P. Neuhaus

Normalised intrinsic mortality risk in liver transplantation: European Liver Transplant Registry study

BACKGROUND No model exists for liver transplantation to estimate the mortality risk in a given patient, and no standard by which to assess performance in different centres. We investigated the intrinsic mortality risk in the absence of known mortality risk factors. METHODS We identified mortality risk factors and risk ratios quantified in data from the European Liver Transplant Registry (22,089 patients at 102 centres in 18 countries) registered from 1988 to 1997. To develop a model of the intrinsic risk and the risk ratios for specific factors, univariate and multivariate analyses were done separately for the overall population, for adults, and for children younger than 15 years, and the number of deaths were estimated. We validated the model by comparing mortality in patients without risk factors with the model-adjusted mortality in patients with risk factors. FINDINGS Overall 5-year and 8-year actuarial survival was 66% (95% CI 65-66) and 61% (60-62). 65% of deaths occurred within 6 months. Retransplantation, transplantation for cancer, acute liver failure, fewer than 20 split-liver grafts per year, and a centre workload of fewer than 25 transplants per year were the main risk factors of 12 identified factors. 1-year and 5-year death rates among adults with no risk factors were similar to model estimates (15 [13-16] vs 14% [13-15], and 22 (20-24) vs 23% [21-24]). Corresponding data for paediatric transplants were 9% (7-12) compared with 11% (9-12) and 13% (10-17) compared with 14% (11-16). The reduction of mortality risk in high-volume centres was even greater in patients without risk factors (48 vs 23%, p<0.001). INTERPRETATION The normalised intrinsic mortality risk can be combined with the relative risk ratios of known risk factors to better estimate the mortality risk of a given procedure in a given patient. Centres can assess performance by removing potential bias of donor and recipient selection.

Methylprednisolone therapy in deceased donors reduces inflammation in the donor liver and improves outcome after liver transplantation: a prospective randomized controlled trial.

Objective:To investigate potential beneficial effects of donor treatment with methylprednisolone on organ function and outcome after liver transplantation. Summary Background Data:It is proven experimentally and clinically that the brain death of the donor leads to increased levels of inflammatory cytokines and is followed by an intensified ischemia/reperfusion injury after organ transplantation. In experiments, donor treatment with steroids successfully diminished these effects and led to better organ function after transplantation. Methods:To investigate whether methylprednisolone treatment of the deceased donor is applicable to attenuate brain death-associated damage in clinical liver transplantation we conducted a prospective randomized treatment-versus-control study in 100 deceased donors. Donor treatment (n = 50) consisted of 250 mg methylprednisolone at the time of consent for organ donation and a subsequent infusion of 100 mg/h until recovery of organs. A liver biopsy was taken immediately after laparotomy and blood samples were obtained after brain death diagnosis and before organ recovery. Cytokines were assessed by real-time reverse transcriptase-polymerase chain reaction. Soluble serum cytokines were measured by cytometric bead array system. Results:After methylprednisolone treatment, steroid plasma levels were significantly higher (P < 0.05), and a significant decrease in soluble interleukins, monocyte chemotactic protein-1, interleukin-2, interleukin-6, tumor necrosis factor-&agr;, and inducible protein-10 was observed. Methylprednisolone treatment resulted in a significant downregulation of intercellular adhesion molecule-1, tumor necrosis factor-&agr;, major histocompatibility complex class II, Fas-ligand, inducible protein-10, and CD68 intragraft mRNA expression. Significantly ameliorated ischemia/reperfusion injury in the posttransplant course was accompanied by a decreased incidence of acute rejection. Conclusions:Our present study verifies the protective effect of methylprednisolone treatment in deceased donor liver transplantation, suggesting it as a potential therapeutical approach.

Hepatocyte culture between three dimensionally arranged biomatrix-coated independent artificial capillary systems and sinusoidal endothelial cell co-culture compartments.

Freshly isolated parenchymal liver cells, the hepatocytes, retain many of the metabolic activities of the tissue in vivo. As isolated cells, they are generally in a catabolic stage and therefore care is essential in fully maintaining their activity. Bioreactors are in development to address this problem. Since they enable an upscale of hepatocyte in vitro culture, they could be used as the main device in hybrid liver support systems. A basic problem in the development of special bioreactors for such systems is that with current techniques of hepatocyte culture, external hepatocyte function in vitro is limited to only a few weeks. In the majority of recently developed culture models for bioreactors, substrate exchange to the hepatocytes is performed by diffusion. This brings a remarkable change in the local situation for the cells in comparison to the in vivo situation. Even the gradients of oxygen and carbon dioxide, as well as the gradients of metabolites are not sufficiently considered in current culture models. An organisation of hepatocytes along such gradients is therefore ruled out, which impairs the typical metabolic function of hepatocytes dependent on their localisation in the sinusoid. A bioreactor concepts, which will allow the cells to operate under physiological flow conditions, may result in a macro environment more similar to the physiological situation. We have recently developed a culture model together with a newly developed bioreactor construction, which address this problem. This model has the following characteristics: perfusion of the cells between independent capillary membrane systems; identical units (Fig. 1) for few hepatocytes in parallel, analog to the liver lobuli; decentral metabolite inand outflow with low gradients; decentral oxygen supply and carbon dioxide removal with low gradients; cell adhesion on hepatocyte membranes coated with biomatrix and aggregation between the capillaries; co-culture compartment for sinusoidal endothelial cells; possibility of upscaling the construction to a large cell mass bioreactor for therapeutic liver support; possibility of further capillary functions, such as dialysis and heat-exchange for DMSO-freezing of the reactor with the cells. In several studies (1 ), this culture model has been investigated over a period of three weeks. With the present report, the initial results of a long-term study over seven weeks are described.

What can be learned from brain‐death models?

Brain death of the donor is an important risk factor influencing graft outcome. In addition to its nonspecific effects, it potentiates graft immunogenicity and increases host alloresponsiveness. Thus brain death in addition to other unspecific injuries such as organ procurement, preservation and consequences of ischemia/reperfusion injury, contributes towards the change of an inert organ to an immunological altered graft. Prior to engraftment, brain death initiates a cascade of molecular and cellular events including the release of proinflammatory mediators leading to cellular infiltrates. Those events may affect the incidence of both acute and chronic changes, developing and contributing to reduced graft survival. Consequently, strategies to reduce the immunogenicity or the pro‐inflammatory status of the graft are becoming more attractive and might even help to improve organ quality and graft function.

Hybrid liver support system in a short term application on hepatectomized pigs.

A short term application of a hybrid liver support system in circuits with continuous plasma-separation was investigated in a model of hepatectomized pigs under general anesthesia. Primary pig hepatocytes were immobilized in a bioreactor with three independent capillary systems. An immune barrier is achieved by avoiding the direct contact of blood cells with the hepatocytes by a plasmaseparation step and by an outflow filtration within the reactor. In three groups (hepatectomized pigs and system with- or without hepatocytes as well as untreated pigs with system without hepatocytes), the short term metabolism of the reactors was positively demonstrated by investigating ammonia detoxification, phenylalanine- and lactate metabolism. Limitations of the presented model are discussed.

Nephrotoxicity after orthotopic liver transplantation in cyclosporin A and FK 506-treated patients

Abstract Neurotoxicity is a serious complication following orthotopic liver transplantation leading to increased morbidity and mortality. Neurotoxicity may be evoked by various perioperative factors, or may be due to drug‐pecific toxicity of immunosuppression. In the present study we evaluated the incidence of central nervous system (CNS) toxicity occurring within the early postoperative period of 121 patients, 61 randomly assigned to FK 506‐ and 60 to CsA‐based immunosuppression as part of a multicentre study. The incidence of moderate or severe CNS toxicity was higher in patients treated with FK 506 (21.3%) than in patients receiving CsA (11.7%). The duration of symptoms was also greater in patients treated with FK 506 than in patients receiving CsA. The incidence of moderate or severe neurotoxicity after retransplantation was markedly greater in patients treated with FK 506 (100% of the patients).

Three-year follow-up of the European Multicenter Tacrolimus (FK506) Liver Study

Abstract TACROLIMUS was initially administered to liver transplant recipients as primary immunosuppressive therapy in conjuction with low-dose steroids at the University of Pittsburgh in 1989. Initial results indicated that tacrolimus was associated with significant improvements in patient and graft survival rates when compared with cyclosporine (CyA)-treated historical controls.1,2 Treatment with tacrolimus also resulted in marked reductions in the incidence of rejection and steroid requirements.2 Subsequently, two international, multicenter, prospectively-randomized, parallel-group trials were initiated (one in Europe and one in the United States) to evaluate and compare the efficacy and safety of tacrolimus- and CyA-based therapy. Results at 6,3–9 12,10–15 and 24 months16–18 have been published previously. This report addresses the continued follow-up of the European study with attention now focusing on 3-year data.

Extracorporeal liver perfusion: applications of an improved model for experimental studies of the liver.

Long-term extracorporeal liver perfusion of up to 24 hours was achieved with an improved model of pig liver perfusion. Functional and structural integrity of the extracorporeal liver was maintained during the entire duration of extracorporeal perfusion. After 24 hours SGOT was 33.5 (± 6.5) U/L, bile production was 11.5 ml/h. Survival of hepatectomized pigs could be extended to 18.9 (± 3.8) hours with extracorporeal liver perfusion (p < 0.01). The improvement of liver perfusion in our particular model is primarily based on optimised perfusion of the low pressure system of the portal and hepatic vein by the application of sinusoidal pressure profiles. These pressure profiles imitate intra-abdominal conditions and achieve homogeneous perfusion of the low pressure system of the portal vein and complete drainage of hepatic venous blood.

Neurological complications in the European multicentre study of FK 506 and cyclosporin in primary liver transplantation.

Abstract Neurological complications were examined in a multi‐centre, randomized, parallel‐group study of 545 patients undergoing primary liver transplantation to compare the efficacy and safety of FK 506‐ and cyclosporin A‐based immunosuppressive regimens (CBIR). In an additional analysis, patients were divided into early and late randomized cohorts to detect the influence of protocol amendements that allowed for FK 506 dose reductions. Initial follow‐up was for 6 months. Tremor, headache and insomnia were the most frequently reported adverse events involving the neurological system. Whereas these neurological symptoms were observed significantly more often in FK 506‐treated patients (P < 0.05 vs. CsA for the overall population), this was no longer the case for the late FK 506 and CBIR cohorts. The risk of FK 506‐treated patients developing tremor was related to the initial i. v. dose, the rate of administration of the i.v. dose and the daily dose (P < 0.01). Headache was significantly correlated with the FK 506 dose (P < 0.05), and insomnia was not related to any dosing variable. Major neurological symptoms, including psychosis, convulsion, coma, aphasia and intracranial haemorrhage, were reported with a low frequency (0.4–5.2%), and differences between both treatment groups were neither significant for the overall population nor for the early and late cohorts of FK 506 and CBIR. Data from the late cohorts showed no differences in the overall incidence of neurological adverse events between FK 506‐and CBIR‐treated patients.

Hepatocyte aggregate culture technique for bioreactors in hybrid liver support systems.

Utilizing a modified culture technique for hepatocytes, a high performance suspension culture is possible in which hepatocytes spontaneously form cell aggregates. The aggregates of 20-100 cells have been histologically confirmed to hold a three-dimensional structure, they show a long-term external metabolism and a survival time comparable with standard adhesion cultures. This technique has several advantages in the construction of large scale bioreactors for hybrid liver support systems.