Singlet oxygen energy illumination during moderate cold ischemia prolongs the survival of concordant hamster xeno–heart transplants

Abstract

Introduction Singlet oxygen energy (SOE) is a potent inhibitor of reactive oxygen species (ROS) in vitro and in vivo in certain dose ranges and can improve the levels of high-energy phosphates (HEP) in concordant hamster xeno–heart transplants. Some data indicate that a certain degree of cold ischemia (CI) might be beneficial to xenotransplants. We investigated if SOE illumination of hamster xeno-hearts during moderate cold ischemia (CI) improved graft survival. Materials and methods Eighteen hearts from Golden Syrian hamsters (70 to 80 g) were subjected to 8 hours of CI in cold (+4°C) saline solution (NaCL, 0.9%) before heterotopic cervical transplantation to Lewis rats (220 g). Among the treatment group ( n = 8), SOE was produced by illuminating the hearts for 10 minutes every 30 minutes with photons at λ 634 nm with the Oxylight equipment. Graft function was evaluated every 6 hours after transplantation with digital exam until cessation of heart beats. Results The graft survival of SOE-illuminated ischemic hamster xenografts was 2.34 ± 0.56 versus 1.15 ± 0.37 days in the control group ( P < .05). All hearts displayed immediate graft function versus 70% in the controls (NS). Conclusions SOE illumination at λ 634 nm during moderate cold ischemia (+4°C) can improve the survival of concordant hamster xeno–heart transplants. The exact mechanism(s) are currently unknown, but the effect might in part be exerted by a combination of reduced production of ROS and increased oxidative phosphorylation.