Further Evaluation of Somah: Long-Term Preservation, Temperature Effect, and Prevention of Ischemia-Reperfusion Injury in Rat Hearts Harvested After Cardiocirculatory Death

Objective. To identify and evaluate the ideal temperature for long-term storage of hearts from donation after cardiocirculatory death, in the novel organ preservation solution Somah. Methods. DCD hearts from Sprague-Dawley rats were harvested after 30 minutes of euthanasia, preserved in Somah at 4 degrees C, 10 degrees C, 21 degrees C, or 37 degrees C for 24 hours and then reperfused with blood:Somah (3:1) perfusate at 37 degrees C for 30 minutes. Myocardial biopsies were taken during storage and before and after reperfusion to assess the structural and functional viability of tissue using multiphoton imaging, biochemistry, and immunofluorescence. Results. Myocyte viability, determined by Live-Dead and esterase assays, was similar at 4 degrees C, 10 degrees C, and 21 degrees C (193, 198 and 217 normalized fluorescence counts [NFC]) with a significant decrease at 37 degrees C (131 NFC). Upon reperfusion, esterase activity was enhanced in DCD hearts stored in Somah at 21 degrees C but noticeably decreased at all other temperatures. High-energy adenosine triphosphate/creatine phosphate (ATP/CP) syntheses and the expression of structural/contractile proteins was well preserved at 21 degrees C, both after 24-hour storage and upon reperfusion. In contrast, hearts stored at all other temperatures demonstrated variable degenerative changes, loss of protein expression, and/or deranged ATP/CP synthesis after 24 hours of storage and/or upon reperfusion. Conclusion. The robust maintenance of structural/functional integrity of cardiac tissue and the preservation of protein expression and cellular energy metabolism in DCD hearts after long-term preservation at subnormothermic temperature suggests that 21 degrees C is ideal for long-term storage of DCD hearts in Somah solution.