Arginine Metabolism in Decidual Macrophages During Pregnancy.

BACKGROUND: Maternal immune tolerance to the semi-allogeneic fetus is essential for successful pregnancy, while immune defense against pathogens must be preserved. Decidual macrophages (DMs) are critical regulators at the maternal-fetal interface, involved in trophoblast invasion, vascular remodeling, and immune modulation.

METHODS: This review integrates findings from human studies, animal models, and in vitro experiments to explore how arginine metabolism regulates macrophage polarization and pregnancy outcomes.

RESULTS: Arginine metabolism influences DM function via two major pathways: iNOS promotes M1 polarization and pro-inflammatory activity, while Arg-1 supports M2 polarization, tissue remodeling, and immune tolerance. Dysregulation of this balance is associated with pregnancy complications such as pre-eclampsia and fetal growth restriction. Pathogens like Helicobacter pylori and Mycobacterium tuberculosis exploit Arg-1 activity to evade host immunity. Clinical studies also suggest that L-arginine supplementation can improve placental function and fetal growth.

CONCLUSION: Arginine metabolism is a key modulator of macrophage polarization and immune balance in pregnancy. Targeting this pathway may offer novel therapeutic strategies to improve maternal and fetal outcomes.