Placental microRNA expression in pregnancies complicated by preeclampsia

Abstract

Objective: The role of posttranscription regulation in preeclampsia is largely unknown. We investigated preeclampsia-related placental microRNA (miRNA) expression using microarray and confirmatory quantitative real-time polymerase chain reaction experiments.

Study design: Placental expressions of characterized and novel miRNAs (1295 probes) were measured in samples collected from 20 preeclampsia cases and 20 controls. Differential expression was evaluated using Student t test and fold change analyses. In pathway analysis, we examined functions/functional relationships of targets of differentially expressed miRNAs.

Results: Eight miRNAs were differentially expressed (1 up-regulated and 7 down-regulated) among preeclampsia cases compared with controls. These included previously identified candidates (miR-210, miR-1, and a miRNA in the 14q32.31 cluster region) and others that are novel (miR-584 and miR-34c-5p). These miRNAs target genes that participate in organ/system development (cardiovascular and reproductive system), immunologic dysfunction, cell adhesion, cell cycle, and signaling.

Conclusion: Expression of miRNAs that target genes in diverse pathophysiological processes is altered in the setting of preeclampsia.

Figure 1. Hierarchical clustering of participants and microRNA expression

Clustering (Gene Cluster 3.0) of expression measures using Centered Correlation as the similarity metric and Average Linkage as the clustering method. Left panel: clustering using all 611 human miRNA probes. Right panel: an enlarged view of a representative section of the clustered image. Columns: samples (P=preeclampsia case and C=control). Rows: miRNA. Differentially expressed miRNA are highlighted. Scales: normalized miRNA expression values for each sample with the sum of squares of all expression values for each miRNA equal to 1.

Figure 2. Fold change comparison* of differentially expressed microRNAs

Fold change comparison of placental miRNA expression between preeclampsia cases and controls. Positive values (green) represent up regulation in preeclampsia while negative values (red) represent down regulation.

Figure 3. Top Network (Score=30) identified by Ingenuity Pathway Analysis

The network was generated through the use of Ingenuity Pathways Analysis (Ingenuity^® Systems, www.ingenuity.com). Identifier of each gene was mapped to its corresponding gene object in the Ingenuity Pathways Knowledge Base (IPKB) and overlaid onto a global molecular network developed from information contained in the IPKB. Shaded genes are genes that are targeted by two or more microRNAs that are differentially expressed in preeclamptic placenta in our study. The IPA edge type and node type descriptions illustrate the type of relationship between the genes and their functions.

Figure 3. Top Network (Score=30) identified by Ingenuity Pathway Analysis

The network was generated through the use of Ingenuity Pathways Analysis (Ingenuity^® Systems, www.ingenuity.com). Identifier of each gene was mapped to its corresponding gene object in the Ingenuity Pathways Knowledge Base (IPKB) and overlaid onto a global molecular network developed from information contained in the IPKB. Shaded genes are genes that are targeted by two or more microRNAs that are differentially expressed in preeclamptic placenta in our study. The IPA edge type and node type descriptions illustrate the type of relationship between the genes and their functions.