Use of liver slices for an artificial liver

A Novel Bioartificial Liver Containing Small Tissue Fragments: Efficiency in the Treatment of Acute Hepatic Failure Induced by Carbon Tetrachloride in Rats

The efficiency of a new bioartificial liver (BAL) containing small tissue fragments in the treatment of acute hepatic failure induced by carbon tetrachloride in rats was evaluated. A day after injection (i.p.) of CCl4 the animals were connected to a BAL containing liver fragments (fragment BAL) and a BAL containing no liver fragments (no-fragment BAL), and extracorporeal hemoperfusion was carried out for 4 h. The activities of alanine transaminase and lactate dehydrogenase as well as the concentrations of ammonia, glucose, urea, and amino acids in plasma were measured. A tendency to the stabilisation of ammonia, glucose, phenylalanine, tyrosine, and other amino acids was revealed at the end of hemoperfusion in poisoned rats connected to the fragment BAL. A statistically significant difference in survival between the animals connected to the fragment BAL and no-fragment BAL was found. The results obtained indicate that the bioreactor containing small liver fragments is effective in the treatment of acute hepatic failure in animals.

Overview of extracorporeal liver support systems and clinical results

Patients with acute liver failure (ALF) continue to have an almost 50% mortality rate despite improvements associated with the use of orthotopic liver transplantation (OLT). Numerous ex vivo methods have been developed in attempts to improve patient survival. These methods can be divided into three groups: detoxification (e.g., dialysis, charcoal adsorption, plasma exchange), which only provides excretory function; ex vivo liver perfusion (e.g., whole organ or tissue perfusion), which provides some metabolic function; and bioartificial or cell-based systems, which combine elements of the first two methods. Clinical trials have shown minimal efficacy of the various detoxification methods in terms of ALF patient survival, while the relative success of OLT has shown the importance of providing metabolic as well as excretory functions. Attempts to provide those additional functions with ex vivo tissue perfusion have been fraught with complications such as clotting and acute tissue rejection, leading to the conceptual development of cell-based bioreactor systems. A number of these bioartificial systems have been clinically evaluated, and the preliminary patient survival rates have encouraged further work in this area.

Evolution of the bioartificial liver: the need for randomized clinical trials

The pursuit of a bioartificial liver is well documented in the literature. Early techniques of artificial liver support that have undergone clinical testing included simple exchange transfusions, extracorporeal xenogeneic or allogeneic liver perfusion, cross-circulation, hemodialysis, charcoal hemoperfusion, and plasmapheresis with plasma exchange. These techniques failed because they were unable to adequately support those hepatic functions essential for survival and because they lacked a back-up therapy, such as liver transplantation, for irreversible forms of liver disease. The concept evolved that hepatic functions essential for survival would be best performed by hepatocytes in an apparatus that allowed sustained or repetitive application. The best results have been achieved with bioartificial liver technologies that employ hepatocytes as implantable systems or extracorporeal devices. Implantable bioartificial liver systems include hepatocytes that have been on coated microcarrier beads, within microencapsulated gel droplets, within biodegradable polymeric substrates, or as spheroid hepatocyte aggregates. Extracorporeal systems include hepatocytes in suspension, on flat plates, and in hollow fiber bioreactors. Several extracorporeal systems have undergone extensive animal testing and are entering the early stages of human clinical trials. Randomized trials are needed to establish the value of bioartificial liver support in the treatment of patients with acute hepatic failure or as a bridge to liver transplantation.

A new approach to the cryopreservation of hepatocytes in a sandwich culture configuration

Current methods of cryopreservation of hepatocytes in single cell suspensions result in low overall yields of hepatocytes, demonstrating long-term preservation of hepatocellular functions. A novel culture method has recently been developed to culture liver cells in a sandwich configuration of collagen layers in order to stabilize the phenotypic expression of these cells in vitro (J. C. Y. Dunn, M. L. Yarmush, H. G. Koebe, and R. G. Tompkins, FASEB J. 3, 174, 1989). Using this culture system, rat hepatocytes were frozen with 15% (v/v) Me2SO to -70 degrees C, and stored at approximately -100 degrees C. Following rapid thawing, long-term function was assessed by measuring albumin secretion in culture for 7-14 days postfreezing. Comparison was made with cryopreservation of liver cells in single cell suspensions. Cryopreservation of liver cells in suspension resulted in only a 2% yield of cells which could be successfully cultured; albumin secretion rates in these cultured cells over 48 hr were 26-30% of secretion rates for nonfrozen hepatocytes. Freezing cultured liver cells in the sandwich configuration after 3, 7, and 11 days in culture maintained 0, 26, and 19% of the secretion rates of nonfrozen hepatocytes, respectively. Morphology of the cryopreserved cells appeared grossly similar to cells without freezing; however, this morphological result was patchy and represented approximately 30% of the cells in culture. These results represent the first demonstration of any quantitative long-term preservation of hepatocellular function by cryopreservation, suggesting that cultured hepatocytes can survive freezing and maintain function.

Microencapsulated hepatocytes: an in vitro and in vivo study

Using a modified alginate-polylysine membrane, we have successfully encapsulated rat hepatocytes with little loss of viability. Urea and albumin release from encapsulated liver cells was comparable to that from non-encapsulated cells during the first 4 days in culture. Histological studies also showed that more than 50% of the encapsulated hepatocytes remained viable 35 days after implantation in the peritoneal cavity of both normal rats and rats with galactosamine induced fulminant hepatic failure. Transplantation of microencapsulated hepatocytes provides a potential clinical treatment for liver failure.

Successful treatment of hepatic coma by a new artificial liver device in the pig

In this study, we tested a new artificial liver device using liver pieces in 8-h hemoperfusion of comatous porcine blood and compared two alternative tissue preparations. Acute hepatic coma in the pigs was induced by complete devascularization of the liver. The animals were killed in stage IV coma (15-25 h after the operation), and 1 l blood was perfused over 200 g fresh or DMSO-preserved liver cubes. After the devascularization GOT, GPT, GLDH, AP, LDH, SDH, bilirubin, free fatty acid, and bile acid levels in serum increased progressively. Ammonia concentrations underwent a rapid increase in the first 9 h of coma development from 126.0 +/- 9.9 to 321.9 +/- 62.2 mumol/l. Most of the amino acids in serum were elevated and molar ratio of BCAA/AAA declined from 3.87 +/- 0.79 to 0.92 +/- 0.24. In the course of hemoperfusion ammonia was removed from the perfusate to 71% of the initial values using fresh and to 39% using preserved tissue. Correspondingly, there was an increase in urea concentrations. Amino acid metabolism was ameliorated during the perfusion; Fischer's quotient increased from 0.91 +/- 0.15 to 1.38 +/- 0.14 (fresh liver) and from 0.89 +/- 0.14 to 2.11 +/- 0.44 (preserved liver); neuroexcitatory amino acids Asp and Glu were markedly elevated. Energy charge of the liver cells increased and reached levels exceeding 0.5 in both experimental groups, a balanced energy metabolism was maintained and suggests active metabolization by the liver pieces. In comparison with fresh tissue, preserved liver cubes proved effective. We consider our artificial liver device capable of temporary hepatic support in acute necrosis of the liver and suppose that its efficiency can be potentiated by combining this system with other procedures.