Circulating Plasma Syncytin-1 mRNA in Preeclampsia—A Pilot Study

The endogenous human retroviral protein syncytin-1 is vital for placental integrity via syncytiotrophoblast formation. Preeclampsia has been associated with reduced placental syncytin-1 expression. The goal of the prospective pilot study was to investigate the role of circulating fetal syncytin-1 mRNA in women with and without preeclampsia (PE). We therefore determined syncytin-1 mRNA in maternal plasma of n = 26 women without and n = 43 women with PE with quantitative real-time PCR. Median circulating syncytin-1 mRNA concentrations were significantly lower in women with PE [1 217 050 copies; IQR 610 900-1 482 069] vs. those without PE [1 992 739 copies; IQR 1 616 811-3 126 225], <i>p</i> < 0.001. The area under the receiver operating curve used to diagnose PE at the time of delivery was 0.913 (95% CI: 0.850-0.977). Sub-analysis of patients with PE at sampling and patients who later developed PE vs. gestational-age-matched controls yielded a diagnostic accuracy of fetal syncytin-1 expression with an AUC of 0.962 (95% CI 0.877-1.000) and a predictive accuracy of 0.924 (95% CI 0.842-0.983). Quantification of the fetal syncytin-1 expression in maternal plasma might be used as a diagnostic and predictive tool in PE.