Neutrophil extracellular traps are critical for pregnancy loss in sphingosine kinase-deficient mice on 129Sv/C57BL/6 background.

Exaggerated maternal immune responses must be strictly controlled to ensure a successful pregnancy. Neutrophil extracellular traps (NETs) have recently been implicated as a potential mechanism for promoting inflammation in pregnancy-related disorders. In this study, we demonstrated that NETs play a key role in the pathogenesis of sphingosine kinase (Sphk)-mediated pregnancy loss. Perturbing the sphingolipid pathway by disrupting Sphk genes during pregnancy led to excessive NET formation exclusively at the fetomaternal interface and early fetal death. Neutrophils that formed NETs were characterized by histone hypercitrullination and peptidylarginine deiminase 4 (PAD4) overexpression. In addition, thrombus formation was enhanced in the decidua, but not in the plasma, of Sphk-deficient mice. Blocking NET formation with a PAD4 inhibitor protected Sphk-deficient mice from pregnancy loss. The PAD4 inhibition significantly reduced the expression of hypercitrullinated histone in neutrophils and ameliorated vascular injury in the decidua of Sphk-deficient mice. Moreover, NET formation was induced in human neutrophils stimulated with Sphk-deficient human decidual cells. Together, these findings indicate that targeting NETs might be a novel therapeutic strategy to treat idiopathic pregnancy loss in humans.-Mizugishi, K., Yamashita, K. Neutrophil extracellular traps are critical for pregnancy loss in sphingosine kinase-deficient mice on 129Sv/C57BL/6 background.