Cyclical shedding/regeneration of the endometrium is likely controlled by endometrial stem/progenitor cells and may be dysregulated in debilitating menstrual disorders (endometriosis). We aimed to determine biological variations in endometrial stem/progenitor cell concentrations and clonogenicity in menstrual fluid between cycles and between women.
Menstrual fluid (day 2) was collected from women (n=11; 30.0±2.4yrs; 22-42) in a menstrual cup over 3 cycles (cycle 27.5±0.5d). Endometrial cells were dissociated, leukocytes depleted and red blood cells lysed. Stem/progenitor cell proportions were determined by flow cytometry and clonogenicity by colony forming assays.
SUSD2+ endometrial mesenchymal stem cells (0.13–7.2%; 2.17±0.95%) and EpCAM+ (0.77–41.0%; 27.0±4.52%) cells were present in all menstrual fluids. However, epithelial progenitor cells (ePC) were not detected in every sample (NCAD+EpCAM+; 13/17 samples; 0-0.61%; 0.29±0.06%, SSEA-1+ EpCAM+; 11/17 samples; 0-0.4%; 0.12±0.05%), with no differences within and between women. Similarly, there were no differences in clonogenicity of CD45- endometrial cells (0.34-1.87%; 0.99±0.21%). Data are %CD45- cells; range; mean±SEM.
There was little variation between stem/progenitor cell shedding between cycles within the same woman or between women. However, occasional outliers may indicate normal variation or underlying pathology. Quantification of stem/progenitor cells in menstrual blood may be a non-invasive prognostic tool for fertility and endometrial disorders.