Background The etiology of about half of the patients with recurrent spontaneous abortion (RSA) remains unclear, and the imbalance of the immune inflammatory response at the mother-foetal interface may be one of the keys to the onset. Granulocyte-colony stimulating factor (G-CSF) is thought to have a protective effect on pregnancy, and its absence may lead to pregnancy failure, but the evidence is scant. This study aims at investigating whether the loss of G-CSF induced RSA by affecting cell

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... munication at the maternal-foetal interface. Results G-CSF was mainly expressed in villus rather than decidua, and the expression in RSA tissues was lower than that in normal tissues. Down-regulation of G-CSF in trophoblasts resulted in decreased cell activity. Trophoblast-derived exosomes inhibited macrophage activation, while G-CSF free exosomes did not. Intraperitoneal injection of G-CSF improved the pregnancy outcome of RSA mice, and the expression of G-CSF and its receptor at the mother-foetal interface also changed. Conclusion The expression of G-CSF was found to be decreased in villi of patients with RSA. The absence of G-CSF weakens the immune suppression of trophoblasts against macrophages, and the function of trophoblasts is impaired, which may be a key factor in the occurrence of RSA. G-CSF decreased the rate of abortion in RSA mice, and might provide some assistance in the treatment of patients with RSA.