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Background: Embryo implantation and decidualization are essential to the establishment and maintenance of successful pregnancy in both rodents and primates. Receptive endometrium synergism with well-developed blastocyst is prerequisite for successful embryo implantation. Melatonin, which is mainly synthesized by the pineal gland in vertebrates, promotes human blastocyst development and increases pregnancy rate. However, the role and underlying mechanism of melatonin on human endometrial receptivity and decidualization still remains poorly defined. Methods: Trophoblast JEG-3 spheroids were cocultured with endometrial epithelial cells. Real-time PCR, Western blot, siRNA transfection, epithelial-stromal cell coculture system, and assay of Ishikawa cell-conditioned medium were used to explore the effects of melatonin on human endometrial decidualization and the underlying molecular pathways. Findings: In this study, we showed that melatonin induces the expression of the endometrial receptive markers, integrin β3 and HOXA10 in the less-receptive endometrial epithelial cell line AN3 CA and increased the attachment rate of trophoblast JEG-3 spheroids on endometrial epithelial AN3 CA cells. In an epithelial-stromal coculture system, we further proved that melatonin-stimulated IFN-γ secretion from Ishikawa cells promotes in vitro decidualization of stromal cells through regulating progesterone receptor B (PRB). Under in vitro decidualization, IFN-γ significantly increases the levels IGFBP1 and PRL, which is abrogated by suppressing PRB. Under in vitro decidualization of endometrial stromal cells, the expression of the decidualization markers, IGFBP1 and PRL, is significantly stimulated by melatonin treatment. Melatonin obviously increases phosphorylated STAT3 level and decreases p-Akt level. Interpretation: Melatonin may play crucial roles in human endometrial receptivity and decidualization. The dialogue between endometrial epithelial and stromal cell mediated by melatonin should be beneficial for decidual process. Funding: National Key R&D Program of China (2018YFC1004403) and National Natural Science Foundation of China (31671563, 31871511). Declaration of Interests: The authors declare that there is no conflict of interest. Ethics Approval Statement: All human procedures were approved by the Institutional Committee on the Use of Human Subjects in Medical Research of Southern Medical University with written consent.

Reproductive capacity in animals and women declines with increasing age. Although ovarian aging is considered as a main cause for the decline of pregnancy rate, whether uterine aging occurs remains unclear. Even if blastocysts are transferred from young donors to older pseudopregnant recipients, the rate of implantation is still low, suggesting the occurrence of uterine aging. In this study, we compared the pregnancy rate and the uterine responsiveness of steroid hormones in ovariectomized mice at age between 2- and 12-month-old. Compared to 2-month-old mice, there is a significant decrease of both pregnancy rate and the number of implantation sites in 12-month-old mice. In ovariectomized mice, the uterine responsiveness of steroid hormones is also significantly different between 2- and 12-month-old mice. On day 4, Muc1 and PR level in 12-month-old mice is significantly higher than that in 2-month-old mice, while Hand2 level is significantly lower in 12-month-old mice. Our data suggest that the abnormal responsiveness of steroid hormones may contribute to the decline of pregnancy rate in 12-month-old mice.

We studied the influence of Pt, Co and MnIr layer on the exchange bias field HE and coercive field HC in perpendicular exchange-biased [Pt/Co]3/MnIr multilayers by magneto-optical Kerr effect. As the thickness of the Pt layer increases, the perpendicular magnetic anisotropy constant Ku first increases and then reaches to saturation, which is resulted from the competition between perpendicular anisotropy and interfacial short-range interaction. The saturation damping constant α0 of the sample increases from about 0.062 to 0.122 when the Pt thickness increases from 0.5 nm to 1.5 nm. However, α0 increases with the decrease of Co thickness. We attributed both of these mainly to spin pumping effect.