Endometrial stromal cells: isolation, expansion, morphological and functional properties

We aimed to study biological properties of human endometrial stromal cells in vitro.

The endometrium samples (n = 5) were obtained by biopsy at the first phase of the menstrual cycle from women with endometrial hypoplasia. In all cases, a voluntary written informed consent was obtained from the patients. Endometrial fragments were dissociated by enzymatic treatment. The cells were cultured in DMEM/F12 supplemented with 10% FBS, 2 mМ L-glutamine and 1 ng/ml FGF-2 in a multi-gas incubator at 5% CO₂ and 5% O₂. At P3 the cells were subjected to immunophenotyping, multilineage differentiation, karyotype stability and colony forming efficiency. The cell secretome was assessed by BioRad Multiplex immunoassay kit.

Primary population of endometrial cells was heterogeneous and contained cells with fibroblast-like and epithelial-like morphology, but at P3 the majority of cell population had fibroblast-like morphology. The cells possessed typical for MSCs phenotype CD90⁺CD105⁺CD73⁺CD34^-CD45^-HLA-DR^-. The cells also expressed CD140a, CD140b, CD146, and CD166 antigents; and were negative for CD106, CD184, CD271, and CD325. Cell doubling time was 29.6 ± 1.3 h. The cells were capable of directed osteogenic, adipogenic and chondrogenic differentiation. The cells showed 35.7% colony forming efficiency and a tendency to 3D spheroid formation. The GTG-banding assay confirmed the stability of eMSC karyotype during long-term culturing (up to P8). After 48 h incubation period in serum-free medium eMSC secreted anti-inflammatory IL-1ra, as well as IL-6, IL-8 and IFNγ, angiogenic factors VEGF, GM-CSF and FGF-2, chemokines IP-10 and MCP-1.

Thus, cultured endometrial stromal cells meet minimal ISCT criteria for MSC. Proliferative potential, karyotype stability, multilineage plasticity and secretome profile make eMSC an attractive object for the regenerative medicine use.