The expression of CD9 in the peri-implantation mouse uterus is upregulated in an ovarian steroid hormone–dependent manner

ObjectiveTo examine the spatiotemporal expression of CD9 protein in the peri-implantation mouse uterus as well as the effects of ovarian steroid hormones on CD9.DesignExperimental animal study.SettingReproductive biological center of Chinese Academy of Sciences.Animal(s)Female Kunming white strain mice (6–8 weeks old).Intervention(s)Subcutaneous injection of P4/E2; uterine tissues were collected at different times after injection.Main Outcome Measure(s)The levels of protein and mRNA were detected in mouse uterus during peri-implantation and after steroid hormones treatment.Result(s)CD9 protein was expressed intensely in the stromal cells on days 1 and 2 of pregnancy. On days 3 and 4, the glandular and luminal epithelial cells exhibited accumulation of CD9 protein. After the initial attachment reaction on day 5, luminal epithelial and stromal cells immediately surrounding the blastocysts exhibited distinct accumulation of CD9. On days 6–8, the accumulation of CD9 occurred in decidual cells. Using ovariectomized mice, we also observed that both progesterone and estrogen upregulated uterine CD9 expression.Conclusion(s)The results of the current investigation showed that CD9 was differentially expressed in the uterus depending on the stage of implantation and was upregulated in ovarian steroid hormone–dependent manner, implicating multiple roles of CD9 in the regulation of embryo implantation during the peri-implantation period.