Expression profiles and functions of ferroptosis-related genes in the placental tissue samples of early- and late-onset preeclampsia patients

Abstract

Background: The accumulation of reactive oxygen species (ROS) resulting from upregulated levels of oxidative stress is commonly implicated in preeclampsia (PE). Ferroptosis is a novel form of iron-dependent cell death instigated by lipid peroxidation that likely plays an important role in PE pathogenesis. This study aimed to investigate the expression profiles and functions of ferroptosis-related genes (FRGs) in early-onset preeclampsia (EOPE) and late-onset preeclampsia (LOPE).

Methods: Gene expression data and clinical information were downloaded from the Gene Expression Omnibus (GEO) database. The "limma" R package was used to screen differentially expressed genes. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-protein interaction (PPI) network analyses were conducted to investigate the bioinformatics functions and molecular interactions of significantly different FRGs. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to verify the expression of hub FRGs in PE.

Results: A total of 4215 differentially expressed genes (DEGs) were identified between EOPE and preterm cases while 556 DEGs were found between LOPE and term controls. Twenty significantly different FRGs were identified in EOPE subtypes, while only 3 FRGs were identified in LOPE subtypes. Functional enrichment analysis revealed that the differentially expressed FRGs were mainly involved in EOPE and enriched in hypoxia- and iron-related pathways, such as the response to hypoxia, iron homeostasis and iron ion binding process. PPI network analysis and verification by RT-qPCR resulted in the identification of the following five FRGs of interest: FTH1, HIF1A, FTL, MAPK8 and PLIN2.

Conclusions: EOPE and LOPE have distinct underlying molecular mechanisms, and ferroptosis may be mainly implicated in the pathogenesis of EOPE. Further studies are necessary for deeper inquiry into placental ferroptosis and its role in the pathogenesis of EOPE.

Keywords: Bioinformatics; Early-onset preeclampsia; Ferroptosis; Preeclampsia.

Fig. 1

Differentially expressed genes in the placental samples of PE patients. A Clinical subtypes of PE patients and controls who delivered preterm or at term. B The principal component analysis (PCA) of the gene expression datasets. C The differentially expressed genes (DEGs) for the different comparisons. D The overlapping genes between the comparisons of EOPE and LOPE patients, LOPE patients and preterm controls, preterm and term controls and EOPE patients and term controls. E Numbers of up- and downregulated genes in the comparisons

Fig. 2

Differentially expressed FRGs in the placental samples of PE patients. A The volcano plot of differentially expressed genes in the placental samples of EOPE patients. B The volcano plot of differentially expressed genes in the placental samples of LOPE patients. C The overlapping genes between FRGs and comparisons of EOPE patients and preterm controls and LOPE patients and term controls. D The overlapping FRGs between drivers, suppressors and markers. E The distribution of up- and downregulated ferroptosis regulators and markers in EOPE and LOPE patients. F The heatmap of differentially expressed FRGs in the placental samples of preeclampsia patients and the dendrogram based on the clustering analysis. Green represents downregulation, while red represents upregulation of the genes. G Deviation plot of up- and downregulated FRGs in the placental samples of EOPE patients

Fig. 3

Representative results of GO analyses. A Bubble plots of the GO analyses. B Results of the GO analyses

Fig. 4

Gene interactions of differentially expressed FRGs in preeclampsia patients. A The network of the differentially expressed FRGs downloaded from the STRING database. B The top 10 hub FRGs distinguished using color shading from yellow to red, according to the score

Fig. 5

The relative expression of differentially expressed FRGs in the placental samples. The control (Con) group included normal placental samples, and the EOPE group included placental samples from patients with preeclampsia. The sample sizes (Con: n = 26, EOPE: n = 22) achieve 81–99% power to reject the null hypothesis of equal means using a 2-sided, 2-sample equal-variance t test. **P < 0.01