3.1 Differential gene expression and cuproptosis related genes in placenta of PE
According to PE pregnant women and normal pregnant women, a three-line table was made to show the differences in age, BMI, peak blood pressure (systolic/diastolic blood pressure), termination week, umbilical blood flow S/D ratio, Apgar score (1 min, 5 min), etc. between the two groups (Table 1). The results showed that the pregnancy termination in PE patients occurred more than one week earlier compared to normal pregnant women (p = 0.013), and the BMI and peak blood pressure (systolic and diastolic blood pressure) of pregnant women were significantly higher than that of normal pregnant women (p = 0.0264; p = 0.000; p = 0.000), while the 1-minute Apgar score of newborns of PE pregnant women was significantly lower than that of normal pregnant women (p = 0.0432). There was no significant difference in other factors between the two groups (p > 0.05).
After data standardization and differential gene expression analysis, 2831 DEGs were found in normal placental tissue and PE placental tissue, including 1722 up-regulated genes and 1109 down-regulated genes (Figure 1A-1B), compared with PE placental tissue, and partial DEG expression was listed by corrected p-value through a heat map (Figure 1C).
Table 1 Comparison of general conditions of pregnant women between the two groups
|
Normal(N=77)
|
PE(n=80)
|
P-value
|
statistic
|
Maternal age(Year)
|
33.2(5.35)
|
33.2(5.89)
|
0.995
|
-0.0063
|
Maternal BMI(kg/m2)
|
24.5(4.84)
|
26.5(5.64)
|
0.0264*
|
-2.2448
|
Gestational week(Week)
|
34.0(4.73)
|
32.3(3.57)
|
0.013*
|
2.5149
|
Umbilical cord diameter
|
1.21(0.290)
|
1.16(0.393)
|
0.38
|
0.8809
|
Mean.umbilical.PI
|
1.30(0.463)]
|
1.39(0.379)
|
0.319
|
-1.0046
|
Maximum.systolic.bp
|
136(23.5)
|
170(18.1)
|
<0.001*
|
-10.0190
|
Maximum.diastolic.bp
|
85.3(14.7)
|
107(9.73)
|
<0.001*
|
-11.0239
|
Apgar.score..1.min
|
7.93(1.82)
|
7.30(1.76)
|
0.0432*
|
2.0409
|
Apgar.score..5.min
|
8.70(1.06)
|
8.71(0.725)
|
0.935
|
-0.0821
|
*p < 0.05
3.2 Multiple analysis of GO, KEGG, and GSEA
In order to understand the biological processes involved in these DEGs, they were enriched and analyzed through GO, KEGG, and GSEA analysis. The GO pathway revealed that DEGs are mainly enriched in oxidative stress, hypoxia reaction, intercellular connection, GTPase (Figure 2A-2F). KEGG pathway found that DEGs were mainly enriched in the PI3K pathway and atherosclerosis (Figure 3A-3D). After genome analysis by the GSEA pathway, it was found that DEGs were mainly concentrated in purine metabolism, cGMP PKG signal pathway, GABA synapse, and other pathways(Figure 4A-4B).
3.3 WGCNA analysis of cuproptosis genes associated with PE
First, we statistically analyzed the differences in the expression of 19 cuproptosis genes in normal placental tissues and PE placental tissues in the database, finding that "NFE2L2", "PDHA1", "PDHB", "DLD", and "GLS" had significant differences in the expression between the two groups (Figure 5A), and the five differential genes had low expression in PE (Table 2&Figure 5B). According to genes with a similar expression, DEGs were grouped into modules using WGCNA, and 28 modules were finally identified (Figure 6A). Then, Pearson correlation coefficient analysis was conducted to connect each module with the clinical characteristics of pregnant women (including systolic blood pressure, diastolic blood pressure, umbilical artery blood flow ratio, etc.) and maternal and fetal outcomes (neonatal APGAR score, neonatal weight, placental weight, etc.). The results showed that the negative correlation coefficient of the blue module was high, indicating that it has a protective role in the occurrence and development of PE (Figure 6B). According to the cut-off standard (| MM | > 0.8 and GS > 0.2), 62 genes in this module were identified as central genes with high weight. Finally, the Wayne map was constructed to intersect DEGs, CRGs, and hub genes. The intersection of DEGs, hub genes, and CRGs from GSE75010 obtained a common central gene: NFE2L2 (Figure 6C-6D).
Table 2. Intersection of differential gene and copper death gene
Gene
|
logFC
|
AveExpr
|
T
|
P Value
|
adj.P.Val
|
β
|
change
|
NFE2L2
|
0.16
|
10.70
|
5.49
|
1.58E-07
|
5.43E-06*
|
6.98
|
Down
|
PDHA1
|
0.13
|
9.34
|
4.49
|
1 38E-05
|
2 29E-04*
|
2.72
|
Down
|
PDHB
|
0.11
|
8.92
|
3.69
|
3.06E-04
|
2.87E-03*
|
-0.19
|
Down
|
DLD
|
0.12
|
9.27
|
3.28
|
1.27E-03
|
8.67E-03*
|
-1.50
|
Down
|
GLS
|
0.11
|
8.19
|
2.55
|
1 17E-02
|
4 47E-02*
|
-3.50
|
Down
|
*
p < 0.05
3.4 Pearson correlation coefficient analysis of cuproptosis genes associated with PE
In order to further study the relationship between the central gene and maternal blood pressure and related factors of maternal and fetal outcomes, Pearson correlation analysis was used to analyze and show that "NFE2L2", "PDHA1", "PDHB", "DLD", "GLS" were associated with peak blood pressure (systolic and diastolic), termination of pregnancy, placental weight, neonatal weight, etc. The results showed that the expression of "NFE2L2" was negatively correlated with the peak blood pressure (systolic and diastolic blood pressure), umbilical blood flow PI, placental weight [log2(fold change) = -2.14, p = 4.31e-03], neonatal weight, and gestational termination week, i.e., the peak blood pressure (systolic and diastolic blood pressure)[log2(fold change) = -7.87, p = 6.89e-06; log2(fold change) = -8.75, p = 2.71e-06], umbilical blood flow PI [log2(fold change) = -2.14, p = 4.31e-03] were negatively correlated, but positively correlated with placental weight [log2(fold change) = -6.68, p = 2.45e-05] (Figure 7A-7C), neonatal weight [log2(fold change) = -12.59, p = 4.74e-08] and gestational termination week [log2(fold change) = -1.12, p = 0.01] (Figure 7D-7F). Other cuproptosis genes were related to some maternal and fetal outcomes, such as "PDHA1" and "DLD", which were inversely proportional to peak blood pressure (systolic and diastolic blood pressure), and were proportional to placental weight and neonatal weight. However, there was no correlation between the termination week of pregnancy and umbilical blood flow PI (Figure S1-S2). "PDHB" was negatively correlated with peak blood pressure (systolic and diastolic blood pressure) and umbilical blood flow PI, meanwhile positively correlated with placental weight and neonatal weight, but it did not affect the termination of pregnancy (Figure S3). "GLS" was negatively correlated with peak systolic blood pressure and umbilical artery PI and positively correlated with placental weight, while there was no correlation in other aspects (Figure S4).
3.5 ROC curve analysis of the potential of cuproptosis gene as a predictor of PE
Based on the correlation between the above factors related to maternal and fetal outcomes and the cuproptosis genes, the results showed that the AUC values of "NFE2L2", "PDHA1", "PDHB", "DLD", and "GLS" were 0.759, 0.692, 0.686, 0.636, and 0.597, respectively, in terms of the potential to distinguish the markers of PE patients and normal pregnant women (Figure 8A-8E). These results pointed that "NFE2L2" was the most closely related cuproptosis gene to predict the occurrence and development of PE, followed by "PDHA1", "PDHB" and "DLD". While, "GLS" resulted as the least closely related to PE. To further clarify the potential influence of the above cuproptosis genes on the occurrence of PE, we conducted a RT-qPCR experiment, which showed that in addition to "GLS", the other four genes had significantly low expression in PE placenta, with a statistically significant difference (p < 0.05)(Figure 8F).