Every month, the human uterine lining rebuilds itself from scratch — a feat of tissue regeneration unmatched by most adult organs. Understanding exactly which stem cells orchestrate this renewal, and how, has direct implications for conditions like endometriosis, infertility, and Asherman's syndrome, where regeneration fails or misfires. A clearer molecular map of these progenitor populations could eventually reshape how clinicians approach uterine repair and fertility restoration.
Using fluorescence-activated cell sorting to isolate three distinct stem/progenitor populations from hysterectomy tissue, followed by single-cell RNA sequencing across thousands of individual cells, investigators identified ten epithelial and six mesenchymal clusters. Two epithelial clusters harbored CDH2+SOX9+ cells with notably elevated expression of TRH and IHH — components of the Indian Hedgehog signaling pathway. Immunolocalization confirmed that N-cadherin, IHH, SSEA1, and the Hedgehog co-receptor BOC co-concentrate in the basal glandular layer, the anatomical origin point for functional-layer regeneration. Within the mesenchymal compartment, two SUSD2+ clusters emerged, one distinguished by high MUSTN1 expression, a marker associated with musculoskeletal progenitor activity whose endometrial role remains to be fully characterized. Trajectory analyses suggested both epithelial and mesenchymal progenitors follow defined differentiation paths toward mature progeny.
This work meaningfully advances a field where the molecular identity of endometrial stem cells has remained disputed. Prior studies established SUSD2 and CDH2 as useful enrichment markers, but lacked single-cell resolution of the downstream signaling architecture. The Hedgehog pathway connection is particularly notable: IHH is already known to mediate epithelial-stromal crosstalk during the menstrual cycle, and this data positions it upstream of progenitor activity specifically. Key limitations include the use of hysterectomy tissue, which may not reflect normal cycling endometrium, and the cross-sectional design, which limits causal inference about differentiation dynamics. As a foundational atlas rather than an interventional study, this work is best characterized as an important incremental contribution — providing the molecular scaffolding that future therapeutic and mechanistic work will depend on.