Fibrinoid-associated neutrophils promote invasive placentation and neutrophil reprogramming at the maternal-fetal interface.

Decidual fibrinoid-associated neutrophils (dFANs) promote invasive placentation through a specific MMP-9-TGF-β axis in first-trimester human pregnancy.

• Why it matters: Understanding how maternal immune cells interact with the placenta is crucial for elucidating mechanisms of successful early pregnancy, which remain poorly understood. Clarifying neutrophil roles could reveal targets for pregnancy complications related to placental invasion.
• What they did: Researchers analyzed first-trimester decidual tissue and blood samples, identifying dFANs localized to Rohr's layer, and compared their phenotypes and functions to peripheral blood neutrophils using flow and mass cytometry, focusing on their secretion of MMP-9 and influence on EVT invasion.
• The result: dFAN-derived MMP-9 activates TGF-β, suppresses PBN cytotoxicity, and promotes a proinvasive neutrophil state, defining a dFAN-dependent axis that supports placental invasion at the maternal-fetal interface.