TREATMENT OF SURGICALLY INDUCED ACUTE LIVER-FAILURE BY TRANSPLANTATION OF CONDITIONALLY IMMORTALIZED HEPATOCYTES

The shortage of human livers available for hepatocyte isolation limits its clinical application. The availability of cloned, conditionally i mmortalized hepatocytes that could be grown in culture but would lose their transformed phenotype and provide metabolic support upon transpl antation would greatly facilitate the treatment of acute liver failure . Toward this goal, we transduced isolated Lewis rat hepatocytes using a replication-defective recombinant retrovirus capable of transferrin g a gene encoding a thermolabile mutant simian virus 40 T antigen (SV4 0ts). The cloned, immortalized hepatocytes proliferate at 33 degrees C . At the nonpermissive temperatures (37-39 degrees C), they stop growi ng and exhibit characteristics of differentiated hepatocytes. These ce lls did not produce tumors when transplanted in mice with severe combi ned immunodeficiency disease or in syngeneic rats. To induce acute liv er failure, Lewis rats were subjected to 90% hepatectomy (Hpx) and giv en 5% oral dextrose. All rats that did not undergo hepatocyte transpla ntation died within 96 hr. Fifty percent of rats that received intrasp lenic injection of 10 x 10(6) primary Lewis rat hepatocytes (G2, n=6) or 10 x 10(6) SV40ts-conditionally immortalized (SV40ts-ci) hepatocyte s (G3, n=8) 1 day before 90% hepatectomy survived, whereas 80% of rats that received an intraperitoneal injection of 200 x 10(6) primary Lew is rat hepatocytes (G4, n=10) or 200 x 10(6) SV40ts-ci hepatocytes (G5 , n=10) on the day of hepatectomy survived. Survival after intraperito neal injection of a cellular homogenate of 200 x 10(6) primary Lewis r at (G7, n=9) or SV40ts-ci hepatocytes (G8, n=10) on the day of Hpx was 33% and 40%, respectively, whereas survival after intraperitoneal inj ection of 200 x 10(6) Lewis rat bone marrow cells (G6, n=7) was 29%. T hus, transplanted, conditionally immortalized hepatocytes can be as ef fective as primary hepatocytes in supporting life during acute liver i nsufficiency. This work represents the first step in developing an hep atocyte cell line that would partially alleviate the organ-donor short age and could be of potential clinical value.