -0.493 with the sham cases excluded, and -0.682 with all cases, both P < 0.05) and ADC (rs  = -0.479 with the sham cases excluded, and -0.766 with all cases, both P < 0.05). There was no correlation between imaging parameters and serum AST/ALT with the sham cases excluded (P = 0.673 for f, 0.568 for D, 0.403 for ADC), and good correlation between D, ADC, and serum AST/ALT (r = 0.747 and 0.748, both P < 0.001) with all cases.

CONCLUSION

IVIM-DWI can quantitatively characterize an animal model of HIRI, with D and ADC sensitive in early detection of cellular injury, as well as fair to good correlation between f, ADC, and microcirculation alteration. J. Magn. Reson. Imaging 2016;43:1327-1336.