Culture Conditions for Mouse Pancreatic Stem Cells

Establishment of a pancreatic stem cell line from fibroblast-derived induced pluripotent stem cells

BACKGROUND

For cell therapies to treat diabetes, it is important to produce a sufficient number of pancreatic endocrine cells that function similarly to primary islets. Induced pluripotent stem (iPS) cells represent a potentially unlimited source of functional pancreatic endocrine cells. However, the use of iPS cells for laboratory studies and cell-based therapies is hampered by their high tumorigenic potential and limited ability to generate pure populations of differentiated cell types in vitro. The purpose of this study was to establish a pancreatic stem cell line from iPS cells derived from mouse fibroblasts.

METHODS

Mouse iPS cells were induced to differentiate into insulin-producing cells by a multi-step differentiation protocol, which was conducted as described previously with minor modifications. Selection of the pancreatic stem cell was based on morphology and Pdx1 expression. The pancreatic potential of the pancreatic stem cells was evaluated using a reverse transcription PCR, real-time PCR, immunofluorescence, and a glucose challenge test. To assess potential tumorigenicity of the pancreatic stem cells, the cells were injected into the quadriceps femoris muscle of the left hindlimb of nude mice.

RESULTS

The iPS-derived pancreatic stem cells expressed the transcription factor--Pdx1--a marker of pancreatic development, and continued to divide actively beyond passage 80. Endocrine cells derived from these pancreatic stem cells expressed insulin and pancreatic genes, and they released insulin in response to glucose stimulation. Mice injected with the pancreatic stem cells did not develop tumors, in contrast to mice injected with an equal number of iPS cells.

CONCLUSION

This strategy provides a new approach for generation of insulin-producing cells that is more efficient and safer than using iPS cells. We believe that this approach will help to develop a patient-specific cell transplantation therapy for diabetes in the near future.

Isolation Efficiency of Mouse Pancreatic Stem Cells Is Age Dependent

Mouse pancreatic stem cells have been isolated from mouse pancreata. This study evaluated the efficacy of isolating mouse pancreatic stem cells using mice of different ages. The pancreata of newborn mice, 8-week-old mice, and 24-week-old mice were harvested and digested by using collagenase. The "duct-like" cells in the digested pancreatic tissue were then inoculated into 96-well plates, cloned by limiting dilution, and cultured in DMEM with 20% FBS. Pancreatic stem cells were isolated from the pancreata of all newborn mice, while cells could only be isolated from 10% of the pancreata of 8-week-old mice and could not be isolated from the pancreata of any 24-week-old mice. These data suggest that young mice may have some pancreatic stem cells and that older mice may only have a few pancreatic stem cells. These data also indicate that it is extremely difficult to isolate pancreatic stem cells from older mice, suggesting that future research focus its efforts on finding methods of isolating pancreatic stem cells from adult mice.