Despite extraordinary advances in heart transplantation during the last decade, little work has been completed in effective long-term organ preservation storage during the time between donor and recipient. Based on U.S. transplantation data, approximately 3,000 are on the waiting list for possible heart transplants and less than half of these people will receive transplants. The shortage of quality transplant organs is a major problem, especially for recipients waiting for hearts. In addition, cardiovascular disease is the number one killer of people, obviously, leaving the heart from those deaths unfeasible for transplantation.
The goal of this research was to develop and optimize a solution for long-term heart preservation suitable for transplantation. There are many factors that affect the tissue after removal. Cold preservation causes ischemia, which puts the tissue under extreme biochemical stress. A lack of O2 in the stored tissues causes a change from aerobic to anaerobic metabolism, which triggers ischemic injury. The negative affects caused by cold storage must be remedied by the storage solution. Supporting the L-arginine/NO/ONOO- pathway and maintaining a proper NO/ONOO- ratio is essential for keeping endothelial functional. The solution has to maintain the L-arginine/NO/ONOO- pathway during storage time and during transplantation.
This research elucidated the L-arginine/NO/ONOO- pathway during heart preservation and how the pathway changes with standard cold storage solutions (University of Wisconsin solution, Celsior solution, and Hepes buffer). The factors which can affect the L-arginine/NO/ONOO- pathway were examined (gender, eNOS co-factors and activators, and NO pre-cursors). The cardio-protective effects of adding L-arginine, NADH, sepiapterin, sildenafil, and BH4 were developed and evaluated utilizing nanomedical sensors for the detection and quantification of NO and ONOO-. Western blot analyses were utilized to give insight into the changes of eNOS expression in the stored cardiac grafts. This gave a clear understanding of the L-arginine/NO/ONOO- pathway in heart preservation.
The culmination of this research was to develop and optimize a solution for long-term cardiac preservation for transplantation. This optimal solution was created using Celsior solution with the addition of several compounds including: L-arginine, sepiapterin, and BH4. This new storage solution was able to maintain hemostasis in the L-arginine/NO/ONOO- pathway by the storage time beyond 10 hours, increasing the NO/ONOO- ratio and by supporting the eNOS enzyme activity in stored hearts.