Genetic modification of liver grafts with an adenoviral vector encoding the Bcl-2 gene improves organ preservation

Background. Liver function after transplantation is determined by the quality of the donor organ and the influences of preservation, flush, and reperfusion injury. In this regard, cell death (apoptosis) plays an important role in organ preservation and rejection. Therefore, we examined the possibility of genetic modification of the liver graft with a recombinant adenovirus vector encoding the Bcl-2 gene to reduce apoptosis during the preservation time. Methods. Liver grafts from C57B1/6 mice were procured and preserved using standard techniques. A replication defective adenovirus vector (ΔE1) containing the human Bcl-2 gene (AdCMVhBcl-2) was developed in our laboratory. An adenovirus vector encoding an irrelevant gene (Escherichia coli β-galactosidase) was used as a control. Each mouse received I x 109 plaque forming units administered i.v. 48 hr before the liver procurement. Analyses of liver enzyme activities were determined in the preservation solution. Apoptosis in liver biopsies was determined by DNA fragmentation with an in situ histochemical assay. Results. Immunohistochemical analysis and RT-PCR confirmed the expression of hBcl-2 in the grafts. Grafts from livers expressing hBcl-2 showed significant reduction of the aspartame amino transferase (AST) and lactate dehydrogenase (LDH) release compared with grafts from the control groups. After rewarming, significant cytoprotection was also observed in grafts from animals treated with AdCMVhBcl-2. Histological analysis correlated with the hepatocellular injury determined with transaminases and LDH in the preservation solution. Significant reduction in the number of apoptotic cells was observed in grafts expressing hBcl-2. Conclusions. We have demonstrated a novel approach to reducing the preservation injury to liver grafts with the human Bcl-2 gene. This approach may allow a longer preservation time, potentially reduce the incidence of primary non function, decrease the immunogenicity of the cold injured organ, and increase the safer use of 'marginal' liver grafts.