There is a worldwide consensus that islet transplantation may be considered a viable option for the treatment of insulin-dependent diabetes mellitus, and clinical trials are underway at many centers around the world. As this approach for curing diabetes transitions into a routine clinical standard of care so the demand for donor islets will escalate. Moreover, the potential for xenotransplantation to relieve the demand on an inadequate supply of human pancreases will also be dependent upon the efficiency of techniques for isolating islets from the source pancreases. Unfortunately, islets are highly vulnerable to irreversible damage after prolonged ischemia, and cold ischemia of the cadaveric pancreas is detrimental to islet yield such that new approaches are needed for improved methods of pancreas preservation to increase the yields of high quality islets. Hypothermia has proved to be the bed-rock of the most widely used methods of organ preservation but the best techniques are still subject to some cold ischemic injury. Oxygen deprivation is still regarded as a key factor and one strategy adopted to try to reduce the oxygen debt during ischemia has been to use perfluorocarbons (PFC) in an attempt to augment oxygen delivery to the cold ischemic organ. However, the Two-Layer Method, in which the organ is submerged at the aqueous/PFC interface, has only proved successful in small animal models. As an alternative approach the hypothesis underpinning this proposal is that PFCs will need to be perfused into the organ to provide effective oxygen delivery to the hypoxic cold ischemic cells. The general aim of the proposed research is to combine three technologies that could impact the quality of donor organs, and notably pancreases. These are: i) hypothermic machine perfusion (HMP);ii) hypothermic blood substitution (HBS);and iii) oxygenation with perfluorochemicals (PFC). Our hypothesis that HMP with PFC-augmented HBS will provide superior hypothermic preservation of pancreases will be tested using two specific aims:
The first aim will be to establish perfusion dynamics with Unisol-PFC, where Unisol is a proprietary HBS. Using an established porcine model, our baseline technology of HMP with Unisol HBS will be adapted to prepare an emulsion of PFC in Unisol (Unisol-PFC) and the perfusion parameters necessary to facilitate efficient perfusion will be determined using a LifePort(R) perfusion machine.
The second aim will be to evaluate the efficacy of PFC-perfusion on the quality of post-perfusion isolation of islets. Using an established model of split-lobe perfusion the goal will be to compare the yield and quality of islets isolated from porcine pancreas lobes perfused with Unisol-PFC compared with Unisol alone. The anticipated outcome of this approach is that the implementation of PFC-augmented perfusion will provide a sustainable reservoir of O2 to meet the markedly reduced demands of the organ during extended cold ischemic storage. In turn, this will provide the means for high energy phosphate regeneration and avert the well recognized consequences of anaerobic glycolysis that the organ is forced to switch to during hypoxia and ischemia. While these studies are specifically designed to focus on the clinical need in islet transplantation, the underlying technology developments will be readily applicable to all transplantable organs.
Insulin-dependent diabetes is one of the major health problems worldwide and there is a great deal of interest in developing a potential cure by transplantation of islet cells isolated from a donor pancreas. A critical component of this approach is the availability of sufficient high quality islets to reverse diabetes in the patient. Current methods of storing organs prior to transplantation, or storing the pancreas prior to islet isolation, rely on hypothermic preservation modalities in which the organ still endures some injury from oxygen deprivation. This research is focused on the development of a new alternative technique to sustain oxygen delivery to the organ using perfusion technology with new inert oxygen-carrying solutions.
