Endocrine Abstracts

JOINT1379

Background: During pregnancy, the pancreatic β-cell mass expands to meet the increased metabolic demands, and it subsequently regresses in the postpartum period as maternal glucose homeostasis returns to normal. The transcriptional changes underlying these adaptations remain unclear. This study seeks to explore the heterogeneity of pancreatic beta cell populations at various stages of pregnancy and postpartum involution, focusing on the molecular mechanisms driving their adaptive plasticity.

Methods: Islets were isolated from non-pregnant mice, pregnant mice at day 14. 5, and postpartum mice at day 4. Single-cell RNA sequencing (scRNA-seq) was performed to analyze the transcriptomic features of the β-cells. Bioinformatics analyses were conducted to identify heterogeneity within these cells. SCENIC analysis was employed to identify the transcription factors most active in proliferating β-cells. Immunofluorescence assays revealed that Pbx4 positivity significantly increased in pancreatic islets of pregnant mice and returned to baseline levels postpartum. In vitro functional assays were conducted on mouse β-cell lines to validate the role of Pbx4 in regulating the expression of cell cycle-related proteins, thereby promoting β-cell proliferation.

Results: Our single-cell transcriptomic analysis identified five functionally distinct β-cell subpopulations. We focused on three dynamically regulated clusters that exhibit stage-specific heterogeneity during gestational adaptation and postpartum recovery, we observed:A polyhormonal subpopulation co-expressing Gcg (glucagon), Sst (somatostatin), and Ppy (pancreatic polypeptide), indicative of endocrine plasticity, decreases during pregnancy and recovers in the postpartum. This suggests that the increased metabolic stress during pregnancy may drive this cell population to differentiate into mature beta cells. A pregnancy-enriched cluster marked by acinar-to-β cell transdifferentiation, with expression of Ctrb1 and Prss2, suggests that acinar cells transdifferentiate into β-like cells during pregnancy to alleviate insulin insufficiency; and a proliferative population marked by Mki67, potentially regulated by the transcription factor Pbx4. Overexpression of Pbx4 in mouse β-cell lines has demonstrated that Pbx4 can upregulate the expression of cyclins, thereby promoting β-cell proliferation.

Conclusion: Using single-cell RNA sequencing, we revealed transcriptomic changes of distinct β-cell subpopulations, including polyhormonal cells, acinar-like clusters, and a proliferative β-cell subset during pregnancy and postpartum. Our analysis reveal novel mechanisms of β-cell adaptation to metabolic challenges during pregnancy-related changes.

Keywords: Pancreatic β-cells, Single-cell RNA-seq, cellular plasticity, Pbx4