Type I diabetes results from the T-cell mediated autoimmune destruction of the insulin producing pancreatic beta cells. Gene therapy is one treatment that is being examined to cure the disease. 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 with reversal of diabetes and pancreatic transdiffereniation of liver tissue. In an attempt to determine if this technology was applicable to human hepatocytes in vivo we have shown that STZ-diabetes could be reversed in the FRG mouse model in which chimeric mouse-human livers can be readily established. Intraperitoneal glucose tolerance tests of the INS-FUR-transduced animals were not significantly different from nondiabetic, control animals and immunohistochemistry of the transduced livers of the FRG mice showed staining for insulin, glucagon and somatostatin, indicating pancreatic transdiffereniation, The aim of the present study was to determine if the transdiffereniation of mouse or human hepatocytes contributed more significantly to pancreatic transdiffereniation of the liver tissue in the humanised mice. RT-PCR and quantitative RT-PCR (RT-qPCR) was performed, together with measurement of human c-peptide. The expression profiles of the human and murine pancreatic genes in the transduced chimeric mice were very similar. RT-qPCR comparing the INS-FUR treated chimeric mouse livers to the untransduced livers showed a significant up-regulation of the following murine and human pancreatic genes: insulin, glucagon, somatostain, glucokinase, GLUT2, Pdx1, NeuroD1, Nkx6.1 and Nkx2.2. The RT-qPCR results did not show a definitive trend to indicate whether the transdifferentiated human or murine hepatocytes contributed the most to diabetes reversal. However, when non-fasting human c-peptide levels (5.61 ± 0.9pmol/L) were compared to non-fasting mouse c-peptide levels (1.8 ± 0.22pmol/L) in INS-FUR-treated FRG mice, it seems likely that transdifferentiated human hepatocytes made a greater contribution to diabetes reversal.