High‐Dose Stabilized Chlorite Matrix WF10 Prolongs Cardiac Xenograft Survival in the Hamster‐to‐Rat Model without Inducing Ultrastructural or Biochemical Signs of Cardiotoxicity

Abstract

WF10 is a stabilized chlorite matrix with immunosuppressive effects. In vitro studies have demonstrated its ability to suppress T cells and delay or abolish antigen presentation. Hence, WF10 may prove useful to prolong graft survival after transplantation. In this study, we evaluated the use of high dose WF10 as a single drug regimen in the hamster-to-rat xenotransplantation model and searched for possible cardiotoxic side effects. WF10 prolonged cardiac xenograft survival, but did not induce tolerence or inhibit pathological signs of acute rejection. Hamsters from the donor population, receiving high dose WF10 for 5 days, were compared with a matched control group. Ultrastructural examination of cardiac tissue as well as biochemical analysis of the cardiac enzymes troponin I, myoglobin and MB isoenzyme of creatine kinase showed no signs of damage. Thus, while prolonging graft survival, high dose WF10 seems to be non-cardiotoxic and as such should not contribute to the differential diagnosis of acute graft failure. Immunosuppression after transplantation is still, despite many improvements, lifelong and dangerous. We must continue to search for new immunosuppressants, hopefully less toxic than the present, and new drug possibilities in this respect need in vitro as well asin vivo investigation. The stabilized chlorite matrix WF10 is currently in advanced clinical testing for the treatment of HIV disease and wound healing (Hinz et al. 1986; Raffanti et al. 1998). In vitro studies have shown that WF10 suppresses CD4 and CD8 T cells and delays antigen presentation (McGrath et al. 1998; McGrath & Kodelja 1999). We have recently evaluated WF10 in the hamster-to-rat cardiac xenograft model and found a positive effect on graft survival accompanied by peripheral CD4 and CD8 T cell suppression (Kemp et al. 2000). Graft failure in these studies was correlated to acute rejection. However, the possible contribution of drug toxicity was not examined. Since the differential diagnosis between rejection and drug toxicity is essential during the clinical setting of graft failure, we have analyzed in this study the effect of high dose WF10 on cardiac xenograft survival and cardiotoxicity in the hamster-to-rat model. Animals. Heart transplantation with Syrian hamsters was performed. Lewis rats weighing 200-300 g (MOL: SPRD) served as recipients and outbread Syrian hamsters (MOL: Breeding centre, Skensved, Denmark) as donors. The animals were 3 to 4 months of age and were maintained under standard laboratory conditions, receiving human care according to the Directive 86/609/EEC (1986) and the ''Guiding Principles in the Use of Animals in Toxicology'' (Society of Toxicology 1989). Transplantation procedure. The heart transplantations were performed using a modified microvascular technique described by Stein-bruchel et al. (1993). Briefly, the donor animals were anaesthetized with fentanyl/fluanisone (1 mg/0.002 mg per 100 g body weight) and diazepam (0.5 mg per 100 g body weight). Heparin (500 IU) was injected into the inferior vena...