Treatment of cirrhosis and liver failure in rats by hepatocyte xenotransplantation

Background & Aims: Hepatocyte transplantation has been proposed as an alternative to liver transplantation for the treatment of hepatic failure. A major limitation to this form of therapy is the availability of human livers as a source of hepatocytes. The use of porcine hepatocytes might address this problem; however, xenogeneic hepatocytes are thought to be functionally incompatible across species and susceptible to irreversible rejection. Methods: Liver cirrhosis was induced with phenobarbital and carbon tetrachloride. Only rats with decompensated liver failure that did not correct 4 weeks after the discontinuation of carbon tetrachloride were subjected to intrasplenic rat or porcine hepatocyte transplantation. The immunologic integrity of cirrhotic rats was assessed by allogeneic skin grafting, and the immune response to transplanted porcine hepatocytes was assessed by enzyme-linked immunosorbent assay. Results: Porcine hepatocytes restored metabolic function and prolonged the survival of cirrhotic rats, as well as rat hepatocytes. Cirrhotic rats retained the ability to reject allogeneic skin grafts and showed an immune response to the engrafted hepatocytes. Despite this, survival of transplanted porcine hepatocytes was accepted in cirrhotic rats for a period of weeks without immunosuppression. Conventional immunosuppression with FK506 allowed successful retransplantation with hepatocytes from a second porcine donor. Conclusions: Hepatocytes transplanted between widely divergent species can function to correct liver failure in cirrhotic rats and prolong their survival. Conventional immunosuppression allows long-term functioning of xenogeneic hepatocyte retransplants and suggests that hepatocyte xenotransplantation might be useful as a bridge to liver transplantation and could potentially provide long-term hepatic support.