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

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.

Modelling the impact of decidual senescence on embryo implantation in human endometrial assembloids

“…Here we report on the development of endometrial assembloids, consisting of gland-like organoids surrounded by a matrix rich in primary EnSC, as novel model to parse the cellular dynamics that govern embryo implantation in cycling human endometrium. While assembloids complement and advance other recently described endometrial organoid models (Boretto et al, 2017, Cheung et al, 2021, Fitzgerald et al, 2019, Luddi et al, 2020, Turco et al, 2017, they still lack the cellular complexity of native endometrium, including uNK cells, macrophages and vascular cells. Nevertheless, we demonstrated that aspects of pathological implantation events can be recapitulated in assembloids, rendering them useful as novel models to study mechanisms of reproductive failure and to evaluate potential therapeutic interventions.…”

Menstrual flow as a non-invasive source of endometrial organoids

“…Currently, endometrial organoids are being used to investigate physiological changes during the normal cycle 5 , and pathological endometrial dysfunction in endometriosis, endometrial cancer and other gynaecological conditions 2 . Implantation of the transferred embryo is a rate-limiting step in Assisted Reproductive Techniques (ART) 27 , and organoids are enabling exploration of the molecular mechanisms underpinning implantation 4 . Our technique will enable patients undergoing fertility treatments to have their endometrial function assessed non-invasively prior to initiating a treatment cycle, allowing the hormonal regime and timing of treatment to be tailored accordingly.…”

“…We, and others, have previously shown that endometrial organoids provide a valuable model for investigating maternalfetal interactions during early pregnancy, and for exploring the pathophysiology of gynaecological complications such as endometriosis and endometrial cancer [2][3][4][5] . To date, the organoids have been derived from biopsy samples, which, while reproducible and robust, necessitate an invasive procedure performed by a trained clinician.…”

Organoids of the Female Reproductive Tract: Innovative Tools to Study Desired to Unwelcome Processes

“…By exposure to a specific hormone treatment protocol encompassing E2 and progesterone (P4), organoids mimicked the full menstrual cycle as well as incipient decidualization (Table 1 and Supplementary Table 3). The robustness of the endometrial organoid platform has been validated by IHC, electron microscopy, array Comparative Genomic Hybridization (aCGH) and transcriptome analysis and, in addition, ion channel functionality and ciliogenesis was demonstrated using these organoid systems (Fitzgerald et al, 2019;Haider et al, 2019;Hennes et al, 2019;Cochrane et al, 2020;Bui et al, 2020;Luddi et al, 2020;Syed et al, 2020). Two groups achieved to derive organoids from trophoblasts, offering the appealing possibility to study trophoblast-endometrium crosstalk in vitro (Haider et al, 2018;Turco et al, 2018).…”