Establishment of a rat liver transplantation model with prolonged biliary warm ischemia time

Shortening the recipient warm ischemia time could be a strategy for expanding the liver donor pool

BACKGROUND

Shortening the recipient warm ischemia time (rWIT) has been proven to be effective for improving the short- and long-term outcomes after liver transplantation (LT) and offsets the negative impact of an extended cold ischemia time. However, few studies have been conducted to explore the prognostic effects of shortening the rWIT in transplantations using a liver graft from an extended-criteria donor (ECD).

AIM

To investigate whether shortening the rWIT could improve the outcomes of ECD LT.

METHODS

Rat ECD autologous orthotopic LT were performed with variable rWITs (0, 10, 20, and 30 minutes). Near-infrared fluorescence imaging (FI) was used for the real-time assessment of liver graft ischemia-reperfusion injury after the anhepatic phase. Survival was assessed, and liver function and histological analyses were performed on the third day after transplantation.

RESULTS

The FI curve growth rate and postoperative three-day survival rate significantly increased, and the liver function and Suzuki score of the liver grafts significantly improved when the rWIT was ≤ 10 minutes (P < 0.05).

CONCLUSION

The post-transplant outcomes were significantly better with a shorter rWIT (10 minutes or less) than with a longer rWIT, which could be a strategy for expanding the liver donor pool.

Treprostinil Supplementation Ameliorates Hepatic Ischemia Reperfusion Injury and Regulates Expression of Hepatic Drug Transporters: An Isolated Perfused Rat Liver (IPRL) Study

Purpose

IR injury is an unavoidable consequence in deceased donor liver transplantation. Cold preservation and warm reperfusion may change the expression and function of drug transporters in the liver due to vasoconstriction, infiltration of neutrophils and release of cytokines. We hypothesize that vasodilation, anti-platelet aggregation and proinflammatory downregulation activities of treprostinil will diminish the IR injury and its associated effects.

Methods

Livers obtained from male SD rats (n = 20) were divided into 1) Control, 2) IR, 3) Treprostinil-1 (preservation only), and 4) Treprostinil-2 (preservation and reperfusion) groups. Control livers were procured and immediately reperfused. Livers in the other groups underwent preservation for 24 h and were reperfused. All the livers were perfused using an Isolated Perfused Rat Liver (IPRL) system. Periodic perfusate, cumulative bile samples and liver tissue at the end of perfusion were collected. Liver injury markers, bile flow rates, m-RNA levels for uptake and efflux transporters (qRT-PCR) were measured.

Results

Cold preservation and warm reperfusion significantly increased the release of AST and ALT in untreated livers. Treprostinil supplementation substantially reduced liver injury. Bile flow rate was significantly improved in treprostinil-2 group. m-RNA levels of Slc10a1, Slc22a1, and Slc22a7 in liver were increased and m-RNA levels of Mdr1a were decreased by IR. Treprostinil treatment increased Abcb11 and Abcg2 m-RNA levels and maintained Slc22a1m-RNA similar to control livers.

Conclusions

Treprostinil treatment significantly reduced liver injury. IR injury changed expression of both uptake and efflux transporters in rat livers. Treprostinil significantly altered the IR injury mediated changes in m-RNA expression of transporters.

Adipose-derived stem cells in the treatment of hepatobiliary diseases and sepsis

Determination of the mesenchymal stem cells is one of the greatest and most exciting achievements that tissue engineering and regenerative medicine have achieved. Adipose-derived mesenchymal stem cells (AD-MSC) are easily isolated and cultured for a long time before losing their stem cell characteristics, which are self-renewal and pluripotency. AD-MSC are mesenchymal stem cells that have pluripotent lineage characteristics. They are easily accessible, and the fraction of stem cells in the adipose tissue lysates is highest among all other sources of mesenchymal stem cells. It is also HLA-DR negative and can be transplanted allogenically without the need for immunosuppression. These advantages have popularized its use in many fields including plastic reconstructive surgery. However, in the field of hepatology and liver transplantation, the progress is slower. AD-MSC have the potential to modulate inflammation, ameliorate ischemia-reperfusion injury, and support liver and biliary tract regeneration. These are very important for the treatment of various hepatobiliary diseases. Furthermore, the anti-inflammatory potential of these cells has paramount importance in the treatment of sepsis. We need alternative therapeutic approaches to treat end-stage liver failure. AD-MSC can provide a means of therapy to bridge to definitive therapeutic alternatives such as liver transplantation. Here we propose to review theoretic applications of AD-MSC in the treatment of hepatobiliary diseases and sepsis.

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.

Using Tree Shrews (Tupaia belangeri) as a Novel Animal Model of Liver Transplantation

Liver transplantation (LT) is most effective and promising approach for end-stage liver disease. However, there remains room for further improvement and innovation, for example, to reduce ischemic reperfusion injury, transplant rejection and immune tolerance. A good animal model of LT is essential for such innovation in transplant research. Although rat LT model has been used since the last century, it has never been an ideal model because the results observed in rat may not be applied to human because these two species are genetically distinct from each other. In this study, we for the first time performed LT using the tree shrew (Tupaia belangeri), a species in the Order Scandentia which is closely related with primates, and evaluated the possibility to adopt this species as a new model of LT. We performed LT on 30 animals using the two-cuff technique, examining the success rate, the survival rate and the immunological reaction. The recipient operation time was 60 min averagely, and we limited the time of the anhepatic phase within 20 min. Twenty-seven (90%) of the animals survived for at least 3 days after the transplantation. Thirteen animals that did not receive any immunosuppressive drug died in 8 days mostly because of acute rejection effect (n=9), similar to the reaction in human but not in experimental rat. The rest 14 animals that were given rapamycin survived significantly longer (38 days) and half of them survived for 60 days until the end of the study. Our results suggest that performing LT in tree shrews can yield high success rate and high survival rate. More importantly, the tree shrews share similar immunological reaction with human. In addition, previous genomics study found that the tree shrews share more proteins with human. In sum, the tree shrews may outperform the experimental rats and could be used as a better and cost-effective animal model for LT.

Vagus Nerve Attenuates Hepatocyte Apoptosis upon Ischemia-Reperfusion via α7 Nicotinic Acetylcholine Receptor on Kupffer Cells in Mice

BACKGROUND

Hepatic ischemia-reperfusion (HIR) injury is a complication of liver surgery. As much as 50% of hepatocytes undergo apoptosis within the first 24 h of reperfusion. The neurotransmitters of the vagus nerve can activate α7 nicotinic acetylcholine receptor (α7nAChR) on macrophages. The function of Kupffer cells (KCs) determines HIR injury. We hypothesize that the vagus nerve could attenuate HIR-induced hepatocyte apoptosis by activating α7nAChR on KCs.

METHODS

Hepatic vagotomized C57BL/6J mice, KC-eliminated C57BL/6J mice, and α7nAChR mice were used for HIR. Primary KCs and hepatocytes were subjected to hypoxia/reoxygenation (HR). Liver injury, hepatocyte apoptosis, reactive oxygen species (ROS) production, and soluble CD163 were measured.

RESULTS

Hepatic vagotomy and α7nAChR caused higher levels of alanine transaminase and liver caspase-3 and -8 activity by HIR. Activating α7nAChR attenuated these changes in wild-type but not in the α7nAChR mice. Furthermore, activating α7nAChR diminished hepatic injury and reduced liver apoptosis by HIR in vagotomized mice. In vitro, activating α7nAChR reduced apoptosis of hepatocytes cocultured with KCs that suffered HR. Similar to the effects by catalase, activating α7nAChR on KCs reduced ROS and H2O2 by HR. The supernatant from KCs, with α7nAChR activated or catalase treated, prevented hepatocyte apoptosis by HR. Finally, KC elimination reduced HIR-induced H2O2 production in mice. Activating α7nAChR significantly attenuated soluble CD163 both in mice by HIR (serum: 240 ± 34 vs. 446 ± 72; mean ± SD; n = 8; P < 0.01) and in KCs by HR (supernatant: 4.23 ± 0.06 vs. 5.60 ± 0.18; n = 3; P < 0.01).

CONCLUSIONS

The vagus nerve could minimize HIR-induced liver apoptosis through activating α7nAChR on KCs possibly by preventing their excessive ROS production.

The rat choledochojejunostomy model for microsurgical training

Purpose

The feasibility of a rat choledochojejunostomy (CJ) training model was investigated, as an introductory model to microsurgery for general surgeons.

Methods

Roux-en-Y CJ was performed on 20 rats. Interrupted 10-0 prolene sutures were used to perform CJ. The animals were observed for 7 days and sacrificed and examined.

Results

The rats were divided into 2 groups of 10 based on surgical order. The CJ time showed a significant decrease from 36.2 ± 5.6 minutes in group 1 to 29.4 ± 5.7 minutes in group 2 (P = 0.015). The bile leakage rate was 40% in group 1 and 10% in group 2. The survival time was 5.4 ± 2.2 days in group 1 and 7 days in group 2 (P = 0.049).

Conclusion

The rat CJ training model is a feasible introductory model for general surgeons with no previous experience in microsurgery.

Analysis of liver fragment subjected to autologous transplant at rat's retroperitoneum

BACKGROUND

To investigate the regeneration process of autologous implants of liver on the retroperitoneum.

METHODS

Thirty male Fisher rats were used divided in to group 1 (G1): studied 60 d after surgery; group 2 (G2): studied 90 d after surgery; group 3 (G3): studied 180 d after surgery; and group C (GC): animals without surgery. Hepatic fragment was processed for histologic and biochemical analysis.

RESULTS

There was inflammatory infiltrate, diffuse hydropic degeneration, necrosis, and moderate fibrosis that reduced in direct relation to the postsurgical time. The concentration of albumin was different between GC and G1 and between G1 and G3 (P = 0.0007). The Catalase (CAT) was related to the time of surgery with GC being different when compared with G1, G2, and G3 (P < 0.0001). The oxidative stress measured through the thiobarbituric acid reactive substances lipid peroxidation was different between the GC and the G2 groups (P = 0.0381).

CONCLUSIONS

The analysis made showed hepatic regeneration in the fragment subjected to autologous transplant at the retroperitoneum.

Warm ischemia may damage peribiliary vascular plexus during DCD liver transplantation

Biliary complications cause significant morbidity and mortality in liver transplantation. Warm ischemia can induce biliary duct injury. This study aimed to investigate the effects of warm ischemia on the peribiliary vascular plexus in rat liver transplantation. A total of 102 Sprague-Dawley rats were divided into three groups: sham-operation group, non-ischemic group, and ischemic group. Liver transplantation was performed in both the non-ischemic group and the ischemic group. The animals were sacrificed on day 1, 3, 7, and 14 to collect the blood and liver samples. Serum levels of bile duct obstruction, viz, alkaline phosphatase and gamma-glutamyl transpeptidase, as well as direct and indirect bilirubin were measured. Liver biopsy samples were examined with hematoxylin-eosin staining and transmission electron microscopy. The levels of enzymes and bilirubin were significantly higher in the ischemic group than the non-ischemic group and sham-operated animals (P<0.05), with return to normal levels in the ischemic group after two weeks. Morphological examination showed microthrombi and endothelial damage in the bile ducts and the peribiliary vascular plexus of the ischemic group. Warm ischemia/reperfusion injury can damage the endothelium of the peribiliary vascular plexus, which might compromise the bile duct microcirculation and lead to ischemic cholangiopathy after liver transplantation.

Ketanserin, a serotonin 2A receptor antagonist, alleviates ischemia-related biliary fibrosis following donation after cardiac death liver transplantation in rats

Biliary fibrosis is a major complication after donation after cardiac death (DCD) liver transplantation. In this process, the roles of serotonin [5-hydroxytryptamine (5-HT)] and the 5-HT2A receptor subtype are still unknown. In this study, we analyzed markers of portal fibroblast (PF)/myofibroblast (MF) transdifferentiation such as transforming growth factor β1 (TGF-β1), phosphorylated smad2/3, α-smooth muscle actin (α-SMA), collagen I, and collagen III in a primary culture system of PFs after the administration of 5-HT or 5-HT plus ketanserin (a selective 5-HT2A receptor antagonist). A rat DCD transplant model was established with 30 minutes of warm ischemia and 4 hours of cold ischemia during organ procurement. Recipients were intraperitoneally injected with ketanserin (1 mg·kg(-1)·day(-1)) or normal saline. Grafts without in situ warm ischemia instead of minimal cold storage (30 minutes) served as controls. The serum biochemistry, the liver contents of 5-HT and hydroxyproline (HYP), and the expression of fibrosis-related genes (including TGF-β1, matrix metalloproteinase 2, procollagen α1, and α-SMA messenger RNA) were determined. The extent of biliary fibrosis was also assessed histopathologically. The results indicated that ketanserin inhibited 5-HT-activated TGF-β1-smad2/3 signaling in vitro and thereby depressed the MF conversion of PFs. Rats receiving DCD livers showed increased liver contents of 5-HT and HYP, impaired biliary function, up-regulation of fibrosis-related genes, and aggravated biliary fibrosis. However, these phenomena were alleviated by treatment with ketanserin. We concluded that the profibrotic activity of 5-HT occurred through the activation of TGF-β1 signaling and the 5-HT2A receptor. Thus, these data suggest that the 5-HT2A receptor may be a potential therapeutic target for ischemia-related biliary fibrosis after DCD liver transplantation.

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.