Subzero 12-hour Nonfreezing Cryopreservation of Porcine Heart in a Variable Magnetic Field

Abstract

Background. A novel subzero nonfreezing heart preservation method has been developed. It uses a refrigerating device that generates a variable magnetic field, allowing the whole organ to be cooled simultaneously to a supercooled state without the use of cryoprotectant. As a fundamental experiment for heart preservation, we verified whether this novel method is able to suppress anaerobic metabolism and reduce damage in the hearts of large animals. Methods. Twelve porcine hearts were collected and preserved for 12 hours using a simple immersion method. The hearts were divided into 2 groups: 6 underwent nonfreezing preservation at −3°C in a variable magnetic field (subzero group), and 6 underwent conventional preservation at 4°C (conventional group). The quantity of anaerobic metabolism and the degree of ultrastructural change in the 2 groups were evaluated and compared. Results. The concentration of adenosine triphosphate in the myocardial tissue was significantly greater in the subzero group than in the conventional group (21.06±5.87 μmol/g vs 5.96±3.41 μmol/g; P < 0.05). The accumulated lactate concentration was significantly lower in the subzero group than in the conventional group (6.58±2.28 μmol/g vs 11.15±3.74 μmol/g; P < 0.05). The Flameng score, an index of ultrastructural changes to the mitochondria, was significantly lower in the subzero group than in the conventional group (1.28±0.40 vs 2.73±0.30; P < 0.05). Conclusions. Subzero nonfreezing preservation using a variable magnetic field resulted in a remarkable suppression of anaerobic metabolism and myocardial protection in porcine hearts.