Chorionic trophoblast cells demonstrate functionally different phenotypes from placental trophoblasts

Abstract

Chorionic trophoblast cells (CTCs) 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 CTCs dealt with two separate questions: (1) The necessity of highly enriched and defined media with inhibitors of oxidative stress and cell transition and their impact on growth and trophoblast phenotype, (2) The functional differences between CTCs and other placental trophoblast lineages of cells (placental cytotrophoblast cells [PTC], and extravillous trophoblast [EVT]). CTCs 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 GATA3, cytokeratin [CK] 7, and vimentin) were assessed. Syncytialization of cells (forskolin treatment) and invasive properties of CTCs (cell invasion assay) were tested and compared with PTCs and EVTs (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 CK7 or GATA3) compared to CTCs grown in complete and enriched media. The CTCs failed to syncytialize, contrasting with the high levels of membrane fusion observed in PTCs. Although CTCs express human leukocyte antigen G (HLA-G) like EVTs, they do not invade. CTCs require several specific constituents for in vitro growth and phenotype maintenance. CTCs are trophoblast lineage cells that barricade immune cell-enriched decidua without invading them. These properties support their location and function, which are distinct from PTCs and EVTs.

Keywords: Amniochorion; Cell invasion; Extravillous trophoblast; Preterm birth; Syncytialization.