Characterization of the myometrial transcriptome in women with an arrest of dilatation during labor

Abstract

Objective: The molecular basis of failure to progress in labor is poorly understood. This study was undertaken to characterize the myometrial transcriptome of patients with an arrest of dilatation (AODIL).

Study design: Human myometrium was prospectively collected from women in the following groups: (1) spontaneous term labor (TL; n=29) and (2) arrest of dilatation (AODIL; n=14). Gene expression was characterized using Illumina® HumanHT-12 microarrays. A moderated Student's t-test and false discovery rate adjustment were used for analysis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) of selected genes was performed in an independent sample set. Pathway analysis was performed on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database using Pathway Analysis with Down-weighting of Overlapping Genes (PADOG). The MetaCore knowledge base was also searched for pathway analysis.

Results: (1) Forty-two differentially expressed genes were identified in women with an AODIL; (2) gene ontology analysis indicated enrichment of biological processes, which included regulation of angiogenesis, response to hypoxia, inflammatory response, and chemokine-mediated signaling pathway. Enriched molecular functions included transcription repressor activity, heat shock protein (Hsp) 90 binding, and nitric oxide synthase (NOS) activity; (3) MetaCore analysis identified immune response chemokine (C-C motif) ligand 2 (CCL2) signaling, muscle contraction regulation of endothelial nitric oxide synthase (eNOS) activity in endothelial cells, and triiodothyronine and thyroxine signaling as significantly overrepresented (false discovery rate <0.05); (4) qRT-PCR confirmed the overexpression of Nitric oxide synthase 3 (NOS3); hypoxic ischemic factor 1A (HIF1A); Chemokine (C-C motif) ligand 2 (CCL2); angiopoietin-like 4 (ANGPTL4); ADAM metallopeptidase with thrombospondin type 1, motif 9 (ADAMTS9); G protein-coupled receptor 4 (GPR4); metallothionein 1A (MT1A); MT2A; and selectin E (SELE) in an AODIL.

Conclusion: The myometrium of women with AODIL has a stereotypic transcriptome profile. This disorder has been associated with a pattern of gene expression involved in muscle contraction, an inflammatory response, and hypoxia. This is the first comprehensive and unbiased examination of the molecular basis of an AODIL.

Figure 1. Microarray analysis of the gene expression profiles of myometrium in spontaneous term labor (TL) and arrest of dilatation (AODIL)

A Volcano plot shows differentially gene expression between AODIL and TL. Dots in the upper right and left quadrants represent genes with a fold change greater than 1.5 and a false discovery rate corrected p-value < 0.25. With these criteria, 42 genes were differentially expressed between the myometrial transcriptome of the two groups.

Figure 2

A: Display of differentially expressed genes in the arrest of dilatation group on the most significantly over-represented MetaCore pathway: chemokine (C-C motif) ligand 2 (CCL2) signaling B: Display of differentially expressed genes in the arrest of dilatation group on the most significantly over-represented MetaCore pathway: Muscle Contraction Regulation of eNOS activity in endothelial cells

Figure 2

A: Display of differentially expressed genes in the arrest of dilatation group on the most significantly over-represented MetaCore pathway: chemokine (C-C motif) ligand 2 (CCL2) signaling B: Display of differentially expressed genes in the arrest of dilatation group on the most significantly over-represented MetaCore pathway: Muscle Contraction Regulation of eNOS activity in endothelial cells

Figure 3

Boxplot of qRT-PCR data for all 9 tested genes in an expanded sample set including those used in the microarray experiment. The data is presented as the −ΔCt values (surrogate of log₂ expression). The boxes encompass 50% of the data from the 1st quartile to the 3^rd quartile. The middle line represents the median value (50%) quartile. The whiskers extend to the most extreme data point, but do not exceed values >1.5 times the interquartile range from the box. The circles represent outliers. TL=spontaneous term labor; AODIL= arrest of dilatation.