Endometriosis at the Single-Cell Level: Molecular Insights and Implications for Assisted Reproduction Success.

Endometriosis is a chronic hormone-responsive disorder linked to infertility, usually characterized by the presence of ectopic endometrium in the pelvis that disrupts local homeostasis. Advances in single-cell "omic" methods have revealed the remarkable cellular diversity within the eutopic endometrium and endometriosis lesions, uncovering distinct populations with unique transcriptional and functional profiles. These studies have highlighted alterations in immune cell subsets, stromal and epithelial cell signaling, and intercellular communication networks that collectively impair oocyte quality, embryo development, and endometrial receptivity in women with endometriosis. By dissecting the molecular signatures of individual cells, single-cell approaches provide insights into the mechanisms driving persistent inflammation, impaired angiogenesis, hormonal dysregulation, and immune dysfunction in endometriosis. Importantly, emerging evidence indicates that infertility and reduced assisted reproductive technology (ART) success in endometriosis reflect coordinated cellular and molecular dysfunction rather than solely anatomical abnormalities. Single-cell analyses of oocytes, granulosa cells, and endometrial cell populations demonstrate transcriptomic and epigenetic alterations affecting mitochondrial function, steroid metabolism, immune regulation, and implantation-related signaling pathways, offering a biological explanation for impaired implantation and variable ART outcomes. Integration of these findings with clinical observations supports the concept that endometriosis-associated reproductive failure arises from combined ovarian and endometrial defects detectable at the cellular level. Current single-cell studies highlight candidate biomarker signatures with the potential to improve patient stratification, predict ART outcomes, and guide individualized therapeutic strategies. As these discoveries are refined into clinically applicable biomarker panels, single-cell technologies are poised to bridge mechanistic understanding and precision reproductive medicine, enabling more personalized management approaches aimed at restoring reproductive competence in patients with endometriosis.