Global Transcriptomic Analysis of Placentas from Women with Gestational SARS-CoV-2 Infection during the Third Trimester of Pregnancy

The COVID-19 pandemic has had a significant and enduring influence on global health, including maternal and fetal well-being. Evidence suggests that placental dysfunction is a potential consequence of SARS-CoV-2 infection during pregnancy, which may result in adverse outcomes such as preeclampsia and preterm birth. However, the molecular mechanisms underlying this association remain unclear, and it is uncertain whether a mature placenta can protect the fetus from SARS-CoV-2 infection. To address the above gap, we conducted a transcriptome-based study of the placenta in both maternal and fetal compartments. We collected placental samples from 16 women immediately after term delivery, seven of which had SARS-CoV-2 infection confirmed by PCR before parturition. Notably, we did not detect any viral load in either the maternal or fetal compartments of the placenta, regardless of symptomatic status. We separately extracted total RNA from placental tissues from maternal and fetal compartments, constructed cDNA libraries, and sequenced them to assess mRNA. Our analysis revealed 635 differentially expressed genes when a false discovery rate (FDR <= 0.05) was applied in the maternal placental tissue, with 518 upregulated and 117 downregulated genes in the SARS-CoV-2-positive women (n = 6) compared with the healthy SARS-CoV-2-negative women (n = 8). In contrast, the fetal compartment did not exhibit any significant changes in gene expression with SARS-CoV-2 infection. We observed a significant downregulation of nine genes belonging to the pregnancy-specific glycoprotein related to the immunoglobulin superfamily in the maternal compartment with active SARS-CoV-2 infection (fold change range from -13.70 to -5.28; FDR <= 0.01). Additionally, comparing symptomatic women with healthy women, we identified 1788 DEGs. Furthermore, a signaling pathway enrichment analysis revealed that pathways related to oxidative phosphorylation, insulin secretion, cortisol synthesis, estrogen signaling, oxytocin signaling, antigen processing, and presentation were altered significantly in symptomatic women. Overall, our study sheds light on the molecular mechanisms underlying the reported clinical risks of preeclampsia and preterm delivery in women with SARS-CoV-2 infection. Nonetheless, studies with larger sample sizes are warranted to further deepen our understanding of the molecular mechanisms of the placenta's anti-viral effects in maternal SARS-CoV-2 infection.