Establishment of a Chronic Rejection Model for Orthotopic Liver Transplantation in the Rat

<i>Background:</i> This study aims to establish a stable chronic rejection model for orthotopic liver transplantation in the rat and to describe the pathological features of this model. <i>Methods:</i> The livers from different strains of rats were transplanted in various allogeneic donor-recipient combinations with appropriate syngeneic grafts used as controls. The rats were untreated after surgery (acute rejection model) or treated with cyclosporin A (1 mg/kg) and hydrocortisone (0.75 mg/kg) to establish chronic rejection as determined by rejection activity index scores from pathological examination of liver specimens. <i>Results:</i> Acute rejection occurred in all of the untreated recipients of allogeneic orthotopic liver transplants, and all died within 30 days. Among the treated recipients, the combinations of Lewis with brown Norway and dark agouti with Lewis rats developed acute rejection, and no changes characteristic of chronic rejection were observed in the few rats that survived beyond 30 days. In contrast, the treated Lewis recipients of livers from Sprague-Dawley rats exhibited chronic rejection in the liver specimens. <i>Conclusion:</i> We have established an animal model for chronic rejection after transplantation of livers from Sprague-Dawley to Lewis rats under short-term immunosuppression induced by small doses of cyclosporin A and hydrocortisone.