Gene silencing in the endocrine pancreas mediated by short-interfering RNA

Objectives: RNA interference as mediated by short-interfering RNA ( siRNA) offers a nonviral means to silence genes in tissue; however, few data exist about gene therapy using siRNA in pancreas tissue. To determine if siRNA treatment could silence an endogenous gene in pancreatic islets, we developed a murine model using the endocrine pancreas. Methods: The insulin 2 (Ins2) gene was targeted with siRNA, and quantitative RT-PCR, fluorescent microscopy, and FACS were used to measure transcript levels and siRNA cellular uptake and transfection efficiency. Isolated pancreatic islets were transfected with siRNA in vitro using a liposomal delivery method in a dose titration ( 50 - 400 nM) or pooled from BALB/c mice having received siRNA ( 100 mu g) via hydrodynamic tail vein injection. Results: The Ins2 transcript level was significantly reduced by 55% in vitro with FACS data showing a transfection efficiency over 45% with the 400 nM concentration. In vivo delivery of siRNA to pancreatic islets revealed a 33% reduction in Ins2 mRNA levels, although siRNA was able to be detected in 19% of isolated islet cells. Conclusion: We have successfully used RNA interference to silence an endogenous tissue-specific gene ( Ins2) in pancreatic islets when transfected in vitro or administered in vivo.