TRANSPLANTATION OF CONDITIONALLY IMMORTALIZED HEPATOCYTES TO TREAT HEPATIC-ENCEPHALOPATHY

Transplantation of hepatocytes has been shown to provide metabolic sup port during liver failure in experimental models, The potential clinic al application of hepatocyte transplantation, however, is Limited by t he need for readily available, well-characterized cells, and a worldwi de shortage of donor organs. A clonal hepatocyte cell Line that could be grown economically in vitro and would exhibit a differentiated, non transformed phenotype following transplantation would be an attractive solution to this problem, To test this alternative, primary Lewis rat hepatocytes were conditionally immortalized by retroviral transductio n with a thermolabile mutant Simian virus 40 (SV40) large T antigen, T he cloned immortalized cells proliferate in culture at 33 degrees C an d stop growing at 37 degrees C to 39 degrees C. Transplanted into norm al livers, these hepatocytes integrate normally into liver cords, When transplanted into the spleens of portacaval-shunted rats, they protec t recipients from hyperammonemia-induced hepatic encephalopathy, The c ells engrafted in the spleen exhibit normal morphology, secrete bile, and express albumin messenger RNA. The protection hom hyperammonemia i s reversed by splenectomy, These studies show that hepatocytes can be conditionally immortalized, expanded in culture, and are capable of pr oviding metabolic support in chronic liver insufficiency. Safeguards t hat could make these cells clinically useful can be accomplished using currently available technology.