Significance of the placental barrier in antenatal viral infections.

The placenta provides a significant physical and physiological barrier to prevent fetal infection during pregnancy. Nevertheless, it is at times breached by pathogens and leads to vertical transmission of infection from mother to fetus. This review will focus specifically on the Zika flavivirus, the HIV retrovirus and the emerging SARS-CoV2 coronavirus, which have affected pregnant women and their offspring in recent epidemics. In particular, we will address how viral infections affect the immune response at the maternal-fetal interface and how the placental barrier is physically breached and discuss the consequences of infection on various aspects of placental function to support fetal growth and development. Improved understanding of how the placenta responds to viral infections will lay the foundation for developing therapeutics to these and emergent viruses, to minimise the harms of infection to the offspring.

Inflammasomes in the Pathophysiology of Maternal Obesity: Potential Therapeutic Targets to Reduce Long-Term Adverse Health Outcomes in the Mother and Offspring.

Over the past 20 years, the prevalence of obesity has risen dramatically worldwide, with an increase in occurrence among women in their reproductive age. Obesity during pregnancy is associated with significantly increased maternal and fetal morbidity and mortality. In addition to the short-term adverse health outcomes, both mother and the child are prone to develop cardiovascular, metabolic and neurological disorders. Although associations between obesity during pregnancy and adverse maternalfetal health outcomes are clear, the complex molecular mechanisms underlying maternal obesity remain largely unknown. This review describes multimeric self-assembling protein complexes, namely inflammasomes, as potential molecular targets in the pathophysiology of maternal obesity. Inflammasomes are implicated in both normal physiological and in pathophysiological processes that occur in response to an inflammatory milieu throughout gestation. This review highlights the current knowledge of inflammasome expression and its activity in pregnancies affected by maternal obesity. Key discussions in defining pharmacological inhibition of upstream as well as downstream targets of the inflammasome signaling cascade; and the inflammasome platform, as a potential therapeutic strategy in attenuating the pathophysiology underpinning inflammatory component in maternal obesity are presented herein.

The Emerging Role of the Prokineticins and Homeobox Genes in the Vascularization of the Placenta: Physiological and Pathological Aspects.

Vasculogenesis and angiogenesis are key processes of placental development, which occur throughout pregnancy. Placental vasculogenesis occurs during the first trimester of pregnancy culminating in the formation of hemangioblasts from intra-villous stem cells. Placental angiogenesis occurs subsequently, forming new blood vessels from existing ones. Angiogenesis also takes place at the fetomaternal interface, allowing essential spiral arteriole remodeling to establish the fetomaternal circulation. Vasculogenesis and angiogenesis in animal models and in humans have been studied in a wide variety of in vitro, physiological and pathological conditions, with a focus on the pro- and anti-angiogenic factors that control these processes. Recent studies revealed roles for new families of proteins, including direct participants such as the prokineticin family, and regulators of these processes such as the homeobox genes. This review summarizes recent advances in understanding the molecular mechanisms of actions of these families of proteins. Over the past decade, evidence suggests increased production of placental anti-angiogenic factors, as well as angiogenic factors are associated with fetal growth restriction (FGR) and preeclampsia (PE): the most threatening pathologies of human pregnancy with systemic vascular dysfunction. This review also reports novel clinical strategies targeting members of these family of proteins to treat PE and its consequent effects on the maternal vascular system.

Decreased Placental FPR2 in Early Pregnancies That Later Developed Small-For-Gestation Age: A Potential Role of FPR2 in the Regulation of Epithelial-Mesenchymal Transition.

We reported earlier that an anti-inflammatory small peptide receptor-formyl peptide receptor-2 (FPR2) was significantly decreased in placentas from third trimester pregnancies complicated with fetal growth restriction (FGR), compared to placentas from uncomplicated control pregnancies, suggesting FPR2 may play a role in the development of FGR. The aim of this study is to investigate whether the actions of FPR2 alters placental growth process in humans. Accordingly, using small-for-gestation age (SGA) as a proxy for FGR, we hypothesize that FPR2 expression is decreased in first-trimester placentas of women who later manifest FGR, and contributes to aberrant trophoblast function and the development of FGR. Chorionic villus sampling (CVS) tissues were collected at 10-12 weeks gestation in 70 patients with singleton fetuses; surplus tissue was used. Real-time PCR and immunoassays were performed to quantitate FPR2 gene and protein expression. Silencing of FPR2 was performed in two independent, trophoblast-derived cell lines, HTR-8/SVneo and JEG-3 to investigate the functional consequences of FPR2 gene downregulation. FPR2 mRNA relative to 18S rRNA was significantly decreased in placentae from SGA-pregnancies (n = 28) compared with controls (n = 52) (p < 0.0001). Placental FPR2 protein was significantly decreased in SGA compared with control (n = 10 in each group, p < 0.05). Proliferative, migratory and invasive potential of the human placental-derived cell lines, HTR-8/SVneo and JEG-3 were significantly reduced in siFPR2 treated cells compared with siCONT control groups. Down-stream signaling molecules, STAT5B and SOCS3 were identified as target genes of FPR2 action in the trophoblast-derived cell lines and in SGA and control chorionic villous tissues. FPR2 is a novel regulator of key molecular pathways and functions in placental development, and its decreased expression in women destined to develop FGR reinforces a placental origin of SGA/FGR, and that it contributes to causing the development of SGA/FGR.

Expression of Homeobox Gene HLX and its Downstream Target Genes are Altered in Placentae From Discordant Twin Pregnancies.

A discordant twin gestation, in which one fetus is significantly growth restricted, compared to the other normal twin, is a unique model that can be used to elucidate the mechanism(s) by which the intrauterine environment affects fetal growth. In many model systems, placental transcription factor genes regulate fetal growth. Transcription factors regulate growth through their activation or repression of downstream target genes that mediate important cell functions. The objective of this study was to determine the expression of the placental HLX homeobox gene transcription factor and its downstream target genes in dizygotic twins with growth discordance. In this cross-sectional study, HLX and its downstream target genes' retinoblastoma 1 (RB1) and cyclin kinase D (CDKN1C) expression levels were determined in placentae obtained from dichorionic diamniotic twin pregnancies (n = 23) where one of the twins was growth restricted. Fetal growth restriction (FGR) was defined as small for gestational age with abnormal umbilical artery Doppler indices when compared with the normal control co-twin. Homeobox gene HLX expression was significantly decreased at both the mRNA and protein levels in FGR twin placentae compared with the normal control co-twin placentae (p < .05). Downstream target genes CDKN1C and RB1 were also significantly decreased and increased, respectively, at both the mRNA and protein levels in FGR twin placentae compared with normal control co-twin placentae (p < .05). Together, these observations suggest an important association between HLX transcription factor expression and abnormal human placental development in discordant twin pregnancies.

G protein coupled receptor 18: A potential role for endocannabinoid signaling in metabolic dysfunction.

Endocannabinoids are products of dietary fatty acids that are modulated by an alteration in food intake levels. Overweight and obese individuals have substantially higher circulating levels of the arachidonic acid derived endocannabinoids, anandamide and 2-arachidonoyl glycerol, and show an altered pattern of cannabinoid receptor expression. These cannabinoid receptors are part of a large family of G protein coupled receptors (GPCRs). GPCRs are major therapeutic targets for various diseases within the cardiovascular, neurological, gastrointestinal, and endocrine systems, as well as metabolic disorders such as obesity and type 2 diabetes mellitus. Obesity is considered a state of chronic low-grade inflammation elicited by an immunological response. Interestingly, the newly deorphanized GPCR (GPR18), which is considered to be a putative cannabinoid receptor, is proposed to have an immunological function. In this review, the current scientific knowledge on GPR18 is explored including its localization, signaling pathways, and pharmacology. Importantly, the involvement of nutritional factors and potential dietary regulation of GPR18 and its (patho)physiological roles are described. Further research on this receptor and its regulation will enable a better understanding of the complex mechanisms of GPR18 and its potential as a novel therapeutic target for treating metabolic disorders.

Optimization and scale-up culture of human endometrial multipotent mesenchymal stromal cells: potential for clinical application.

We have previously identified and purified multipotent mesenchymal stromal cell (MSC)-like cells in the highly regenerative endometrial lining of the human uterus (eMSC) as CD140b⁺CD146⁺ cells. Due to ease of accessibility with minimal morbidity via biopsy, we are proposing to use eMSC in cell-based therapies; however, culture conditions compliant with Good Manufacturing Practice have not been established for eMSC. The aim of this study was to optimize serum-free and xeno-free culture conditions for expansion of eMSC for potential clinical use. Real-time cell assessment (Xcelligence) and MTS viability assays were used to measure attachment and proliferation of freshly isolated, flow cytometry-sorted CD140b⁺CD146⁺ eMSC cultured in several commercially available and in-house serum-free and xeno-free media in combination with five attachment matrices (fibronectin, collagen, gelatin, laminin, and Cell Start-XF®). Comparisons were made with a standard serum-containing medium, DMEM/F-12/10% fetal bovine serum. Under all conditions examined, eMSC attachment and proliferation was greatest using a fibronectin matrix, with Lonza TP-SF® and our in-house DMEM/SF/FGF2/EGF serum-free xeno-product-containing medium similar to serum-containing medium. Hypoxia increased eMSC proliferation in the DMEM/SF/FGF2/EGF serum-free medium. Culture of eMSC for 7 days on a fibronectin matrix in DMEM/SF/FGF2/EGF serum-free media in 5% O2 maintained greater numbers of undifferentiated eMSC expressing CD140b, CD146, and W5C5 compared to culture under similar conditions in Lonza TP-SF medium. However, the percentage of cells expressing typical MSC phenotypic markers, CD29, CD44, CD73, and CD105, were similar for both media. EMSC showed greater expansion in 2D compared to 3D culture on fibronectin-coated microbeads using the optimized DMEM/SF/FGF2/EGF medium in 5% O2. In the optimized 2D culture conditions, eMSC retained CFU activity, multipotency, and MSC surface phenotype, representing the first steps in their preparation for potential clinical use.

The role of homeobox genes in the development of placental insufficiency.

Intrauterine growth restriction (IUGR) is an adverse pregnancy outcome associated with significant perinatal and pediatric morbidity and mortality, and an increased risk of chronic disease later in adult life. While a number of maternal, fetal and environmental factors are known causes of IUGR, the majority of IUGR cases are of unknown cause. These IUGR cases are frequently associated with placental insufficiency, possibly as a result of placental maldevelopment. Understanding the molecular mechanisms of abnormal placental development in IUGR associated with placental insufficiency is therefore of increasing importance. Here, we review our understanding of transcriptional control of normal placental development as well as human IUGR associated with placental insufficiency. We also assess the potential for understanding transcriptional control as a means for revealing new molecular targets for the detection, diagnosis and clinical management of IUGR associated with placental insufficiency.

Placental syndecan expression is altered in human idiopathic fetal growth restriction.

Pregnancy represents a hypercoagulable state characterized by increased thrombin generation. However, placentas from fetal growth restriction (FGR) pregnancies are characterized by increased fibrin deposition and thrombi in the vasculature, indicative of a further increase in thrombin activation and a disturbance in coagulation in this clinical setting. The cause of the coagulation disturbance observed in FGR pregnancies is currently unknown. Anticoagulant mechanisms are crucial in the regulation of thrombin activity, and current evidence suggests that syndecans are the principal placental anticoagulant proteoglycans. The aim of this study was to determine the localization, distribution, and expression of syndecans 1 to 4 in placentas complicated by idiopathic FGR compared with gestation-matched controls. Immunohistochemistry results revealed that all of the syndecans were localized to cells located closely to the maternal and fetal circulation. The mRNA and protein expression levels of both syndecan 1 and syndecan 2 were significantly decreased in FGR samples compared with controls. This is the first study to demonstrate the differential expression of syndecans 1 to 4 in idiopathic FGR placentas compared with controls. Reduced levels of syndecan expression may result in increased placental thrombosis in the uteroplacental circulation and may therefore contribute to the pathogenesis of FGR.

The role of placental homeobox genes in human fetal growth restriction.

Fetal growth restriction (FGR) is an adverse pregnancy outcome associated with significant perinatal and paediatric morbidity and mortality, and an increased risk of chronic disease later in adult life. One of the key causes of adverse pregnancy outcome is fetal growth restriction (FGR). While a number of maternal, fetal, and environmental factors are known causes of FGR, the majority of FGR cases remain idiopathic. These idiopathic FGR pregnancies are frequently associated with placental insufficiency, possibly as a result of placental maldevelopment. Understanding the molecular mechanisms of abnormal placental development in idiopathic FGR is, therefore, of increasing importance. Here, we review our understanding of transcriptional control of normal placental development and abnormal placental development associated with human idiopathic FGR. We also assess the potential for understanding transcriptional control as a means for revealing new molecular targets for the detection, diagnosis, and clinical management of idiopathic FGR.

Homeobox gene HLX is a regulator of HGF/c-met-mediated migration of human trophoblast-derived cell lines.

Homeobox gene transcription factors play a critical role in normal placental development and are expressed in specialized trophoblast cells. Abnormal trophoblast function is associated with clinically significant pregnancy disorders, including fetal growth restriction (FGR). Our previous studies demonstrated that homeobox gene HLX is expressed in proliferating and migrating (but not invading) human trophoblast cells and that HLX expression is significantly decreased in human FGR. We have also shown that HLX is a regulator of colony-stimulating-factor-1-dependent trophoblast proliferation. Hepatocyte growth factor (HGF) activates trophoblast cell migration in a paracrine fashion, and its receptor, c-met, is expressed on trophoblast cells. Given that HGF is a regulator of trophoblast migration, we hypothesize that HLX is a mediator of HGF/c-met-dependent trophoblast migration but not invasion. Here we investigated the potential role of HLX in HGF/c-met-mediated trophoblast migration and invasion in two human trophoblast-derived cell lines, SGHPL-4 and HTR-8/SVneo. Results showed that in cultured trophoblast cells, HGF stimulation significantly increased HLX mRNA and protein expression. HLX inactivation significantly decreased trophoblast migration but not invasion. When HLX was inactivated in the presence of HGF stimulation, migration remained significantly decreased. SU11274-mediated inhibition of the receptor c-met significantly decreased HLX mRNA and protein expression. In the presence of HGF stimulation, HLX expression remained significantly decreased with c-met inhibition. This is the first study to show that homeobox gene HLX is a downstream effector gene of HGF, that HLX regulates human trophoblast-derived cell migration, and that HGF, via receptor c-met, acts through HLX to control cell migration.

Downstream targets of homeobox gene HLX show altered expression in human idiopathic fetal growth restriction.

Fetal growth restriction (FGR), a clinically significant pregnancy disorder, is poorly understood at the molecular level. This study investigates idiopathic FGR associated with placental insufficiency. Previously, we showed that the homeobox gene HLX is expressed in placental trophoblast cells and that HLX expression is significantly decreased in human idiopathic FGR. Here, we used the novel approach of identifying downstream targets of HLX in cell culture to detect potentially important genes involved in idiopathic FGR. Downstream targets were revealed by decreasing HLX expression in cultured trophoblast cells with HLX-specific small interfering RNAs to model human idiopathic FGR and comparing these levels with controls using a real-time PCR-based gene profiling system. Changes in candidate HLX target mRNA levels were verified in an independent trophoblast cell line, and candidate target gene expression was assessed in human idiopathic FGR-affected placentae (n = 25) compared with gestation-matched controls (n = 25). The downstream targets RB1 and MYC, cell cycle regulatory genes, showed significantly increased mRNA levels in FGR-affected tissues compared with gestation-matched controls, whereas CCNB1, ELK1, JUN, and CDKN1 showed significantly decreased mRNA levels (n = 25, P < 0.001, t-test). The changes for RB1 and CDKN1C were verified by Western blot analysis in FGR-affected placentae compared with gestation-matched controls (n = 6). We conclude that cell cycle regulatory genes RB1, MYC, CCNB1, ELK1, JUN, and CDKN1C, which control important trophoblast cell functions, are targets of HLX.

Homeodomain protein HLX is expressed primarily in cytotrophoblast cell types in the early pregnancy human placenta.

Homeobox genes are a large family of transcription factors. Of these, the HLX homeobox gene (previously known as HLX1 and HB24) is important for normal placentation. We have previously shown that HLX mRNA expression is significantly reduced in fetal growth-restricted human placentae compared with control placentae. In this study, a rabbit polyclonal antibody to the homeodomain protein HLX was raised and characterised. Western analysis revealed a protein of 50 kDa. HLX protein was detected in cellular nuclei in the cytotrophoblast-derived cell lines HTR8/SVneo, SGHPL-4, JEG-3, JAR and BeWo. Dual labelling with cytokeratin 7 was used to determine the spatial distribution of HLX in the early placenta and fetal membranes, showing both a perinuclear and punctate nuclear distribution for HLX. In the early pregnancy placenta HLX was localised to villous cytotrophoblast, and extravillous cytotrophoblast nuclei in the proximal regions of the cytotrophoblast cell columns, but was not detected at significant levels in the syncytiotrophoblast. In first trimester placental bed biopsies, HLX expression was not localised to the nucleus but instead was found in the cytoplasm. We conclude that HLX is primarily expressed in cytotrophoblast cell types in the human placenta and propose that HLX is involved in cytotrophoblast proliferation and downregulation of cell differentiation.