Persistence of impaired hepatic microcirculation after nonarterialized liver transplantation in the rat

The role of graft reperfusion sequence in the development of non-anastomotic biliary strictures following orthotopic liver transplantation: A meta-analysis

BACKGROUND

Liver transplant is a potential cure for liver failure and hepatic malignancy but there are many techniques which have been described for vascular reconstruction. This study was to compare the prevalence of non-anastomotic biliary stricture and other surgical complications based on Clavien-Dindo scoring system, in initial portal reperfusion (sequential) versus simultaneous or initial artery reperfusion.

DATA SOURCES

Meta-analysis of published studies comparing the outcomes of both techniques was carried out. Data search was conducted across the major databases and studies were selected under the guidance of the Cochrane guidelines for systematic reviews and meta-analysis.

RESULTS

Seven studies were included to address the primary and the secondary outcomes. No statistical difference was found in the incidence of non-anastomotic biliary strictures (OR = 0.40; P = 0.14), regardless of reperfusion technique. The pooled estimate of the Clavien-Dindo grading of complications was not significantly different between the techniques, though Clavien-Dindo II complications were higher in the simultaneous or initial artery reperfusion group than the initial portal reperfusion group (OR = 2.73; P = 0.01). Similarly, there was no difference in the operative time, hospital stay and other outcomes addressed in this report.

CONCLUSIONS

The available evidence suggests that there is no significant difference demonstrated in the rate of non-anastomotic biliary strictures or other complications, between the two techniques, except for Clavien-Dindo II complications.

Review article: the role of the microcirculation in liver cirrhosis

BACKGROUND

Intrahepatic microvascular derangements and microcirculatory dysfunction are key in the development of liver cirrhosis and its associated complications. While much has been documented relating to cirrhosis and the dysfunction of the microcirculation in the liver parenchyma, far less is known about the state of the extrahepatic microcirculation and the role this may have in the pathogenesis of multiple organ failure in end stage liver cirrhosis.

AIM

To provide an update on the role of the microcirculation in the pathophysiology of cirrhosis and its associated complications and briefly discuss some of the imaging techniques which may be used to directly investigate the microcirculation.

METHODS

A Medline literature search was conducted using the following search terms: 'cirrhosis', 'microcirculation', 'circulation', 'systemic', 'inflammation', 'peripheral', 'hepatorenal' and 'hepatopulmonary'.

RESULTS

Significant heterogeneous microvascular alterations exist in patients with cirrhosis. Data suggest that the systemic inflammation, associated with advanced cirrhosis, induces microcirculatory dysregulation and contributes to haemodynamic derangement. The resultant vasoconstriction and hypoperfusion in the systemic extrahepatic microvasculature, is likely to be instrumental in the pathophysiology of organ failure in decompensated cirrhosis, however the mechanistic action of vasoactive agents used to correct the circulatory disturbance of advanced cirrhosis is poorly understood.

CONCLUSIONS

Further research into the role of the microcirculation in patients with liver cirrhosis, will improve physicians understanding of the pathophysiology of cirrhosis, and may provide a platform for real time evaluation of an individual's microcirculatory response to vasoactive mediators, thus guiding their therapy.

Isovolemic hemodilution with glutaraldehyde-polymerized human placenta hemoglobin (PolyPHb) attenuated rat liver ischemia/reperfusion injury

This study was to investigate whether glutaraldehyde-polymerized human placenta hemoglobin (PolyPHb) could attenuate ischemia/reperfusion (I/R)-induced liver injury. Isovolemic hemodilution of SD rats was performed by exchanging 15% total blood volume with PolyPHb. I/R was induced by left liver lobes pedicle cross-clamping for 60 min and reperfusion for 2 h. Blood pressure moderately elevated after PolyPHb infusion and returned to basal level within 10 min. The hepatic histopathological damage and the activities of liver injury markers were reduced by PolyPHb. The TUNEL staining and caspase assay indicated hepatic apoptosis was also inhibited. Therefore, our findings suggest PolyPHb can reduce liver I/R injury.

Hypothermic oxygenated perfusion (HOPE) protects from biliary injury in a rodent model of DCD liver transplantation

BACKGROUND & AIMS

The use of livers from donors after cardiac arrest (DCD) is increasing in many countries to overcome organ shortage. Due to additional warm ischemia before preservation, those grafts are at higher risk of failure and bile duct injury. Several competing rescue strategies by machine perfusion techniques have been developed with, however, unclear effects on biliary injury. We analyze the impact of an end-ischemic Hypothermic Oxygenated PErfusion (HOPE) approach applied only through the portal vein for 1h before graft implantation.

METHODS

Rat livers were subjected to 30-min in situ warm ischemia, followed by subsequent 4-h cold storage, mimicking DCD-organ procurement and conventional organ transport. Livers in the HOPE group underwent also passive cold storage for 4h, but were subsequently machine perfused for 1h before implantation. Outcome was tested by liver transplantation (LT) at 12h after implantation (n=10 each group) and after 4 weeks (n=10 each group), focusing on early reperfusion injury, immune response, and later intrahepatic biliary injury.

RESULTS

All animals survived after LT. However, reperfusion injury was significantly decreased by HOPE treatment as tested by hepatocyte injury, Kupffer cell activation, and endothelial cell activation. Recipients receiving non-perfused DCD livers disclosed less body weight gain, increased bilirubin, and severe intrahepatic biliary fibrosis. In contrast, HOPE treated DCD livers were protected from biliary injury, as detected by cholestasis parameter and histology.

CONCLUSIONS

We demonstrate in a DCD liver transplant model that end-ischemic hypothermic oxygenated perfusion is a powerful strategy for protection against biliary injury.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Simultaneous orthotopic liver-kidney transplantation with hepatic arterial reconstitution in rats

Although combined liver-kidney (LK) transplantation has been effectively used in patients with end-stage liver disease and concurrent renal failure, a small animal model has been rarely described because of the technical difficulties. Herein, we have described techniques of a modified simultaneous LK transplantation model in rats. We have modified the techniques to perform 47 combined LK transplants in rats with reconstructed hepatic artery and renal vessels by a microvascular sleeve method and an end-to-end anastomosis technique without cross-clamping the vena cava and abdominal aorta, respectively. An average donor operation time was 34.4+/-6.3 min with cold ischemia times of 49.7+/-6.5 min and 61.3+/-4.1 min for liver and kidney grafts, respectively. The total time for recipient operation was 96.8+/-9.4 min with a 4-wk survival rate of 92.3% (36/39). A cumulative hepatic and renal arterial patency rate reached 90.2% (37/41). Normal grafts function tests were observed within the first week post-transplant, as well as normal histopathology studies of the 2 grafts in wk 4 post-transplant. Our method proves to be practical and may contribute to a wider use of the model in the studies of allograft rejection and tolerance induction during combined LK transplantation.

Attenuation of small-for-size liver graft injury by FTY720: significance of cell-survival Akt signaling pathway

To investigate the protective mechanism of FTY720 in small-for-size liver grafts, we applied a rat orthotopic liver transplantation model using 40% of liver grafts. FTY720 was administered (1 mg/kg, i.v.) at 20 min before graft harvesting in the donor, immediately before total hepatectomy and immediately after graft reperfusion in the recipient. The 7-day graft survival rates in the FTY720 group were significantly improved compared with the control group [100% (6/6) vs. 40% (4/10), p = 0.034]. FTY720 significantly reduced serum ALT and AST levels at 24 h after liver transplantation. The cell-survival Akt signaling pathway was activated in FTY720 groups by phosphorylation of Glycogen Synthase Kinase-3beta, Bad and Forkhead Transcription Factor at 6 and 24 h after liver transplantation. The cleaved-caspases 3, 7 and 9 were down-regulated, accompanied with less apoptotic nuclei after FTY720 treatment. Acute-phase inflammatory MAPK pathway was down-regulated by dephosphorylation of c-Raf, Mek and Erk in the treatment groups. A20 and endothelial nitric oxide synthase were up-regulated together with down-regulation of iNOS. Hepatic sinusoids were well preserved in the FTY720 group but disrupted in the control group. In conclusion, FTY720 attenuates small-for-size liver graft injury by activation of cell-survival Akt signaling and down-regulation of the MAPK pathway.

In Vivo Trafficking and Targeted Delivery of Magnetically Labeled Stem Cells

Targeted delivery of intravenously administered genetically altered cells or stem cells is still in an early stage of investigation. We developed a method of delivering iron oxide (ferumoxide)-labeled mesenchymal stem cells (MSCs) to a targeted area in an animal model by applying an external magnet. Rats with or without an external magnet placed over the liver were injected intravenously with ferumoxide-labeled MSCs and magnetic resonance imaging (MRI) signal intensity (SI) changes, iron concentration, and concentration of MSCs in the liver were monitored at different time points. SI decreased in the liver after injection of MSCs and returned gradually to that of control rat livers at approximately day 29. SI decreases were greater in rats with external magnets. Higher iron concentration and increased labeled cell numbers were detected in rat livers with external magnets. The external magnets influenced the movement of labeled MSCs such that the cells were retained in the region of interest. These results potentially open a new area of investigation for delivering stem cells or genetically altered cells.