COEXPRESSION OF FAS LIGAND AND BCL-2 IN RAT LIVER TRANSPLANTATION

Abstract

227 The host lymphocytes infiltrated into the graft express a high amount of Fas antigens and thus are susceptible to Fas ligand (FasL). Expression of FasL on the graft by gene transduction is expected to introduce apoptosis to these lymphocytes to protect rejection, but the FasL-expressing graft cells may be also induced apoptosis as the graft usually expresses Fas antigens. In this study, bcl-2, a strong antiapoptotic gene, was cotransfected with FasL-gene in rat liver graft to protect the Fas-mediated cell death and to prolong recipient survival. Methods. Orthotopic liver transplantation was performed in a strain combination of DA to LEW rats. Genes of FasL alone, Bcl-2 alone, FasL and Bcl-2 in combination, and LacZ (control) were transducted to the donor liver by the HVJ-liposome method via portal vein three days prior to the grafting. Two rats in each group were sacrificed on day 5 and 8 to study the transfected gene expression, and cell apoptosis in the graft (stained by TUNEL method). Results. The HVJ-liposome method was successfully expressed the transducted gene at a rate of 5% to 10% of the hepatocytes and the expression continued for 2 weeks. Twenty percent of FasL-transducted rats died within 24 hours. Their livers were swelled with reddish change and histologically observed a marked cellular infiltration, severe hemorrhage, and hepatocyte apoptosis. Three days after gene transduction, the donor liver was transplanted into the recipients; recipient survival was shown in Table. FasL and/or Bcl-2 transduction significantly prolonged graft survival. A marked low number of hepatocyte apoptosis was histologically observed in the bcl-2-transfected allograft.Table: No Caption available. Conclusion. FasL expression in the graft liver was effective to protect rejection, and Bcl-2 expression protected the graft from rejection and Fas-mediated apoptosis. Regulation of FasL expression is required to minimize the damage in the gene-transfected liver.