The Biological Characteristics of Eutopic and Ectopic Endometrial Progenitor Cells in Endometriosis

Aim: The aim of this study was to identify the biological characteristics and potential roles of endometrial progenitor cells in the pathogenesis of endometriosis. Background: It is generally believed that progenitor cells in human endometrium are responsible for rapid endometrial regeneration. However, the biological characteristics and potential roles of the paired eutopic and ectopic endometrial progenitor cells in endometriosis remain unclear. Objective: This study intends to isolate the epithelial progenitor (EP) cells and endometrial mesenchymal stem cells (eMSCs) from the eutopic and ectopic endometria from endometriosis patients, further to reveal their features and functions respectively. Methods: The distributions of EP cells and eMSCs and the expression of steroid hormone receptors in the endometrium and endometriotic tissues were assessed by immunohistochemistry. EP cells and eMSCs were sorted from paired eutopic and ectopic endometria with epithelial cell adhesion molecule (EpCAM) magnetic beads. The clonogenicity, cell viability after being treated with estradiol and progesterone, and cell markers expression were evaluated with colony forming on Matrigel, CCK-8 and immunofluorescence staining, respectively. The differentially expressed genes (DEGs) were further identified with RNA sequencing. Results: SSEA-1- and PDGFRβ-positive cells were distributed in the epithelial and stromal layers. The ERβ staining was much more intense in endometriotic tissues, but PR expression was almost absent. The ectopic EP cells exhibit strong clonogenicity and ERβ expression but weak PR expression, leading to progesterone resistance. There are 12604 and 13242 DEGs revealed by RNA sequencing between eutopic and ectopic EP cells or eMSCs. GO and KEGG analyses revealed that the functions and pathways of DEGs enriched in cellular energy metabolism and regulation of the immune response, respectively. Additionally, ERβ targets were mainly enriched in ectopic EP cells. Conclusion: Both EP cells and eMSCs may engage in ectopic lesion formation in endometriosis by modifying the metabolic mode and immune tolerance. These data not only help to understand the molecular mechanism of endometriosis but also could potentially contribute to the discovery of therapeutic targets for endometriosis.