2688-P: To Study the Effect of Ischemia and Reperfusion on Human Islet Cell Injury in an In Vitro Setting

Introduction and Objective: Ischemia-reperfusion injury (IRI) is defined as cellular dysfunction and death that follow the restoration of blood flow to previously ischemic tissues. The reperfusion injury in islets occurs during intraportal infusion of islets and restoration of blood supply to the islets after engraftment. Many studies have been reported previously on the role and mechanism of ischemia induced beta cell dysfunction; however, the impact of reperfusion has not been discussed. Our main focus is to explore the molecular mechanism of IRI in ex vivo cultured islets. Methods: Purified human islets were subjected to IRI or Ischemia alone for 24 to 48 hours. Gene expressions of proinflammatory cytokines, and ER stress markers, were assessed along with viability, functional assays and O2 consumption rate. Results: Ischemia showed a significant decrease in islet viability, which was further worsened post-reperfusion. LDH release assay was used to validate the viability data. Oxygen consumption rates reduced as culture times increased, ischemia had low oxygen consumption, and reperfusion caused a further decline (P<0.05). Proinflammatory genes IL-1β, TNF-α, TF, CCL2, and CXCL8 were significantly upregulated in IRI group but not in the ischemia alone group (P < 0.05). ER stress marker XBP1 was upregulated in IRI but not in ischemia indicates its regulatory role in IRI mediated inflammation in islets. Conclusion: IRI injury causes islet cell stress, shown by upregulation of inflammatory genes, and loss of oxygen consumption rate which is mediated by IRE1/XBP1 signaling.