Organoids as powerful models of endometrium epithelium in transcriptomic, cellular and functional mimicry

Abstract

Organoids have emerged as revolutionary biomimetic systems that offer a physiologically relevant in vitro model to study the specific tissue or organ of origin. In the field of female reproductive biology, endometrial organoids have proven their high value in the exploration of intricate physiological processes of the endometrium such as hormonal differentiation (decidualization) and embryo-receptivity, as well as to understand the pathophysiology of diseases associated with endometrial deficits. Moreover, organoid-based adhesion models have emerged as appropriate in vitro platform that faithfully reproduces the receptive endometrium. These in vitro models offer new tools to explore the molecular mechanisms of the early embryo-endometrium interaction and to bypass the barrier of ethical restrictions. This review highlights recent advances in the endometrial research domain, focusing on endometrial epithelial organoid models that closely replicate the cellular, transcriptomic and functional characteristics of the native tissue. A comprehensive overview of the transcriptomic changes during the menstrual cycle is provided, as well as of the detailed comparison between the different cell populations of the endometrium and the endometrial organoid model. Here, we provide evidence that endometrial organoids mimic the native endometrial tissue and offer relevant tools to advance our understanding of endometrial (patho)biology, enabling us to gain insights into molecular pathways.

Keywords: Endometrium; Ion channels; Organoids; Transcriptomics.

Fig. 1

Transcriptomic landscape of the human endometrial epithelium across the menstrual cycle. Hormonal levels of E2 (blue) and P4 (purple) are shown, as well as the associated histologically and transcriptomically defined endometrial cycle phases. Transcriptomically, the cycle can be divided in four phases (phase 1-4), while the histological classification considers three phases, i.e. menstrual, proliferative and secretory phase. The proliferative and secretory phases exhibit further subdivisions into early and late, and early, mid, and late stages, respectively. Variations in cellular activity and differentiation observed during phase transitions are mainly characterized by cell mitosis, cilium assembly, cell secretion, and abrupt opening and gradual closing of the WOI. Key gene expression profiles are depicted per phase. Figure created with BioRender.com

Fig. 2

Plasma membrane receptor transcriptomics in human endometrial epithelial cells and organoids. (a) Dot plot displaying the log₂-transformed expression levels of genes encoding selected ion channels and receptors potentially implicated in embryo implantation and endometrial receptivity in endometrial epithelial cells across the different phases of the menstrual cycle [1]). This panel represents members of the Transient Receptor Potential (TRP) superfamily. (b) Expression of the same genes in endometrial organoids under different hormone exposure conditions, modeling cycle phases in vitro. Dot size indicates the proportion of expressing cells; color shows mean expression (log₂). CACNA1 genes represents proteins of the voltage-gated calcium channel family, F2RL1encodes the Protease Activated Receptor 2 (PAR2), KCNMA1 encodes the beta subunit of the calcium activated BK channel, KCNN4encodes the Potassium Calcium-Activated Channel Subfamily N Member 4, SCNN1A encodes the epithelial sodium channel (ENAC), PIEZO1the mechanosensitive ion channel PIEZO1, and CFTR (Cystic Fibrosis Transmembrane Conductance Regulator)

Fig. 3

Schematic overview of the spatio-temporal organization of the human endometrial epithelium in vivo and its corresponding 3D organoid model in vitro. In organoid models, the proliferative and secretory phases are recapitulated by exposure to estrogen receptor (ER) agonist for the proliferative phase, and a combination of ER agonist + progesterone receptor (PGR) agonist + cAMP for the secretory phase. Corresponding markers are depicted in the organoids. Figure created with BioRender.com