High Proliferative Placenta-Derived Multipotent Cells Express Cytokeratin 7 at Low Level

The purpose of this study was to investigate the immunophenotypes and gene expression profile of high proliferative placenta-derived multipotent cells (PDMCs) population at different stages of culture. We demonstrated that the colonies resulting from single cells were either positive or negative for CK7, whereas only PDMC clones with weak CK7 expression (CK7^low-clones) were highly proliferative. Interestingly, vimentin positive (Vim⁺) placental stromal mesenchymal cells did not express CK7 in situ, but double CK7⁺Vim⁺ cells detection in tissue explants and explants outgrowth indicated CK7 inducible expression in vitro. PCNA presence in CK7⁺Vim⁺ cells during placental explants culturing confirmed belonging of these cells to proliferative subpopulation. Transcription factors CDX2 and EOMES were expressed in both CK7^low-clones and subset of stromal mesenchymal cells of first-trimester placental tissue in situ. Meanwhile, CK7^low -clones and stromal mesenchymal cells of full-term placental tissue in situ expressed ERG heterogeneously. SPP1, COL2A1, and PPARG2 mesodermal-related genes expression by CK7^low-clones additionally confirms their mesenchymal origin. Inherent stem cell-related gene expression (IFTM3, POU5F1, and VASA) in CK7^low-clones might indicate their enrichment for progenitors. Finally, in CK7^low-clones we observed expression of such trophoblast-associated genes as CGB types I and II, fusogenic ERVW-1, GCM1, and GATA3. Thus, our results indicate that PDMCs acquired the representative immunophenotype signature under culture conditions.