G-CSF: A vehicle for communication between trophoblasts and macrophages which may cause problems in recurrent spontaneous abortion

The etiology of approximately half of patients with recurrent spontaneous abortion (RSA) has yet to be established. Granulocyte-colony stimulating factor (G-CSF) exerts a protective effect on pregnancy and its absence may lead to pregnancy failure. However, the effects and mechanisms of G-CSF activities have not been fully explored. Therefore, we aimed at evaluating whether a loss of G-CSF induces RSA by affecting cell communication at the maternal-foetal interface. Villous and decidual tissues were obtained from participants and expression levels of G-CSF determined by qRT-PCR, Western blot and immunohistochemistry. G-CSF levels in trophoblasts were downregulated by siRNA. Exosomes were extracted from trophoblasts and co-cultured with macrophages. Molecular expression levels of key genes were determined by qRT-PCR and Western blot. Migration and proliferation of cells were evaluated by transwell and CCK8 assays. The RSA mice models were intraperitoneally administered with G-CSF to assess pregnancy outcomes and expression profiles of G-CSF as well as its receptor at the mother-foetal interface. Relative to the decidua, G-CSF was highly expressed in the villus, and expression levels were low in RSA tissues compared to normal tissues. Down-regulation of G-CSF in the trophoblast cell line (HTR-8/SVneo) by siRNA was associated with a decrease in cell activities. Trophoblast-derived exosomes inhibited the activation of the macrophage cell line (RAW264.7), whereas G-CSF free exosomes had no effects on macrophage activation. Intraperitoneal administration of G-CSF improved pregnancy outcomes in RSA mice and increased the amounts of G-CSF at the maternal-foetal interface. G-CSF levels were downregulated in villi of RSA patients. The absence of G-CSF impaired the proliferation as well as migration capacities of trophoblasts, and weakened the suppression of trophoblasts against macrophages. This implies that suppressed G-CSF levels may be a key factor in RSA occurrence. G-CSF decreased the rate of abortion in RSA mice, thus, it could be a treatment option for RSA patients. • G-CSF is decreased in patients with RSA comparing with normal pregnant women. • G-CSF regulates trophoblast - macrophage communication through exosomes. • G-CSF decreases the rate of abortion in RSA mice.