Polarized macrophages promote gestational beta cell growth through extracellular signal-regulated kinase 5 signalling

Area of Science:

• Endocrinology
• Immunology
• Cell Biology

Background:

• Gestational diabetes mellitus (GDM) is characterized by impaired insulin secretion and glucose intolerance.
• Pancreatic beta cells must proliferate during pregnancy to meet increased insulin demands.
• The role of pancreatic macrophages in regulating beta cell function during pregnancy is not fully understood.

Purpose of the Study:

• To investigate the impact of pancreatic macrophage depletion on gestational beta cell proliferation and glucose tolerance.
• To elucidate the molecular mechanisms underlying the crosstalk between pancreatic macrophages and beta cells.

Main Methods:

• Utilized genetic animal models, including beta-cell-specific extracellular signal-regulated kinase 5 (ERK5) knockout and epidermal growth factor receptor (EGFR) knockout mice.
• Employed in vivo and in vitro co-culture systems to study macrophage-beta cell interactions.
• Analyzed gestational beta cell proliferation and glucose response.

Main Results:

• Beta cell-derived placental growth factor (PlGF) recruits and polarizes naive macrophages to an M2-like phenotype.
• These M2-like macrophages secrete epidermal growth factor (EGF), activating ERK5 signaling in beta cells, thereby promoting beta cell proliferation.
• Activation of beta cell ERK5 signaling enhances PlGF production and secretion, establishing a positive feedback loop.

Conclusions:

• A novel regulatory loop involving PlGF, EGF, and ERK5 signaling between macrophages and beta cells controls gestational beta cell expansion.
• Pancreatic macrophages are crucial for maintaining beta cell function and glucose homeostasis during pregnancy.
• Targeting this macrophage-beta cell axis may offer therapeutic strategies for GDM.