Role of HIF-1α-SERPINE1 axis in hypoxia-induced trophoblast invasion and its relevance to preeclampsia.

OBJECTIVE: Preeclampsia (PE), the pregnancy-specific multisystem condition, exhibits typical features of deficient trophoblast invasion and dysfunctional spiral arterial remodeling, representing a major factor inducing maternal and perinatal incidence and mortality globally. The present work focused on investigating the precise mechanism underlying the regulation of trophoblast invasion by hypoxia-inducible factor 1α (HIF-1α)-SERPINE1 axis under hypoxic conditions and its implications in the pathogenesis of PE, using an integrative approach including clinical cohort, in vitro cell model, along with in vivo gene-edited mouse model.

METHODS: Plasma SERPINE1 levels were measured in 78 patients and 83 normal pregnant women controls recruited between July 2021 and July 2022 through a longitudinal cohort analysis. In vitro, we cultivated HTR-8/SVneo trophoblasts under21% O₂ or 1% O₂ conditions, with interventions including SERPINE1 knockdown, HIF-1α overexpression, and co-transfection using HIF-1α overexpression plasmid with SERPINE1 siRNA. HIF-1α, SERPINE1, and epithelial-mesenchymal transition (EMT) indicators (E-cadherin, N-cadherin, Vimentin) levels were detected through RT-qPCR and Western blotting. Transwell Matrigel assays evaluated cell invasion. A CRISPR/Cas9-generated SERPINE1 knockout (KO) mouse model was used to assess pregnancy outcomes with WT controls included for comparison.

RESULTS: Clinical data showed that plasma SERPINE1 contents were not significantly different in PE versus control groups during mid-to-late pregnancy. In vitro, hypoxia induced HIF-1α stabilization, which transcriptionally upregulated SERPINE1. This cascade downregulated E-cadherin but upregulated N-cadherin/Vimentin, enhancing EMT while accelerating trophoblast invasion. SERPINE1 knockdown suppressed EMT and invasion under hypoxia (but not normoxia), while HIF-1α overexpression promoted these processes-effects attenuated by co-transfection with SERPINE1 siRNA. SERPINE1 KO female mice exhibited complete fetal loss after mating, whereas WT controls achieved normal pregnancy, highlighting the indispensable role of SERPINE1 in pregnancy maintenance.

CONCLUSION: The HIF-1α-SERPINE1 axis critically regulates trophoblast invasion via hypoxia-induced EMT, which is essential for spiral artery remodeling. While SERPINE1 is indispensable for normal placental development, the discrepancy between elevated placental SERPINE1 and unchanged plasma levels in PE highlights the complexity of systemic biomarkers and points to the necessity of placental-specific detection strategies. This study identifies SERPINE1 as the obligate HIF-1α downstream mediator coupling hypoxia to trophoblast EMT, providing a mechanistic framework for PE pathogenesis and early detection.