Characteristics of Human Endometrial Stem Cells in Tissue and Isolated Cultured Cells: An Immunohistochemical Aspect

Background: The aim of this study was to investigate the percentage of the stem cells population in human endometrial tissue sections and cultured cells at fourth passage. Methods: Human endometrial specimens were divided into two parts, one part for morphological studies and the other part for in vitro culture. Full thickness of human normal endometrial sections and cultured endometrial cells at fourth passage were analyzed via immunohistochemistry for CD146 and some stemness markers such as Oct4, Nanog, Sox2, and Klf4 and the expression of typical mesenchymal stem cell markers CD90, CD105. Results: 11.88 &plusmn; 1.29% of human endometrial cells whitin tissue sections expressed CD146 marker vs. 28&plusmn;2.3% of cultured cells, CD90 and CD105 were expressed by functionalis stroma (85&plusmn;2.4 and 89&plusmn;3.2%) than basalis stroma (16&plusmn;1.4 and 17&plusmn;1.9%), respectively (P<0.05). Oct4 and Nanog-expressing cells comprise 1.43&plusmn;0.08 and 0.54&plusmn;0.01% of endometrial stromal cells in endometrial sections vs. 12&plusmn;3.1% and 8&plusmn;2.9% of cultured cells, respectively. They reside near the glands in the basal layer of endometrium. Sox2 and Klf4 were not commonly expressed in tissue samples and cultured cells. CD9 and EpCAM were expressed by epithelial cells of the endometrium, rather than by stroma or perivascular cells. Conclusion: The human endometrial stem cells and pluripotency markers may be localized more in basalis layer of endometrium. The immunostaining observations of endometrial cells at fourth passage were correlated with the immunohistochemistry data.