Organoids of Human Endometrium: A Powerful In Vitro Model for the Endometrium-Embryo Cross-Talk at the Implantation Site.

Alice Luddi,Mattia Criscuoli,Giuseppe Belmonte,Eugenio Paccagnini,Bianca Semplici,Mariangela Gentile,Giuseppe Morgante,Laura Governini,Vincenzo De Leo,Paola Piomboni,Natasa Zarovni,Valentina Pavone

doi:10.3390/cells9051121

Abstract

Embryo implantation has been defined as the “black box” of human reproduction. Most of the knowledge on mechanisms underlining this process derives from animal models, but they cannot always be translated to humans. Therefore, the development of an in vitro/ex vivo model recapitulating as closely and precisely as possible the fundamental functional features of the human endometrial tissue is very much desirable. Here, we have validated endometrial organoids as a suitable 3D-model to studying epithelial endometrial interface for embryo implantation. Transmission and scanning electron microscopy analyses showed that organoids preserve the glandular organization and cell ultrastructural characteristics. They also retain the responsiveness to hormonal treatment specific to the corresponding phase of the menstrual cycle, mimicking the in vivo glandular-like aspect and functions. Noteworthy, organoids mirroring the early secretive phase show the development of pinopodes, large cytoplasmic apical protrusions of the epithelial cells, traditionally considered as reliable key features of the implantation window. Moreover, organoids express glycodelin A (GdA), a cycle-dependent marker of the endometrial receptivity, with its quantitative and qualitative features accounting well for the profile detected in the endometrium in vivo. Accordingly, organoids deriving from the eutopic endometrium of women with endometriosis show a GdA glycosylation pattern significantly different from healthy organoids, confirming our prior data on endometrial tissues. The present results strongly support the idea that organoids may closely recapitulate the molecular and functional characteristics of their cells/tissue of origin.

Highlights

Embryo implantation is the process by which human embryo orientates towards, attaches to, and invades the underlying maternal endometrial tissue
Our results demonstrated that hormonal treatments are able to affect the expression of genes involved in endometrial receptivity, according to what expected for the different phases of the endometrial cycle; PAEP, VEGF, MMP26 and IGF1, and appear significantly increased in ORG-msp (Figure 4), confirming these molecules as suitable markers of implantation window and proving this in vitro approach as an effective model to closely mimic the molecular modifications typically occurring in vivo during endometrial remodeling
The decrease in glycodelin A (GdA) expression in patients with endometriosis that we reported here by in vitro organoid model confirms data already displayed in endometrial tissue biopsies, further confirming that this model faithfully recapitulates in vivo endometrium [26]

Summary

Introduction

Embryo implantation is the process by which human embryo orientates towards, attaches to, and invades the underlying maternal endometrial tissue. It is believed that molecules secreted by uterine glands may be important mediators for uterine receptivity, blastocyst implantation, stromal cell decidualization and embryo growth [14,15,16] In this regard, GdA ( known as placenta protein 14, PP14), is proposed as a strong candidate for a potential biomarker of endometrial receptivity [17]. A new sixth and more acidic glycoform appears exclusively during the implantation window [26] This selective expression suggests a crucial role in the endometrial receptivity of this glycoform of GdA that has been already suggested to act as a key regulatory protein during the embryo attachment to the recipient endometrial epithelium [23]. Endometrial expression of GdA, as well as its glycoforms composition significantly change during the menstrual cycle in women affected by endometriosis [26]

Methods

Results

Conclusion