Regeneration of pancreatic islets in vivo by ultrasound-targeted gene therapy

This study uses a novel approach to gene therapy in which plasmid DNA is targeted to the pancreas in vivo using ultrasound-targeted microbubble destruction (UTMD) to achieve islet regeneration. Intravenous microbubbles carrying plasmids are destroyed within the pancreatic microcirculation by ultrasound, achieving local gene expression that is further targeted to beta-cells by a modified rat insulin promoter (RIP3.1). A series of genes implicated in endocrine development were delivered to rats 2 days after streptozotocin-induced diabetes. The genes, PAX4, Nkx2.2, Nkx6.1, Ngn3 and Mafa, produced alpha-cell hyperplasia, but no significant improvement in beta-cell mass or blood glucose level 30 days after UTMD. In contrast, RIP3.1-NeuroD1 promoted islet regeneration from surviving beta-cells, with normalization of glucose, insulin and C-peptide levels at 30 days. In a longer-term experiment, four of six rats had a return of diabetes at 90 days, accompanied by beta-cell apoptosis on Tunel staining. Pretreatment with the JNK inhibitor SP600125 successfully blocked beta-cell apoptosis and resulted in restoration of beta-cell mass and normalization of blood glucose level for up to 90 days. This technique allows in vivo islet regeneration, restoration of beta-cell mass and normalization of blood sugar, insulin and C-peptide in rats without viruses. Gene Therapy (2010) 17, 1411-1420; doi:10.1038/gt.2010.85; published online 27 May 2010