1685-P: Islet Encapsulation with Tannic Acid Delays Allogeneic Islet Graft Rejection

Abstract

Type 1 diabetes (T1D) is defined by the destruction of insulin-producing cells. Islet transplantation can restore glucose homeostasis and prevent serious hypoglycemic events; however, long-term graft survival is low. Oxidative stress can mediate islet transplantation rejection and suppressing oxidative stress with nanothin islet encapsulation materials comprised of alternating layers of tannic acid (TA), an immunomodulatory antioxidant, and poly(N-vinylpyrrolidone) (PVPON), a scaffold polymer, may allow for improved graft survival without systemic immunosuppression. We hypothesize that (PVPON/TA)-encapsulation of islets will prolong graft function following allotransplantation into immunocompetent recipients without utilizing systemic immunosuppression. Allogeneic transplantation of encapsulated C57BL/6 islets into diabetic non-obese diabetic (NOD) mice (n=12) significantly delayed graft failure by more than 90 days compared to controls and significantly reduced free radical-adduct formation produced by neutrophils and macrophages at the graft site. Gene expression displayed a 5- and 20-fold increase of anti-inflammatory genes Retnla and Arg1, respectively, and 3-fold reductions in Ccl5, Cxcl10, Prf1, and Grzmb mRNA accumulation in (PVPON/TA) versus control grafts. Flow cytometry analysis of encapsulated grafts contained fewer numbers of infiltrating dendritic cells and CD8 T cells and reduced frequencies of CCL5+, CXCR3+, MHC-II+ macrophages and perforin+ CD8 T cells by 3-fold compared to controls. Encapsulated grafts also reduced the frequencies of TNF+ and MHC-II+ dendritic cells by 2-fold. Additionally, encapsulation increased the frequency of arginase-1+ and CD206+ alternatively-activated macrophages 4-fold, suggesting that (PVPON/TA)-encapsulation may be a promising technique to prolong clinical islet graft function by skewing macrophage phenotypes and suppressing cytotoxic T cell effector responses in the absence of systemic immunosuppression. Disclosure J. Barra: None. V. Kozlovskaya: None. E. Kharlampieva: None. H.M. Tse: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK099550); JDRF (SRA-2016-270-S-B, JDRF 2-SRA-2019-692-S-B); National Science Foundation (NSF-DMR 1608728); National Institute of General Medical Sciences (T32GM008111)