Early Detection of Apoptosis and Fas Ligand Expression in Hepatic Graft-versus-Host Disease after Rat Small Bowel Transplantation

Abstract

Background. The liver is one of the primary targets of acute graft-versus-host disease (GVHD), which is the principal complication that occurs after allogeneic intestinal transplantation. The purpose of this study is to investigate the involvement of the Fas/Fas ligand system in hepatic GVHD after rat semiallogeneic intestinal transplantation.Materials and methods. Liver samples were serially harvested from LEW × BN F1 (LBNF1) recipients of either LEW heterotopic intestinal allografts (group 1) or LBNF1 isografts (group 2), on Days 1, 3, 5, 9, and 13 posttransplant.Results. In group 1, hepatic injuries as assessed by either serum aspartate aminotransferase (AST) level, alanine aminotransferase (ALT) level, or cellular infiltration on HE staining became apparent after Day 13. The incidence of apoptosis, examined by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end-labeling (TUNEL), was observed to steadily increase in the liver from Day 5 accompanied by a progression of GVHD: 17.5 ± 3.1 and 3.1 ± 0.4 cells/field (200×) in groups 1 and 2, respectively. In an immunohistochemical study, Fas was constitutively expressed in the liver in both groups, while Fas ligand was expressed most extensively on Day 13 in group 1. Immunoreactivity of both Fas and Fas ligand was observed in hepatocytes, in addition to leukocytes. Analysis by reverse transcription polymerase chain reaction also revealed the expression of Fas mRNA to be constitutive in both groups, while that of Fas ligand mRNA increased significantly from Day 5 and peaked on Day 13 in group 1, and the expression was 10 times stronger than that for isogeneic combination (group 2).Conclusion. Early detection of upregulated Fas ligand and increased apoptosis is thus considered to be potentially a useful tool for the diagnosis of hepatic GVHD.