Human decidual stromal cells express HLA-G: Effects of cytokines and decidualization.

BACKGROUND: Decidual stromal cells (DSC) are the main cellular component of the decidua, the maternal tissue in close contact with fetal trophoblast. Although of mesenchymal origin, DSC exert numerous immune functions that seem to be relevant for the immunological relationship between the mother and fetus. HLA-G, an antigen preferentially expressed by trophoblast, appears to participate in the immune tolerance by the mother of the semiallogeneic fetus. METHODS AND RESULTS: We show by flow cytometry, fluorescence microscopy, western blotting and RT-PCR that DSC isolated and maintained in culture express HLA-G weakly but consistently. We also detected this antigen by flow cytometry in fresh DSC. Interleukin (IL)-10, a cytokine associated with normal pregnancy, increased the expression of HLA-G by DSC (P < 0.00001), whereas IL-2, a cytokine involved in spontaneous abortion, showed no effect. Decidualization by progesterone and cAMP also up-regulated the expression of HLA-G by DSC (P < 0.001). Interferon gamma, a cytokine implicated in the vascular remodelling of the decidua necessary for embryo implantation, also increased the expression of HLA-G by DSC (P < 0.05). CONCLUSIONS: Our results suggest the existence of a network in which hormones together with cytokines regulate the expression of HLA-G by DSC, and that may be of relevance in the maintenance of maternal-fetal tolerance.

Contractile activity of human decidual stromal cells.

We previously demonstrated that human decidual stromal cells (DSC), the main cellular component of the decidua, are similar in antigen phenotype and structure to myofibroblasts, cells with contractile activity. In this work we isolated and maintained DSC in fibroblast medium, in which these cells show a stable phenotype similar to that of DSC in vivo. Flow cytometric observations showed that most DSC expressed alpha-smooth muscle (alpha-SM) actin, an intermediate filament that is considered a marker of myofibroblasts and is responsible for the contractile activity of these cells. alpha-SM actin mRNA was detected by RT-PCR in these cells. The contractile activity of DSC was determined by the gel contraction assay; we found that TGF beta 1 and platelet-derived-growth factor, cytokines that are known to be inducers of myofibroblast contractility, also induced contractility of DSC. IL-2, a Th1 cytokine-related with spontaneous abortion, also activated DSC contractility. Our results confirmed that DSC are phenotypically and functionally related with myofibroblast.

Follicular dendritic cells are related to bone marrow stromal cell progenitors and to myofibroblasts.

Follicular dendritic cells (FDC) are involved in the presentation of native Ags to B cells during the secondary immune response. Some authors consider FDC to be hemopoietic cells, whereas others believe them to be mesenchymal cells. The low proportion of FDC in the lymphoid follicle, together with technical difficulties in their isolation, make these cells difficult to study. We show that Fibroblast Medium can be used successfully to isolate and maintain FDC lines. In this culture medium, we obtained 18 FDC lines from human tonsils, which proliferated for as long as 18 wk and showed a stable Ag phenotype as detected by flow cytometry and RT-PCR. FDC lines were CD45-negative and expressed Ags associated to FDC (CD21, CD23, CD35, CD40, CD73, BAFF, ICAM-1, and VCAM-1) and Ags specific for FDC (DRC-1, CNA.42, and HJ2). These cell lines were also able to bind B cells and secrete CXCL13, functional activities characteristic of FDC. Nevertheless, the additional expression of STRO-1, together with CD10, CD13, CD29, CD34, CD63, CD73, CD90, ICAM-1, VCAM-1, HLA-DR, alkaline phosphatase, and alpha-smooth muscle actin (alpha-SM actin) indicated that FDC are closely related to bone marrow stromal cell progenitors. The expression of alpha-SM actin also relates FDC with myofibroblasts. Like myofibroblasts, FDC lines expressed stress fibers containing alpha-SM actin and were able to contract collagen gels under the effect of TGFbeta1 and platelet-derived growth factor. These findings suggest that FDC are a specialized form of myofibroblast and derive from bone marrow stromal cell progenitors.