Project Details
Abstract
Estrogen plays an important role in normal pre-implantation, embryonic development in the
reproductive tract, and the changes of uterine endometrium induced by estrogen have been
well documented. However, the influence of high levels of E2 during embryonic implantation
is still controversial. Elevated ratios of estradiol to progesterone were shown to inhibit
blastocyst metabolism and implantation. In the studies of assisted reproductive technology
(ART), they has been reported that controlled ovarian hyperstimulation (COH) used for ART
inhibits embryo implantation. It has been proposed that high E2 levels after COH impair
endometrial receptivity. It appears to be important to maintain the concentrations of estrogen
and progesterone at appropriate levels relative to each other.
However, it is not clear whether the hormones acted directly on the embryo or indirectly
through the mother's reproductive tract. The effects of estrogen depend on the existence of
their specific receptors. Estrogen receptor (ER) mRNA was found in oocytes and fertilized
eggs. The message level began to decline at the two-cell stage and reached its lowest level at
the five- to eight-cell stage. It was not detectable at the morula stage but reappeared at the
blastocyst stage. Interestingly, ER mRNA was detected at the blastocyst stage and was likely
of embryonic and not maternal origin. The embryonic expression of ER genes in the
blastocyst suggests a possible functional requirement for ER at this stage of development.
Since estrogen elicits its functions primarily through its receptor protein, a direct estrogen
effect on the blastocyst should require the presence of ER protein in the blastocyst. A direct
demonstration of ER expression at the protein level was studied in 1996. These findings that
ER is present in both the inner cell mass and trophectoderm cells in the blastocyst and that ER
expression persists at least until the early egg cylinder stage in all cell types suggests that ER
may be important for implantation and/or early embryogenesis.
To examine whether estrogen has a direct influence in the implanting blastocyst and early
egg cylinder embryo, we employed in vitro culture systems which obtaining an environment
without the complication of maternal effects. These systems have been used by our lab and
others to mimic certain aspects of post-implantation embryonic development. To date, there is
no literature regarding the direct action and the mechanism of estrogen on the implanting and
early egg cylinder embryo. In this series of studies, we will use the model to evaluate the
physiological and pharmacological role of estrogen in the implanting blastocyst and early egg
cylinder embryo.
Project IDs
Project ID:PC10107-0220
External Project ID:NSC101-2314-B182A-110
External Project ID:NSC101-2314-B182A-110
Status | Finished |
---|---|
Effective start/end date | 01/08/12 → 31/07/13 |
Keywords
- estrogen receptor
- implantation
- blastocyst
- postimplantation embryodevelopment
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