Effects of a bioartificial liver support system on acetaminophen induced acute liver failure canines

Model of Acute Liver Failure in an Isolated Perfused Porcine Liver-Challenges and Lessons Learned

Acute liver failure (ALF) is a rare but devastating disease associated with substantial morbidity and a mortality rate of almost 45%. Medical treatments, apart from supportive care, are limited and liver transplantation may be the only rescue option. Large animal models, which most closely represent human disease, can be logistically and technically cumbersome, expensive and pose ethical challenges. The development of isolated organ perfusion technologies, originally intended for preservation before transplantation, offers a new platform for experimental models of liver disease, such as ALF. In this study, female domestic swine underwent hepatectomy, followed by perfusion of the isolated liver on a normothermic machine perfusion device. Five control livers were perfused for 24 h at 37 °C, while receiving supplemental oxygen and nutrition. Six livers received toxic doses of acetaminophen given over 12 h, titrated to methemoglobin levels. Perfusate was sampled every 4 h for measurement of biochemical markers of injury (e.g., aspartate aminotransferase [AST], alanine aminotransferase [ALT]). Liver biopsies were taken at the beginning, middle, and end of perfusion for histological assessment. Acetaminophen-treated livers received a median dose of 8.93 g (8.21–9.75 g) of acetaminophen, achieving a peak acetaminophen level of 3780 µmol/L (3189–3913 µmol/L). Peak values of ALT (76 vs. 105 U/L; p = 0.429) and AST (3576 vs. 4712 U/L; p = 0.429) were not significantly different between groups. However, by the end of perfusion, histology scores were significantly worse in the acetaminophen treated group (p = 0.016). All acetaminophen treated livers developed significant methemoglobinemia, with a peak methemoglobin level of 19.3%, compared to 2.0% for control livers (p = 0.004). The development of a model of ALF in the ex vivo setting was confounded by the development of toxic methemoglobinemia. Further attempts using alternative agents or dosing strategies may be warranted to explore this setting as a model of liver disease.

Bioartificial liver support systems

A variety of bioartificial liver support systems were developed to replace some of the liver's function in case of liver failure. Those systems, in contrast to purely artificial systems, incorporate metabolically active cells to contribute synthetic and regulatory functions as well as detoxification. The selection of the ideal cell source and the design of more sophisticated bioreactors are the main issues in this field of research. Several systems were already introduced into clinical studies to prove their safety. This review briefly introduces a cross-section of experimental and clinically applied systems and tries to give an overview on the problems and limitations of bioartificial liver support.

Protective effects of medical ozone combined with traditional Chinese medicine against chemically-induced hepatic injury in dogs

AIM

To investigate the protective effect of medical ozone (O(3)) combined with Traditional Chinese Medicine (TCM) Yigan Fuzheng Paidu Capsules (YC) against carbon tetrachloride (CCl(4))-induced hepatic injury in dogs.

METHODS

Thirty healthy dogs were divided randomly into five groups (n = 6 in each group), namely control, oleanolic acid tablet (OAT), O(3), YC and O(3) + YC, given either no particular pre-treatment, oral OAT, medical ozone rectal insulfflation every other day, oral YC, or oral YC plus medical ozone rectal insulfflation every other day, respectively, for 30 consecutive days. After pre-treatment, acute hepatic injury was induced in all dogs with a single-dose intraperitoneal injection of CCl(4). General condition and survival time were recorded. The biochemical and hematological indexes of alanine aminotransferase (ALT), aspartate aminotransferase/alanine aminotransferase (AST/ALT), serum total bilirubin (TBIL), prothrombin time (PT), blood ammonia (AMMO), and blood urea nitrogen (BUN) were measured after CCl(4) injection. Hepatic pathological changes were also observed.

RESULTS

Compared to the other four groups, the changes of group O(3) + YC dogs' general conditions (motoricity, mental state, eating, urination and defecation) could be better controlled. In group O(3) + YC the survival rates were higher (P < 0.05 vs group control). AST/ALT values were kept within a normal level in group O(3) + YC. Hepatic histopathology showed that hepatic injury in group O(3) + YC was less serious than those in the other four groups.

CONCLUSION

Medical ozone combined with TCM YC could exert a protective effect on acute liver injury induced by CCl(4).

Functional evaluation of a new bioartificial liver system in vitro and in vitro

AIM

To evaluate the functions of a new bioartificial liver (BAL) system in vitro and in vitro.

METHODS

The BAL system was configured by inoculating porcine hepatocyte spheroids into the cell circuit of a hollow fiber bioreactor. In the experiments of BAL in vitro, the levels of alanine aminotransferase (ALT), total bilirubin (TB), and albumin (ALB) in the circulating hepatocyte suspension and RPMI-1640 medium were determined during 6 h of circulation in the BAL device. In the experiments of BAL in vitro, acute liver failure (ALF) model in canine was induced by an end-side portocaval shunt combined with common bile duct ligation and transaction. Blood ALT, TB and ammonia levels of ALF in canines were determined before and after BAL treatment.

RESULTS

During 6 h of circulation in vitro, there was no significant change of ALT, whereas the TB and ALB levels gradually increased with time both in the hepatocyte suspension and in RPMI-1640 medium. In the BAL treatment group, blood ALT, TB and ammonia levels of ALF in canines decreased significantly.

CONCLUSION

The new BAL system has the ability to perform liver functions and can be used to treat ALF.

Functional evaluation of a new bioartificial liver system in vivo and in vivo

AIM: To evaluate the functions of a new bioartificial liver (BAL) system in vitro and in vitro.

MEHTODS: The BAL system was configurated by inoculating porcine hepatocyte spheroids into the cell circuit of a hollow fiber bioreactor. In the experiments of BAL in vitro, the levels of alanine aminotransferase (ALT), total bilirubin (TB), and albumin (ALB) in the circulating hepatocyte suspension and RPMI-1640 medium were determined during 6 h of circulation in the BAL device. In the experiments of BAL in vitro, acute liver failure (ALF) model in canine was induced by an end-side portocaval shunt combined with common bile duct ligation and transaction. Blood ALT, TB and ammonia levels of ALF in canines were determined before and after BAL treatment.

RESULTS: During 6 h of circulation in vitro, there was no significant change of ALT, whereas the TB and ALB levels gradually increased with time both in the hepatocyte suspension and in RPMI-1640 medium. In the BAL treatment group, blood ALT, TB and ammonia levels of ALF in canines decreased significantly.

CONCLUSION: The new BAL system has the ability to perform liver functions and can be used to treat ALF.

Splicing of SV40T gene exons and construction of a retroviral vector pLLTSN

AIM: To construct an immortalization vector for hepatocytes immortalization, and two exons of simian virus 40 large T antigen gene (SV40T) were spliced and a retroviral vector pLLTSN without intron was constructed.

METHODS: The two exons of SV40T were amplified respectively by high fidelity polymerase chain reaction (PCR) by using the plasmid pUC19-SV40T as the template. Then SV40T gene was spliced by overlapping extension (SOE), and cloned into theEcoRⅠand BamHⅠsites of the retroviral vector pLXSN. The positive recombinant clones were screened and identified by PCR by using colonies directly as templates, and by restriction endonuclease digestion analysis, and DNA sequence analysis.

RESULTS: The 2.1 kb SV40T gene was spliced. Among the ten colonies randomly screened, four were proved positive, and one of them was verified by plasmid DNA sequencing.

CONCLUSION: The retroviral vector pLLTSN containing SV40T without intron is successfully constructed.

Gene transfection for rat primary cultured hepatocytes

AIM: To study the efficient and stable gene transfection method of rat primary cultured hepatocytes by liposome.

METHODS: Rat hepatocytes were isolated by collegenase perfusion, and the pEGFP-N₃ plasmid containing GFP and Neo gene was transfected into rat primary hepatocyte with liposome. The expression of GFP and Neo was observed by fluorescence microscopy and in situ hybridization.

RESULTS: The rate of live hepatocytes obtained was 95%. Under fluorescence microscope, hepatocyte transfected with pEGFP-N₃ plasmid showed green fluorescence. By using in situ hybridization method, expression of Neo gene was observed in hetpatocyte transfected with pEGFP-N₃.

CONCLUSION: Rat hepatocyte can be transfected by pEGFP-N₃. pEGFP-N₃ expression vector and makes it easy to assess the expression of target gene in transfected hepatocyte, and it can be used for localization of transplantated hepatocyte.

Bioartificial liver inoculated with porcine hepatocyte spheroids for treatment of canine acute liver failure model

The aim of this study was to evaluate a novel bioartificial system in a canine model of acute liver failure. An acute liver failure model in canines was induced by an end-side portocaval shunt combined with common bile duct ligation and transection. The bioartificial liver system, which utilized blood perfusion through a hollow fiber bioreactor from BIOLIV A3A inoculated with 1.0 - 3.1 x 1010 porcine hepatocyte spheroids, was developed for the treatment of acute liver failure. Sixteen acute liver failure model canines were divided between a group treated with bioartificial liver (n=8) and a control group (n=8) for 5 h. Blood alanine aminotransferase (ALT), alkaline phosphatase (AKP), total bilirubin (TBi), direct bilirubin (DBi), prothrombin time (PT), ammonia levels, and the ratio of branched chain to aromatic amino acids (Fischer's ratio) were determined. ALT, AKP, TBi, DBi, and ammonia levels were significantly elevated, PT was significantly prolonged, and Fischer's ratio decreased significantly in the canine model of the two groups on day 14 after operation compared to baseline. There were no significant differences between the two groups in laboratory data before treatment. In canines treated with the bioartificial liver system, ALT, AKP, TBi, DBi, and ammonia levels decreased significantly, PT was significantly shortened, Fischer's ratio was significantly elevated after treatment, and the survival rate by day 7 after treatment was 100%. In canines in the control group, on the other hand, there were no significant differences in ALT, AKP, TBi, DBi, PT, and ammonia levels between pretreatment and posttreatment, though these indices decreased to a slight degree after treatment. The survival rate by day 7 after treatment was 62.5% in the control group. Fischer's ratio decreased after treatment. ALT, AKP, TBi, DBi, PT, and ammonia levels in the bioartificial liver system group were lower, and Fischer's ratio and survival rate were higher than those in the control group after treatment. These results indicate that the novel bioartificial liver system we developed has a significant impact on the course of canine acute liver failure model and has potential advantages for clinical use in patients with acute liver failure.

Hepatic stem cells: Existence and origin

Stem cells are not only units of biological organization, responsible for the development and the regeneration of tissue and organ systems, but also are units in evolution by natural selection. It is accepted that there is stem cell potential in the liver. Like most organs in a healthy adult, the liver maintains a perfect balance between cell gain and loss. It has three levels of cells that can respond to loss of hepatocytes: (1) Mature hepatocytes, which proliferate after normal liver tissue renewal, less severe liver damage, etc.; they are numerous, unipotent, “committed” and respond rapidly to liver injury; (2) Oval cells, which are activated to proliferate when the liver damage is extensive and chronic, or if proliferation of hepatocytes is inhibited; they lie within or immediately adjacent to the canal of Hering (CoH); they are less numerous, bipotent and respond by longer, but still limited proliferation; (3) Exogenous liver stem cells, which may derive from circulating hematopoietic stem cells (HSCs) or bone marrow stem cells; they respond to allyl alcohol injury or hepatocarcinogenesis; they are multipotent, rare, but have a very long proliferation potential. They make a more significant contribution to regeneration, and even completely restore normal function in a murine model of hereditary tyrosinaemia. How these three stem cell populations integrate to achieve a homeostatic balance remains enigmatic. This review focuses on the location, activation, markers of the three candidates of liver stem cell, and the most importantly, therapeutic potential of hepatic stem cells.

TECA hybrid artificial liver support system in treatment of acute liver failure

AIM: To assess the efficacy and safety of TECA type hybr id artificial liver support system (TECA-HALSS) in providing liver function of detoxification, metabolism and physiology by treating the patients with acute liv er failure (ALF).

METHODS: The porcine liver cells (1-2) × 10¹⁰ were separated from the Chinese small swine and cultured in the bioreactor of TECA-BALSS at 37.0 °C and circulated through the outer space of the hollow fiber tubes in BALSS. The six liver failure patients with various degree of hepatic coma were treated by TECA-HALSS and with conventional medicines. The venous plasma of the patients was separated by a plasma separator and treated by charcoal adsorbent or plasma exchange. The plasma circulated through the inner space of the hollow fiber tubes of BALSS and mixed with the patients’ blood cells and flew back to their blood circulation. Some small molecular weight substances were exchanged between the plasma and porcine liver cells. Each treatment lasted 6.0-7.0 h. Physiological and biochemical parameters were measured before, during and after the treatment.

RESULTS: The average of porcine liver cells was (1.0-3.0) × 10¹⁰ obtained from each swine liver using our modified enzymatic digestion method. The survival rate of the cells was 85%-93% by trypan blue stain and AO/PI fluorescent stain. After cultured in TECA-BALSS bioreactor for 6 h, the survival rate of cells still remained 70%-85%. At the end of TECA-HALSS treatment, the levels of plasma NH₃, ALT, TB and DB were significantly decreased. The patients who were in the state of drowsiness or coma before the treatment improved their appetite significantly and regained consciousness, some patients resumed light physical work on a short period after the treatment. One to two days after the treatment, the ratio of PTA increased warkedly. During the treatment, the heart rates, blood pressure, respiration condition and serum electrolytes (K⁺, Na⁺ and Cl^-) were stable without thrombosis and bleeding in all the six patients.

CONCLUSION: TECA-HALSS treatment could be a rapid, safe and efficacious method to provide temporary liver support for patients with ALF.

Experimental research on TECA-I bioartificial liver support system to treat canines with acute liver failure

AIM: To evaluate the efficacy and safety of the TECA-I bioartificial liver support system (BALSS) in treating canines with acute liver failure (ALF).

METHODS: Ten canines with ALF induced by 80% liver resection received BALSS treatment (BALSS group). Blood was perfused through a hollow fiber tube containing 1 × 10¹⁰ porcine hepatocytes. Four canines with ALF were treated with BALSS without porcine hepatocytes (control group), and five canines with ALF received drug treatment (drug group). Each treatment lasted 6 h.

RESULTS: BALSS treatment yielded beneficial effects for partial liver resection-induced ALF canines with survival and decreased plasma ammonia, ALT, AST and BIL. There was an obvious decrease in PT level and increase in PA level, and there were no changes in the count of lymphocytes, immunoglobulins (IgA, IgG and IgM) and complement (C3 and C4) levels after BALSS treatment. In contrast, for the canines with ALF in non-hepatocyte BALSS group (control group) and drug group, there were no significant changes in ammonia, ALT, AST, BIL, PT and PA levels. ALF canines in BALSS group, control group and drug group lived respectively an average time of 108.0 h ± 12.0 h, 24.0 h ± 6.0 h and 20.4 h ± 6.4 h, and three canines with ALF survived in BALSS group.

CONCLUSION: TECA-I BALSS is efficacious and safe for ALF canines induced by parcial liver resection.