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Compensatory Response by Late Embryonic Tubular Epithelium to the Reduction in Pancreatic Progenitors.

Nishimura W, Kapoor A, El Khattabi I, Jin W, Yasuda K, Bonner-Weir S, Sharma A - PLoS ONE (2015)

Bottom Line: Previously we reported that in Pdx1tTA/+;tetOMafA (bigenic) mice inducing expression of transcription factor MafA in Pdx1-expressing (Pdx1+) cells throughout embryonic development inhibited the proliferation and differentiation of 1°MPC cells, resulting in reduced pancreatic mass and endocrine cells by embryonic day (E) 17.5.However, by birth (P0), as we now report, such bigenic pups had significantly increased pancreatic and endocrine volumes with endocrine clusters containing all pancreatic endocrine cell types.Thus, these bigenic mice provide a novel way to characterize the competency of 1°MPC for their ability to specify endocrine progenitors, a critical limitation in our understanding of endocrine differentiation.

View Article: PubMed Central - PubMed

Affiliation: Section of Islet Cell & Regenerative Biology, Joslin Diabetes Center, Boston, Massachusetts, United States of America.

ABSTRACT
Early in pancreatic development, epithelial cells of pancreatic buds function as primary multipotent progenitor cells (1°MPC) that specify all three pancreatic cell lineages, i.e., endocrine, acinar and duct. Bipotent "Trunk" progenitors derived from 1°MPC are implicated in directly regulating the specification of endocrine progenitors. It is unclear if this specification process is initiated in the 1°MPC where some 1°MPC become competent for later specification of endocrine progenitors. Previously we reported that in Pdx1tTA/+;tetOMafA (bigenic) mice inducing expression of transcription factor MafA in Pdx1-expressing (Pdx1+) cells throughout embryonic development inhibited the proliferation and differentiation of 1°MPC cells, resulting in reduced pancreatic mass and endocrine cells by embryonic day (E) 17.5. Induction of the transgene only until E12.5 in Pdx1+ 1°MPC was sufficient for this inhibition of endocrine cells and pancreatic mass at E17.5. However, by birth (P0), as we now report, such bigenic pups had significantly increased pancreatic and endocrine volumes with endocrine clusters containing all pancreatic endocrine cell types. The increase in endocrine cells resulted from a higher proliferation of tubular epithelial cells expressing the progenitor marker Glut2 in E17.5 bigenic embryos and increased number of Neurog3-expressing cells at E19.5. A BrdU-labeling study demonstrated that inhibiting proliferation of 1°MPC by forced MafA-expression did not lead to retention of those progenitors in E17.5 tubular epithelium. Our data suggest that the forced MafA expression in the 1°MPC inhibits their competency to specify endocrine progenitors only until E17.5, and after that compensatory proliferation of tubular epithelium gives rise to a distinct pool of endocrine progenitors. Thus, these bigenic mice provide a novel way to characterize the competency of 1°MPC for their ability to specify endocrine progenitors, a critical limitation in our understanding of endocrine differentiation.

No MeSH data available.


Related in: MedlinePlus

P1 transgenic pancreases contain significantly larger endocrine clusters compared to E17.5.At P1 bigenic islets had relatively normal organization as compared to controls for expression of glucagon (green, AB, red, EF), somatostatin (green, CD), pancreatic polypeptide (green, EF), ghrelin (green, GH) and insulin (red, A-D, G-J). DBA-expressing branching ducts were observed in both neonates (green, IJ). DAPI (blue). Bar: 50 μm. Quantification of these data show increases in the insulin+ and glucagon+ area of bigenic pancreas from E17.5 to P1 compared to controls (KL). Total pancreatic area in Pdx1tTA/+;tetOMafA also shows enhanced growth (M). Blood glucose levels from each group of neonates (n = 8 for each group) show that bigenic neonates were significantly hyperglycemic at P1 (N). Mean ± s.e.m.
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pone.0142286.g005: P1 transgenic pancreases contain significantly larger endocrine clusters compared to E17.5.At P1 bigenic islets had relatively normal organization as compared to controls for expression of glucagon (green, AB, red, EF), somatostatin (green, CD), pancreatic polypeptide (green, EF), ghrelin (green, GH) and insulin (red, A-D, G-J). DBA-expressing branching ducts were observed in both neonates (green, IJ). DAPI (blue). Bar: 50 μm. Quantification of these data show increases in the insulin+ and glucagon+ area of bigenic pancreas from E17.5 to P1 compared to controls (KL). Total pancreatic area in Pdx1tTA/+;tetOMafA also shows enhanced growth (M). Blood glucose levels from each group of neonates (n = 8 for each group) show that bigenic neonates were significantly hyperglycemic at P1 (N). Mean ± s.e.m.

Mentions: We examined whether the remaining E17.5 tubular epithelial cells could function as bipotent/multipotent progenitors by allowing bigenic embryos to reach term. Pancreatic size in bigenic mice significantly increased between E17.5 and P1 (Fig 4A and 4C) but remained smaller than the controls (Fig 4E and 4F). Bigenic neonates showed a rapid growth in the pancreas mainly along the embryonic ductal structures (Fig 4B and 4D). P1 pancreatic sections from bigenic pups stained for endocrine hormones and ductal marker DBA showed endocrine cell clusters containing all endocrine cell types (Fig 5A–5J) with a greater increase in the relative acinar and endocrine cell volumes between E17.5 to P1 in bigenics than in controls. From E17.5 to P1, the insulin+ area in Pdx1tTA/+;tetOMafA mice increased 3.8-fold (p<0.01) compared to 1.3-fold in controls (Fig 5K), glucagon+ area increased 3.0-fold (p = 0.02) and 1.1-fold in bigenics and controls, respectively (Fig 5L), and total pancreatic area increased 4.8-fold (p<0.01) and 2.0-fold (p<0.01), respectively (Fig 5M). Although a significant growth was seen in the bigenic pancreas between E17.5 and P1, bigenic pancreas was still dramatically smaller than control (Fig 4). Additionally the partial recovery of endocrine cells in P1 bigenic pancreas was insufficient to prevent the development of hyperglycemia, with P1 bigenic pups having significantly higher blood glucose values (313.9±11.2 mg/dl) than the monogenic (Pdx1tTA/+ or tetOMafA) or wild type animals (99.9±9.1, 98.5±8.2 and 92.0±8.0 mg/dl, respectively) (Fig 5N).


Compensatory Response by Late Embryonic Tubular Epithelium to the Reduction in Pancreatic Progenitors.

Nishimura W, Kapoor A, El Khattabi I, Jin W, Yasuda K, Bonner-Weir S, Sharma A - PLoS ONE (2015)

P1 transgenic pancreases contain significantly larger endocrine clusters compared to E17.5.At P1 bigenic islets had relatively normal organization as compared to controls for expression of glucagon (green, AB, red, EF), somatostatin (green, CD), pancreatic polypeptide (green, EF), ghrelin (green, GH) and insulin (red, A-D, G-J). DBA-expressing branching ducts were observed in both neonates (green, IJ). DAPI (blue). Bar: 50 μm. Quantification of these data show increases in the insulin+ and glucagon+ area of bigenic pancreas from E17.5 to P1 compared to controls (KL). Total pancreatic area in Pdx1tTA/+;tetOMafA also shows enhanced growth (M). Blood glucose levels from each group of neonates (n = 8 for each group) show that bigenic neonates were significantly hyperglycemic at P1 (N). Mean ± s.e.m.
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pone.0142286.g005: P1 transgenic pancreases contain significantly larger endocrine clusters compared to E17.5.At P1 bigenic islets had relatively normal organization as compared to controls for expression of glucagon (green, AB, red, EF), somatostatin (green, CD), pancreatic polypeptide (green, EF), ghrelin (green, GH) and insulin (red, A-D, G-J). DBA-expressing branching ducts were observed in both neonates (green, IJ). DAPI (blue). Bar: 50 μm. Quantification of these data show increases in the insulin+ and glucagon+ area of bigenic pancreas from E17.5 to P1 compared to controls (KL). Total pancreatic area in Pdx1tTA/+;tetOMafA also shows enhanced growth (M). Blood glucose levels from each group of neonates (n = 8 for each group) show that bigenic neonates were significantly hyperglycemic at P1 (N). Mean ± s.e.m.
Mentions: We examined whether the remaining E17.5 tubular epithelial cells could function as bipotent/multipotent progenitors by allowing bigenic embryos to reach term. Pancreatic size in bigenic mice significantly increased between E17.5 and P1 (Fig 4A and 4C) but remained smaller than the controls (Fig 4E and 4F). Bigenic neonates showed a rapid growth in the pancreas mainly along the embryonic ductal structures (Fig 4B and 4D). P1 pancreatic sections from bigenic pups stained for endocrine hormones and ductal marker DBA showed endocrine cell clusters containing all endocrine cell types (Fig 5A–5J) with a greater increase in the relative acinar and endocrine cell volumes between E17.5 to P1 in bigenics than in controls. From E17.5 to P1, the insulin+ area in Pdx1tTA/+;tetOMafA mice increased 3.8-fold (p<0.01) compared to 1.3-fold in controls (Fig 5K), glucagon+ area increased 3.0-fold (p = 0.02) and 1.1-fold in bigenics and controls, respectively (Fig 5L), and total pancreatic area increased 4.8-fold (p<0.01) and 2.0-fold (p<0.01), respectively (Fig 5M). Although a significant growth was seen in the bigenic pancreas between E17.5 and P1, bigenic pancreas was still dramatically smaller than control (Fig 4). Additionally the partial recovery of endocrine cells in P1 bigenic pancreas was insufficient to prevent the development of hyperglycemia, with P1 bigenic pups having significantly higher blood glucose values (313.9±11.2 mg/dl) than the monogenic (Pdx1tTA/+ or tetOMafA) or wild type animals (99.9±9.1, 98.5±8.2 and 92.0±8.0 mg/dl, respectively) (Fig 5N).

Bottom Line: Previously we reported that in Pdx1tTA/+;tetOMafA (bigenic) mice inducing expression of transcription factor MafA in Pdx1-expressing (Pdx1+) cells throughout embryonic development inhibited the proliferation and differentiation of 1°MPC cells, resulting in reduced pancreatic mass and endocrine cells by embryonic day (E) 17.5.However, by birth (P0), as we now report, such bigenic pups had significantly increased pancreatic and endocrine volumes with endocrine clusters containing all pancreatic endocrine cell types.Thus, these bigenic mice provide a novel way to characterize the competency of 1°MPC for their ability to specify endocrine progenitors, a critical limitation in our understanding of endocrine differentiation.

View Article: PubMed Central - PubMed

Affiliation: Section of Islet Cell & Regenerative Biology, Joslin Diabetes Center, Boston, Massachusetts, United States of America.

ABSTRACT
Early in pancreatic development, epithelial cells of pancreatic buds function as primary multipotent progenitor cells (1°MPC) that specify all three pancreatic cell lineages, i.e., endocrine, acinar and duct. Bipotent "Trunk" progenitors derived from 1°MPC are implicated in directly regulating the specification of endocrine progenitors. It is unclear if this specification process is initiated in the 1°MPC where some 1°MPC become competent for later specification of endocrine progenitors. Previously we reported that in Pdx1tTA/+;tetOMafA (bigenic) mice inducing expression of transcription factor MafA in Pdx1-expressing (Pdx1+) cells throughout embryonic development inhibited the proliferation and differentiation of 1°MPC cells, resulting in reduced pancreatic mass and endocrine cells by embryonic day (E) 17.5. Induction of the transgene only until E12.5 in Pdx1+ 1°MPC was sufficient for this inhibition of endocrine cells and pancreatic mass at E17.5. However, by birth (P0), as we now report, such bigenic pups had significantly increased pancreatic and endocrine volumes with endocrine clusters containing all pancreatic endocrine cell types. The increase in endocrine cells resulted from a higher proliferation of tubular epithelial cells expressing the progenitor marker Glut2 in E17.5 bigenic embryos and increased number of Neurog3-expressing cells at E19.5. A BrdU-labeling study demonstrated that inhibiting proliferation of 1°MPC by forced MafA-expression did not lead to retention of those progenitors in E17.5 tubular epithelium. Our data suggest that the forced MafA expression in the 1°MPC inhibits their competency to specify endocrine progenitors only until E17.5, and after that compensatory proliferation of tubular epithelium gives rise to a distinct pool of endocrine progenitors. Thus, these bigenic mice provide a novel way to characterize the competency of 1°MPC for their ability to specify endocrine progenitors, a critical limitation in our understanding of endocrine differentiation.

No MeSH data available.


Related in: MedlinePlus