Mesenchymal stem/stromal cells in post-menopausal endometrium

Study question: Does post-menopausal endometrium contain mesenchymal stem/stromal cells (MSC) that have adult stem cell properties and can be prospectively isolated from a biopsy?

Summary answer: Perivascular W5C5(+) cells isolated from post-menopausal endometrial biopsies displayed characteristic MSC properties of clonogenicity, multipotency and surface phenotype irrespective of whether the women were or were not pre-treated with estrogen to regenerate the endometrium.

What is known already: Recently MSCs have been identified in human premenopausal endometrium, and can be prospectively isolated using a single marker, W5C5/SUSD2.

Study design, size, duration: Endometrial tissue of both the functional and basal layers, from 17 premenopausal (pre-MP) women, 19 post-menopausal (post-MP) women without hormonal treatment and 15 post-menopausal women on estrogen replacement therapy (post-MP+ E2), was collected through a prospective phase IV clinical trial over 2 years.

Participants/materials, setting, methods: Post-menopausal women <65 years of age were treated with or without E2 for 6-8 weeks prior to tissue collection. Serum E2 levels were determined by estradiol immunoenzymatic assay. Endometrial tissue was obtained from women by biopsy (curettage) just prior to the hysterectomy. The effect of E2 on endometrial thickness and glandular and luminal epithelial height was determined using image analysis. Endometrial tissue was dissociated into single cell suspensions and MSC properties were examined in freshly isolated and short-term cultured, magnetic bead-purified W5C5(+) cells. MSC properties were assessed using clonogenicity, serial cloning, mesodermal differentiation in adipogenic, chondrogenic, osteogenic and myogenic induction culture media, and surface phenotype analysis by flow cytometry. Estrogen receptor α expression in W5C5(+) cells was examined using dual colour immunofluorescence. Vascularity was analysed using CD34 and alpha smooth muscle actin immunostaining and subsequent image analysis.

Main results and the role of chance: A small population of stromal cells with MSC properties was purified with the W5C5 antibody from post-menopausal endometrium, whether atrophic from low circulating estrogen or regenerated from systemic estrogen treatment, similar to premenopausal endometrium. The MSC derived from post-menopausal endometrium treated with or without E2 fulfilled the minimum MSC criteria: clonogenicity, surface phenotype (CD29(+), CD44(+), CD73(+), CD105(+), CD140b(+), CD146(+)) and multipotency. The post-menopausal endometrial MSCs also showed comparable properties to premenopausal eMSC with respect to self-renewal in vitro and W5C5 expression. The W5C5(+) cells were located perivascularly as expected and did not express estrogen receptor α.

Limitations, reasons for caution: The properties of the MSC derived from post-menopausal endometrium were evaluated in vitro and their in vivo tissue reconstitution capacity has not been established as it has for premenopausal endometrial MSC.

Wider implications of the findings: The endometrium is an accessible source of MSC obtainable with minimum morbidity that could be used for future clinical applications as a cell-based therapy. This study shows that menopausal women can access their endometrial MSC by a simple biopsy for use in autologous therapies, particularly if their endometrium has been regenerated by short-term E2 treatment, provided they have an intact uterus and are not contraindicated for short-term E2 treatment. Endometrial MSC in post-menopausal women possess key MSC properties and are a promising source of MSC independent of a woman's age.

Study funding/competing interests: This study was supported by the National Health and Medical Research Council (NHMRC) of Australia grant (1021126) (C.E.G., A.R.) and Senior Research Fellowship (1042298) (C.E.G.), Australian Gynaecological Endoscopic Society grant (A.R.) , Monash International Postgraduate Research Scholarship (DU), Australian Stem Cell Centre, South East Melbourne Alliance for Regenerative Therapies and Australian Stem Cell Centre top up scholarships (DU) and Victorian Government's Operational Infrastructure Support Program. Competing interests: AR receives Preceptorship fees from AMS, advisory board fees and sponsored study from Astellas, and conducts investigator led studies sponsored by AMS and Boston Scientific for other projects.

Trial registration number: CTNRN12610000563066.