Syncytin-1 and Glial Cells Missing a: Hypoxia-Induced Deregulated Gene Expression along with Disordered Cell Fusion in Primary Term Human Trophoblasts

Abstract

Background/Aims: Pre-eclampsia, a major cause of perinatal morbidity, is characterized by alterations in placental oxygen availability and trophoblast differentiation. We investigated how different levels of hypoxia alter the expression of syncytin-1, glial cells missing a (GCMa) and syncytin-1 receptor ASCT2 and affect syncytialization in primary term human trophoblasts. Methods: Cells were incubated at 1, 3, 6 and 21% O₂ for 24, 48 and 72 h with or without cyclic adenosine monophosphate (cAMP). Gene expression was analyzed by real-time PCR. Syncytialization was assessed using β-human chorionic gonadotropin measurement and desmoplakin immunostaining. Results: Following incubation with cAMP at 21% O₂, peak gene expression of syncytin-1 and GCMa was found after 24 h along with syncytium formation at 72 h. Conversely, incubation at 1% O₂ led to a time-dependent reduction of GCMa and syncytin-1 at the transcriptional level. Cell fusion occurred at 21 and 6% O₂ and was suppressed at 1% O₂. ASCT2 mRNA levels were preserved at normoxia and downregulated at 1% O₂ after 48 h. Conclusion: Our data support the premise that the expression of GCMa and syncytin-1 precedes syncytialization of trophoblasts, e.g. at 6% O₂, which is assumed to resemble physiological conditions. Severe hypoxia is associated with reduced GCMa and syncytin-1 transcripts and altered fusion of primary trophoblasts.

Reduced Syncytin-1 Expression Levels in Placental Syndromes Correlates with Epigenetic Hypermethylation of the ERVW-1 Promoter Region

“…Human CTs were isolated using the trypsin-DNase-dispase-collagenase-hyaluronidase/percoll method [16], [50]–[53] from 3 independent control, 3 IUGR, 3 PE, 3 PE/IUGR and 2 HELLP/IUGR placentae. For quality control see Ruebner et al [16].…”

Hypoxic stress induces, but cannot sustain trophoblast stem cell differentiation to labyrinthine placenta due to mitochondrial insufficiency

“…The support of syncytiotrophoblast formation at 20% but not 1% O 2 has been reported in first and third trimester cytotrophoblasts, but alternate lineage choice or intracellular enzymatic regulation of the process was not studied 68, 69 . It has been reported that glycogen synthase kinase (GSK)3 increase and phosphoinositol 3 kinase (PI3K-Akt) activity decrease is causal for hypoxia-induced Gcm1 protein degradation also at 1% O 2 which also occurs in hypoxia associated preeclampsia 23 .…”

Placenta-derived extracellular vesicles induce preeclampsia in mouse models

“…9 Syncytin expresses on mouse syncytiotrophoblasts, 10 induces trophoblast fusion during placental development, 11,12 and contributes to PE pathogenesis. 13,14 Blood samples collected at the baseline, 17-18 dpc, and postpartum using 3.8% of sodium citrate as an anticoagulant were centrifuged at 1500×g for 20 min at 25°C to collect platelet-poor plasma (PPP). PPP was incubated with a FITC-conjugated polyclonal syncytin antibody (FabGennix International Inc., Frisco, TX) for 30 min at room temperature and analyzed using flow cytometry (Beckon Dickinson, San Jose, CA).…”