| Background Nowadays, with the development of Assisted Reproductive Technology (ART) used in infertility, people can achieve high ovulation rates by choosing different super-ovulation protocols. However implantation rates per embryo transfer is still only average around 10-15%. One of the critical reasons is the uterine receptivity. It is known that ovulation and fertilization triggers embryonic development and endometrial differentiation by corpus luteum progesterone production. These two synchronous processes couple about one week later, when the blastocyst begins to implant in the now receptive endometrium. This bifactorial, transient period when implantation can start, is called the implantation or nidation window. Implantation cannot occur before and after this implantation window. There are many molecular factors associated with this nidation window, such as integrins, leukemia inhibitory factor (L1F), Pinopode, Calcitonin (CT), VEGF and so on. They expression are strongly correlated with implantation following embryo transfer, and furthermore detection of integrin beta3 and LIF in assessment cycles may be extremely useful for the assessment of uterine receptivity during controlled ovarian hyper-stimulation (COH). So integrin beta3 and LIF are as markers of uterine receptivity.Recently, many scholars think that super-ovulation can affect the uterine receptivity compared with the nature ovulation cycle. It means that the process of implantation is suffered from theapplication of COM such as CC/HMG. They also brought out many data to demonstrate it. Over the last two decades, Gonadotropin releasing hormone (GnRH) agonists have been widely used in controlled ovarian stimulation protocols in ART in combination with gonadotropins to prevent a premature LH surge. GnRH agonists induce an initial rise of gonadotropins (flare-up) before they achieve suppression through desensitization. However, situation where an immediate and dose-dependent suppression of the gonadotropins is required, the drawback of the GnRH agonist is in their initial stimulatory effect on hormone secretion and the relatively long period (2-3 weeks) of chronic exposure before complete suppression can occur. Hence, GnRH antagonists have been introduced into ovarian stimulation protocols recently. The first antagonist was synthesized > 20 years ago. Its clinical application was hampered by a high histaminergic potential. Now, new substances were developed which lacked the histaminergic side-effects. These antagonists can produce an immediate and dose-related inhibition of gonadotropin releasing by competitive binding to pituitary GnRH receptors, also can avoid the "flare-up effect" seen with the GnRH agonists, and have been approved for ovarian stimulation to prevent a premature LH surge. All treatment related effects are reversible and no teratogenic, mutagenic or contact sensitizing properties were found in toxicological studies. The human results on the GnRH antagonist clearly demonstrate its safety profile and potential usefulness in the clinic. One advantage of the antagonists seems to be a lower incidence of ovarian hyperstimulation syndrome (OHSS), a serious side-effect of ovarian stimulation treatment. Therefore, GnRH antagonists are also suitable for the use in controlled ovarian stimulation for ART. However, the GnRH antagonist regimens have been associated with a slightly lower pregnancy rate and poor uterine receptivity than the established GnRH agonist protocols, but there is no experiment data to demonstrate it.Objective To compare the uterine receptivity with different ovarian stimulation protocols, the endometrial expression of integrin beta3 and LIF in mice's during the implantation window underwent different ovarian stimulation were studied.Materials and Methods Forty mice were randomly allocated into 4 groups. (1)GnRH antagonist group: GnRH antagonist was given first for desensitizing the pituitary, and then the PMSGwas added for ovarian stimulation. (2) GnRH agonist group: GnRH agonist was given fi...
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