Potential role of epigenetic mechanisms in regulation of trophoblast differentiation, migration, and invasion in the human placenta

Overexpression of long non-coding RNA H19 promotes invasion and autophagy via the PI3K/AKT/mTOR pathways in trophoblast cells

BACKGROUND

Preeclampsia (PE), characterized by hypertension and proteinuria, is a leading cause of perinatal and maternal mortality. Considering that mutation of H19 gene is closely associated with PE, we aimed to explore the functional role of long non-coding RNA H19 (lncRNA-H19) in trophoblast cells.

METHODS

Expression of lncRNA-H19 in placenta tissues from patients with PE and healthy pregnant women after delivery was determined by quantitative reverse transcription PCR. Then, lncRNA-H19 was abnormally expressed in JEG-3 and HTR-8 cells by stable cell transfection. Cell viability and invasion were assessed by using CCK-8 and Matrigel-coated Millicell system, respectively. Expression of key proteins associated with invasion and autophagy as well as key kinases in the phosphatidylinositol-3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) pathways were measured by Western blot analysis. Number of GFP-labeled autophagosomes was counted under a confocal microscope.

RESULTS

Level of lncRNA-H19 in the placenta tissues from PE patients was higher than that from healthy controls. LncRNA-H19 overexpression reduced cell viability but increased invasion of JEG-3 and HTR-8 cells. LncRNA-H19 silence showed the opposite effects. In addition, lncRNA-H19 overexpression promoted autophagy in trophoblast cells. Furthermore, phosphorylated levels of key kinases in the PI3K/AKT/mTOR pathways were enhanced by lncRNA-H19 overexpression while were reduced by lncRNA-H19 silence.

CONCLUSION

LncRNA-H19, which was up-regulated in PE, reduced cell viability but promoted invasion and autophagy in trophoblast cells, along with activation of the PI3K/AKT/mTOR pathways. Our study provides a theoretical basis for pathogenesis of PE, aiding to identification of novel therapeutic strategies for PE.

Hypomethylation of the miRNA-34a gene promoter is associated with Severe Preeclampsia

PURPOSE

PE is a pregnancy-specific complication, which genetic and epigenetic factors play key roles in its pathogenesis. DNA methylation is a main epigenetic alteration with important roles in gene regulation. Micro RNAs (miRNAs) as another member of epigenetic machinery regulate the gene expression and involve in different biological pathways including apoptosis and placental development. Therefore, the present study performed to assess the association between miRNA-34a promoter methylation and PE susceptibility.

METHODS

The placenta of 104 PE pregnant women and 119 normotensive pregnant women were collected after delivery. The methylation status of the miRNA-34a promoter was assessed using Methylation Specific PCR (MSP).

RESULTS

The frequency of the hemi-methylated (MU) miR-34a promoter was significantly lower in PE women compared to the controls (17.3 vs. 29.4%) (OR, 0.45 [95% CI, 0.2-0.9], P = 0.016). The overall methylation rate was 23.1% in PE women and 41.2% in the control group and was significantly lower in PE women (OR, 0.4 [95% CI, 0.2-0.8], P = 0.004). The frequency of hemi-methylated (MU) and overall methylated (MU+MM) promoter of miR-34a gene was significantly lower in severe PE but not in mild PE women compared to the controls [(OR, 0.3 [95% CI, 0.1-0.8], P = 0.02) and (OR, 0.3 [95% CI, 0.1-0.7], P = 0.009), respectively]. There was an association between hemi-methylated (MU) and overall methylated (MU+MM) promoter and late onset PE [(OR, 0.4 [95% CI, 0.2-0.9], P = 0.03) and (OR, 0.4 [95% CI, 0.2-0.8], P = 0.01), respectively].

CONCLUSIONS

An association was found between hypo-methylation of the miR-34a promoter and PE and PE severity.

Embryo Implantation: War in Times of Love

Contrary to widespread belief, the implantation of an embryo for the initiation of pregnancy is like a battle, in that the embryo uses a variety of coercive tactics to force its acceptance by the endometrium. We propose that embryo implantation involves a three-step process: (1) identification of a receptive endometrium; (2) superimposition of a blastocyst-derived signature onto the receptive endometrium before implantation; and finally (3) breaching by the embryo and trophoblast invasion, culminating in decidualization and placentation. We review here the story that is beginning to emerge, focusing primarily on the cells that are in "combat" during this process.

Cell cycle and histone modification genes were decreased in placenta tissue from unexplained early miscarriage

Genetic defect is a major cause of early miscarriage, but still in many cases the etiology are not fully understood. Recent studies have shown that dysregulation of genes in placenta tissue are participated in the pathogenesis of unexplained early miscarriage. The aim of our study is to explore mRNA expression profile in placental chorionic villi and to reveal the underlying mechanism of unexplained early miscarriage. Chorionic villous were isolated and extracted from early miscarriage (n=3) and control pregnancy (n=3) placenta with normal chromosome karyotype using MLPA assay, and then mRNA expression profiles were determined by microarray. For verification the reproducibility of the microarray, three up-regulated genes and six down-regulated genes were chosen and examined by real-time PCR (n=30). A total of 81 genes were up-regulated and 231 genes were down-regulated when compared to the control group, and the differences were reached statistically significances (P<0.05). After Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, we found that almost down-regulation genes are associated with cell cycle and histone modification, and these genes are participated in several important physiological processes, such as cell proliferation, nuclear division, chromatic assembly, DNA packing and modification. These results indicated that cell cycle and histone modification genes, and related signaling pathway maybe contribute to the genesis and development of unexplained early miscarriage. Further studies and validations are necessary to elucidate the exact roles of these genes in miscarriage pathogenesis, which can develop tools for early detection and management.