HIF1A and EPAS1 mRNA and protein expression during in vitro culture of human primary term cytotrophoblasts and effect of oxygen tension on their expression.
During the first trimester of pregnancy, placenta formation probably occurs in a low-oxygen environment necessary to protect cytotrophoblasts from oxidative stress and to allow proper gene regulation. Transcription factors involved in gene regulation under low oxygen tension are the hypoxia-inducible factors, mainly HIF1A, EPAS1 and their dimerization partner HIF1B. Little is known about their expression during in vitro culture of cytotrophoblasts under chronic hypoxia. We assessed HIF1A and EPAS1 expression in a 4-day in vitro culture of primary term cytotrophoblasts under 21% O2and 2.5% O2. Copy numbers and relative mRNA expression were assessed by real-time quantitative polymerase chain reaction. Protein levels were quantified by immunoblot and densitometric analysis. In undifferentiated cytotrophoblasts, EPAS1 transcripts were four times more abundant than HIF1A transcripts (2.14e7and 5e6copies/μg total RNA, respectively). During cell culture, HIF1A mRNA expression increased after 24h and then decreased to stay stable. The expression was even lower when cells were grown under 2.5% O2. EPAS1 mRNA expression increased during cytotrophoblast differentiation. The expression was higher when cells were under 21% O2than when they were under 2.5% O2. Interestingly, HIF1A, but not EPAS1, was detected in the nuclei of undifferentiated cytotrophoblasts, and in the nuclei of cytotrophoblasts that grew under 21% O2. During cytotrophoblast differentiation, no variation in HIF1A protein levels was detected. To the contrary, EPAS1 protein level increased during differentiation, and oxygen tension had no effect on EPAS1 protein level. In conclusion, HIF1A and EPAS1 expression was not inhibited by chronic hypoxia during in vitro cytotrophoblast differentiation.
Laboratoire de recherche en obstétrique, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Tour Cl. Bernard +1, Avenue Hippocrate 54, Brussels, Belgium. Electronic address: christophe.depoix@uclouvain.be.
Christophe Louis
CL
Depoix
Laboratoire de recherche en obstétrique, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Tour Cl. Bernard +1, Avenue Hippocrate 54, Brussels, Belgium.
Olivier
O
Flabat
Laboratoire de recherche en obstétrique, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Tour Cl. Bernard +1, Avenue Hippocrate 54, Brussels, Belgium.
Frédéric
F
Debiève
Laboratoire de recherche en obstétrique, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Tour Cl. Bernard +1, Avenue Hippocrate 54, Brussels, Belgium.
Corinne
C
Hubinont
D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000008:administration & dosage*; D010920:Placenta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D010100:Oxygen; D012333:RNA, Messenger; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human
Chronic hypoxia; Cytotrophoblast; EPAS1; HIF1A; In vitro culture