BASIC–LIVER, PANCREAS, AND BILIARY TRACT Treatment of Cirrhosis and Liver Failure in Rats by Hepatocyte Xenotransplantation HIDEO NAGATA,* MASAHIRO ITO,* JIN CAI,* ALBERT S. EDGE, ‡ JEFFREY L. PLATT, § and IRA J. FOX* *Department of Surgery, University of Nebraska Medical Center, Omaha, Nebraska; ‡ Diacrin, Inc., Charlestown, Massachusetts; and § Departments of Surgery, Immunology, and Pediatrics, Mayo Clinic, Rochester, Minnesota See editorial on page 568. Background & Aims: Hepatocyte transplantation has been proposed as an alternative to liver transplanta- tion 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; how- ever, xenogeneic hepatocytes are thought to be func- tionally 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 trans- planted porcine hepatocytes was assessed by en- zyme-linked immunosorbent assay. Results: Porcine hepatocytes restored metabolic function and pro- longed the survival of cirrhotic rats, as well as rat hepatocytes. Cirrhotic rats retained the ability to re- ject allogeneic skin grafts and showed an immune response to the engrafted hepatocytes. Despite this, survival of transplanted porcine hepatocytes was ac- cepted in cirrhotic rats for a period of weeks without immunosuppression. Conventional immunosuppres- sion with FK506 allowed successful retransplantation with hepatocytes from a second porcine donor. Conclusions: Hepatocytes transplanted between widely divergent species can function to correct liver fail- ure 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 sup- port. O rthotopic liver transplantation is presently the only therapy that significantly improves the prognosis of patients with hepatic failure and cirrhosis. Transplanta- tion of the liver, however, is a complex procedure that is associated with significant morbidity and mortality. In addition, the supply of livers available for transplantation limits the number of procedures to a small fraction of those needed and imposes a need to allocate transplant- able livers to some patients and deny livers to others. 1 One way to overcome the technical difficulties of liver transplantation is to transplant isolated hepatocytes. Be- cause transplantation of hepatocytes can be accomplished by percutaneous injection into the liver or spleen, it is much less invasive and technically demanding than transplantation of the intact liver. The transplantation of hepatocytes has been used for more than 2 decades in experimental animals 2-8 and has recently been used in a few human subjects. 9-13 The lack of an adequate supply of human hepatocytes, however, severely limits the use of hepatocyte transplantation as an alternative strategy in the treatment of liver diseases. One possible solution to the limited supply of human hepatocytes for transplantation is the use of hepatocytes from other animal species, that is, xenotransplantation. Animal donors could potentially provide an unlimited supply of hepatocytes of predictable quality and at the precise time needed. Animals bred and raised as a source of donor hepatocytes could be screened for infectious agents or physiological abnormalities, would be amena- ble to genetic or immunologic manipulation, and may be resistant to the recurrence of certain diseases, such as hepatitis. 14,15 Xenotransplantation might also avoid the expense and waiting time associated with the transplan- Abbreviations used in this paper: DMEM, Dulbecco’s modified Eagle medium; PT, prothrombin time; SSC, standard saline citrate. © 2003 by the American Gastroenterological Association 0016-5085/03/$35.00 doi:10.1053/gast.2003.50065 GASTROENTEROLOGY 2003;124:422–431