Auxiliary liver transplantation: regeneration of the native liver and outcome in 30 patients with fulminant hepatic failure--a multicenter European study

"Small Hepatocytes" in the Liver

Mature hepatocytes (MHs) in an adult rodent liver are categorized into the following three subpopulations based on their proliferative capability: type I cells (MH-I), which are committed progenitor cells that possess a high growth capability and basal hepatocytic functions; type II cells (MH-II), which possess a limited proliferative capability; and type III cells (MH-III), which lose the ability to divide (replicative senescence) and reach the final differentiated state. These subpopulations may explain the liver's development and growth after birth. Generally, small-sized hepatocytes emerge in mammal livers. The cells are characterized by being morphologically identical to hepatocytes except for their size, which is substantially smaller than that of ordinary MHs. We initially discovered small hepatocytes (SHs) in the primary culture of rat hepatocytes. We believe that SHs are derived from MH-I and play a role as hepatocytic progenitors to supply MHs. The population of MH-I (SHs) is distributed in the whole lobules, a part of which possesses a self-renewal capability, and decreases with age. Conversely, injured livers of experimental models and clinical cases showed the emergence of SHs. Studies demonstrate the involvement of SHs in liver regeneration. SHs that appeared in the injured livers are not a pure population but a mixture of two distinct origins, MH-derived and hepatic-stem-cell-derived cells. The predominant cell-derived SHs depend on the proliferative capability of the remaining MHs after the injury. This review will focus on the SHs that appeared in the liver and discuss the significance of SHs in liver regeneration.

A non-human primate model of acute liver failure suitable for testing liver support systems

Acute hepatic failure is associated with high morbidity and mortality for which the only definitive therapy is liver transplantation. Some fraction of those who undergo emergency transplantation have been shown to recover native liver function when transplanted with an auxiliary hepatic graft that leaves part of the native liver intact. Thus, transplantation could have been averted with the development and use of some form of hepatic support. The costs of developing and testing liver support systems could be dramatically reduced by the availability of a reliable large animal model of hepatic failure with a large therapeutic window that allows the assessment of efficacy and timing of intervention. Non-lethal forms of hepatic injury were examined in combination with liver-directed radiation in non-human primates (NHPs) to develop a model of acute hepatic failure that mimics the human condition. Porcine hepatocyte transplantation was then tested as a potential therapy for acute hepatic failure. After liver-directed radiation therapy, delivery of a non-lethal hepatic ischemia-reperfusion injury reliably and rapidly generated liver failure providing conditions that can enable pre-clinical testing of liver support or replacement therapies. Unfortunately, in preliminary studies, low hepatocyte engraftment and over-immune suppression interfered with the ability to assess the efficacy of transplanted porcine hepatocytes in the model. A model of acute liver failure in NHPs was created that recapitulates the pathophysiology and pathology of the clinical condition, does so with reasonably predictable kinetics, and results in 100% mortality. The model allowed preliminary testing of xenogeneic hepatocyte transplantation as a potential therapy.

Follistatin-controlled activin-HNF4α-coagulation factor axis in liver progenitor cells determines outcome of acute liver failure

BACKGROUND AND AIMS

In patients with acute liver failure (ALF) who suffer from massive hepatocyte loss, liver progenitor cells (LPCs) take over key hepatocyte functions, which ultimately determines survival. This study investigated how the expression of hepatocyte nuclear factor 4α (HNF4α), its regulators, and targets in LPCs determines clinical outcome of patients with ALF.

APPROACH AND RESULTS

Clinicopathological associations were scrutinized in 19 patients with ALF (9 recovered and 10 receiving liver transplantation). Regulatory mechanisms between follistatin, activin, HNF4α, and coagulation factor expression in LPC were investigated in vitro and in metronidazole-treated zebrafish. A prospective clinical study followed up 186 patients with cirrhosis for 80 months to observe the relevance of follistatin levels in prevalence and mortality of acute-on-chronic liver failure. Recovered patients with ALF robustly express HNF4α in either LPCs or remaining hepatocytes. As in hepatocytes, HNF4α controls the expression of coagulation factors by binding to their promoters in LPC. HNF4α expression in LPCs requires the forkhead box protein H1-Sma and Mad homolog 2/3/4 transcription factor complex, which is promoted by the TGF-β superfamily member activin. Activin signaling in LPCs is negatively regulated by follistatin, a hepatocyte-derived hormone controlled by insulin and glucagon. In contrast to patients requiring liver transplantation, recovered patients demonstrate a normal activin/follistatin ratio, robust abundance of the activin effectors phosphorylated Sma and Mad homolog 2 and HNF4α in LPCs, leading to significantly improved coagulation function. A follow-up study indicated that serum follistatin levels could predict the incidence and mortality of acute-on-chronic liver failure.

CONCLUSIONS

These results highlight a crucial role of the follistatin-controlled activin-HNF4α-coagulation axis in determining the clinical outcome of massive hepatocyte loss-induced ALF. The effects of insulin and glucagon on follistatin suggest a key role of the systemic metabolic state in ALF.

Liver regeneration and inflammation: from fundamental science to clinical applications

Liver regeneration is a complex process involving the crosstalk of multiple cell types, including hepatocytes, hepatic stellate cells, endothelial cells and inflammatory cells. The healthy liver is mitotically quiescent, but following toxic damage or resection the cells can rapidly enter the cell cycle to restore liver mass and function. During this process of regeneration, epithelial and non-parenchymal cells respond in a tightly coordinated fashion. Recent studies have described the interaction between inflammatory cells and a number of other cell types in the liver. In particular, macrophages can support biliary regeneration, contribute to fibrosis remodelling by repressing hepatic stellate cell activation and improve liver regeneration by scavenging dead or dying cells in situ. In this Review, we describe the mechanisms of tissue repair following damage, highlighting the close relationship between inflammation and liver regeneration, and discuss how recent findings can help design novel therapeutic approaches.

Human liver regeneration following massive hepatic necrosis: Two distinct patterns

BACKGROUND AND AIM

Massive hepatic necrosis is a rare but often fatal complication of various liver injuries. Nevertheless, some patients can survive by spontaneous hepatic regeneration. It is known that surviving hepatocytes and/or progenitor cells can participate in this process but the mechanism of hepatic recovery is vague.

METHODS

We examined 13 explanted human livers removed for acute liver failure. Combined immunohistochemistry, digital image analysis, and three-dimensional reconstruction of serial sections were applied.

RESULTS

Two patterns of regeneration could be distinguished. In livers with centrilobular necrosis, the surviving injured periportal hepatocytes started to proliferate and arrange into acinar structures and expressed α-fetoprotein. If the injury wiped out almost all hepatocytes, large areas of parenchymal loss were invaded by an intense ductular reaction. The cells at the distal pole of the ductules differentiated into hepatocytes and formed foci organized by the branches of the portal vein. The expanding foci often containing complete portal triads were arranged around surviving central veins. Their fusion eventually could be an attempt to re-establish the hepatic lobules.

CONCLUSIONS

Regeneration of human livers following massive hepatic necrosis can occur in two ways-either through proliferation of α-fetoprotein-positive acinary-arranged hepatocytes or through ductular progenitor cells, with the latter being less efficient. Further investigation of these regenerative pathways may help identify biomarkers for likelihood of complete regeneration and hence have therapeutic implications.

Auxiliary Liver Transplantation as a Transient Treatment for Acute Liver Failure: Two Cases

Introduction

Acute liver failure is an uncommon condition associated with a high mortality. Most patients do not survive without liver transplantation. In the last decades, auxiliary liver transplantation has emerged as a therapeutic option.

Clinical Case

The authors present two cases of acute liver failure that required liver transplantation. Given the patients' young age and the preserved macroscopic liver pattern evaluated in surgery, auxiliary liver transplantation was executed using different surgical approaches. Afterwards, following confirmed full native liver regeneration, the patients were submitted to auxiliary liver hepatectomy, which was accomplished without complications.

Conclusion

Auxiliary liver transplantation can be regarded as an effective temporary treatment for acute liver failure in selected cases, allowing an immunosuppression-free life.

Simplified technique for auxiliary orthotopic liver transplantation using a whole graft

BACKGROUND

Acute liver failure is associated with a high mortality rate and the main purposes of treatment are to prevent cerebral edema and infections, which often are responsible for patient death. The orthotopic liver transplantation is the gold standard treatment and improves the 1-year survival.

AIM

To describe an alternative technique to auxiliary liver transplant on acute liver failure.

METHOD

Was performed whole auxiliary liver transplantation as an alternative technique for a partial auxiliary liver transplantation using a whole liver graft from a child removing the native right liver performed a right hepatectomy. The patient met the O'Grady's criteria and the rational to indicate an auxiliary orthotopic liver transplantation was the acute classification without hemodynamic instability or renal failure in a patient with deterioration in consciousness.

RESULTS

The procedure improved liver function and decreased intracranial hypertension in the postoperative period.

CONCLUSION

This technique can overcome some postoperative complications that are associated with partial grafts. As far as is known, this is the first case of auxiliary orthotopic liver transplantation in Brazil.

Two sides of one coin: massive hepatic necrosis and progenitor cell-mediated regeneration in acute liver failure

Massive hepatic necrosis is a key event underlying acute liver failure, a serious clinical syndrome with high mortality. Massive hepatic necrosis in acute liver failure has unique pathophysiological characteristics including extremely rapid parenchymal cell death and removal. On the other hand, massive necrosis rapidly induces the activation of liver progenitor cells, the so-called "second pathway of liver regeneration." The final clinical outcome of acute liver failure depends on whether liver progenitor cell-mediated regeneration can efficiently restore parenchymal mass and function within a short time. This review summarizes the current knowledge regarding massive hepatic necrosis and liver progenitor cell-mediated regeneration in patients with acute liver failure, the two sides of one coin.

Heterotopic auxiliary rat liver transplantation with flow-regulated portal vein arterialization in acute hepatic failure

In acute hepatic failure auxiliary liver transplantation is an interesting alternative approach. The aim is to provide a temporary support until the failing native liver has regenerated.(1-3) The APOLT-method, the orthotopic implantation of auxiliary segments- averts most of the technical problems. However this method necessitates extensive resections of both the native liver and the graft.(4) In 1998, Erhard developed the heterotopic auxiliary liver transplantation (HALT) utilizing portal vein arterialization (PVA) (Figure 1). This technique showed promising initial clinical results.(5-6) We developed a HALT-technique with flow-regulated PVA in the rat to examine the influence of flow-regulated PVA on graft morphology and function (Figure 2). A liver graft reduced to 30 % of its original size, was heterotopically implanted in the right renal region of the recipient after explantation of the right kidney.  The infra-hepatic caval vein of the graft was anastomosed with the infrahepatic caval vein of the recipient. The arterialization of the donor's portal vein was carried out via the recipient's right renal artery with the stent technique. The blood-flow regulation of the arterialized portal vein was achieved with the use of a stent with an internal diameter of 0.3 mm. The celiac trunk of the graft was end-to-side anastomosed with the recipient's aorta and the bile duct was implanted into the duodenum. A subtotal resection of the native liver was performed to induce acute hepatic failure. (7) In this manner 112 transplantations were performed. The perioperative survival rate was 90% and the 6-week survival rate was 80%. Six weeks after operation, the native liver regenerated, showing an increase in weight from 2.3±0.8 g to 9.8±1 g. At this time, the graft's weight decreased from 3.3±0.8 g to 2.3±0.8 g. We were able to obtain promising long-term results in terms of graft morphology and function. HALT with flow-regulated PVA reliably bridges acute hepatic failure until the native liver regenerates.

Efforts to expand the donor pool for liver transplantation

Liver transplantation has become a victim of its own success in that there are no longer enough suitable livers for transplantation while at the same time the indications for transplantation increase. Efforts to expand the number of recipients who benefit from this life-saving procedure are being made, in particular through the use of split grafts and live donors. However, such grafts are associated with increased morbidity and mortality related to their reduced size.

Detection of PERV by polymerase chain reaction and its safety in bioartificial liver support system

AIM: To establish a method detecting porcine endogenous retrovirus (PERV) in China experimental minipigs and to evaluate the safety of PERV in three individuals treated with bioartificial liver support systems based on porcine hepatocytes.

METHODS: Porcine hepatocytes were isolated with two-stage perfusion method, then cultured in the bioreactor, which is separated by a semipermeable membrane (0.2 μm) from the lumen through which the patients’ blood plasma was circulated. After post-hemoperfusion, patients’ blood was obtained for screening. Additionally, samples of medium collected from both intraluminal and extraluminal compartments of the laboratory bioreactor and culture supernate in vitro was analyzed. The presence of viral sequences was estimated by polymerase chain reaction (PCR) and reverse transcriptase-polymerase chain reaction (RT-PCR). Finally, the infection of virus in the supernate of common culture was ascertained by exposure to the fetal liver cells.

RESULTS: PERV-specific gag sequences were found in the porcine hepatocytes using RT-PCR. and were detected in all samples from the intraluminal, extraluminal samples and culture supernate. However, culture supernatant from primary porcine hepatocytes (cleared of cellular debris) failed to infect human fetal liver cells. Finally, RT-PCR detected no PERV infection was found in the blood samples obtained from three patients at various times post-hemoperfusion.

CONCLUSION: The assays used are specific and sensitive, identified by second PCR. PERVs could be released from hepatocytes cultured in bioreactor without the stimulation of mitogen and could not be prevented by the hollow fiber semipermeable membrane, indicating the existence of PERV safety in extracorporeal bioartificial liver support system (EBLSS).

Auxiliary partial orthotopic living donor liver transplantation: Kyoto University experience

Auxiliary partial orthotopic liver transplantation (APOLT) was initially indicated as a potentially reversible fulminant hepatic failure and non-cirrhotic metabolic liver disease to compensate for enzyme deficiency without complete removal of the native liver. We expand our indication of APOLT for small-for-size grafts to support the function of implanted grafts during the early post-operative period, and for ABO-incompatibility to sustain a patient's life if the patient has a graft failure. We retrospectively reviewed 31 patients undergoing APOLT from living donor. The indication of APOLT was fulminant hepatic failure in 6, non-cirrhotic metabolic liver disease in 6, small-for-size grafts in 13 and ABO-incompatible cases in 6. The cumulative survival rate for APOLT at 1 and 5 years was 57.9% and 50.6%, and 78.8% and 73.8% for standard LDLT. None of the patients who underwent transplantation with APOLT for fulminant hepatic failure had long-term patient survival. The incidence of acute cellular rejection was higher in APOLT (58.1%) than standard LDLT (35.0%). Biliary complication was higher and the need for retransplantation was greater in APOLT than standard LDLT (p < 0.01). The results suggest that the indications of APOLT should be reconsidered in view of the risk for complications and retransplantation.

Establishment of a new pig model for auxiliary partial orthotopic liver transplantation

AIM: To establish a new pig model for auxiliary partial orthotopic liver transplantation (APOLT).

METHODS: The liver of the donor was removed from its body. The left lobe of the liver was resected in vivo and the right lobe was used as a graft. After the left lateral lobe of the recipient was resected, end-to-side anastomoses of suprahepatic inferior vena cava and portal vein were performed between the donor and recipient livers, respectively. End-to-end anastomoses were made between hepatic artery of graft and splenic artery of the host. Outside drainage was placed in donor common bile duct.

RESULTS: Models of APOLT were established in 5 pigs with a success rate of 80%. Color ultrasound examination showed an increase of blood flow of graft on 5^th d compared to the first day after operation. When animals were killed on the 5^th d after operation, thrombosis of hepatic vein (HV) and portal vein (PV) were not found. Histopathological examination of liver samples revealed evidence of damage with mild steatosis and sporadic necrotic hepatocytes and focal hepatic lobules structure disorganized in graft. Infiltration of inflammatory cells was mild in portal or central vein area. Hematologic laboratory values and blood chemical findings revealed that compared with group A (before transplantation), mean arterial pressure (MAP), central venous pressure (CVP), buffer base (BB), standard bicarbonate (SB) and K⁺ in group B (after portal vein was clamped) decreased (P<0.01). After reperfusion of the graft, MAP, CVP and K+ restored gradually.

CONCLUSION: Significant decrease of congestion in portal vein and shortened blocking time were obtained because of the application of in vitro veno-venous bypass during complete vascular clamping. This new procedure, with such advantages as simple vessel processing, quality anastomosis, less postoperative hemorrhage and higher success rate, effectively prevents ischemia reperfusion injury of the host liver and deserves to be spread.

Up-regulation of hepatocyte growth factor caused by an over-expression of transforming growth factor beta, in the rat model of fulminant hepatic failure

BACKGROUND

The role of transforming growth factor beta (TGF-beta), a potent regulator of cellular growth, was investigated in the rat model of fulminant hepatic failure (FHF).

MATERIALS AND METHODS

The rat FHF model was created by a combination of a 68% partial hepatectomy (PH) and 7% of necrosis (each n = 25 in Groups 1, 2 and 3). Adenovirus mediated gene transfer of mature human TGF-beta1 gene was performed by the systemic injection of AxCAhTGFb1 (1 x 10(9) pfu) in Group 1, 3 days before FHF. In control Groups 2 and 3, recombinant lacZ adenovirus (AxCAlacZ, Group 2) and normal saline (1 ml, Group 3) were used, instead of AxCAhTGFb1.

RESULTS

An excessive expression of TGF-beta1 in Group 1 resulted in an inhibition of hepatocyte proliferation (24-48 h after FHF) and gaining of liver weight (24-48 h), increased expression of HGF in liver tissue (24 h), and decreased expression of TGF-alpha (24 h), compared to those in control Groups 2 and 3. Serum IL-6 levels were also elevated by a TGF-beta1 over-expression at 24 hrs after FHF in Group 1.

CONCLUSIONS

The forced expression of TGF-beta1 in the FHF liver yields both a secondary increase of HGF production and a suppression of liver regeneration, which might explain the mechanism of increased serum HGF observed in a clinical FHF. TGF-beta1 is thus thought to have an important role in inhibiting liver regeneration after FHF.

Auxiliary partial orthotopic liver transplantation (APOLT) in the treatment of acute liver failure

BACKGROUND

Auxiliary partial orthotopic liver transplantation (APOLT) has been developed in order to benefit from the efficacy of orthotopic liver transplantation (OLT) in the treatment of fulminant hepatic failure (FHF), but to avoid the negative counterpart of OLT which is to eliminate the possibility of native liver (NL) regeneration and which consequently implies a life-long immunosuppression.

METHODS

In our institution we performed 16 consecutive APOLTs in 15 patients between October 1992 and December 1999. Patients' mean age was 30 years (range 0.5-65 years). The causes of FHF were viral (HAV = 3; HBV = 3), drugs (n = 4), or others (n = 5). None of the patients had a history of chronic liver disease. The decision to transplant was taken when the patients met well-defined criteria. All but one of the patients were in a coma.

RESULTS

Five patients died, 10 patients are alive (66.7%). Regeneration of the NL occurred in 11 of the 15 patients (73.3%) and in 8 of the 10 survivors. Six of these 8 patients have permanently stopped immunosuppressive therapy. These results can be favorably compared with those of OLT for FHF. In the European Transplant Registry, the survival rate is 57% at 5 years (2612 patients receiving OLT for FHF between 1988 and 1998). In our experience the survival rate is 59% at 5 years (42 patients receiving OLT for FHF between 1987 and 1999).

CONCLUSIONS

APOLT is feasible in both adults and children; it rapidly restored liver function and reversed encephalopathy. Right APOLT seems more advisable since the right liver provides more functional hepatocytes; however, left APOLT harvested in an adult appears sufficient for a child. APOLT should be proposed only to patients with high chances of liver regeneration: age of recipient, etiology of liver failure, interval between onset of jaundice and occurrence of encephalopathy, and quality of liver graft are early prognostic indicators. Better results have been observed with younger patients (less than 40 years old) presenting with FHF (rather than subfulminant hepatic failure (SHF)) and due to HAV, HBV, or paracetamol.

Auxiliary partial orthotopic liver transplantation for Crigler-Najjar syndrome type I

OBJECTIVE

To determine if auxiliary partial orthotopic liver transplantation (APOLT) has the long-term potential to correct the underlying abnormality in Crigler-Najjar syndrome type 1 (CNS1) without the need for total liver replacement.

BACKGROUND

Orthotopic liver transplantation has been used successfully to replace the defective enzyme in CNS1. Experimental studies have shown that only 1% to 2% of the normal hepatocyte mass is needed for bilirubin conjugation. If APOLT corrects the underlying metabolic abnormality, it has the advantage of preserving the native liver, which would serve as a "safety net" should the graft fail, and there is the potential for gene therapy in the future with possible withdrawal of immunosuppression.

METHODS

Seven APOLT procedures were performed in six recipients with CNS1. Median age at transplantation was 10.5 years. Six transplants were performed as a left auxiliary liver transplant, and one was performed as a right auxiliary liver transplant. Median serum bilirubin level at transplantation was 320 micromol/L. All patients required 12 to 16 hours of phototherapy daily before the transplant to maintain serum bilirubin levels between 250 and 350 micromol/L.

RESULTS

Median serum bilirubin level was 50 micromol/L at day 5 after the transplant and 23 micromol/L at a median follow-up of 32 months. In four children, early severe acute rejection developed, requiring conversion to tacrolimus; one underwent a second transplant for chronic rejection and graft atrophy but died from lymphoproliferative disease 6 months after the second transplant.

CONCLUSIONS

This report shows that APOLT is technically feasible and provides adequate hepatocyte mass to correct the underlying metabolic abnormality in CNS1.