The protective effects of theranostic magnetic nanoparticles as carriers for siRNA (MN-siRNA) on baboon pancreatic islet cells after transplant
Thomas Pomposelli, Peter Wang, Yuichi Ariyoshi, Kazuhiro Takeuchi, Hironosuke Watanabe, Anna Moore, Kazuhiko Yamada St Elizabeth's Medical Center, Tufts University School of Medicine, Brighton, MA, USA Columbia University Medical Center, NY, USA Michigan State University, MI, USA
Background:
To utilize a novel technology involving MN‐siRNA conjugated nanoparticles to protect against apoptotic damage to islet cells before transplant
Methods:
Donor islets were cultured for 2 days with MN‐siRNA that targeted the pro-apoptotic Caspase genes. The protective effects on the islets were first assessed in vitro by direct islet counts before and after culture. Apoptosis was also directly analyzed via DNA apoptotic ladder assays. Next, the insulin secreting effects of the islets were assessed in vivo after transplanting a marginal number into diabetic non-human primate recipients via direct infusion into the portal circulation. The animals were maintained on a standard immunosuppressive protocol.
Results:
It is generally accepted that greater than 10K/IEQ is required to maintain stable blood glucose levels in non-human primates. By transplanting a marginal number of islet cells (4,400 – 8,750IEQ) we have shown a dramatic reduction in insulin requirements compared to control cases without MN‐siRNA labeling. Also, we have demonstrated the anti-apoptotic effects of the SiRNA conjugated islets in vitro with apoptotic ladder assays, as well as directly with minimal loss of islets after 2 day culture when compared to controls. We have also shown histologic evidence of positive insulin staining cells from recipient livers.
Conclusion:
It has been theorized that the reason for failure of islet transplantation is apoptotic injury to the islets after transplant. Our data have demonstrated for the first time the protective effects of magnetic nanoparticles as carriers for siRNA. The use of MN‐siRNA on pancreatic islets may ultimately make living pancreas donation a clinical reality.
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