Retinoic Acid Is a Negative Regulator of sFLT1 Expression in Decidual Stromal Cells, and Its Levels Are Reduced in Preeclamptic Decidua

Signaling via retinoic acid receptors mediates decidual angiogenesis in mice and human stromal cell decidualization

At the maternal-fetal interface, tightly regulated levels of retinoic acid (RA), the physiologically active metabolite of vitamin A, are required for embryo implantation and pregnancy success. Herein, we utilize mouse models, primary human cells, and pharmacological tools to demonstrate how depletion of RA signaling via RA receptor (RAR) disrupts implantation and progression of early pregnancy. To inhibit RAR signaling during early pregnancy, BMS493, an inverse pan-RAR agonist that prevents RA-induced differentiation, was administered to pregnant mice during the peri-implantation period. Attenuation of RA/RAR signaling prior to embryo implantation results in implantation failure, whereas attenuation of RA/RAR signaling after embryo implantation disrupts the post-implantation decidual vasculature and results in pregnancy failure by mid-gestation. To inhibit RAR signaling during human endometrial stromal cell (HESC) decidualization, primary HESCs and decidualized primary HESCs were transfected with silencing RNA specific for human RARA. Inhibition of RA/RARA signaling prevents initiation of HESC decidualization, but not maintenance of the decidualized HESC phenotype. These data show that RA/RAR signaling is required for maintenance of the decidual vasculature that supports early pregnancy in mice, and distinct RAR signaling is required for initiation, but not maintenance of primary HESC decidualization in vitro.

Inhibitory effect of all-trans retinoic acid on ferroptosis in BeWo cells mediated by the upregulation of heme Oxygenase-1

INTRODUCTION

This study aimed to explore the association between ferroptosis, a newly identified type of cell death, and the role of retinoic acid in developing pregnancy complications. Therefore, the effects of all-trans retinoic acid (ATRA) on ferroptosis susceptibility in BeWo cells were assessed to understand abnormal placental development.

METHODS

BeWo cells were used as surrogates for cytotrophoblasts. The effect of ATRA on ferroptosis sensitivity was assessed on BeWo cells pretreated with ATRA or dimethyl sulfoxide (DMSO; control), following which the LDH-releasing assay was performed. The effects of ATRA pretreatment on the antioxidant defense system (including glutathione [GSH], mitochondrial membrane potential, and heme oxygenase-1 [HMOX1]) in BeWo cells were assessed using assay kits, RT-qPCR, and HMOX1 immunostaining. To evaluate the effect of ATRA on BeWo cells, HMOX1 was silenced in BeWo cells using shRNA.

RESULTS

ATRA pretreatment increased ferroptosis resistance in BeWo cells. Although with pretreatment, qPCR indicated upregulation of HMOX1, no significant change was observed in the GSH levels or mitochondrial membrane potential. This was corroborated by intensified immunostaining for heme oxygenase-1 protein (HO-1). Notably, the protective effect of ATRA against ferroptosis was negated when HO-1 was inhibited. Although HMOX1-silenced BeWo cells exhibited heightened ferroptosis sensitivity compared with controls, ATRA pretreatment counteracted ferroptosis in these cells.

DISCUSSION

ATRA pretreatment promotes BeWo cell viability by suppressing ferroptosis and upregulating HMOX1 and this can be used as a potential therapeutic strategy for addressing placental complications associated with ferroptosis.

Interleukin-17 promotes proliferation, migration, and invasion of trophoblasts via regulating PPAR-γ/RXR-α/Wnt signaling

To investigate the effect of Interleukin 17 (IL-17) on the invasive capacity of trophoblast cells and the underlying mechanism, we collected placental tissues samples from pregnant women with preeclampsia (PE) and healthy pregnant women. The expression levels of IL-17 mRNA and protein in tissue samples were determined using qRT-PCR and Western blot, respectively. Cell viability and cell proliferation was determined using CCK-8 assay, and colony formation assay, respectively. Cell migration and invasion capacity were determined using transwell cell migration assay. Our results showed that the mRNA expression of IL-17 was significantly increased in PE patients and may be used as a sensitive biomarker for PE (P < 0.01). IL-17 overexpression promoted cell viability, migration, and invasion of human extravillous trophoblast cell line, HTR8/SVneo; however, IL-17 knockdown inhibited these effects. Additionally, IL-17 activated PPAR-γ/RXR-α signaling pathway, which promoted proliferation, migration, and invasion of trophoblast cells. Moreover, PPAR-γ/RXR-α heterodimers activated Wnt signaling. In conclusion, our study provides evidence that IL-17 is overexpressed in PE and promotes proliferation, migration and invasion of trophoblast cells via activating PPAR-γ/RXR-α/Wnt signaling.

Clinical consequences of defective decidualization

Decidualization is characterized by a series of genetic, metabolic, morphological, biochemical, vascular and immune changes occurring in the endometrial stroma in response to the implanting embryo or even before conception and involves the stromal cells of the endometrium. It is a fundamental reproductive event occurring in mammalian species with hemochorial placentation. A growing body of experimental and clinical evidence strongly suggests that defective or disrupted decidualization contributes to the establishment of an inappropriate maternal-fetal interface. This has relevant clinical consequences, ranging from recurrent implantation failure and recurrent pregnancy loss in early pregnancy to several significant complications of advanced gestation. Moreover, recent evidence indicates that selected diseases of the endometrium, such as chronic endometritis and endometriosis, can have a detrimental impact on the decidualization response in the endometrium and may help explain some aspects of the reduced reproductive outcome associated with these conditions. Further research efforts are needed to fully understand the biomolecular mechanisms ans events underlying an abnormal decidualization response. This will permit the development of new diagnostic and therapeutic strategies aimed to improve the likelihood of achieveing a successful pregnancy.

Evidence for Corpus Luteal and Endometrial Origins of Adverse Pregnancy Outcomes in Women Conceiving with or Without Assisted Reproduction

Preeclampsia may arise from impaired decidualization in some women. Transcriptomics of mid-secretory biopsy endometrial stromal cells decidualized in vitro and of early gestation choriodecidua from women who experienced preeclampsia with severe features overlapped significantly with the classical endometrial disorders giving rise to the concept of "endometrium spectrum disorders". That is, recurrent implantation failure and miscarriage, endometriosis, normotensive intrauterine growth restriction, preeclampsia and preterm birth may all lie on a continuum of decidual dysregulation, in which phenotypic expression is determined by the specific molecular pathway(s) disrupted and severity of disruption. Women conceiving by programmed IVF protocols showed widespread dysregulation of cardiovascular function and increased rates of adverse pregnancy outcomes including preeclampsia. Programmed cycles preclude development of a corpus luteum (CL), a major regulator of endometrial function. Lack of circulating CL product(s) that are not replaced in programmed cycles (eg, relaxin) could adversely impact the maternal cardiovascular system directly and/or compromise decidualization, thereby increasing preeclampsia risk.

Pathogenesis of Preeclampsia and Therapeutic Approaches Targeting the Placenta

Preeclampsia (PE) is a serious pregnancy complication, affecting about 5–7% of pregnancies worldwide and is characterized by hypertension and damage to multiple maternal organs, primarily the liver and kidneys. PE usually begins after 20 weeks’ gestation and, if left untreated, can lead to serious complications and lifelong disabilities—even death—in both the mother and the infant. As delivery is the only cure for the disease, treatment is primarily focused on the management of blood pressure and other clinical symptoms. The pathogenesis of PE is still not clear. Abnormal spiral artery remodeling, placental ischemia and a resulting increase in the circulating levels of vascular endothelial growth factor receptor-1 (VEGFR-1), also called soluble fms-like tyrosine kinase-1 (sFlt-1), are believed to be among the primary pathologies associated with PE. sFlt-1 is produced mainly in the placenta during pregnancy and acts as a decoy receptor, binding to free VEGF (VEGF-A) and placental growth factor (PlGF), resulting in the decreased bioavailability of each to target cells. Despite the pathogenic effects of increased sFlt-1 on the maternal vasculature, recent studies from our laboratory and others have strongly indicated that the increase in sFlt-1 in PE may fulfill critical protective functions in preeclamptic pregnancies. Thus, further studies on the roles of sFlt-1 in normal and preeclamptic pregnancies are warranted for the development of therapeutic strategies targeting VEGF signaling for the treatment of PE. Another impediment to the treatment of PE is the lack of suitable methods for delivery of cargo to placental cells, as PE is believed to be of placental origin and most available therapies for PE adversely impact both the mother and the fetus. The present review discusses the pathogenesis of PE, the complex role of sFlt-1 in maternal disease and fetal protection, and the recently developed placenta-targeted drug delivery system for the potential treatment of PE with candidate therapeutic agents.

The Inhibition of Protein Kinase C β Contributes to the Pathogenesis of Preeclampsia by Activating Autophagy

Background

Preeclampsia is a devastating hypertensive disorder of pregnancy with unknown mechanism. Recent studies have considered abnormal autophagy as a new cellular mechanism for this disorder, while little is known about how autophagy is specifically involved and what factors are implicated. Here, we report a previously unrecognized preeclampsia-associated autophagic regulator, PKCβ, that is involved in placental angiogenesis.

Methods

PKCβ levels were evaluated by quantitative real-time PCR, western blotting, immunofluorescence and by the analysis of public data. The autophagy-regulating role of PKCβ inhibition in preeclampsia pathogenesis was studied in a mouse model, and in human umbilical vein endothelial cells (HUVECs) and human choriocarcinoma cells (JEG-3).

Findings

PKCβ was significantly downregulated in human preeclamptic placentas. In a mouse model, the selective inhibition of PKCβ by Ruboxistaurin was sufficient to induce preeclampsia-like symptoms, accompanied by excessive autophagic flux and a disruption in the balance of pro- and anti-angiogenic factors in mouse placentas. In contrast, autophagic inhibition by 3-methyladenine partially normalized hypertension, proteinuria and placental angiogenic imbalance in PKCβ-inhibited mice. Our in vitro experiments demonstrated that PKCβ inhibition activated autophagy, thus blocking VEGFA-induced HUVEC tube formation and resulting in the significant upregulation of sFLT1 and downregulation of VEGFA in JEG-3 cells.

Interpretation

These data support a novel model in which autophagic activation due to PKCβ inhibition leads to the impairment of angiogenesis and eventually results in preeclampsia.

Funding

Shanghai Key Program of Clinical Science and Technology Innovation, National Natural Science Foundation of China and Shanghai Medical Center of Key Programs for Female Reproductive Diseases.

Transcription factor AP2A affects sFLT1 expression and decidualization in decidual stromal cells: Implications to preeclampsia pathology

Preeclampsia (PE) yields a spectrum of phenotypic expression, leading to varying degrees of hypertension, maternal renal dysfunction and placental insufficiency with resultant maternal and neonatal morbidity. Increased sFLT1 expression contributing to angiogenic factor imbalance, placental hypoxia, failed immune adaptation to the fetus and defective decidualization are among the commonly proposed theories of PE pathogenesis. Recently researchers have focused their attention on the events that occur at the maternal fetal interface as potential contributors to PE pathogenesis. Decidual stromal cells (DSC) isolated from preeclamptic women show diminished ability to decidualize upon stimulation and reduced capacity to downregulate sFlt-1 levels. In this study, we sought to gain insight into the molecular mechanism(s) involved in the aberrant decidualization capacity of PE DSC. Our findings using qRT-PCR show that PE DSCs have 6-fold higher basal levels of transcription factor AP2A (TFAP2A) RNA compared to women without PE and that expression of TFAP2A increases during decidualization but only in DSCs of normotensive (NT) women. Silencing of TFAP2A using Trilencer siRNA upregulated sFLT1 expression only in NT-DSCs but suppressed the expression of decidualization markers PRL, IGFBP1 and their regulator FOXO1 in cells from both groups. Collectively, our observations suggest that TFAP2A acts as a repressor of sFLT1 and plays a necessary role in decidualization possibly through interacting with another factor that is aberrantly expressed in PE DSCs.

Aberrant retinoic acid production in the decidua: Implications for pre-eclampsia

Fine-tuning of the endometrium during the evanescent 'window of implantation' relies upon an array of diverse and redundant signaling molecules, particularly the ovarian steroids E2 and P4, but also growth factors, eicosanoids, and vitamins including the vitamin A compounds (retinoids). Pregnancy complications such as preeclampsia (PE) can result from aberrations in the production or function of these molecules that arise during this critical period of decidual development. Such aberrations may be reflected by incomplete decidualization, reduced spiral artery modification, and/or loss of immune tolerance to the developing fetus. Our understanding of the role of the active retinoid metabolite all-trans retinoic acid (RA) in maintaining immune balance in certain tissues, along with data describing its role in decidualization, present a compelling argument that aberrant RA signaling in the decidua can play a significant role in the etiology of PE. Recent findings that decidualization and expression of the anti-angiogenic gene product, 'soluble fms-like tyrosine kinase-1' (sFLT1) are negatively correlated and that sFLT1 expression is directly inhibited by RA, provide additional evidence of the critical role of this retinoid in regulating early vascular development in the decidua. This review provides insight into the production and function of RA in the decidua and how modifications in its metabolism and signaling might lead to certain pregnancy disorders such as PE.

Transcription factor ID1 is involved in decidualization of stromal cells: Implications in preeclampsia

Decidual stromal cells (DSC) from women with preeclampsia (PE) show defective decidualization upon in vitro treatment with cAMP. Decidualization is associated with a multitude of gene expression changes and is a prerequisite for embryo implantation. We reason that the process of decidualization involves a cascade of changes in transcriptional regulators. Our prior studies have found defective decidualization of PE-DSCs as reflected by low prolactin (PRL) levels and other decidualization markers. Transcription factor array analysis identified inhibitor of DNA binding (ID1) and FOXO1 as top differentially expressed genes during decidualization. Unlike ID1, FOXO1 involvement in decidualization has been established. We hypothesized that ID1 plays a major role in regulating stromal cell decidualization. Our data shows basal ID1 mRNA expression is significantly higher in PE DSCs. Cyclic AMP-mediated decidualization significantly upregulates ID1 mRNA expression in DSCs and siRNA-mediated knockdown of ID1 significantly interferes with decidualization as shown by a reduction in PRL and FOXO1 expression, and morphologic criteria. Thus ID1 may serve as a master regulator of stromal cell differentiation and defects in ID1 expression may affect decidualization as seen in PE-DSCs.

Effect of isotretinoin (13-cis-retinoic acid) on levels of soluble VEGF receptors (sVEGFR1, sVEGFR2, sVEGFR3) in patients with acne vulgaris

Background/aim: The effect of isotretinoin on soluble VEGFRs has not been previously investigated. This study evaluate the effects of isotretinoin (13-cis-retinoic acid) on soluble VEGFR1 (sVEGFR1), soluble VEGFR2 (sVEGFR2) and soluble VEGFR3 (sVEGFR3).Methods: The study included 38 patients (28 females, 10 males) receiving systemic isotretinoin treatment and 38 healthy individuals (28 females, 10 males) with similar age and gender characteristics. The blood samples of the patient group at third months and blood samples of the control group were compared in terms of sVEGFR1, sVEGFR2 and sVEGFR3 concentrations.Results: It was significant that sVEGFR1 was low and sVEGFR3 was high in patients receiving isotretinoin (p: .038, p: .021, respectively). There was no significant change in sVEGFR2 levels between the groups (p: .519).Conclusions: We think that the effect of isotretinoin on sVEGFR1, sVEGFR2 and sVEGFR3 may be secondary to its effects on the VEGF family. However, after clarifying the effect of isotretinoin on the VEGF family, we think that it can be used in some tumors and vascular diseases.

Genetic variants of VEGFR-1 gene promoter in acute myocardial infarction

BACKGROUND

Coronary artery disease (CAD) including acute myocardial infarction (AMI) is a common complex disease caused by atherosclerosis. Vascular epithelial growth factor receptor-1 (VEGFR-1) stimulates angiogenesis and vascular permeability, and functions as a decoy to sequester VEGF and prevent initiation of intracellular signaling. VEGFR-1 knockout mice exhibit significantly higher mortality due to heart failure, cardiac hypertrophy, and cardiac dysfunction. An evident increase in macrophage infiltration and cardiac fibrosis are also observed after transverse aortic constriction. Therefore, VEGFR-1 gene variants may be involved in CAD. In this study, VEGFR-1 gene promoter was genetically and functionally analyzed in large cohorts of AMI patients and ethnic-matched controls.

RESULTS

A total of 16 DNA sequence variants (DSVs) including six single-nucleotide polymorphisms (SNPs) were found in the VEGFR-1 gene promoter and 5'-untranslated region. Five novel DSVs and one SNP were only identified in AMI patients group. These DSVs and SNP significantly altered the transcriptional activity of the VEGFR-1 gene promoter in both HEK-293 and H9c2 cells (P < 0.05). Further electrophoretic mobility shift assay indicated that the DSVs and SNPs evidently affected the binding of transcription factors.

CONCLUSIONS

The genetic variants in VEGFR-1 gene identified in AMI patients may alter the transcriptional activity of the VEGFR-1 gene promoter and change VEGFR-1 level, contributing to AMI development.