[Extended donor criteria defined by the German Medical Association : study on their usefulness as prognostic model for early outcome after liver transplantation]

Einleitung

Die Expansion des Spenderpools durch die Verwendung von Spenderorganen, die erweiterte Spenderkriterien erfüllen, verringert die Wartelistenmortalität mit einem erhöhten Risiko für das Patienten- und Transplantatüberleben nach Lebertransplantation. Die Eignung der Anzahl der erfüllten erweiterten Spenderkriterien nach der aktuellen Definition der Bundesärztekammer (BÄK-Score) für die Voraussage der frühen Ergebnisse nach Lebertransplantation ist unbekannt.

Patientenkollektiv

Untersucht wurden 257 erwachsene Empfänger, die zwischen dem 01.01.2007 und dem 31.12.2010 insgesamt 291 konsekutive Lebertransplantate erhielten.

Methoden

Primäre Studienendpunkte waren die 30-Tage-Mortalität, 3-Monats-Mortalität, das 3-Monats-Patientenüberleben, 3-Monats-Transplantatüberleben und die Notwendigkeit einer akuten Retransplantation innerhalb von 30 Tagen. Der BÄK-Score wurde als prognostisches Modell mit der ROC-Kurven-Analyse mit Bestimmung der Sensitivität, Spezifität und Gesamtmodellkorrektheit des Modells für die Voraussage der primären Studienendpunkte untersucht. Weiterhin wurden Kaplan-Meier-Überlebensanalysen, Log-Rank-Tests, Cox-Regressionsanalysen, logistische Regressionen und χ²-Tests durchgeführt.

Ergebnisse

Die Anzahl der erfüllten erweiterten Spenderkriterien hatte keinen signifikanten Einfluss auf die primären Studienendpunkte (p > 0,05) und das Patientenüberleben (p > 0,05). Die ROC-Kurven-Analyse zeigte für die Voraussage der primären Studienendpunkte Flächen ≤ 0,561 mit einer Gesamtkorrektheit des Modells < 58% bei einer Sensitivität < 52%.

Schlussfolgerung

Die Anzahl der erfüllten erweiterten Spenderkriterien nach der aktuellen Definition der Bundesärztekammer kann die frühe Prognose innerhalb der ersten 3 Monate nach Lebertransplantation als prognostisches Modell nicht voraussagen.

Fabrication and characterization of an electrically contacted vapor cell

We demonstrate the use of electrically contacted vapor cells to switch the transmission of a probe laser. The excitation scheme makes use of electromagnetically induced transparency involving a Rydberg state. The cell fabrication technique involves thin-film-based electric feedthroughs, which are well suited for scaling this concept to many addressable pixels like in flat panel displays.

[Surgical and interventional treatment of liver metastases]

The liver is the most common target organ for metastatic disease. The majority of patients undergoing surgical treatment for liver metastases have colorectal primaries. Endocrine liver metastases, or metastases from other tumors such as mammary carcinoma, sarcomas, renal tumors or gastrointestinal stromal tumors (GIST) are appreciably less common for surgical treatment. The gold standard of treatment is resection of the metastatic lesions. In the meantime, advances in surgical techniques and improved perioperative patient management make it possible to perform extensive resections with acceptable morbidity and mortality rates. In the event of metastases that are not primarily resectable, various downstaging procedures are available, with the aid of which secondary resectability can be achieved. Among the interventional treatment options that should be applied only in palliative intent, radiofrequency ablation is in widespread use.

[Surgical therapy of hepatocellular carcinoma]

Hepatocellular carcinoma (HCC) accounts for most primary malignancies of the liver. The most important risk factor is liver cirrhosis. HCC can be traced by the tumor marker alpha-fetoprotein. Patients with a known liver cirrhosis should regularly be screened, including sonography and alpha-fetoprotein evaluation. Surgical therapy - either partial liver resection or liver transplantation - is the only treatment that can potentially achieve long-term survival. The presence of liver cirrhosis is likely to induce postoperative liver insufficiency and is associated with higher local tumor recurrence rate. Patients without liver cirrhosis or Child-Pugh A patients with tumors smaller than 5 cm may be considered as the ideal target group for resection. For more advanced stages of cirrhosis and tumors of less than 5 cm up to 7 cm in size, liver transplantation offers a better prognosis. Long waiting time for a suitable organ negatively influences liver transplantation outcome. Living donor liver transplantation is a novel therapeutic option that improves posttransplant survival and extends the indication for transplantation in hepatocellular carcinoma.

Hepatic metastases from leiomyosarcoma: A single-center experience with 34 liver resections during a 15-year period

OBJECTIVE

To describe a large single-center experience with hepatic resection for metastatic leiomyosarcoma.

SUMMARY BACKGROUND DATA

Liver resection is the treatment of choice for hepatic metastases from colorectal carcinoma. In contrast, the role of liver resection for hepatic metastases from leiomyosarcoma has not been defined.

METHODS

The records of 26 patients who between 1982 and 1996 underwent a total of 34 liver resections for hepatic metastases from leiomyosarcoma were reviewed. There were 23 first, 9 second, and 2 third liver resections. The records were analyzed with regard to survival and predictive factors.

RESULTS

In the 23 first liver resections, there were 15 R0, 3 R1, and 5 R2 resections. Median survival was 32 months after R0 resection and 20.5 months after R1/2 resection. The 5-year survival rate was 13% for all patients and 20% after R0 resection. In 10 patients with extrahepatic tumor at the time of the first liver resection, 6 R0 and 4 R2 resections were achieved. After R0 resection, the median survival was 40 months (range 5-84 months), with a 5-year survival rate of 33%. After repeat liver resection, the median survival was 31 months (range 5-51 months); after R0 resection, median survival was 31 months and after R1/2 resection it was 28 months. There was no 5-year survivor in the overall group after repeat liver resection.

CONCLUSIONS

Despite frequent tumor recurrence, the long-term outcome after liver resection for hepatic metastases from leiomyosarcoma is superior to that after chemotherapy and chemoembolization. Although survival after tumor debulking also seems to be more favorable than after nonoperative therapy, these data indicate that only an R0 resection offers the chance of long-term survival. The presence of extrahepatic tumor should not be considered a contraindication to liver resection if complete removal of all tumorous masses appears possible. In selected cases of intrahepatic tumor recurrence, even repeated liver resection might be worthwhile. In view of the poor results of chemoembolization and chemotherapy in hepatic metastases from leiomyosarcoma, liver resection should be attempted whenever possible.

Enhanced oxygen delivery reverses anaerobic metabolic states in prolonged sandwich rat hepatocyte culture

It must be assumed that current petri dish primary hepatocyte culture models do not supply sufficient amounts of oxygen and thus cause anaerobic metabolism of the cells. This is contrary to the physiologic state of the cells. In vivo the liver is a highly vascularized organ with a rather high blood flow rate of a mixture of arterial and venous blood. The aim of the present study was to show the oxygen dependence of primary rat hepatocytes in long-term culture and to define appropriate conditions that could allow hepatocytes to maintain tissue specific functions in an aerobic environment. To this purpose matrix overlaid hepatocytes were either cultured on gas-permeable (fluorinated hydrocarbon films) or gas-impermeable (polystyrene) supports at 10% and 20% ambient oxygen concentration (v/v), respectively. Tissue-specific functions were assessed by studying albumin and urea secretion as well as xenobiotic metabolism. The mRNA expression and catalytic activities of the cytoprotective antioxidant enzymes mitochondrial manganese superoxide dismutase (MnSOD), cytosolic copper and zinc superoxide dismutase, peroxisomal catalase, and cytosolic glutathione peroxidase were investigated to assess intracellular responses to the defined variations in oxygen supply. Hepatocytes could successfully be maintained at aerobic conditions in long-term culture on gas-permeable PTFE films. At 50% (10%, v/v) of currently used oxygen levels lactate accumulation was prevented, a plateau-like albumin secretion reestablished, urea secretion improved, and xenobiotic metabolism proceeded at physiological rates. mRNA expression of cytoprotective enzymes responded to the pericellular availability of oxygen and was most pronounced in the case of MnSOD. However, the biggest stress factor for the hepatocytes still appeared to be the isolation procedure, as mRNA expression and catalytic activities were most elevated shortly thereafter. In conclusion, this study clearly shows the oxygen dependence of primary rat hepatocytes in long-term culture and indicates means to establish appropriate conditions for the aerobic culture of primary rat sandwich hepatocytes with full maintenance of function. The long-term culture of hepatocytes on oxygenating supports at in vivo-like oxygen tensions therefore appears to be more physiologic and beneficial for the cells.

Development of a small-scale bioreactor for drug metabolism studies maintaining hepatospecific functions

1. The aim of the study was the development of a small-scale liver cell bioreactor maintaining tissue monoxygenase activity and hepatospecific activities over at least 2 weeks. 2. For characterization the antihypertensive drug urapidil was used as a model compound to study maintenance of metabolic activity. Tissue-specific parameters assessed included urea and albumin secretion as well as cellular integrity. The problem of the use of serum in bioreactor cultures is addressed. 3. Bioreactor runs could be performed in serum- and lactate-free cultures with a joint recovery of oxidative biotransformation capacity for urapidil as well as tissue-specific markers. LDH release was reduced with older cultures. Fibronectin was shown as a contributing factor for cell attachment. 4. In the present study the design and function of a modular, small-scale-type bioartificial liver cell culture model is thus described lending itself for drug metabolism studies but maintaining also typical hepatospecific properties.

3-D coculture of hepatic sinusoidal cells with primary hepatocytes-design of an organotypical model

Models for cocultures of parenchymal (PC) and nonparenchymal cells (NPC) of the liver relied on mixing the cells in a two-dimensional configuration or on establishing spheroidal aggregates. In vivo hepatic nonparenchymal cells, such as endothelial cells and Kupffer cells, are separated from parenchymal cells by extracellular matrix (ECM). Due to their location outside of the space of Disse they can form a barrier toward the sinusoid. Hepatocytes are attached to ECM of the space of Disse via two opposing sinusoidal surfaces. No three-dimensional coculture model reflecting this specific microenvironment of the liver cell plates in vivo has been available to date. We designed a three-dimensional model by positioning NPC on top of PC enclosed as a monolayer within a collagen sandwich. A gas-permeable membrane support can be used to allow the supply of oxygen to the resulting cell plate also from underneath the cell layers. Morphological analysis was performed by inverse and cross-sectional studies by light microscopy, scanning, and transmission electron microscopy of the coculture model. Cuboidal hepatocytes formed confluent layers below the NPC layer. They regularly expressed bile canaliculi at intercellular contact zones. Both sinusoidal surfaces expressed microprojections. Characteristic NPC including endothelial cells, Kupffer cells, and Ito cells completely covered the second matrix layer within a week. Kupffer cells were located on top of endothelial cells. Ito cells were intermingled and could be identified by their intracytoplasmic lipid droplets. LPS stimulation of cocultures resulted in a depression of albumin secretion. Phase I and phase II metabolites of the cytochrome P-450 1A1 substrate ethoxyresorufin were generated independently from the presence of cocultured NPC. This study describes the development of a novel three-dimensional coculture model, which intends to mimic more closely the microenvironment of the hepatic sinusoid by respecting the specific plate structure of the liver parenchyma. The model could serve as a complex tool to study potential collaborations between PC and NPC of the liver.

Tacrolimus (FK 506) biotransformation in primary rat hepatocytes depends on extracellular matrix geometry

Established in vitro models for studies of hepatic drug biotransformation include the use of primary hepatocytes. In normal liver the space of Disse provides the possibility of bilateral attachment to extracellular matrix for each hepatocyte. This configuration is disrupted by the cell isolation procedure of normal liver tissue, which delivers suspensions of round shaped cells. In standard culture configurations this unphysiologic cell shape terminates in a morphological dedifferentiation and inability to biotransform drugs. This study analyses the relevance of extracellular matrix geometry in hepatocyte monolayer configurations for expression and activity of cytochrome P450 3A. This enzyme is involved in the biotransformation of a large number of pharmaceuticals including the immunosuppressants tacrolimus and sirolimus. Morphological analysis of primary rat hepatocytes cultured with and without overlay of collagen type I was performed by transmission and scanning electron microscopy. Expression and activity of cytochrome P450 3A was studied by Western blot and the use of two model drugs specific for this enzyme. To this purpose the immunosuppressive drugs tacrolimus and sirolimus were used. Metabolites were analyzed by HPLC and HPLC/MS. Two sided attachment to extracellular matrix induces profound changes of the hepatocellular morphology in vitro resulting in the reconstitution of a polyhedric cell shape. This phenomenon is paralleled by an enhanced expression of cytochrome P450 3A and corresponding metabolic activity. As shown for tacrolimus biotransformation, the model may be useful to study complex metabolic patterns. In addition this model may facilitate studies of the kinetics of hepatocellular drug biotransformation in a setting with prolonged stability.

Reconstruction of liver tissue in vitro: geometry of characteristic flat bed, hollow fiber, and spouted bed bioreactors with reference to the in vivo liver

Bioreactors currently being developed for hybrid artificial livers vary greatly with respect to their microenvironment. The specific architecture modifies the relationship parenchymal and nonparenchymal cells have with the exchange surfaces of the bioreactor. Most designs are either based on hollow fiber, spouted bed, or flat bed devices. This diversity is contrasted by the uniform and unique organization of the in vivo liver. The liver cells are arranged as plates and both sinusoidal surfaces of the hepatocytes are enclosed within the matrix of the space of Disse. In this study we intended to define the in vivo liver tissue characteristics in a manner useful for an organotypical approach to hepatic tissue engineering. Transmission electron microscopy of an in vivo liver was utilized to describe these ratios. The ratios defined in this study are based on the constant hepatocellular expression of two sinusoidal surfaces. A relationship is established between the expression of the sinusoidal surfaces and their use as attachment and exchange surfaces inside a bioreactor. The presence of biliary surfaces and nonparenchymal cell surfaces is compared. The functional relevance of an in vivo like extracellular matrix geometry for oxidative biotransformation of primary hepatocytes in vitro was studied using the two model drugs cyclosporin and rapamycin. The generation of the hydroxylated cyclosporin metabolites AM 9 and AM 1 and four rapamycin metabolites was analyzed by high performance liquid chromatography (HPLC). It is shown that the cell-specific biotransformation rates at 1 week in culture in matrix overlayed hepatocytes was 5-10 times that of hepatocytes without matrix overlay. Bilaminar membrane (BLM) bioreactors were used to reconstruct extracellular matrix geometry, three-dimensional cell plates, and sinusoidal analogs in between cell plates.

A novel bioreactor design for in vitro reconstruction of in vivo liver characteristics

We have constructed a bioreactor aimed at imitating the three-dimensional micro- and macroenvironment of the liver. In vivo hepatocytes are arranged in plates of cell monolayers and are specifically attached with both sinusoidal surfaces to the space of Disse which contains extracellular matrix. Nonparenchymal cells are located on the other side of the space of Disse toward the sinusoid. For supporting monolayer hepatocytes with bipolar attachment to the extracellular matrix, we used a double gel culture technique that sandwiches hepatocytes between two layers of collagen. In double gel cultures, albumin production increases during an adaptive period to the in vitro environment. In contrast to conventional single gel hepatocytes, double gel hepatocytes maintain expression of sinusoidal microvilli and a polyhedric cell shape in culture as seen by transmission electron microscopy. Albumin production in the bioreactor was stable. The organotypical bioreactor concept is an example of organ mimicry and may provide the basis for the organ-otypical development of a full-sized hybrid artificial liver.