Imbalance polarization of M1/M2 macrophages in miscarried uterus

Background Lipopolysaccharides (LPS) is well known to manifest a miscarriage-inducing effector during early pregnancy and activate macrophage to induce M1 macrophage polarization. However, the role of macrophage polarization in LPS-related miscarriage-inducing effect is not apparent.Methods In this work, gene expression changes and the percentage of M1/M2 macrophages and monocytes in LPS-induced miscarried uterus were firstly analyzed by RNA sequencing (RNA-seq) and Flow Cytometry. To explore the origin that contributes to M1/M2 macrophage differentiation, the expression of monocyte chemotactic protein (MCP-1), CCL3, and CCL4, chemokines related to monocyte/macrophage migration, was tested by quantitative real time PCR (qRT-PCR).Results We found that percentage of M1 macrophages rose, while the percentage of M2 macrophages declined down in the injected mice uterus. Meanwhile, the percentage of M1 and M2 macrophages showed no significant difference in the spleens of LPS injected mice compared to PBS injected control mice. Expression of Mcp-1, Ccl3, and Ccl4 and numbers of monocytes were remarkably up-regulated in LPS-induced miscarried mice uterus.Conclusion These results indicated that polarization and proportion changes of macrophage in the uterus may contribute to miscarriage. Our work provides new evidence correlating the aberrant regulation of M1/M2 macrophage polarization with deleterious miscarriage-inducing effects. This will help us understand the roles of critical immune cell differentiation in maintaining normal pregnancy.