Browsing by Subject "Organ preservation"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Application of NMR in the characterization of existing and development of new methods for pancreas preservation
    (2012-10) Scott III, William Earl
    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.
  • Thumbnail Image
    Item
    Tissue-engineered islet graft design and assessment
    (2012-10) Suszynski, Thomas Mark
    Diabetes mellitus is a metabolic disease characterized by an inability to maintain normoglycemia and is usually associated with an insufficient beta-cell mass. Islet transplantation (IT, a beta-cell replacement therapy) has exhibited promise in reversing the diabetic state, yet it remains an experimental therapy only among a small subset of patients and widespread availability remains elusive. A main reason for its limited use is the large islet dose required to produce insulin independence, often requiring tissue from multiple donor pancreata. Abundant evidence exists suggesting that acute and chronic islet loss and dysfunction occur in the post-IT period. The minimum islet dose could be reduced if the quality (potency, viability) of the islet product is improved. Since islets do not possess the cellular machinery to produce energy effectively in the absence of oxygen, strategies that improve oxygenation during the ischemic period (donor cardiac death to complete revascularization) are important to develop. Due to the many steps involved in the process (pancreas preservation, and islet isolation, purification, culture, assessment, transplant and engraftment), the quality of an islet preparation can change. Thus, it is critical to develop improved islet quality assessment tools that enable accurate and quantitative characterization of islet viability and potency, which can be performed prospectively, and which do not require much tissue for assessment or which rely on non-invasive methods. Furthermore, intrahepatic IT may not be the optimal approach, and tissue-engineered strategies for extrahepatic IT may be better. The work presented herein focuses on improving islet quality assessment, examining the oxygenation status of the intraportally transplanted islet, and developing a tissue-engineered strategy for the design and non-invasive assessment of islet graft viability - all with the hope that someday IT could be used to successfully treat many more diabetics.