M Rahimipour - Department of Anatomy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
M Salehnia - Department of Anatomy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
M Jafarabadi - Reproductive Health Research Center, Tehran University of Medical Sciences, Tehran, Iran

Background: Implantation is a complex process that involves fine coordination and dialogue between the embryo and endometrium. Embryonic development to the blastocyst stage and uterine differentiation to the receptive phase are both essential for initiation and progression of a successful implantation. The process of implantation consists of apposition, adhesion, and the invasion of the blastocyst to the uterine wall.Objective: This experimental study aimed to evaluate the effects of 17a-estradiol (E2) and progesterone (P4) on the interaction between mouse embryo and human endometrial mesenchymal stromal cells, and gene expressions related to implantation [alpha-V and beta-3 integrins, interleukin-1 receptor (IL-1R), and leukemia inhibitory factor receptor (LIFR)] using an in vitro two dimensional model.Materials and Methods: In this experimental study, the endometrial stromal cells were isolated enzymatically and mechanically, and cultured to the fourth passage. Next, their immunophenotype was confirmed by flow cytometric analysis as mesenchymal stromal cells. The cells were cultured as either the experimental group in the presence of E2 (0.3 nmol) and P4 (63.5 nmol) or control group without any hormone treatment. Mouse blastocysts were co-cultured with endometrial mesenchymal stromal cells in both groups for 48 hours. Their interaction was assessed under an inverted microscope and scanning electron microscopy (SEM). Expressions of alpha-V and beta-3 integrins, LIFR, and IL-1R genes were analyzed by real-time reverse transcription-polymerase chain reaction (RT-PCR).Results: Similar observations were seen in both groups by light microscopy and SEM. We observed the presence of pinopode-like structures and cell secretions on the apical surfaces of endometrial mesenchymal stromal cells in both groups. The trophoblastic cells expanded and interacted with the mesenchymal monolayer cells. At the molecular level, expression of IL-1R significantly increased in the hormonal treated group compared to the control (p≤0.05). Expressions of the other genes did not differ.Conclusion: This study has shown that co-culture of endometrial mesenchymal stromal cells with mouse embryo in media that contained E2 (0.3 nmol) and P4 (63.5 nmol) could effectively increase the expression of IL-1R, which is involved in embryo implantation. However, there were no significant effects on expressions of alpha-V and beta-3 integrins, LIFR, and on the morphology and ultrastructure of endometrial mesenchymal stromal cells.

Estrogen, Implantation, Interleukin-1 receptor, Mesenchymal stromal cells, Progesterone