| Background:In gestation physiology, endometrial receptivity for an embryo’s implantation is a critical factor in establishing pregnancy. The period of endometrial receptivity, known as the "implantation window,"is short, approximately 4 days long, between Days 20 and 24 of the menstrual cycle. At the time of insemination of serum in the endometrium, it manifests an inflammatory-like response, which is accompanied by edema and hyperemia.Aquaporins (AQPs) primarily transportr water across the plasma membrane and mediate the rapid, bulk and osmotically driven transmembrane movement of fluid. Therefore, their expression in the uterus has recently raised considerable interest in the field of fertility research. Aquaporin-1 (AQP1) is water selective and members of the classical AQPs family. AQP1, a 28-kDa protein initially isolated from red blood cells, localizes in endothelial cells. Furthermore, AQP1 were found to be most concentrated within the endometrium at the time of implantation, suggesting that AQP1 may have a physiological role in uterine receptivity.Previous experiments revealed a role for AQPs in angiogenesis, microvascular modifications and endothelial cell migration. Angiogenesis, increased vascular permeability and successful remodeling of spiral arteries are important events during endometrial development and implantation. The angiogenesis process is intense in the secretory phase. MVD is most commonly used to indirectly estimate angiogenesis factors. AQP1 is important for HUVECs activity and angiogenesis. Study showed estradiol (E2) dose-dependently increased the expression levels of AQP1 mRNA and protein in human umbilical vein endothelial cells (HUVECs) and mifepristone was determined to be an ER agonist in the endometrium. So, mifepristone may directly affect endometrial arterioles at the time of implantation, as well as inhibit endometrial receptivity and embryo implantation in vivo and in vitro. These data suggest that mifepristone may affect AQPs1 expression in human endometrium at the time of implantation.Mifepristone was the first progesterone receptor (PR) modulator approved for clinical use and has been used widely as an early-stage abortion drug. Currently, mifepristone is prescribed as an emergency contraceptive, for use within the first 9 weeks of pregnancy. It was recently determined that the dosage required for effective contraception is lower than originally suggested, which is expected to increase both acceptability and continuation rates. Studies have shown that low-dose mifepristone might be an effective contraceptive regimen with few side effects. For example, daily administration of mifepristone (1 mg/day) blocked endometrial development while allowing biphasic ovarian cycles and regular bleeding in women. However, the contraceptive mechanisms of mifepristone remain undetermined.In the present study, we used immunohistochemistry, reverse transcriptase-polymerase chain reaction (RT-PCR) and MTT to investigate the mechanism of low-dose mifepristone as an anti-implantation contraceptive drug.Methods And Materials:Endometrial biopsies were obtained from normally cycling IVF-ET patients for tubal resection or man infertility. The criteria of study subjects:the patients were reproductive age (aged 25-35 years) with mormal menstrual cycles (26-31 days), and had no hormone or immunosuppressant therapy for the last 3 months. Endometrial biopsies were obtained at the"window of implantation" (days 20-24 of an ideal cycle). Each endometrial tissue was chopped into 1-2mm3 pieces and divided into three equal parts, then assigned to three groups (control group,65 nmol/L group and 200 nmol/L group). HUVECs were treated with 0 nmol/L,65 nmol/L,200 nmol/L and 1000 nmol/L, respectively. The AQP1 expression was examined by immunochemistry and RT-PCR; The effect of mifepristone on the MVD was detected by inverted microscope. The HUVECs activity was analysed by using MTT assay.Results:1. HE-stained sections show no significantly morphologic distinction between pre-cultured and post-cultured endometrial tissue.2. The IHC and RT-PCR analyses demonstrated that expression of AQPl was increased by mifepristone in a dose-dependent manner, with the highest AQPl expression levels detected in subjects treated with 200 nmol/L mifepristone (P<0.05).3. The MVD of endometrial tissue was similar between the three groups (P>0.05).4. Mifepristone (200nmol/L, 1000nmol/L) increase the activity of HUVECs after 12h (P<0.05).5. The activity of HUVECs was significantly decreased (P<0.05) after the addition of AQP1siRNA in 200nmol/L and 1000nmol/L mifepristone group.Conclusion:1. Low-dose mifepristone may negatively regulate implantation by increasing AQP1 protein and mRNA expression. The findings from this study provide further evidence to support the potential contraceptive activity of low-dose mifepristone.2. Mifepristone increase the HUVECs activity and the effect may be achieved by the influence of AQP1... |
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