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Pancreatic progenitor cells represent both a potential source of transplantable islets for the treatment of diabetes and a valuable instrument for the investigation of the tumorigenesis of pancreatic carcinoma. It has been reported that pancreatic ductal cells of adults have the characteristics of pancreatic progenitors, but whether these cells can generate endocrine cells requires verification. Here, the differentiation of daughter cells of CD24(-) pancreatic ductal cells into insulin-secreting cells in vitro is reported. Crude pancreatic ductal cells were first obtained from adult mice by gradient centrifugation, and then the CD24(-) cells were isolated with a fluorescence-activated cell sorter. The isolated cells were cultured in serum-containing medium at clonal density to form epithelial colonies (ECs). The ECs were then stimulated with basic fibroblast growth factor (bFGF). After 72 h, insulin-secreting cells were observed in the ECs. These results indicate that the daughter cells of CD24(-) pancreatic ductal cells can differentiate into insulin-secreting cells in vitro when stimulated with exogenous bFGF. Therefore, CD24(-) pancreatic ductal cells have the potential to be pancreatic progenitor cells.

Aim: To observe whether pancreatic and duodenal homeobox factor-1 enhances the differentiation of pancreatic ductal epithelial cells into insulin-producing cells in vitro., Methods: Rat pancreatic tissue was submitted to digestion by collegenase, ductal epithelial cells were separated by density gradient centrifugation and then cultured in RPMI1640 medium with 10% fetal bovine serum. After 3-5 passages, the cells were incubated in a six-well plate for 24 h before transfection of recombination plasmid XlHbox8VP16. Lightcycler quantitative real-time RT-PCR was used to detect the expression of PDX-1 and insulin mRNA in pancreatic epithelial cells. The expression of PDX-1 and insulin protein was analyzed by Western blotting. Insulin secretion was detected by radioimmunoassay. Insulin-producing cells were detected by dithizone-staining., Results: XlHbox8 mRNA was expressed in pancreatic ductal epithelial cells. PDX-1 and insulin mRNA as well as PDX-1 and insulin protein were significantly increased in the transfected group. The production and insulin secretion of insulin-producing cells differentiated from pancreatic ductal epithelial cells were higher than those of the untransfected cells in vitro with a significant difference (1.32 +/- 0.43 vs 3.48 +/- 0.81, P < 0.01 at 5.6 mmol/L; 4.86 +/- 1.15 vs 10.25 +/- 1.32, P < 0.01 at 16.7 mmol/L)., Conclusion: PDX-1 can differentiate rat pancreatic ductal epithelial cells into insulin-producing cells in vitro. In vitro PDX-1 transfection is a valuable strategy for increasing the source of insulin-producing cells.

Background: The pancreas has a strong regeneration potential in mammals. Previous studies suggested that pancreas regeneration is correlated with proliferation and differentiation of pancreatic stem cells, but the field of pancreatic stem cells is still in its infancy. This study was undertaken to detect the expression of pancreas/duodenal homeobox-1 (PDX-1) and proliferation of pancreatic duct epithelial cells in remnant pancreas during regeneration after partial pancreatectomy in rats, and characterize the source of pancreatic stem cells., Methods: Partial pancreatectomy (90%) was performed on four- to five-week-old Sprague-Dawley rats, and duct epithelial cells and acinar cells were detected by immunohistochemical staining and scored using the 5-bromo-2-deoxyuridine (BrdU) labelling index at various time points. Western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR) were used to assess the expression of PDX-1 protein and mRNA, respectively., Results: At 24 hours after partial pancreatectomy, proliferation started in the main, large and small duct cells, and persisted in small duct cells to day 5. The experimental and control groups were significantly different (P<0.001). BrdU-positive acinar cells were greatly increased and reached a peak on day 5. PDX-1 protein was only faintly detectable in pancreatic ductal cells on day 1 after partial pancreatectomy. On days 2 and 3, a 2-3 fold increase in PDX-1 protein was observed, corresponding to the characteristic 42 kD protein in Western blotting. The operated and sham-operated groups also differed significantly (P<0.05). PDX-1 protein expression on days 5 and 7 after operation did not differ from that of the control group. RT-PCR revealed that PDX-1 mRNA expression did not significantly differ between the operated group and the sham-operated group at various time points., Conclusions: Pancreatic stem cells in pancreatic ductal epithelial cells are involved in the regeneration of remnant pancreas and the expression of PDX-1 in ductal cells is due to posttranscriptional regulation.