Extracellular matrix composition and hypoxia regulate the expression of HLA-G and integrins in a human trophoblast cell line

During human placentation, extravillous cytotrophoblast cells emerge from chorionic villi contacting the decidua to invade the uterine wall. When isolated from first-trimester placentae, cytotrophoblast cells undergo step-wise differentiation in vitro that recapitulates the phenotypic heterogeneity observed in vivo. We examined a cell line, HTR-8/SVneo, that has been established from human first-trimester cytotrophoblast to determine whether these cells possess some of the unique cytotrophoblast characteristics that have been described previously. Exposure during serum-free culture to hypoxic conditions (2% oxygen concentration) increased HTR-8/SVneo cell proliferation and reduced invasion of a three-dimensional basement membrane (Matrigel), During culture on surfaces coated with individual extracellular matrix proteins, HTR-8/SVneo cells expressed cytokeratin but not the trophoblast-specific major histocompatibility protein, HLA-G. However, HLA-G expression was induced in HTR-8/SVneo cells that contacted Matrigel, Expression of the alpha 5 integrin subunit was relatively unaffected by matrix composition, whereas alpha 1 was up-regulated and alpha 6 was down-regulated after transferring cells to Matrigel. Hypoxia increased alpha 6 and decreased both alpha 1 and HLA-G expression on Matrigel, HTR-8/SVneo cells retain several important characteristics associated with primary cultures of first-trimester human cytotrophoblast cells, including their altered behavior in response to a changing maternal environment.