321 Preconditioning with Diazoxide reduces ischemia-reperfusion injury to rodent and non-human primate pancreata and islets
Monday November 16, 2015 from 15:30 to 17:00
Plenary Room 1

Yong Wang MD, United States

Assistant Professor

Department of Surgery

Unviersity of Illinois at Chicago


Preconditioning with Diazoxide reduces ischemia-reperfusion injury to rodent and non-human primate pancreata and islets

Yong Wang1, Matt Bochenek1, James McGarrigle1, Chun-Chieh YeH1, Enza Marchese1, Mohammad Nourmohammadzadeh1, Xing Yuan1, Ling-Jia Wang1, Jose Oberholzer1.

1Department of Surgery, University of Illinois at Chicago, Chicago, IL, United States

Introduction: Islet transplantation is a promising treatment for TIDM, but varying degrees of long-term insulin independence have been observed in the transplanted patient. There are many confounding factors that can influence transplantation outcomes, with organ quality often considered as a key facto. In order to achieve complete and long-term insulin free in islet transplanted TIDM patients, as well as increase islet isolation efficiency as islets isolated from one donor could be sufficient for one recipient, it is critical to improve pancreas quality before islet isolation. Diazoxide (DZ) is a pharmacological opener of ATP-sensitive K+ channels and has been used for mimicking ischemic preconditioning and shows protection against ischemic damage in many tissue types. Here, we investigated whether Diazoxide supplementation to University of Wisconsin (UW) solution in both rodent and non-human primate (NHP) ischemia models has cellular protection during pancreas preservation and eventually improve in vivo islet transplant outcomes
Research Design and Methods:  The pancreata from C57/B6 mice and Cynomolgus monkey were flushed with UW or UW+DZ (150 µM) solution and cold preserved for 6, 8 or 10 hrs prior to islet isolation.  Islet yield, in vitro and in vivo function, mitochondrial morphology, and apoptosis were evaluated.
Results: (1) Significantly higher islet yields were observed in the UW+DZ group than in the UW control (237.5/mouse pancreas ± 25.6 vs. 108.7/mouse pancreas ± 49.3, p < 0.01; 57,887/NHP pancreas vs. 23,574 IEq/NHP pancreas; p = 0.021. and 5,396 IEq/gram vs. 1,646 IEq/gram, p = 0.019). (2) The UW+DZ treated islets have a significantly higher insulin content than the UW control (60.96 ng/ mouse islet ± 13.94 vs. 42.09 ng/ mouse islet ± 8.15, p = 0.002; 59.22 ng/ NHP islet vs. 40.35 ng/NHP islet) and higher insulin positive cells per islet than the UW control (96.15% vs. 82.74% in mouse and 95.12% vs. 79.23% in NHP, p < 0.05). (3) The UW+DZ treated islets have improved glucose induced insulin secretion index (GSI) compared to US control (3.67 ± 0.51 vs. 2.28 ± 1.67, respectively; p = 0.022). (4) DZ prevents ischemic-induced beta-cell apoptosis (live cells: 66.45% ± 5.58 for the UW+DZ vs. 17.12% ± 12.28 for UW control, p < 0.001; Necrotic/late apoptotic cells:  25.49% ± 4.90 for the UW+DZ vs. 62.85 % ± 37.30 for UW control, p = 0.038). (5) The DZ-treated islets had well-preserved mitochondrial morphology with much less mitochondrial swelling and fragmentation.  Additionally, The DZ-treated islets have superior responses of mitochondrial potentials and calcium influx in response to glucose challenge. (6) The islets from the UW+DZ group from both rodent and NHP models had a significantly higher cure rate and improved glucose tolerance in nude mice transplant model than the UW control, indicating better in vivo graft function.
(7) The histology examination of islet grafts also supported in vivo transplant outcomes, showing that the UW + DZ islet grafts have better cell morphology and insulin staining while UW control islets have degenerative grafts and significant higher amount of beta-cell necrosis and demise.
Conclusion:  This study is the first to report mitoprotective effects of Diazoxide for pancreas preservation and islet isolation. In the future it will be necessary to further understand the underlying mechanism for the mitoprotection and test this promising approach for pancreas preservation and islet isolation process in humans.

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