Autophagy suppression of trophoblast cells induces pregnancy loss by activating decidual NK cytotoxicity and inhibiting trophoblast invasion

BACKGROUND: The crosstalk between trophoblast cells and decidual NK cells plays an important role in the establishment and maintenance of normal pregnancy. Recent studies reported that autophagy can induce immune tolerance at the maternal fetal interface, while the mechanism remains unclear. METHODS: Autophagy levels in the villi of normal and recurrent spontaneous abortion (RSA) patients were detected by transmission electron microscopy. After co-cultured with trophoblast cells pretreated with 3-MA or rapamycin, NK cells were collected and the expression of killer receptors was detected by flow cytometry (FCM). The invasiveness of trophoblasts was tested by Cell invasion assay. RESULTS: Compared with elective pregnancy termination patients, the level of autophagy in the villi of RSA patients was significantly decreased. Inducing the autophagy level in trophoblast cells with rapamycin could significantly inhibit the cytotoxicity of NK cells in the co-culture system, and supplement of IGF-2 could rectify this effect. Meanwhile, autophagy suppression of trophoblasts reduced the level of Paternally Expressed Gene 10 (PEG10), leading to the impairment of trophoblast cell invasion. In addition, NK cells educated by autophagy-inhibited trophoblasts further decreased the proliferation and invasiveness of trophoblasts. In pregnant mice model, injection with 3-MA promoted the cytotoxicity of uterine NK cells, and increased the embryo absorption rate. CONCLUSION: Autophagy suppression of trophoblasts increase the cytotoxicity of NK cells and damage the trophoblasts invasion possibly by targeting IGF-2 and PEG10, respectively, which ultimately leads to miscarriage.