Characterisation of mesenchymal stromal cells in the postmenopausal endometrium

Background: Recently MSC have been identified in the regenerative endometrial lining of the uterus and specific markers (W5C5/SUSD2) for their prospective isolation identified. Postmenopausal endometrium is atrophic but regenerates with systemic estrogen treatment and has even lead to a successful IVF pregnancy in a 64 year old woman. The aim of this study was to determine whether postmenopausal endometrium contains a population of endometrial MSC (eMSC) that might be responsible for its regenerative capacity which could be exploited for future clinical applications. We hypothesized that eMSC are present in postmenopausal endometrium at similar frequency as in premenopausal endometrium.

Method: Single-cell suspensions of endometrial stromal cells were obtained from hysterectomy tissues of 17 premenopausal (pre-MP), 19 postmenopausal (post-MP) and from biopsies just prior to hysterectomy for 15 postmenopausal women enrolled into a phase IV clinical trial of estrogen replacement therapy (2 mg oral estradiol valerate daily) (post-MP+E2) for 8 weeks. The proliferative potential and differentiation of W5C5+ cells were assessed by colony forming unit CFU assays and differentiation-induction media culture. EMSC surface markers were determined using flow cytometry. Results: In post-MP+E2 Passage 1 (P1) stromal cultures, 3.7 ± 1.8% (n = 7) of the cells were W5C5+ cells and 7.7 ± 6.3% (n = 8) in post-MP cultures (p = 0.69). The cloning efficiency for post-MP+E2 W5C5+ P1 cells was 3.41 ± 2.71% (n = 6), and comparable to post-MP W5C5+ cells (3.73 ± 1.19%; n = 8) but statistically lower than P1 Pre-MP cells (p < 0.05) (n = 6). W5C5, CD140b, CD146, CD29, CD44, CD73, CD105 surface markers were present on W5C5+ cells from both PostMP groups. PostMP W5C5+ cells differentiated into chondrocytes, adipocytes, myocytes and osteocytes, but to a lesser degree than PreMP W5C5+ cells. Conclusion: Postmenopausal endometria possess eMSC at similar frequency and potency irrespective of whether or not it is regenerated with estrogen. Human endometrium is a promising source of MSC for cell-based therapies independent of a woman's age or menopausal status.