Chromogranin A-positive hormone-negative endocrine cells in pancreas in human pregnancy

Abstract

Introduction: We sought to determine whether chromogranin A-positive hormone-negative (CPHN) endocrine cells are increased in the pancreas of pregnant women, offering potential evidence in support of neogenesis.

Methods: Autopsy pancreata from pregnant women (n = 14) and age-matched non-pregnant control women (n = 9) were obtained. Staining of pancreatic sections for chromogranin A, insulin and a cocktail of glucagon, somatostatin, pancreatic polypeptide and ghrelin was undertaken, with subsequent evaluation for CPHN cell frequency.

Results: The frequency of clustered β-cells was increased in pregnant compared to non-pregnant subjects (46.6 ± 5.0 vs. 31.8 ± 5.0% clustered β-cells of total clustered endocrine cells, pregnant vs. non-pregnant, p < .05). Frequency of endocrine cocktail cells was lower in pregnant women than non-pregnant women (36.2 ± 4.0 vs. 57.0 ± 6.8% clustered endocrine cocktail cells of total clustered endocrine cells, pregnant vs. non-pregnant, p < .01). No difference in frequency of CPHN cells was found in islets, nor in clustered or single cells scattered throughout the exocrine pancreas, between pregnant and non-pregnant women. The frequency of CPHN cells in pregnancy was independent of the number of pregnancies (gravidity).

Conclusions: Our findings of no increase in CPHN cell frequency in pancreas of pregnant women suggest that this potential β-cell regenerative mechanism is not that by which the increased β-cell mass of pregnancy is achieved. However, an increase in the percentage of clustered β-cells was found in pregnancy, with decreased frequency of other endocrine cells in clusters, suggesting a compensatory shift from other pancreatic endocrine cell types to β-cells as a mechanism to meet the increased insulin demands of pregnancy.

Keywords: beta cell; pancreas; pregnancy; regeneration.

FIGURE 1

Examples of immunofluorescent images of insulin (A, B) and endocrine cocktail (C, D) immunoreactivity in islets or as clustered cells in four different pancreas sections of non‐pregnant and pregnant cases. Merged images showing insulin in white (A and B) and endocrine cocktail in green (C and D) with DAPI in blue (all images). Yellow arrows indicate clustered β‐cells and white arrows indicate clustered endocrine cocktail cells in both non‐pregnant and pregnant cases. There was no change in frequency of total clustered endocrine cells (of total endocrine cells counted in all compartments of pancreas) in pregnancy (3.8 ± 0.7 vs. 3.5 ± 0.5% of clustered endocrine cells, Pregnant vs. non‐pregnant, p = ns) (E). Frequency of clustered β‐cells (of total clustered endocrine cells) was higher in pregnant cases compared to non‐pregnant cases (46.6 ± 5.0 vs. 31.8 ± 5.0% of clustered β‐cells, pregnant vs. non‐pregnant, p < .05) (F). The frequency of clustered endocrine cocktail cells (of total clustered endocrine cells) was lower in pregnant cases compared to non‐pregnant cases (57.02 ± 6.8 vs. 36.2 ± 4.02% of clustered endocrine cocktail cells, pregnant vs. non‐pregnant, p < .01) (G). Scale bar, 100 μm (all images)

FIGURE 2

Example of a chromogranin A‐positive hormone‐negative (CPHN) cell in pancreas from a control (non‐pregnant subject) (A) and pregnant subject (B). Individual layers are stained for endocrine cocktail (Glucagon, Somatostatin, Pancreatic Polypeptide and Ghrelin) [green], insulin [white], Chromogranin A (ChrgA) [red] and DAPI [blue] are shown along with the merged image. Insets, magnified images of the desired areas (indicated by red squares) of low power images to clearly demonstrate the CPHN cells. Yellow arrows indicate CPHN cells in both control and pregnant subjects. Scale bars, 50 μm (for low power images) and 10 μm for the insets

FIGURE 3

The frequency of CPHN cells in control (non‐pregnant subjects) and pregnant subjects. There was no difference in CPHN cells in any compartment (islets, clusters or as single cells) in pregnant vs. non‐pregnant women (0.6 ± 0.2 vs. 0.4 ± 0.2 CPHN cells/islet section, pregnant vs. non‐pregnant, p = ns (A); 2.1 ± 0.9 vs. 1.0 ± 0.2 clustered CPHN cells/mm², pregnant vs. non‐pregnant, p = ns (B); 2.0 ± 0.6 vs. 0.8 ± 0.2 single CPHN cells/mm², pregnant vs. non‐pregnant, p = ns (C)