Application of NMR in the characterization of existing and development of new methods for pancreas preservation

Abstract

Islet transplantation is an emerging treatment for type-1 diabetes. Pancreas preservation has been identified as an area for improvement since many pancreata are exposed to >6-8 hours of cold ischemia reducing viable islet yields. Traditionally utilized methods of preservation depend on low temperatures and specialized preservation solutions to maintain viability. Oxygenation during preservation has been identified as a potential means to extend preservation and improve isolation outcomes. The two-layer method (TLM) was developed to oxygenate pancreata during preservation. After initial excitement, since it relies on oxygen delivery by surface diffusion alone, and oxygenation of human sized pancreata in this manner is impossible; its use clinically has faded. Persufflation (PSF), gaseous oxygen perfusion, offers an alternate means of actively delivering oxygen to tissue via the vasculature. Due to the inability of small animal models to properly demonstrate oxygen limitations, and the lack of consistent availability of human pancreata a porcine model was developed. In order to aid in the development and proper assessment of new techniques, the use of 31P-NMR spectroscopy to monitor ATP during preservation was investigated. It was able to confirm that while TLM may provide adequate oxygenation for maintenance of ATP levels in smaller pancreata (rat) it indeed is unable to maintain ATP in larger organs such as the pig or human pancreas. In contrast PSF demonstrated the ability to maintain pig or human pancreata for at least 24 hours with only a minimal decay in ATP levels observed. The relevance of these findings was confirmed both histologically as well as by the gold standard, islet isolation. Paired studies demonstrated the ability of PSF to maintain and possibly improve outcomes while extending preservation times to at least 24 hours. The methods developed in this dissertation can be applied to the development and comparison of other novel methods of preservation in the pancreas and other organs.