Placental transcriptome profiles in late-onset preeclampsia: a cross-sectional observational analysis stratified by fetal sex

Background Preeclampsia is a hypertensive disorder of pregnancy with significant maternal and fetal health implications. While the molecular mechanisms underlying early-onset preeclampsia have been studied extensively, less is known about late-onset preeclampsia, particularly with regard to fetal sex-specific effects. Understanding transcriptional changes in the placenta may provide insight into persistent mechanisms or downstream consequences of the disease, thereby contributing to our understanding of its pathophysiology. While the initiating events of late-onset preeclampsia occur earlier in gestation, analysis of term placental tissue can reveal cumulative effects of disease processes and identify biological pathways that remain altered at delivery. Methods We conducted a cross-sectional observational analysis of placental gene expression using RNA sequencing in a subset of 58 term placentas (21 male-bearing and 37 female-bearing pregnancies) drawn from two large prospective birth cohorts. Pregnancies were classified based on clinical diagnosis of late-onset preeclampsia (diagnosed ≥20 weeks’ gestation according to ISSHP criteria) or uncomplicated and assessed for differential gene expression. Cell type proportions were estimated using CIBERSORTx from a placenta-specific reference single-cell dataset. Weighted gene co-expression network analysis identified modules of co-expressed genes associated with late-onset preeclampsia and fetal sex. Results Differential gene expression analysis identified 150 genes with altered expression in male-bearing placentas from pregnancies with late-onset preeclampsia compared to those from uncomplicated pregnancies. No differentially expressed genes were identified in female-bearing placentas. Cell type deconvolution revealed increased abundance of CD14+ monocytes and CD8+ activated T cells (log odds of 1.42 and 1.44 respectively) and reduced fetal GZMK natural killer cells (log odds of 0.60) in male-bearing placentas from affected pregnancies. In female-bearing placentas, late-onset preeclampsia was associated with increased fetal nucleated red blood cells and maternal plasma cells (log odds of 1.33 and 1.40 respectively). Male-specific co-expression analysis identified gene modules enriched for biological processes including RNA processing, immune regulation, and metabolism. Conclusions Placental transcription and cellular responses to late-onset preeclampsia differ by fetal sex. Evidence of altered immune cell composition and gene co-expression in male-bearing placentas suggests a sex-specific vulnerability. These findings highlight the importance of considering fetal sex in molecular investigation and clinical management of preeclampsia.