Endometrial immune response modulation by embryo quality.

SCHAFIR A. 1, GRASSO E. 1, FERNANDEZ A. 2, FERNÁNDEZ L. 1, CASTAGNOLA L. 1, MATERAZZI L.1, HAUK V. 1, PÉREZ LEIRÓS C. 1, MARTÍNEZ G. 4, PIETRASANTA L. 2 GORI S. 1 AND RAMHORST R 1.

St Paul

Congreso; American Society of Reproductive Immunology; 2025

Problem: Successful embryo implantation is contingent upon adequate decidualization of the endometrium and the presence of a competent embryo. Endometrial stromal cells fulfill a multifaceted role, functioning as "multitasking superstars" by conditioning immune cells and interacting with the embryo. However, the impact of embryo secretome on implantation remains to be fully elucidated. The objective of this study is to investigate the endometrial-embryo-immune interactome, with a particular focus on embryo quality biosensing.Methods: First, we performed a bioinformatic analysis using data from public databases (GSE18290 and GSE234354) focusing on protein-protein interactions between the secretome of a competent blastocyst and a receptive endometrium using String resources. Then, Atomic Force Microscopy and Spectroscopy (AFM-FS) was used to investigate the effect of human embryo-conditioned media (ECM) obtained from normal or impaired developing/arrested embryos on the nanomechanical properties of a stromal cell line (HESC) decidualized by medroxyprogesterone and dibutyryl cAMP for 8 days (Dec).To evaluate whether the embryo secretome could directly alter the profile and function of immune cells, we performed a new bioinformatics study, this time focusing on protein-protein interactions between the blastocyst secretome and immune cells residing in the endometrium in the secretory phase, with special focus on dendritic cells (DC). Then, we isolated PBMCs from healthy women using Ficoll-Hypaque. Total PBMCs were cultured with rhIL-10 for 18h and purified monocytes were differentiated into immature DCs (rhGM-CSF+rhIL-4) for 5 days, both in the presence/absence of embryo conditioned media. The immune profiles were then evaluated by flow cytometry. Finally, to evaluate the effect of DC conditioning by ECM on embryo implantation, the first trimester human trophoblast cell line (HTR-8/SV-neo) was cultured for 48h to form blastocyst-like spheroids, which were selected and seeded in the presence/absence of supernatants from conditioned DC cultures and monitored for 48h to measure migration rate.Results: In the context of bioinformatics studies, a network comprising specific genes implicated in embryo attachment and cell-cell junctions was obtained. Concomitantly, stromal cells that had been treated with decidualization stimuli exhibited a substantial decrease in cellular stiffness, thereby suggesting that they would be more permisive to embryo implantation. Intriguingly, decidualized stromal cells that had been exposed to embryo conditioned media from arrested embryos demonstrated increased stiffness. In the context of immune populations, bioinformatics analysis revealed interactions involving cytokine signaling, with the blastocyst potentially able to regulate the immune response at multiple points. In this regard, the presence of conditioned media from arrested embryos prevented the production of IL-10 by both CD4+ and CD8+ lymphocytes. In addition, DCs exposed to conditioned media from normally developing embryos resulted in the induction of HLA-G expression, a key tolerogenic marker (p