Isolated rat hepatocytes were transduced in primary culture with a human lentivirus containing pancreatic duodenal homeobox 1 (PDX1, now known as
insulin promoter factor 1, homeodomain
transcription factor [IPF1]).
Insulin expression and secretion of the newly engineered cells were assessed in vitro by RT-PCR, in situ hybridisation, immunostaining and radioimmunoassay. PDX1-transduced hepatocytes were further studied in vivo by injecting them under the renal
capsule of diabetic SCID mice.
RESULTS: Isolated rat hepatocytes were efficiently transduced with the lentiviral vector, as assessed by green fluorescent reporter gene expression. The transduced cells exhibited
insulin at both
mRNA (RT-PCR, in situ hybridisation) and
protein levels (immunostaining and radioimmunoassay). Moreover, insulin secretion by the engineered cells was dependent on
glucose and sulfonylurea. Other beta cell genes, including those encoding solute carrier family 2 (facilitated
glucose transporter), member 2 (Slc2a2),
glucokinase (Gck),
ATP-binding cassette, sub-family C (CFTR/MRP), member 8 (Abcc8), the
potassium inwardly-rectifying channel, subfamily J, member 11 (Kcnj11) and
proprotein convertase subtilisin/kexin type 1 (Pcsk1) were also expressed. The PDX1-transduced hepatocytes expressed several pancreatic
transcription factors related to early pancreatic endocrine development (endogenous Pdx1,
neurogenic differentiation factor 1 [Neurod1], and NK6
transcription factor related, locus 1 [Nkx6-1]) as well as the late-stage pancreatic
transcription factors (paired box gene 4 [Pax4], paired box gene 6 [Pax6], and v-maf musculoaponeurotic
fibrosarcoma oncogene homolog A [Mafa]).
Transplantation of 3 x 10(6) transdifferentiated liver cells under the renal
capsule of seven
streptozotocin-induced diabetic SCID mice resulted in significant reduction of non-fasting
blood glucose levels from 30.7 +/- 1.3 to 8.7 +/- 3.7 mmol/l (mean +/- SEM, p = 0.01), in 6 to 8 weeks. Removal of the graft resulted in severe hyperglycaemia.
CONCLUSIONS/INTERPRETATION: