Human decidual stromal cells express CD34 and STRO-1 and are related to bone marrow stromal precursors

Decidual stromal cells (DSC) are the main cellular component of the human decidua, but thus far their ascription to a given cell lineage is uncertain. In previous studies, these cells have been isolated and maintained in culture, and their antigen phenotype has been analysed to determine their affiliation. However, the presence in the culture medium of high proportions of fetal calf serum (FCS) may inhibit the expression of some surface antigens. In the present study, we show by flow cytometry that CD34 is rapidly down-regulated in human DSC cultured in RPMI 1640 with 20% FCS. For this reason, we used fibroblast medium, which contains only a small proportion (2%) of FCS, to isolate and culture these cells. Under these conditions DSC exhibited a stable antigen phenotype highly similar to that of these cells in vivo. Flow cytometry results confirmed that DSC cultured in fibroblast medium expressed CD34 protein, and reverse transcription-polymerase chain reaction findings showed that they have CD34 mRNA. Decidual stromal cells were also positive for STRO-1, an antigen that identifies stromal precursors of the bone marrow which also expresses CD34. The expression of CD10, CD13, alkaline phosphatase and a-smooth muscle actin by DSC, and the absence of expression of CD14 and CD45, further confirmed their relationship with the stromal precursors.