Circulating immune cells from early- and late-onset preeclampsia displays distinct profiles with differential impact on endothelial activation

Preeclampsia (PE) affects 5-8% of pregnancies and has detrimental effects on maternal-fetal health. PE is characterized by de novo hypertension after 20 weeks of gestation and end-organ damage. Systemic inflammatory imbalance has been associated with PE, but its contribution to the pathology is poorly understood. Our objective was to investigate maternal systemic immune changes in early-onset PE (EOPE) and late-onset PE (LOPE) vs uncomplicated pregnancies (CTRL), and their contribution to endothelial activation, hallmark of hypertension. Blood samples were analyzed by flow cytometry, multiplex assay, intracellular cytokine staining (ICS), and single-cell RNA sequencing. We performed co-cultures between circulating immune cells and human umbilical veins endothelial cells (HUVECs) to assess endothelial activation. We found that EOPE had decreased Treg (4.64±0.33, p<0.05) and monocytes (33.92±3.08, p<0.01), whereas LOPE had decreased Treg (4.60±0.30, p<0.05) and Th2 cells (7.50±0.62, p<0.01) vs CTRL. Compared to CTRL, elevated cytokines/chemokines, and growth factors were observed in LOPE, whereas EOPE primarily showed decreased levels. Using ICS, we observed more monocytes producing IL-12, TNF, and IL-1 (all p<0.05) in LOPE vs CTRL. At the transcriptomic level, we found differentially expressed genes (DEGs) between EOPE and CTRL, predominantly related to upregulation of immune activation pathways. Lastly, EOPE peripheral blood mononuclear cells (PBMCs) induced heightened endothelial activation in vitro observed by increased ICAM-1 and ET-1 (p<0.05), whereas LOPE PBMCs required LPS stimulation. While significant proteomic changes are observed in the LOPE group, the EOPE displayed changes mostly at the transcriptomic levels and could induce endothelial activation in vitro.