Is there a specific surface marker that identifies human endometrial epithelial progenitor cells with adult stem cell activity using in vitro assays?

N-cadherin isolates clonogenic, self-renewing human endometrial epithelial progenitor cells with high proliferative potential that differentiate into cytokeratin⁺ gland-like structures in vitro and identifies their location in some cells of gland profiles predominantly in basalis endometrium adjacent to the myometrium.

Human endometrium contains a small population of clonogenic, self-renewing epithelial cells with high proliferative potential that differentiate into large gland-like structures, but their identity and location is unknown. Stage-specific embryonic antigen-1 (SSEA-1) distinguishes the epithelium of basalis from functionalis and is a marker of human post-menopausal (Post-M) endometrial epithelium.

Prospective observational study of endometrial epithelial cells obtained from hysterectomy samples taken from 50 pre-menopausal (Pre-M) and 24 Post-M women, of which 4 were from women who had taken daily estradiol valerate 2 mg/day for 8 weeks prior.

Gene profiling was used to identify differentially expressed surface markers between fresh EpCAM (Epithelial Cell Adhesion Molecule)-magnetic bead-selected basalis-like epithelial cells from Post-M endometrium compared with predominantly functionalis epithelial cells from Pre-M endometrium and validated by qRT-PCR. In vitro clonogenicity and self-renewal assays were used to assess the stem/progenitor cell properties of magnetic bead-sorted N-cadherin⁺ and N-cadherin⁻ epithelial cells. The cellular identity, location and phenotype of N-cadherin⁺ cells was assessed by dual colour immunofluorescence and confocal microscopy for cytokeratin, proliferative status (Ki-67), ERα, SSEA-1, SOX9 and epithelial mesenchymal transition (EMT) markers on full thickness human endometrium.

CDH2 (N-cadherin gene) was one of 11 surface molecules highly expressed in Post-M compared to Pre-M endometrial epithelial cells. N-cadherin⁺ cells comprise a median 16.7% (n = 8) and 20.2% (n = 5) of Pre-M endometrial epithelial cells by flow cytometry and magnetic bead sorting, respectively. N-cadherin⁺ epithelial cells from Pre-M endometrium were more clonogenic than N-cadherin⁻ cells (n = 12, P = 0.003), underwent more population doublings (n = 7), showed greater capacity for serial cloning (n = 7) and differentiated into cytokeratin⁺ gland-like organoids. N-cadherin immunolocalised to the lateral and apical membrane of epithelial cells in the bases of glands in the basalis of Pre-M endometrium and Post-M gland profiles, co-expressing cytokeratin, ERα but not SSEA-1 or SOX9, which localized on gland profiles proximal to N-cadherin⁺ cells. N-cadherin⁺ cells were quiescent (Ki-67⁻) in the basalis and in Post-M endometrial glands and co-localized with EMT markers vimentin and E-cadherin.

The raw and processed data files from the gene microarray have been deposited in the National Center for Biotechnology Information Gene Expression Omnibus data set with accession number GSE35221.

This is a descriptive study in human endometrium only using in vitro stem cell assays. The differential ability of N-cadherin⁺ and …