Knockdown of Intraislet IKKβ by Spherical Nucleic Acid Conjugates Prevents Cytokine-Induced Injury and Enhances Graft Survival

Background. The efficiency of islet graft survival after intraportal implantation is compromised by host innate immune responses and the production of proinflammatory cytokines that cause acute cellular injury. This reaction activates intraislet nuclear factor-kappa B (NF-kappa B), causing production of gene products that have detrimental effects on beta-cell survival and function. We hypothesized that small interfering RNA targeting of IKK beta, a crucial kinase in the NF-kappa B activation pathway, in islets before transplantation would ameliorate the detrimental effects of cytokines and improve islet survival after transplantation. Methods. To test this hypothesis, we prepared small interfering RNA-based spherical nucleic acid nanoparticle conjugates targeting IKK beta IKK beta SNA-NCs). We treated isolated islets with IKK beta SNA-NCs and assessed the functional consequences of IKK beta knockdown in vitro and after intraportal transplantation in mice. Results. Treatment of freshly isolated mouse islets with IKK beta SNA-NCs reduced constitutive IKK beta expression and protected against proinflammatory cytokine-induced NF-kappa B activation, resulting in improved cell viability and decreased expression of gene products associated with beta-cell dysfunction. Intraportal transplantation of a marginal mass (50 islets) of syngeneic islets treated with nanoparticle conjugates targeting IKK beta resulted in reversion to normoglycemia in 50% of streptozotocin-induced diabetic recipients (n=12) compared with 0% of controls (n=12). Histologic analyses showed reduced CD11b(+) cellular infiltration and decreased islet apoptosis. Conclusions. These results are consistent with the hypothesis that inhibition of intraislet NF-kappa B activation ameliorates the detrimental effects of host cytokines and demonstrates that preconditioning freshly isolated islets in culture with IKK beta SNA-NCs may be a promising therapy to enhance islet graft function and survival after transplantation.