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Isolation of human islets induces islet-intrinsic NF-kappaB which predicts impaired graft function and accelerated rejection

Shane Grey¹, Mark Cowley¹, Anita Weinberg¹, Stacey Walters¹, Jenny Gunton¹, Tom Loudovaris³, Helen Thomas³, Tom Kay³, Wayne Hawthorne², Phillip O’Connell²

¹Immunology, Garvan Institute, Sydney, NSW; ²The Centre for Transplant and Renal Research, Westmead Hospital, Sydney, NSW; ³Immunology and Diabetes Unit, St Vincent’s Hospital, Melbourne, Victoria, Australia

In the context of islet transplantation, experimental models show that induction of islet intrinsic NF-κB-dependent pro-inflammatory genes can contribute to islet graft rejection. Isolation of human islets triggers activation of the NF-κB and mitogen-activated kinase (MAPK) stress response pathways. However, the down stream NF-κB-target genes induced in human islets during the isolation process are poorly described. Therefore in this study, using microarray, bioinformatic, and RTqPCR approaches, we determined the pattern of genes expressed by a set of 14 human islet preparations. We found that isolated human islets express a panel of genes reminiscent of cells undergoing a marked NF-κB-dependent pro-inflammatory response. Expressed genes included; matrix metallopeptidase 1 (MMP1) and Fibronectin 1 (FN1), factors involved in tissue remodelling, adhesion and cell migration; cytokines, including IL-1band IL-8; A20 and ATF3, genes regulating cell survival; and notably high expression of a set of chemokines that would favour the recruitment of neutrophils and monocytes, including CXCL2, CCL2, CXCL12, CXCL1, CXCL6, CCL28. Of note, the inflammatory profile of isolated human islets was maintained after transplantation into RAG-/- recipients. Thus human islets can provide a reservoir of NF- κB-dependent inflammatory factors that have the potential to contribute to the anti-islet-graft immune response. To test this hypothesis we extracted rodent islets under optimal conditions, forced activation of NF-κB, and transplanted them into allogenic recipients. These NF-κB activated islets not only expressed the same chemokine profile observed in human islets, but also struggled to maintain normoglycemia post transplantation. Further, NF-κB activated islets were rejected with a faster tempo as compared to non-NF-κB-activated rodent islets. Thus isolated human islets can make cell autonomous contributions to the ensuing allograft response by elaborating inflammatory factors that contribute to their own demise. These data highlight the potential importance of islet intrinsic pro-inflammatory responses as targets for therapeutic intervention.