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

Decidual fibrinoid-associated neutrophils (dFANs) secrete MMP-9 and promote trophoblast invasion, supporting invasive placentation at the maternal-fetal interface.

• Why it matters: Understanding immune cell roles in early pregnancy is crucial, as disruptions can lead to pregnancy complications. The specific contribution of neutrophils at this stage remains unclear, limiting insights into placental development.
• What they did: Researchers analyzed first-trimester human decidual tissue and blood samples, identifying dFANs in Rohr's layer and comparing them to peripheral blood neutrophils using flow and mass cytometry. They examined dFAN functions, including MMP-9 secretion and effects on EVT invasion, and explored the MMP-9-TGF-β axis's role in immune modulation.
• The result: dFANs' secretion of MMP-9 enhances EVT invasion and activates TGF-β, which suppresses neutrophil cytotoxicity and shifts neutrophils toward a proinvasive state, revealing a mechanism that facilitates placental invasion.