Blastocysts in the Mouse Uterus: The Effect of Ovariectomy, Progesterone and Oestrogen

Abstract

The effects of ovariectomy at different stages of early pregnancy, and the response to various amounts of exogenous progesterone and oestrogen, were studied in Q-strain mice. When the ovaries were removed on the third day of pregnancy, unimplanted blastocysts were retained in the uterus and no lysis of the zona pellucida occurred; removal on the following morning permitted lysis of the zona pellucida but again no implantation; by the afternoon the ovaries were no longer required for the initiation of implantation, but in the absence of progesterone no sites were maintained. A single dose of oestrogen eliminated all unimplanted blastocysts from the uteri of ovariectomized mice. Daily treatment with a low dose of progesterone after ovariectomy on the third day altered the appearance of the uterus but did not permit implantation unless oestrogen was also given. Under all the above conditions, some reduction in the number of embryos occurred. The maximum number of implantation sites in ovariectomized mice was achieved by daily injection of a high dose of progesterone, with no added oestrogen. An intermediate level of progesterone induced abortive implantation in mice ovariectomized on the third day, and abnormal development of implantation sites after ovariectomy on the fourth day. When the start of progesterone injections was postponed, either after ovariectomy or during lactational delay, it proved more difficult to induce implantation with the progesterone preparation alone, in the absence of added oestrogen.

Differences in H3K4 trimethylation in in vivo and in vitro fertilization mouse preimplantation embryos

“…Interestingly, H3K4me3 levels in TSA-treated groups were increased compared to those in IVF embryos, similar to the levels of K3K4me3 in in vivo embryos. Furthermore, normal embryonic development to the blastocyst stage within the reproductive tract (from the oviduct to the uterine horn) requires the presence of ovarian estrogen (McLaren, 1971;Dey et al, 2004). These findings, together with our results, suggest that H3K4me3 is regulated by the acetylation of H3 and by the maternal environment, and that local factors play important roles in epigenetic modification and the establishment of nuclear totipotency during later stages of development.…”

Differential G protein-coupled cannabinoid receptor signaling by anandamide directs blastocyst activation for implantation

“…We sought to address the mechanism of differential effects of anandamide in blastocyst function and implantation. We first examined whether anandamide at varying levels differentially influences MAPK signaling in blastocysts undergoing experimentally induced dormancy (18,26,27). We observed that anandamide at 7 nM rapidly induced phosphorylation of ERK and its translocation into nuclei of trophectoderm cells of dormant blastocysts within 5 min, showing a peak between 15 and 30 min (Fig.…”

“…Preimplantation ovarian estrogen secretion on day 4 of pregnancy is essential for implantation. This process is deferred if ovaries are removed before the preimplantation estrogen secretion, resulting in delayed implantation that can be main- tained for many days by continued P 4 treatment with the uterus remaining in a quiescent state and blastocysts in dormancy (18,26,27). Dormant blastocysts, if cultured in vitro, gain metabolic competence (29).…”

Induction of Blastocyst Implantation in Mice by Cyclic Amp

“…It also is known that oestrogen administration stimulates uterine adenyl cyclase activity (Rosenfeld & O'Malley, 1970) and increases the uterine levels of cyclic AMP (Szego & Davis, 1967). Furthermore, oestrogen activates 'delayed' mouse blastocysts (McLaren, 1971) by rapidly increasing the synthesis of RNA and protein (Weitlauf & Greenwald, 1968;Holmes & Dickson, 1975). Apparently, oestrogen is functioning in the uterine target tissue through the first and second messenger system referred to by Robison, Butcher & Sutherland (1968) in which cyclic AMP is the second messenger.…”