Takehiko Uesugi

in Vitro Evaluation of Metabolic Functions of a Bioartificial Liver

The purpose of this study is to develop a bioartificial liver (BAL) with such a simple structure that it can be prepared within several hours and through which whole blood can be perfused as in current hemodialyzers. Hepatocytes were isolated from 37 pigs; each liver weighed 300 to 400 g. The average yield of hepatocytes was 2.4 +/- 0.6 x 10(10) cells per liver, with a cell viability of 89.6 +/- 3.9%. To prepare a BAL device, a cartridge, composed of hollow fibers made of cellulose diacetate was used. Nominal cut-off molecular weight of the hollow fibers was 68 kDa, and the internal diameter was 195 microm. One hundred milliliters of hepatocyte suspension, containing 1 x 10(10) cells, was inoculated into the inner space of the hollow fibers, and both the inlet and outlet of the hollow fiber cartridge were closed. It took only 3 hrs from administration of the pigs anesthesia to the start of an in vitro evaluation of the prepared BAL device. To evaluate the functions of this BAL quantitatively, using a pharmacokinetic method, a mixture of fresh human blood and Dulbeccos modified Eagle medium was circulated in the shell space of the hollow fibers at 200 ml/min. Chemicals (lidocaine, ammonia, and galactose) were then loaded into the perfusion medium. The average intrinsic clearance of the BAL device was found to be 46 ml/min for lidocaine and 8.8 ml/min for ammonia. The galactose elimination capacity of the BAL device was 1.34 mg/min. The metabolic function of the BAL device decreased by 81%, 49%, and 64% of the initial function for lidocaine, ammonia, and galactose, respectively, after 10 days of in vitro circulation.

Humoral injury in porcine livers perfused with human whole blood

BACKGROUND We investigated the influence of humoral injury during xenoperfusion of porcine livers by human blood. METHODS The porcine livers were perfused under physiological conditions for 9 hr. The perfusates consisted of porcine whole blood in group 1, human whole blood in group 2, and human whole blood with soluble complement receptor type 1 (300 microg/ml) in group 3. RESULTS Liver enzyme release and serum hemoglobin in group 2 increased significantly after 3 hr of xenoperfusion, compared with those in group 1 and group 3 (P<0.05). Severe histological damage with minimal cellular infiltration was observed in group 2 after 6 hr of xenoperfusion, but was present only at trace levels in group 1 and group 3. In group 2, von Willebrand factor, a possible target of natural antibodies, was induced on sinusoidal endothelial cells after 3 hr of xenoperfusion, correlating with diffuse deposition of human IgM and membrane attack complex. In group 3, von Willebrand factor, human IgM, and membrane attack complex staining in the intralobular region were present at trace levels. In group 3, the indocyanine green removal capacity, representing hepatocyte function, was significantly higher than in group 2 (P<0.05). CONCLUSIONS Based on these results, we suggest that humoral injury is a major cause of liver damage during liver xenoperfusion. The pattern of humoral injury in xenoperfused livers may be attributed to anatomical features of the liver and unique responses of sinusoidal endothelial cells to xenoperfusion.

Effectiveness of Endoscopic Nasobiliary Drainage for Postoperative Bile Leakage after Hepatic Resection

The effectiveness of endoscopic nasobiliary drainage (ENBD) for postoperative bile leakage after hepatic resection was investigated retrospectively. Between 1997 and 2002 a series of 486 hepatectomies without biliary reconstruction were performed. Bile leakage was divided into two categories. Type A was defined as bile leakage communicating with the main bile tree fistulographically or endoscopic cholangiographically, and type B was bile leakage without such a patency of bile flow. Bile leakage developed in 31 patients (6.4%) (types A/B = 16/15). Type A frequently occurred at the major Glisson’s sheath. In contrast, most type B cases occurred at the peripheral bile duct at the cut surface of the liver. Among the type A patients, 10 of 11 were effectively treated with ENBD. For the type B patients, 12 of 15 patients were successfully treated with intraabdominal drainage via surgical drains inserted during the operation or percutaneous tubes newly inserted for biliary fluid collection. ENBD was effective in two of three type B patients. The duration of bile leakage significantly shortened after initiation of ENBD in type A patients (15.3 ± 6.9 vs. 25.8 ± 13.2 days, p < 0.05). The classification based on communication with the main bile tree is useful for determining therapeutic strategy. Type A leakage has a good indication for ENBD, whereas type B can be treated with intraabdominal drainage in most cases, although ENBD may be effective in some intractable type B cases. It is preferable to initiate ENBD as early as possible to shorten the duration of bile leakage and the subsequent hospital stay.

Evaluation of ammonia and lidocaine clearance, and galactose elimination capacity of xenoperfused pig livers using a pharmacokinetic analysis.

BACKGROUND We introduced the pharmacokinetic method into the functional evaluation of xenogeneic extracorporeal liver perfusion as an artificial liver assist device, and examined the influence of xenogeneic humoral injury on the metabolic function of xenoperfused pig livers. METHODS Isolated pig livers were perfused with fresh porcine blood (group 1; n=5) or fresh human blood (group 2; n=5) for 9 hr. Clearance (CL) of ammonia and lidocaine, and galactose elimination capacity (Vmax) were determined at three points during the perfusion using a one-compartment pharmacokinetic model. RESULTS Concentrations of ammonia and lidocaine decreased exponentially and those of galactose decreased linearly after a bolus injection in both groups. A one-compartment model provided satisfactory curve fittings for these test substances. No decreases of ammonia CL, lidocaine CL, or galactose Vmax were observed until 9 hr in either group. No differences were observed between the two groups with respect to these metabolic functions. In group 1, only slight interlobular edema was observed at 9 hr. In group 2, membrane attack complex was diffusely deposited at 3 hr and severe interlobular damage was histologically observed at 9 hr, although hepatocellular damage was minimal even at 9 hr. Alpha glutathione S-transferase and mitochondrial aspartate aminotransferase were comparable between the two groups. CONCLUSIONS Pharmacokinetic analysis allowed the evaluation of ammonia CL, lidocaine CL, and galactose Vmax of the perfused pig livers. Despite xenogeneic humoral injuries, the xenoperfused livers maintained these metabolic functions at the same levels as the alloperfused livers for 9 hr.

The protective role of Kupffer cells in humoral injury of xenoperfused rat livers

BACKGROUND The role of Kupffer cells in a hepatic xenograft rejection is still unclear. We investigated the effect of blocking Kupffer cells on xenogeneic humoral injury using rat livers as the xenoperfusion models. METHODS Rat livers were perfused with fresh human blood after pretreatment either with normal saline (group 1; n = 8) or with gadolinium chloride (GdCl3) solution (group 2; n = 8). Tissue injury was evaluated by alanine aminotransferase release and histological examination. Tumor necrosis factor-alpha (TNF-alpha) production from rat livers was measured by enzyme-linked immunosorbent assay and also examined by immunohistochemistry. In addition, Kupffer cells were isolated after pretreatment either with normal saline or with GdCl3 solution and incubated with human serum. Localization of human C3 and IgM was examined by immunofluorescence. RESULTS Alanine aminotransferase release in group 2 was significantly higher than in group 1 (P = 0.015). Histological examination revealed more severe tissue injury in group 2. The mean TNF-alpha level was not significantly different between the two groups. In immunohistochemistry, TNF-alpha was positive primarily on vascular endothelial cells in both groups. Immunofluorescence of saline-treated Kupffer cells showed an uptake of human C3 in the cytoplasm, whereas no uptake was observed in GdCl3-treated cells. The uptake of human IgM did not differ between the two groups. CONCLUSIONS These results suggest that Kupffer cells have a protective role in preventing xenogeneic humoral injury. Their ability to absorb xenogeneic complements may contribute to this protective mechanism.

Method for evaluating metabolic functions of drugs in bioartificial liver

Lidocaine and galactose loading tests were performed on a bioartificial liver (BAL), an extracorporeal medical device incorporating living hepatocytes in a cartridge without a transport barrier across the membranes. The concentration changes were analyzed using pharmacokinetic equations to evaluate the efficacy and limitation of the proposed method. Lidocaine and galactose were found to be suitable drugs for a quantitative evaluation of the BAL functions, as they did not interact with the plasma proteins or blood vessels, making their concentrations easy to determine. The drug concentration changes after drug loading were easily analyzed using pharmacokinetic equations, and the BAL functions quantitatively expressed by pharmacokinetic parameters, such as the clearance (CL) and galactose elimination capacity (GEC). In addition, these two drugs have already been used in clinical tests to evaluate human liver functions over long periods, and lidocaineCL values andGEC values reported for a normal human liver. Thus, a comparison of theCL andGEC values for theBAL and a natural liver revealed what proportion of normal liver functions could be replaced by the BAL.

In vitro evaluation method of bioartificial liver function : constant infusion test

Abstract Various types of bioartificial livers (BALs), which are extracorporeal medical devices incorporating living hepatocytes in cartridges, have been developed. However, it is difficult to compare metabolic functions among BAL types or to know what proportion of the normal liver functions could be replaced by a BAL, because there is not a well-established method for the quantitative evaluation of BAL functions. In our series of studies, we have proposed methods for performing drug-loading tests and procedures to analyze drug concentration changes for the quantitative evaluation and expression of BAL metabolic functions. In this study, constant infusion tests of lidocaine were performed on a BAL device developed in our laboratory, and lidocaine concentration changes in the perfusion medium were analyzed by using pharmacokinetic equations. The lidocaine clearance value of the BAL was precisely determined by a constant infusion test, demonstrating the usefulness of the constant infusion test for quantitative evaluation of BAL functions.