Neutrophils regulate the process of embryo implantation

Neutrophils exert roles in multiple stages of the reproductive cycle; however, their specific manifestations remain unclear. In the present study, we explored the role of neutrophils in the process of embryonic implantation and revealed the presence of multiple types of functionally redundant neutrophils at the maternal-fetal interface during early pregnancy. In pregnant C57BL mice, the level of circulating neutrophils increased on embryonic day 8.5 in early pregnancy. Similarly, in pseudopregnant female mice that underwent in vivo induced decidualization on day 4 , the level of circulating neutrophils was also elevated on E8.5. Depletion of neutrophils in pregnant mice using the Combo depletion strategy led to a decrease in the blastocyst implantation rate. Three subsets of neutrophils were present at the maternal-fetal interface of pregnant mice, among which the CD11b+Ly6Glo and CD11b+Ly6Ghi subsets exhibited high similarity.