Explants-isolated human placenta and umbilical cord cells share characteristics of both epithelial and mesenchymal stem cells

In recent years, identification of new sources of adult stem cells developed rapidly, pursuing to find easily available tissues, which will give rise to homogenous stem cells populations. Up to present, bone marrow-derived mesenchymal stem cells (BM-MSCs) are unanimously considered to fulfill the criteria for being used in clinical settings, but adipose stem cells, placental and umbilical cord stem cells, and other tissue-derived stem cells are making their way to being used at least in autologous transplantation. We isolated cellular populations from placental tissue and umbilical cord using the explants method. The placental (PL) and umbilical cord (UC)-derived cells were cultured and expanded in appropriate conditions for generation of stem cells. We assessed the stemness characteristics of the tissue-isolated cells and compared them to an established MSCs line. For this purpose, we determined the immunophenotype, morphological and ultrastructural characteristics, as well as functional abilities of PL- and UC-derived cells. Flow cytometric evaluation of cells revealed presence of CD90, CD73, and CD105 stem cells markers, while the cells were negative for CD34, CD45 and HLA-DR. Immunocytochemical staining showed that 100% of PL- and UC-derived cells are positive for vimentin and CD105 expression, while cytokeratin was revealed in less than 10% in both tissue-isolated cells. Morphological and ultrastructural characteristics of cells exposed analogous cellular size and intracellular organization, similar to MSCs, but detailed view of UC-derived cells by transmission electron microscopy (TEM) demonstrated presence of intercellular junctions-desmosomes, similar to epithelial cells. Both PL- and UC-derived cells confirmed their trilineage potential, being able to differentiate into adipocytes, osteoblasts, and chondrocytes in different proportions. Flow chamber in vitro assay was used to determine to what extent PL- and UC-derived cells are able to adhere to substrates (VCAM and ICAM) and we showed progressively decreased adhesion of both cellular types, inversely proportional to the generated shear stress. We may conclude that explants-isolated placental and umbilical cord cells are endowed with characteristics of both epithelial and mesenchymal stem cells, and purification procedures are additionally required for safe use of these cells in diverse clinical applications.