Transplantation of human islets has great potential as an effective means of treating insulin dependent diabetes mellitus. Primary non-function is the main cause of islet graft failure and it results in the need for multi-donor transplants. Hepatocyte growth factor (HGF) increases 2-cell proliferation and promotes revascularization of islets, while interleukin-1 receptor antagonist (hIL-1Ra) inhibits islet cell apoptosis. Caspase-3 is the converging point of different apoptotic pathways and thus its silencing protects islets from apoptosis. We will test the hypothesis that ex vivo transduction of human islets with a replication deficient adenoviral (Adv) vector encoding hHGF and hIL-1Ra cDNAs or hHGF cDNA and caspase-3-shRNA improves the outcome of islet transplantation for treating type 1 diabetes. In preliminary studies, we constructed Adv-hHGF-hIL-1Ra by cloning hVEGF or hHGF and hIL-1Ra coding sequences and polyA signal under separate CMV promoters in Adenoquick plasmid. There was a dose and time dependent expression of these genes after transduction of Adv-hHGF-hIL-1Ra into human islets. Transduced islets were viable as evidenced by insulin release upon glucose challenge. Co-expression of hHGF and hIL-1Ra by islets showed decrease in caspase-3 activity and apoptosis induced by the inflammatory cytokine cocktail. Compared to non-treated islets, transduction of islets with Adv-hHGF-hIL-1Ra prior to transplantation under the kidney capsules of NOD-SCID mice reduced blood glucose and increased the level of serum insulin and c-peptide levels upon glucose challenge. Transduction of islets with Adv-caspase-3-shRNA also prevented islets from cytokine induced apoptosis and improve islet transplantation. These results indicate that the bipartite Adv vector efficiently expresses both growth factor and antiapoptotic genes, decreases apoptosis and improves the outcome of islet transplantation.
Our specific aims are to determine whether ex vivo transduction with i) ex vivo transduction with Adv- hHGF-hIL-1Ra prevent primary islet nonfunction and early graft rejection after transplantation, ii)? i) Adv- hHGF-hIL-1Ra will improve islet function after intraportal transplantation;ii) ex vivo transduction with Adv- hHGF-caspase-3-shRNA be superior to Adv-hHGF-hIL-1Ra in protecting islet grafts after transplantation;and iii) ex vivo transduction with Adv-hHGF-hIL-1Ra and Adv-hHGF-caspase-3-shRNA protect islets from non- specific inflammatory and adaptive immune responses in both immunodeficient and immunocompetent mice. The broad significance of this research is the potential to achieve dramatic improvement in the treatment efficiency of type 1 diabetes by human islet transplantation.
The proposed ex vivo transduction of human islets with replication deficient adenoviral vectors encoding growth factor and antiapoptotic genes will increase the survival and function of human islets by promoting revascularization and inhibiting the rapid apoptotic islet cell death after Intraportal transplantation. This will decrease the number of islets required to achieve normoglycemia in type I diabetic patients.
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