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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

Proliferation of DBA+ epithelial tubules and not insulin+ cells contributes to increased number of insulin+ cells in Pdx1tTA/+;tetOMafA pancreas at E19.5 and later.Bigenic pancreas at both E17.5 and E19.5 showed proliferation (Ki67, red) of DBA+ (green, A-D) and insulin+ (green, E-H) cells. Quantification of the proportion of DBA+ cells or insulin+ cells that were Ki67+ showed significantly increased proliferation of DBA+ cells between E17.5 and E19.5 (I) in bigenic but not control pancreas whereas the proportion of insulin+ cells that were Ki67+ (J) at E19.5 compared to that at E17.5 increased in controls but not bigenic. The bigenic had significantly more replicating DBA+ cells at E19.5 than controls. N = 3 Mean ± s.e.m. Bar: 20 μm.
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pone.0142286.g006: Proliferation of DBA+ epithelial tubules and not insulin+ cells contributes to increased number of insulin+ cells in Pdx1tTA/+;tetOMafA pancreas at E19.5 and later.Bigenic pancreas at both E17.5 and E19.5 showed proliferation (Ki67, red) of DBA+ (green, A-D) and insulin+ (green, E-H) cells. Quantification of the proportion of DBA+ cells or insulin+ cells that were Ki67+ showed significantly increased proliferation of DBA+ cells between E17.5 and E19.5 (I) in bigenic but not control pancreas whereas the proportion of insulin+ cells that were Ki67+ (J) at E19.5 compared to that at E17.5 increased in controls but not bigenic. The bigenic had significantly more replicating DBA+ cells at E19.5 than controls. N = 3 Mean ± s.e.m. Bar: 20 μm.

Mentions: Endocrine cells formed during second transition remain quiescent until towards the end of gestation when they start to proliferate. In case of β-cells, this proliferation requires Pdx1 expression [22]. To discriminate between the possibilities that the increased qqβ-cells seen at birth were due to proliferation of the few endocrine cells present at E17.5 or from neogenesis or newly differentiated cells, we examined the co-expression of proliferation marker (Ki67) with DBA+ and insulin+ cells at E17.5 and E19.5 (Fig 6). At E17.5, 31.2±1.7% of DBA+ cells were Ki67+ in the bigenics while only 25.4±2.5% in controls. At E19.5, the proportion of DBA+ cells expressing Ki67 in Pdx1tTA/+;tetOMafA bigenics (41.7±2.9%, p = 0.02) was significantly increased than in controls (28.9±2.5%) (Fig 6A–6D and 6I). As shown previously [17], at E17.5 larger clusters of insulin+ cells were present in controls, but only occasional single insulin+ cells were seen in bigenic pancreas (Fig 6E and 6F). However by E19.5, we detected small clusters of insulin+ cells in the bigenic pancreas and a further increased size of insulin+ clusters in controls (Fig 6E–6H). At E17.5, the proportion of insulin+Ki67+ cells was comparable in Pdx1tTA/+;tetOMafA (3.1±1.6%) and control embryos (3.8±1.0%). At E19.5, the proliferation of insulin+ cells in bigenic (5.6±3.4%) did not differ from that at E17.5, while in controls insulin+ Ki67+ cells showed a tendency to increase (10.5±3.0%, p = 0.09) compared to E17.5 (3.8±1.0%). Thus at E19.5, embryonic tubular epithelial cells had greater proliferation in bigenic than in control pancreas, without significant changes in proliferation of insulin+ cells. These data support that the increased number of insulin+ cells seen in the bigenic pancreas at E19.5 and P1 (Figs 5 and 6) results from neogenesis, via proliferation and subsequent differentiation of DBA+ tubular cells, and not from increased proliferation of the few insulin+ cells present at E17.5.


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)

Proliferation of DBA+ epithelial tubules and not insulin+ cells contributes to increased number of insulin+ cells in Pdx1tTA/+;tetOMafA pancreas at E19.5 and later.Bigenic pancreas at both E17.5 and E19.5 showed proliferation (Ki67, red) of DBA+ (green, A-D) and insulin+ (green, E-H) cells. Quantification of the proportion of DBA+ cells or insulin+ cells that were Ki67+ showed significantly increased proliferation of DBA+ cells between E17.5 and E19.5 (I) in bigenic but not control pancreas whereas the proportion of insulin+ cells that were Ki67+ (J) at E19.5 compared to that at E17.5 increased in controls but not bigenic. The bigenic had significantly more replicating DBA+ cells at E19.5 than controls. N = 3 Mean ± s.e.m. Bar: 20 μm.
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pone.0142286.g006: Proliferation of DBA+ epithelial tubules and not insulin+ cells contributes to increased number of insulin+ cells in Pdx1tTA/+;tetOMafA pancreas at E19.5 and later.Bigenic pancreas at both E17.5 and E19.5 showed proliferation (Ki67, red) of DBA+ (green, A-D) and insulin+ (green, E-H) cells. Quantification of the proportion of DBA+ cells or insulin+ cells that were Ki67+ showed significantly increased proliferation of DBA+ cells between E17.5 and E19.5 (I) in bigenic but not control pancreas whereas the proportion of insulin+ cells that were Ki67+ (J) at E19.5 compared to that at E17.5 increased in controls but not bigenic. The bigenic had significantly more replicating DBA+ cells at E19.5 than controls. N = 3 Mean ± s.e.m. Bar: 20 μm.
Mentions: Endocrine cells formed during second transition remain quiescent until towards the end of gestation when they start to proliferate. In case of β-cells, this proliferation requires Pdx1 expression [22]. To discriminate between the possibilities that the increased qqβ-cells seen at birth were due to proliferation of the few endocrine cells present at E17.5 or from neogenesis or newly differentiated cells, we examined the co-expression of proliferation marker (Ki67) with DBA+ and insulin+ cells at E17.5 and E19.5 (Fig 6). At E17.5, 31.2±1.7% of DBA+ cells were Ki67+ in the bigenics while only 25.4±2.5% in controls. At E19.5, the proportion of DBA+ cells expressing Ki67 in Pdx1tTA/+;tetOMafA bigenics (41.7±2.9%, p = 0.02) was significantly increased than in controls (28.9±2.5%) (Fig 6A–6D and 6I). As shown previously [17], at E17.5 larger clusters of insulin+ cells were present in controls, but only occasional single insulin+ cells were seen in bigenic pancreas (Fig 6E and 6F). However by E19.5, we detected small clusters of insulin+ cells in the bigenic pancreas and a further increased size of insulin+ clusters in controls (Fig 6E–6H). At E17.5, the proportion of insulin+Ki67+ cells was comparable in Pdx1tTA/+;tetOMafA (3.1±1.6%) and control embryos (3.8±1.0%). At E19.5, the proliferation of insulin+ cells in bigenic (5.6±3.4%) did not differ from that at E17.5, while in controls insulin+ Ki67+ cells showed a tendency to increase (10.5±3.0%, p = 0.09) compared to E17.5 (3.8±1.0%). Thus at E19.5, embryonic tubular epithelial cells had greater proliferation in bigenic than in control pancreas, without significant changes in proliferation of insulin+ cells. These data support that the increased number of insulin+ cells seen in the bigenic pancreas at E19.5 and P1 (Figs 5 and 6) results from neogenesis, via proliferation and subsequent differentiation of DBA+ tubular cells, and not from increased proliferation of the few insulin+ cells present at E17.5.

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