The viability and regeneration of artificial cell microencapsulated rat hepatocyte xenograft transplants in mice

Artificial liver support based on artificial cells with emphasis on encapsulated hepatocytes

Artificial liver support requires more than a detoxification system. We have investigated additional approaches. Microencapsulated hepatocytes increased the survival time of fulminant hepatic failure (FHF) rats. They also lowered the bilirubin in Gunn rats. Xenograft of microencapsulated rat hepatocytes into mice are immunoisolated. The viability of hepatocyte increased from 62 to 100% after 29 days. This is because of accumulation of a hepatic stimulatory factor (> 100,000 D) secreted by the hepatocytes in the artificial cells. A novel two-step method of cell encapsulation greatly improved immunoisolation and biocompatibility. Other metabolic approaches included a multienzyme system for conversion of ammonia to essential amino acid, and removal of bilirubin.

Artificial cells: 35 years

The first artificial cells were prepared 35 years ago. They contain biologically active materials. They are now being used in medicine and biotechnology. Artificial cells containing adsorbents are already a routine form of treatment in hemoperfusion. This includes treatment for acute poisoning, high blood aluminum and iron, kidney failure, some types of acute liver failure, and other conditions. Artificial cells are being tested for use as red blood cell substitutes. Artificial cells containing cell culture are being tested in animals for the treatment of diabetes, liver failure, and others. Artificial cells containing enzymes are being tested for treatment in hereditary enzyme deficiency diseases and other diseases. Artificial cells containing complex enzyme system can convert wastes like urea and ammonia into useful amino acids. In biotechnology, artificial cells are being used for the production of monoclonal antibodies, interferons, and other biotechnological products. They are also being investigated for use in other applications in biotechnology, chemical engineering, and medicine.

Artificial cells in immobilization biotechnology

Artificial cells contain biologically active materials. Artificial cells containing adsorbents have been a routine form of treatment in hemoperfusion for patients. This includes acute poisoning, high blood aluminum and iron, and supplement to dialysis in kidney failure. Artificial cells are being tested for use as red blood cell substitutes. Artificial cells encapsulated cell culture are being tested in animals for the treatment of diabetes and liver failure. A novel 2 step method has prevented xenograft rejection. Artificial cells containing enzymes are being studied for treatment in hereditary enzyme deficiency diseases and other diseases. Recent demonstration of extensive enterorecirculation of amino acids in the intestine has allowed its oral administration to deplete specific amino acids. Artificial cells containing complex enzyme system convert wastes like urea and ammonia into essential amino acids. Artificial cell is being used for the production of monoclonal antibodies, interferons and other biotechnological products. It is also being investigated for drug delivery, and for use in other applications in biotechnology, chemical engineering and medicine.

Effects of hepatic stimulatory factor released from free or microencapsulated hepatocytes on galactosamine induced fulminant hepatic failure animal model

This paper describes the presence of a cell free hepatocyte stimulating factor secreted by hepatocyte cultures. Hepatocytes were isolated from 70-90 grams Wistar-Lewis rats. Free or microencapsulated hepatocytes in alginate matrix were cultured separately. Cell free supernatant was collected from the culture medium in which was cultured free hepatocytes; microencapsulated hepatocytes or control microcapsules containing no microcapsules. This was tested in the galactosamine rats. A galactosamine dose of 2.7 g/Kg of body weight given intraperitoneally to Wistar-Lewis rats resulted in reproducible hepatic necrosis with 90% mortality. Cell free supernatant from one day old free hepatocyte cultures was able to increase survival time and incorporation of 3H-thymidine in liver of galactosamine induced fulminant hepatic failure rats at the time of maximal liver damage. The cell free supernatant of one day old microencapsulated hepatocyte cultures did not have the same stimulatory effect either on survival time or incorporation of thymidine. Another study was carried out as follows. The microcapsules containing hepatocytes were ruptured. The supernatant of the microcapsule contents was collected. This was found to have hepatic stimulatory effect as shown by survival time and incorporation of thymidine. This suggests that hepatocytes are a source of a factor(s) which is capable of stimulating liver regeneration in the galactosamine induced fulminant hepatic failure rats at the time of maximal liver damage. Since the molecular weight cut off of this particular preparation of microcapsule is molecular larger than albumin, this suggests that the molecular weight of this factor is in the macromolecular range.

Restoration of liver function in Gunn rats without immunosuppression using transplanted microencapsulated hepatocytes

Microencapsulation of cells within synthetic semipermeable membranes is a novel technique that enables the transplantation of cell cultures without the need for immunosuppression. We have previously shown that transplanted isolated encapsulated hepatocytes can provide sufficient short-term metabolic support to improve the survival of animals with galactosamine-induced fulminant hepatic failure. Here we have demonstrated the feasibility of isolated encapsulated hepatocyte transplantation in providing long-term metabolic liver support in Gunn rats. Gunn rats have a congenital inability to conjugate bilirubin and thus exhibit lifelong hyperbilirubinemia. We studied the feasibility of isolated encapsulated hepatocyte transplantation in restoring this specific liver function. Free hepatocytes, isolated from male Wistar rats, were microencapsulated with collagen within a trilayered sodium alginate-poly-L-lysine-sodium alginate membrane using techniques developed in our laboratory. A total of 45 Gunn rats underwent intraperitoneal transplantation with free hepatocytes (5 x 10(7], isolated encapsulated hepatocytes (5 x 10(7], control (empty) microcapsules or no transplant (untreated controls). Serum bilirubin levels were monitored daily for 10 days after transplantation, and subsequent weekly samples were obtained for up to 1 mo. Microcapsules were studied by light and electron microscopy 1 mo after transplantation. During the first week after transplantation, the mean maximum reduction in serum bilirubin levels for the isolated encapsulated hepatocytes, free hepatocytes and control microcapsule transplanted groups was 45.7%, 18.6% and 14.3%, respectively. For up to 1 mo thereafter the mean reduction in serum bilirubin levels in these respective groups was 34.8%, 13.5% and 3.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocytes immobilised by microencapsulation in artificial cells: effects on hyperbilirubinemia in Gunn rats

The possibility of using hepatocytes encapsulated in a calcium-alginate-polylysine matrix to lower bilirubin levels in hyperbilirubinemia was investigated. The animal model was the Gunn rat. The microencapsulated hepatocytes were injected intraperitoneally. 15 X 10(6) microencapsulated hepatocytes from Wistar rats, lowered the bilirubin from 14 mg/100 ml to 6 mg/100 ml after 20 days. The bilirubin is still depressed after 90 days. After encapsulation, Sprague-Dawley hepatocytes were as effective as free hepatocytes in lowering bilirubin levels in Gunn rats. After 68 days, the free Sprague-Dawley hepatocytes were not rejected.