Characterization of the down-regulated genes identified in preeclampsia placenta

Hierarchical lncRNA regulatory network in early-onset severe preeclampsia

BACKGROUND

Recent studies have shown that several long non-coding RNAs (lncRNAs) in the placenta are associated with preeclampsia (PE). However, the extent to which lncRNAs may contribute to the pathological progression of PE is unclear.

RESULTS

Here, we report a hierarchical regulatory network involved in early-onset severe PE (EOSPE). We have carried out transcriptome sequencing on the placentae from patients and normal subjects to identify the differentially expressed genes (DEGs), including some lncRNAs (DElncRNAs). We then constructed a high-quality hierarchical regulatory network of lncRNAs, transcription factors (TFs), and target DEGs, containing 1851 lncRNA-TF interactions and 6901 TF-promoter interactions. The lncRNA-to-target regulatory interactions were further validated by the triplex structures between the DElncRNAs and the promoters of the target DEGs. The DElncRNAs in the regulatory network were clustered into 3 clusters, one containing DElncRNAs correlated with the blood pressure, including FLNB-AS1 with targeting 27.89% (869/3116) DEGs in EOSPE. We further demonstrated that FLNB-AS1 could bind the transcription factor JUNB to regulate a series members of the HIF-1 signaling pathway in trophoblast cells.

CONCLUSIONS

Our results suggest that the differential expression of lncRNAs may perturb the lncRNA-TF-DEG hierarchical regulatory network, leading to the dysregulation of many genes involved in EOSPE. Our study provides a new strategy and a valuable resource for studying the mechanism underlying gene dysregulation in EOSPE patients.

The Placental Function Beyond Pregnancy: Insights from Latin America

Currently, more than 100,000 papers had been published studying the placenta in both physiological and pathological contexts. However, relevant health conditions affecting placental function, mostly found in low-income countries, should be evaluated deeper. This review will raise some - of what we think necessary - points of discussion regarding challenging topics not fully understood, including the paternal versus maternal contribution on placental genes imprinting, placenta-brain communication, and some environmental conditions affecting the placenta. The discussions are parts of an international effort to fulfil some gaps observed in this area, and Latin-American research groups currently evaluate that.

Chorionic villus-derived mesenchymal stem cells induce E3 ligase TRIM72 expression and regulate cell behaviors through ubiquitination of p53 in trophoblasts

Preeclampsia is a significant contributor for maternal or fetal morbidity and mortality, which is characterized by reduced invasion capacity of trophoblasts and is regulated by extracellular matrix (ECM). It is still under investigation whether chorionic villus-derived mesenchymal stem cells (CVMSC) could affect the functionality of trophoblasts. In this study, CVMSC-derived exosomes were isolated; their effect on trophoblasts was investigated based on the CCK8 assay, migration assay, and apoptosis detection. And the underlying mechanism of this effect was investigated using mRNA sequencing, western blot, co-immunoprecipitation, luciferase report assay, and ubiquitination assay. The results show that CVMSC-derived exosomes promote migration and proliferation of trophoblasts, and also reduce cell apoptosis. mRNA sequencing confirmed that after treatment of CVMSC-derived exosomes, Tripartite Motif Containing 72 (TRIM72) expression was upregulated and Tumor Protein P53 (P53) expression was downregulated, both significantly in trophoblasts. Subsequent study confirms that TRM72 can directly interact with P53 and promote P53 ubiquitination and proteasomal degradation, reducing apoptosis rate and elevating proliferation and migration in trophoblasts. Our study confirms that CVMSC-derived exosomes promote trophoblast migration and proliferation by upregulating TRIM72 expression, and subsequently advance P53 ubiquitination and proteasomal degradation.

Distinct placental molecular processes associated with early-onset and late-onset preeclampsia

Background: Patients with preeclampsia display a spectrum of onset time and severity of clinical presentation, yet the underlying molecular bases for the early-onset and late-onset clinical subtypes are not known. Although several transcriptome studies have been done on placentae from PE patients, only a small number of differentially expressed genes have been identified due to very small sample sizes and no distinguishing of clinical subtypes. Methods: We carried out RNA-seq on 65 high-quality placenta samples, including 33 from 30 patients and 32 from 30 control subjects, to search for dysregulated genes and the molecular network and pathways they are involved in. Results: We identified two functionally distinct sets of dysregulated genes in the two major subtypes: 2,977 differentially expressed genes in early-onset severe preeclampsia, which are enriched with metabolism-related pathways, notably transporter functions; and 375 differentially expressed genes in late-onset severe preeclampsia, which are enriched with immune-related pathways. We also identified some key transcription factors, which may drive the widespread gene dysregulation in both early-onset and late-onset patients. Conclusion: These results suggest that early-onset and late-onset severe preeclampsia have different molecular mechanisms, whereas the late-onset mild preeclampsia may have no placenta-specific causal factors. A few regulators may be the key drivers of the dysregulated molecular pathways.

Collagen I Induces Preeclampsia-Like Symptoms by Suppressing Proliferation and Invasion of Trophoblasts

Preeclampsia is a common obstetric disorder affecting 2-8% of pregnancy worldwide. Fibrosis is an important histological change occurring in preeclamptic placenta, and might depend on the excess deposition of collagen I. However, the role of fibrotic placenta and collagen I in the pathogenesis of preeclampsia remains unclear. Therefore, we analyzed the collagen deposition and the expression of Collagen I in human placenta by Masson staining, Sirius red staining and western blotting. Further, the role of collagen I in preeclampsia pathogenesis was studied in C57BL/6 mice. HTR-8/SVneo cells were used to investigate the mechanisms underlying the effects of collagen I in trophoblasts by transcriptome sequencing and pharmacological agonists. Human preeclamptic placenta exhibited a significantly higher degree of fibrosis in stem villi and terminal villi than normal placenta, and was characterized by collagen I deposition. In vivo, a single injection of collagen I on gestational day 0.5 led to an increase in systolic pressure of pregnant mice from gestational days 4.5-17.5, to a decrease in weight and number of embryos, and to enhanced placental collagen I expression and degree of fibrosis compared with control mice. In vitro, collagen I attenuated the proliferation and invasion of HTR-8SV/neo cells. This effect could be reversed by treatment with agonists of ERK and β-catenin. Moreover, transcriptome sequencing demonstrated that signaling pathways related to cell proliferation and invasion were significantly downregulated in HTR-8SV/neo cells. Thus, we propose that collagen I induced preeclampsia-like symptoms by suppressing the proliferation and invasion of trophoblasts through inhibition of the ERK phosphorylation and WNT/β-catenin signaling pathways. Our findings could pave the way to the discovery of small-molecule inhibitors for preeclampsia treatment and future studies with larger sample size are required.

Preliminary evidence of a paternal-maternal genetic conflict on the placenta: Link between imprinting disorder and multi-generational hypertensive disorders

There has been great research progress on hypertensive disorders in pregnancy (HDP) in the last few decades. Failure of placentation, especially a lack of uterine spiral artery remodeling, is the main pathological finding of HDP. Currently, members of the vascular endothelial growth factor family are used as markers for the early prediction of onset of HDP. Epidemiologic research has also shown that HDP can have effects on the next generation infants, representing a Development Origins of Health and Disease-related disease. However, the precise pathogenic mechanism and the effect of HDP on the offspring remain unclear. The group of strong pro-inflammatory molecules known as "danger signals" have been shown to be released from the placental trophoblast surface and increase in the maternal circulation in HDP, which are then possibly transported into the fetal circulation. These signals, including fatty acids or adipocytokines, may alter the offspring's health in later life. Moreover, a hypoxic condition alters placental methylation, and the change may be passed onto the fetus. Although the genetic origin of the disease is still unknown, a hypothesis has been put forward that a paternal-maternal genetic conflict, mainly at imprinting lesion sites, may be a key factor for disease initiation. In particular, an imbalance in paternal and maternal factors may impede proper placentation, trophoblast invasion, decidualization or immune moderation so as to achieve better nutrition for the fetus (paternal) versus ensuring safe delivery and further pregnancy (maternal). Here, we review this research progress on HDP and focus on this novel genetic conflict concept, which is expected to provide new insight into the cause, pathophysiology, and multi-generational effects of HDP.