The human endometrium has an immense regenerative capacity. Previously we identified a small population of clonogenic endometrial stromal cells or mesenchymal stem cells (MSC).1 Prospective isolation of MSC allows for their characterisation. We hypothesise that the expression of MSC marker, CD146, and pericyte/fibroblast marker, platelet-derived growth factor receptor-β (PDGFRβ), will enable the prospective isolation of endometrial MSCs. The aims of this study were to (1) determine if CD146 and PDGFRβ will prospectively isolate endometrial MSCs with clonogenic activity, (2) identify their location in human endometrium, and (3) determine the differentiation capacity of CD146+PDGFRβ+ stromal cells.
Endometrial tissue from 13 ovulating women undergoing hysterectomy was digested with collagenase to produce single cell suspensions. Leukocytes and epithelial cells were removed. Stromal cells were analysed by flow cytometry, FACS sorted into enriched and depleted populations, and cultured for clonal analysis.1 Immunohistochemistry was performed on full thickness human endometrium. Sorted populations of stromal cells were passaged for culture in various differentiation media, and analysed for adipogenic, myogenic, chondrogenic or osteogenic differentiation by histological stains and RT-PCR.
A small, consistent population of CD146+ endometrial stromal cells was identified (7.8 ± 1.1%, n = 8). In contrast, PDGFRβ expression varied (34.1 ± 9.7%, n = 5), and 2.5% of cells were CD146+PDGFRβ+. Clonogenicity of CD146+ stromal cells was significantly higher than CD146- stromal cells, 2.5 ± 1.1% and 1.2 ± 0.6%, respectively (n = 6, P = 0.03). CD146+ stromal cells were located perivascularly, similar to bone marrow MSCs, whereas PDGFRβ weakly stained the stroma, with stronger staining observed around the blood vessels. CD146+ cells differentiated into adipocytes, smooth muscle cells, chondrocytes and osteoblasts.
This study identified CD146 as a marker of clonogenic endometrial stromal cells, and supports the perivascular location of endometrial MSCs. It also demonstrated that CD146+ cells can differentiate into four mesenchymal lineages. These data suggest that CD146 can be used for the prospective isolation of endometrial MSCs, which may be further enriched by PDGFRβ co-expression.
(1)Chan RW, Schwab KE and Gargett CE (2004) Biology of Reproduction 70, 1738.
Platelet-derived growth factor regulates the secretion of extracellular vesicles by adipose mesenchymal stem cells and enhances their angiogenic potential
