Proteins linked to a protein transduction domain efficiently transduce pancreatic islets

The resounding success of a new immunosuppressive, regimen known as the Edm onton protocol demonstrates that islet cell transplantation is becoming a t herapeutic reality for diabetes. However, under the Edmonton protocol, a si ngle donor does not provide enough islets to attain the insulin independenc e of a transplant recipient. This limitation is mainly caused by islet apop tosis triggered during isolation. In this study, we describe a highly effic ient system of transiently transferring anti-apoptotic proteins into pancre atic islets, thus opening an exciting new therapeutic opportunity to improv e the viability of transplantable islets. We fused beta -galactosidase to t he 11-amino acid residues that constitute the protein transduction domain ( PTD) of the HIV/TAT protein and transduced pancreatic islets ex vivo with t his fusion protein in a dose-dependent manner with >80% efficiency. We obse rved that transduction of the anti-apoptotic proteins Bcl-X-L and PEA-15 fu sed to TAT/PTD prevented apoptosis induced by tumor necrosis factor-alpha i n a pancreatic beta -cell line, indicating that TAT/PTD anti-apoptotic prot eins retained their biological activity. Finally, we demonstrated that TAT- fusion proteins did not affect the insulin secretion capability of islets, as determined by glucose static incubation and by reversion of hyperglycemi a in diabetic immunodeficient mice.