P–400 Endometrial changes in estrogen and progesterone receptor expression during implantation in an oocyte donation program
Authors: Klonos E G , Pados G , Karteris E , Katopods P , Tarlatzis B 
Published: August 2021

Abstract

Study question
Which are the endometrial changes during implantation in assisted reproduction techniques?

Summary answer
Synchronization between blastocyst development and the acquisition of endometrial receptivity is a prerequisite for the success of in vitro fertilisation (IVF).

What is known already
Implantation is the final and most important stage of embryogenesis and is of paramount importance in achieving a successful pregnancy. Progesterone and estrogen are steroid hormones responsible for the regulation of the implantation window and the current study hypothesised that their receptors may be implicated in women undergoing oocyte donation. Implantation is directly dependent on the synchronization of the fertilized egg’s progression into a blastocyst and the specific differentiation of the endometrium through molecular and cellular changes regulated by agents with an endocrine, paracrine or autocrine activity.

Study design, size, duration
The study was conducted at the 1st Dept. of OB-GYN, Centre for Human Reproduction of the Aristotle University of Thessaloniki, ‘Papageorgiou’ General Hospital and the ‘Biogenesis’ Assisted Reproduction Centre, (both in Thessaloniki, Greece).

Participants/materials, setting, methods
The participants recruited for this prospective study included 15 oocyte donors (age range, 25–32 years; mean age, 28.9±2.89) undergoing IVF treatment. The inclusion criteria were white race, no uterine-ovarian pathology, age &lt;35 years and no prior known medical pathology. All donors had undergone extensive preoperative work-up, which included common blood tests, karyotyping, specific test for cystic fibrosis and pap smear. All donors were non-smokers and had given their informed consent.

Main results and the role of chance
Both ERα and PR-B were expressed abundantly on both days (0 and 5; Fig. 1B). The ERα nodal staining percentage on day 0 was age-related, with patients aged &lt;30 years showing 100% staining and those aged &gt;30 years showing 90% staining (Mann-Whitney U test; P = 0.014; Fig. 2A)Both steroid hormone receptors showed significant variation between days 0 and 5, both in the nodal and stromal preparations. According to Wilcoxon signed-rank test; for ER (nodes% and stromal%) Day 0/5, P = 0.0001; for PR (nodes% and stromal%) Day 0/5, P = 0.0001 and P = 0.035, respectively; for ER (Grade nodes and stromal) Day 0/5, P = 0.0001; and for PR (Grade nodes and stromal) Day 0/5, P = 0.0001 and P = 0.016, respectively (Fig. 2B and ​andC;C; Table I).

Limitations, reasons for caution
Immunohistochemistry is less quantitative than western blotting. Alternatively, ELISA or a gene expression assessment of both receptors using RT-qPCR could have been conducted. However, due to ethical restrictions, sufficient tissue for protein extraction could not be obtained in order to pursue this further.
Wider implications of the findings: It was shown herein that both ER-a and PR-B were expressed abundantly on days 0 and 5, showing significant variation in the nodal and stromal preparations. Age appeared to be a critical factor, since ER-a nodal staining showed higher values in the age group of oocyte donors &lt;30 years old.

Trial registration number
15