Chorionic trophoblast cells demonstrate functionally different phenotypes from placental trophoblasts

Chorionic trophoblast cells are one of the principal components of the fetal membrane and join with the decidua to form a feto–maternal interface. Recent success in isolating chorionic trophoblast cells dealt with two separate questions: (i) the necessity of highly enriched and defined media with inhibitors of oxidative stress and cell transition and their impact on growth and trophoblast phenotype, (ii) the functional differences between chorionic trophoblast cells and other placental trophoblast lineages of cells (placental cytotrophoblast cells, and extravillous trophoblast). Chorionic trophoblast cells were cultured either in defined media with various inhibitors or in media from which inhibitors were removed individually. Cellular morphology and growth (microscopy and crystal violet staining) and cellular and molecular biological features (immunofluorescence staining for GATA-binding protein 3, cytokeratin 7, and vimentin) were assessed. Syncytialization of cells (forskolin treatment) and invasive properties of chorionic trophoblast cells (cell invasion assay) were tested and compared with placental cytotrophoblast cells and extravillous trophoblasts (HTR8/SVneo), respectively. Removal of various growth-supporting agents from the media delayed cell growth and inclined towards cellular transition (increase in vimentin compared to cytokeratin 7 or GATA-binding protein 3) compared to chorionic trophoblast cells grown in complete and enriched media. The chorionic trophoblast cells failed to syncytialize, contrasting with the high levels of membrane fusion observed in placental cytotrophoblast cells. Although chorionic trophoblast cells express human leukocyte antigen G like extravillous trophoblasts, they do not invade. Chorionic trophoblast cells require several specific constituents for in vitro growth and phenotype maintenance. Chorionic trophoblast cells are trophoblast lineage cells that barricade immune cell-enriched decidua without invading them. These properties support their location and function, which are distinct from placental cytotrophoblast cells and extravillous trophoblasts.