Possible cause of primary graft non-function after orthotopic liver transplantation: a hypothesis with rat models

Small-for-size liver graft injury--impact on tumor behavior

The success of liver transplantation has led to an ever-increasing demand for liver grafts. Since the first successful living donor liver transplantation, this surgical innovation has been well established in children and has significantly relieved the crisis of donor organ shortage for children. However, the extension of living donor liver transplantation to adult recipients is limited by the graft volume. The major concern of adult-to-adult living donor liver transplantation is the adequate graft that can be harvested from a living donor. Small-for-size graft injury is frequently observed. To develop novel effective treatments attenuating small-for-size liver graft injury during living donor liver transplantation, it is important to explore the precise mechanism of acute phase small-for-size graft damage. Recently, a number of clinical studies and animal experiments have been conducted to investigate the possible key issues on acute phase small-for-size liver graft injury, such as mechanical injury from shear stress, subsequent inflammatory responses, and imbalance of vasoregulatory factors. This review focuses on the mechanism of small-for-size liver graft injury based on the number of clinical and experimental studies. The latest research findings of the significance of acute phase liver graft injury on late phase tumor recurrence and metastasis are also addressed.

Elimination of Kupffer cells and nafamostat mesilate rinse prevent reperfusion injury in liver grafts from agonal non-heart-beating donors

BACKGROUND

We hypothesized that microcirculatory disturbance was an obstacle to liver transplantation (LTx) from non-heart-beating donors (NHBDs) and that it was attributed mainly to a deterioration of sinusoidal endothelial cells (SECs) and sinusoidal narrowing. This study was designed to examine porcine orthotopic LTx using livers obtained from pretreated agonal NHBDs, and to determine whether the maintenance of the liver microcirculation would result in successful LTx from agonal NHBDs.

METHODS

Pigs were allocated to five groups: (i) control group; (ii) NM group, in which grafts were rinsed with nafamostat mesilate (NM) rinse; (iii) LD group, in which Kupffer cells in grafts were eliminated by liposome-encapsulated dichloromethylene diphosphonate (L-DMDP); (iv) LDNM group, in which grafts pretreated with L-DMDP were rinsed with NM rinse; (v) heart-beating donor (HBD) group. In all groups, but the HBD group, the livers were pretreated with FK506 and prostaglandin I2 analogue, and were preserved in University of Wisconsin solution after cardiac arrest. Thereafter orthotopic LTx was performed.

RESULTS

After reperfusion, it was histologically demonstrated that elimination of Kupffer cells prevented SECs deterioration and NM rinse prevented sinusoidal narrowing. The hepatic energy charge recovered in all groups except the control group. In the LDNM group, three of four recipients survived more than 7 days.

CONCLUSIONS

For a successful LTx from agonal NHBDs, it is important to prevent microcirculatory disturbance caused by SEC deterioration and sinusoidal narrowing after reperfusion. Combination therapy consisting in the elimination of Kupffer cells and NM rinse prevented primary graft non-function in liver grafts from agonal NHBDs.

Rescue hepatectomy for initial graft non-function after liver transplantation

BACKGROUND

Early retransplantation is the therapy of choice in patients with initial graft nonfunction (INF). In rare cases the patients' conditions deteriorate dramatically with severe cardiovascular and/or pulmonary insufficiency while on the waiting list for retransplantation. In this life-threatening situation removal of the graft and temporary portocaval shunt before allocation of a new liver proved to be effective. Our experience with this two-stage hepatectomy and subsequent liver transplantation in patients with complicated INF is reported.

METHODS

Hepatectomy was performed in 20 patients with INF associated with severe cardiovascular and pulmonary insufficiency while on the waiting list for emergency liver retransplantation. The mean age was 41.75+/-16.64 years. The time period between primary transplantation and hepatectomy was 2.80+/-2.84 days with a range from 1 to 9 days.

RESULTS

Hepatectomy reduced the need for vasopressive agents and improved pulmonary function in the majority of patients. Four patients died before a liver was available due to brain death in one patient and multiorgan failure in three patients. In the remaining 16 patients liver transplantation could be performed after 19.82+/-15.34 hr (range 6.58 to 72.50 hr). Two of the 16 transplanted patients died on the first postoperative day due to multiorgan failure and pneumonia. The remaining 14 of 16 patients survived retransplantation, but 7 died between days 13 and 105 mostly due to sepsis. Seven patients were discharged from the hospital in good condition and show long-term survival.

CONCLUSION

Hepatectomy was able to stabilize the cardiovascular and pulmonary function. This study confirms the beneficial effects of hepatectomy and subsequent liver transplantation as a life-saving procedure in patients with INF complicated by cardiovascular and/or pulmonary instability.

A stable prostacyclin analog, beraprost sodium, attenuates platelet accumulation and preservation-reperfusion injury of isografts in a rat model of lung transplantation

BACKGROUND

Recent studies have shown that the extent of platelet accumulation in the vasculature of transplanted organs correlates with the degree of preservation-reperfusion injury. In this study, we examined the effect of a stable prostacyclin analog, beraprost sodium, which possesses potent antiplatelet activity, on parameters of platelet accumulation and preservation-reperfusion injury of isografts in a rat model of lung transplantation.

METHODS

The heart-lung blocks of donor rats were flushed with and preserved in modified Euro-Collins solution at 4 degrees C for 6 hr or 24 hr. The left lung was transplanted into recipient rats and reperfused for 1 hr. Lung injury was evaluated by the pulmonary blood flow ratios to the lung isografts, the weight gain of the isografts, and histological examination. Small portions of the lung isografts were excised and stained with an antibody specific for rat platelets. A scoring system was developed to semiquantitate the intensity of antibody staining (score 0-4). The recipient rats received oral administration of beraprost sodium (0.3 mg/kg) before lung transplantation. Control animals received no beraprost sodium.

RESULTS

In the 6-hr preservation study, administration of beraprost sodium significantly reduced the score for platelet accumulation (1.8+/-0.4 vs. 3.3+/-0.5, P<0.01). This observation was accompanied by a significantly decreased degree of preservation-reperfusion injury as evidenced by an increased blood flow ratio (13.7+/-2.6% vs. 4.5+/-3.6%, P<0.01) and a reduced weight gain (0.7+/-0.2 g vs. 1.1+/-0.2 g, P<0.01). Histological examination revealed severe capillary congestion in three of six cases in the control group, while no capillary congestion was observed in the beraprost group. In the 24-hr preservation study, no differences were seen in platelet accumulation scores or parameters of lung injury.

CONCLUSION

Beraprost sodium, an antiplatelet agent, reduces platelet accumulation and preservation-reperfusion injury of lung transplants at 6 hr in this rat isograft model.

Selective bowel decontamination of recipients for prevention against liver injury following orthotopic liver transplantation: evaluation with rat models

Gut-derived substances can activate Kupffer cells to provoke hepatic necrosis after partial hepatectomy in rats. A similar situation may occur during orthotopic liver transplantation (OLT), as congestion in the intestinal wall, caused by portal vein occlusion, is inevitable during the operation. The contribution of such substances to liver injury following OLT was investigated in rats. Oral administration of polymyxin B sulfate for 7 days significantly altered intestinal bacterial flora in rats; Enterobacteriaceae diminished and anaerobes such as Bifidobacterium , Lactobacillus, Bacteroides, and Eubacterium increased in number, compared with the control rats. Also, this treatment significantly reduced endotoxin concentration in the portal blood 30 minutes after blood reflow following portal vein occlusion. When OLT was performed in rats using the liver preserved in cold University of Wisconsin solution for 18 hours, tissue factor activity in Kupffer cells (KC) isolated from the transplanted liver 1 hour after the operation was significantly higher than in that of normal rats. This increase was significantly reduced by pretreatment of the recipients with polymyxin B sulfate. In these recipients, serum alanine aminotransferase activity, tumor necrosis factor alpha (TNF alpha) concentration, and histological extent of liver necrosis were significantly attenuated at 24 hours after the operation compared with those of control rats. We conclude that the substances derived from bacilli sensitive to polymyxin B sulfate in the gut may be a contributing factor to liver injury following OLT in rats; we feel that this probably occurs by entering of the substances into the portal blood during the ahepatic phase of the operation to activate KC. Selective bowel decontamination of recipients with polymyxin B sulfate would be a candidate for protection against early graft failure following OLT.

Recombinant human tissue factor pathway inhibitor as a possible anticoagulant targeting hepatic sinusoidal walls

The expression of tissue factor pathway inhibitor (TFPI) was investigated in sinusoidal endothelial cells in the liver and endothelial cells in the lung. Northern blot analysis revealed that TFPI mRNA was expressed in the lung, but minimal in the liver. Also, immunohistochemical examination showed that TFPI was not expressed on the sinusoidal endothelial cells in contrast to marked expression on endothelial cells in the lung, suggesting that anticoagulant activity to inhibit blood coagulation induced by tissue factor is reduced in the hepatic sinusoids compared to the microvessels of other organs. When recombinant human TFPI was intravenously injected in rats, it disappeared rapidly from the circulation, but was detected by electron microscopy on the surface of sinusoidal endothelial cells and microvilli of hepatocytes in the space of Disse. In these rats, the TFPI reappeared in the circulation following an intravenous injection of heparin sodium with reduced immunohistochemical staining of the TFPI on hepatic sinusoidal walls. It is concluded that exogenous TFPI can increase anticoagulant activity on the hepatic sinusoidal walls by binding to heparinoids on the cell surface. It may act effectively even in the hepatic sinusoids with damaged endothelial cells.