Hypoxia-inducible factor-1 mediates the biological effects of oxygen on human trophoblast differentiation through TGFβ3
Isabella Caniggia, … , Maciej Kuliszewski, Martin Post
Isabella Caniggia, … , Maciej Kuliszewski, Martin Post
Published March 1, 2000
Citation Information: J Clin Invest. 2000;105(5):577-587. https://doi.org/10.1172/JCI8316.
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Article

Hypoxia-inducible factor-1 mediates the biological effects of oxygen on human trophoblast differentiation through TGFβ3

Abstract

During early pregnancy, placentation occurs in a relatively hypoxic environment that is essential for appropriate embryonic development. Intervillous blood flow increases around 10 to 12 weeks of gestation and results in exposure of trophoblast cells to increased oxygen tension. Before this time, low oxygen appears to prevent trophoblast differentiation toward an invasive phenotype. Using human villous explants of 5–8 weeks’ gestation, we found that low oxygen tension triggered trophoblast proliferation, fibronectin synthesis, α5 integrin expression, and gelatinase A activity. These biochemical markers were barely detectable under oxic conditions. We therefore examined the placental expression of hypoxia-inducible factor-1 (HIF-1), a master regulator of oxygen homeostasis, and determined that expression of HIF-1α subunit during the first trimester of gestation parallels that of TGFβ3, an inhibitor of extravillous trophoblast differentiation. Expression of both molecules is high in early pregnancy and falls around 9 weeks of gestation, when placental pO2 levels are believed to increase. Increasing oxygen tension induced a similar decrease in expression in cultured explants. Moreover, antisense inhibition of HIF-1α expression in hypoxic explants inhibited expression of TGFβ3, arrested cell proliferation, decreased α5 expression and gelatinase A activity, and triggered biochemical markers of an invasive trophoblast phenotype such as α1 integrin and gelatinase B expression. These data suggest that the oxygen-regulated early events of trophoblast differentiation are in part mediated by TGFβ3 through HIF-1 transcription factors.

Authors

Isabella Caniggia, Homa Mostachfi, Jennifer Winter, Max Gassmann, Stephen J. Lye, Maciej Kuliszewski, Martin Post

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Figure 1

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Low oxygen tension induces trophoblast outgrowth and increases prolifera...
Low oxygen tension induces trophoblast outgrowth and increases proliferation, fibronectin synthesis, and gelatinase activity in villous explant cultures. (a) Villous explants from 5 to 8 weeks of gestation were maintained in culture for 5 days under normal (20% O2) or low (3% O2) oxygen tension. Note that exposure of villous explants to 3% O2 dramatically increases budding and outgrowth of EVT from the distal end of the villous tips when compared with villous explants kept at 20% O2. ×25, ×50. (b) Section of explants, cultured in either 3% or 20% O2, were stained for Ki67, a marker of cellular proliferation and α5 integrin. Strong positive nickel-enhanced immunoreactivity for Ki67 was observed in EVT of the outgrowth (EVT) of explants cultured in 3% O2. Similar immunolocalization was observed for α5 integrin. A few immunopositive cells for both Ki67 and α5 integrin were noted in explants kept at 20% O2 (arrows). S, villous stroma. (c) Explants incubated for 4 days in either low or normal pO2 conditions were metabolically labeled with [35S]methionine for 18 hours. Fibronectin was isolated from conditioned medium using gelatin-Sepharose beads. Samples were subjected to SDS-PAGE, and the position of the marker (with Mr = 200 × 103) is indicated. (d) Samples of medium conditioned by explants, cultured in either 3 or 20% O2, were collected at day 5 and subjected to analysis by gelatin zymography. Arrows indicate positions of gelatinase activity (gelatinase A/MMP-2: 60 and 68 kDa; gelatinase B/MMP-9: 92 kDa).