275. Pancreatic Transdiffereniation of Human Hepatocytes in the Livers of a Humanized Mouse Model

Abstract

Type I diabetes (TID) results from the T-cell mediated autoimmune destruction of the insulin producing pancreatic beta (β) cells. Exogenous insulin therapy cannot achieve precise physiologic control of blood glucose concentrations and debilitating complications develop, which greatly increase morbidity and mortality for patients. Gene therapy is one strategy that holds considerable promise to cure TID. In earlier studies using an improved surgical technique that isolates the liver from the circulation, we introduced furin-cleavable human insulin (INS-FUR) to the livers in several animal models of diabetes. Reversal of diabetes with normal glucose tolerance and pancreatic transdifferentiation of the liver tissue was seen in streptozotocin (STZ)-diabetic Wistar rats, non-obese spontaneous diabetic mice and pancreatecomised diabetic pigs using the HMD lentiviral vector to deliver the INS-FUR. The aims of the present study were (1) to determine if STZ-diabetes could be reversed in the FRG mouse model in which chimeric mouse-human livers can be readily established, and (2) to determine if pancreatic transdiffereniation was evident in the engrafted human hepatocytes. Successful engraftment of human hepatocytes was verified by measurement of human albumin levels and diabetes was subsequently induced by STZ. Following delivery of the INS-FUR vector (3.5×108transduction units) to overtly diabetic FRG mice (blood glucose >13mM), mice were monitored for changes in body weight and blood glucose levels. Reversal of diabetes was seen for a period of 2 months, which was the experimental endpoint. Intraperitoneal glucose tolerance tests (IPGTTs) of the INS-FUR-transduced animals were not significantly different from nondiabetic, control animals. RT-PCR showed expression of human insulin, glucagon and somatostatin and a number of human β-cell transcription factors, including Pdx1, Neurod1 and Neurogenin 3, indicating pancreatic transdifferentiation of hepatocytes in vivo. Double fluorescent staining for human albumin and insulin was seen in transduced liver samples. We have shown, for the first time that using our technology, human hepatocytes can be induced to undergo pancreatic transdiffereniation in vivo. These human hepatocytes have likely contributed to the reversal of diabetes seen in the animals. Our data suggest that this regimen may ultimately be employed clinically to cure TID.