Microvascular endothelial cell activation is present in the umbilical placental microcirculation in fetal placental vascular disease

Maternal exposure to nano-titanium dioxide impedes fetal development via endothelial-to-mesenchymal transition in the placental labyrinth in mice

BACKGROUND

Extensive production and usage of commercially available products containing TiO2 NPs have led to accumulation in the human body. The deposition of TiO2 NPs has even been detected in the human placenta, which raises concerns regarding fetal health. Previous studies regarding developmental toxicity have frequently focused on TiO2 NPs < 50 nm, whereas the potential adverse effects of large-sized TiO2 NPs received less attention. Placental vasculature is essential for maternal-fetal circulatory exchange and ensuring fetal growth. This study explores the impacts of TiO2 NPs (100 nm in size) on the placenta and fetal development and elucidates the underlying mechanism from the perspective of placental vasculature. Pregnant C57BL/6 mice were exposed to TiO2 NPs by gavage at daily dosages of 10, 50, and 250 mg/kg from gestational day 0.5-16.5.

RESULTS

TiO2 NPs penetrated the placenta and accumulated in the fetal mice. The fetuses in the TiO2 NP-exposed groups exhibited a dose-dependent decrease in body weight and length, as well as in placental weight and diameter. In vivo imaging showed an impaired placental barrier, and pathological examinations revealed a disrupted vascular network of the labyrinth upon TiO2 NP exposure. We also found an increase in gene expression related to the transforming growth factor-β (TGF-β) -SNAIL pathway and the upregulation of mesenchymal markers, accompanied by a reduction in endothelial markers. In addition, TiO2 NPs enhanced the gene expression responsible for the endothelial-to-mesenchymal transition (EndMT) in cultured human umbilical vein endothelial cells, whereas SNAIL knockdown attenuated the induction of EndMT phenotypes.

CONCLUSION

Our study revealed that maternal exposure to 100 nm TiO2 NPs disrupts placental vascular development and fetal mice growth through aberrant activation of EndMT in the placental labyrinth. These data provide novel insight into the mechanisms of developmental toxicity posed by NPs.

Perinatal Derivatives: Where Do We Stand? A Roadmap of the Human Placenta and Consensus for Tissue and Cell Nomenclature

Progress in the understanding of the biology of perinatal tissues has contributed to the breakthrough revelation of the therapeutic effects of perinatal derivatives (PnD), namely birth-associated tissues, cells, and secreted factors. The significant knowledge acquired in the past two decades, along with the increasing interest in perinatal derivatives, fuels an urgent need for the precise identification of PnD and the establishment of updated consensus criteria policies for their characterization. The aim of this review is not to go into detail on preclinical or clinical trials, but rather we address specific issues that are relevant for the definition/characterization of perinatal cells, starting from an understanding of the development of the human placenta, its structure, and the different cell populations that can be isolated from the different perinatal tissues. We describe where the cells are located within the placenta and their cell morphology and phenotype. We also propose nomenclature for the cell populations and derivatives discussed herein. This review is a joint effort from the COST SPRINT Action (CA17116), which broadly aims at approaching consensus for different aspects of PnD research, such as providing inputs for future standards for the processing and in vitro characterization and clinical application of PnD.

Failure of physiologic transformation of spiral arteries, endothelial and trophoblast cell activation, and acute atherosis in the basal plate of the placenta

BACKGROUND

Failure of physiologic transformation of spiral arteries has been reported in preeclampsia, fetal growth restriction, fetal death, and spontaneous preterm labor with intact or ruptured membranes. Spiral arteries with failure of physiologic transformation are prone to develop atherosclerotic-like lesions of atherosis. There are striking parallels between preeclampsia and atherosclerotic disease, and between lesions of atherosis and atherosclerosis. Endothelial activation, identified by intercellular adhesion molecule-1 expression, is present in atherosclerotic-like lesions of heart transplantation, and is considered a manifestation of rejection. Similarly, endothelial activation/dysfunction has been implicated in the pathophysiology of atherosclerosis and preeclampsia. Intercellular adhesion molecule-1-overexpressing-activated endothelial cells are more resistant to trophoblast displacement than nonactivated endothelium, and may contribute to shallow spiral artery trophoblastic invasion in obstetrical syndromes having failure of physiologic transformation.

OBJECTIVE

We sought to determine whether failure of spiral artery physiologic transformation was associated with activation of interstitial extravillous trophoblasts and/or spiral artery endothelium and presence of acute atherosis in the placental basal plate.

STUDY DESIGN

A cross-sectional study of 123 placentas (19-42 weeks' gestation) obtained from normal pregnancies (n = 22), preterm prelabor rupture of membranes (n = 26), preterm labor (n = 23), preeclampsia (n = 27), intrauterine fetal death (n = 15), and small for gestational age (n = 10) was performed. Failure of spiral artery physiologic transformation and presence of cell activation was determined using immunohistochemistry of placental basal plates containing a median of 4 (minimum: 1; maximum: 9) vessels per placenta. Endothelial/trophoblast cell activation was defined by the expression of intercellular adhesion molecule-1. Investigators examining microscopic sections were blinded to clinical diagnosis. Pairwise comparisons among placenta groups were performed with Fisher exact test and Wilcoxon rank sum test using a Bonferroni-adjusted level of significance (.025).

RESULTS

We found that 87% (94/108) of placentas having spiral arteries with failure of physiologic transformation (actin-positive and cytokeratin-negative) in the basal plate, and 0% (0/15) of placentas having only spiral arteries with complete physiologic transformation (cytokeratin-positive and actin-negative), had arterial endothelial and/or interstitial extravillous trophoblasts reactive with the intercellular adhesion molecule-1 activation marker (P < .001). A significant correlation (R² = 0.84) was found between expression of spiral artery endothelial and interstitial extravillous trophoblast intercellular adhesion molecule-1 (P < .001) in activated placentas. Lesions of atherosis were found in 31.9% (30/94) of placentas with complete and/or partial failure of physiologic transformation of spiral arteries that were intercellular adhesion molecule-1-positive, in none of the 14 placentas with failure of physiologic transformation that were intercellular adhesion molecule-1-negative, and in none of the 15 placentas with complete spiral artery physiologic transformation without failure (P = .001). All placentas (30/30, 100%) with atherosis were identified in placentas having concomitant spiral artery endothelial and interstitial extravillous trophoblast activation.

CONCLUSION

Failure of spiral artery physiologic transformation in the placental basal plate is associated with interstitial extravillous trophoblast and arterial endothelial activation along with increased frequency of spiral artery atherosis. These findings may be used to improve the characterization of different disorders of the placental bed such as in refining the existing tools for the early prediction of risk for preterm, preeclamptic, and other abnormal pregnancies.

Fetuses Delivered Following Preterm Prelabor Rupture of the Membranes are Capable of Stimulating a Proinflammatory Response in Endothelial Cells

OBJECTIVE

Preterm premature rupture of the membranes (PROM) has been attributed to ascending infection and a choriodecidual inflammatory response (ie, on the maternal side). However, on the fetal side those most at risk of morbidity have a systemic proinflammatory cytokine response. We have recently defined a similar proinflammatory response in pregnancies complicated by vascular disease on the fetal side of the placenta. A factor(s) present in fetal plasma from these pregnancies can stimulate human umbilical vein endothelial cells (HUVECs) to express mRNA for the proinflammatory cytokines, interleukin (IL)-6 and IL-8. The hypothesis of this study was that a similar factor(s) was present in preterm PROM.

METHODS

A standard culture of HUVECs was incubated with fetal plasma, obtained immediately following delivery, from normal pregnancies delivering vaginally at term (n=16) and pregnancies delivering following preterm PROM (n=19). Expression of mRNA for IL-6 and IL-8 was assessed by reverse transcription polymerase chain reaction (RT-PCR) and standardized to GAPDH mRNA expression.

RESULTS

Endothelial cell expression of IL-6 mRNA (median [25-75th centile] 0.295 [0.252-0.507] vs term vaginal delivery 0.208 [0.151-0.307]; P=.009) was enhanced in response to the fetal plasma from PROM cases compared to pregnancies delivering vaginally at term. In contrast, mRNA expression of IL-8 (median [25-75th centile] preterm PROM 0.41 [0.21-0.78] vs term vaginal delivery 0.49 [0.16-0.68]; P=.46) was not different in the two groups.

CONCLUSIONS

We have demonstrated that in fetuses delivered following preterm PROM there is a factor(s) capable of stimulating a local endothelial cell proinflammatory cytokine (IL-6) response. This factor(s) that we have demonstrated may be responsible for the increased cytokine production seen in fetuses with the fetal inflammatory response syndrome.

Analysis of homeobox gene action may reveal novel angiogenic pathways in normal placental vasculature and in clinical pregnancy disorders associated with abnormal placental angiogenesis

Homeobox genes are essential for both the development of the blood and lymphatic vascular systems, as well as for their maintenance in the adult. Homeobox genes comprise an important family of transcription factors, which are characterized by a well conserved DNA binding motif; the homeodomain. The specificity of the homeodomain allows the transcription factor to bind to the promoter regions of batteries of target genes and thereby regulates their expression. Target genes identified for homeodomain proteins have been shown to control fundamental cell processes such as proliferation, differentiation, and apoptosis. We and others have reported that homeobox genes are expressed in the placental vasculature, but our knowledge of their downstream target genes is limited. This review highlights the importance of studying the cellular and molecular mechanisms by which homeobox genes and their downstream targets may regulate important vascular cellular processes such as proliferation, migration, and endothelial tube formation, which are essential for placental vasculogenesis and angiogenesis. A better understanding of the molecular targets of homeobox genes may lead to new therapies for aberrant angiogenesis associated with clinically important pregnancy pathologies, including fetal growth restriction and preeclampsia.

Chronic glucocorticoid exposure potentiates placental chorionic plate artery constriction: implications for aberrant fetoplacental vascular resistance in fetal growth restriction

Fetal growth restriction (FGR) is a serious pregnancy complication, resulting in significant perinatal morbidity and mortality. Increased vascular resistance in the fetoplacental circulation is a hallmark of FGR and is associated with enhanced vasoconstriction of the resistance arteries in the placenta, the chorionic plate arteries (CPAs). Although the cause is unknown, FGR is associated with excess exposure to glucocorticoids (GCs), key mediators of vascular resistance in the systemic circulation. We hypothesized that GCs alter CPA reactivity, thereby contributing to the altered blood flow dynamics seen in FGR. We aimed to examine the acute and chronic effects of GCs on CPA reactivity and the operational mechanisms. Glucocorticoid receptors were highly expressed by CPA. 11β-Hydroxysteroid isoenzyme type 2 was detected within the endothelium, whereas 11β-hydroxysteroid isoenzyme type 1 was absent. Acute GC treatment significantly attenuated U46619-induced constriction. This effect was reversed by cotreatment with mifepristone or an endothelial NOS inhibitor. In contrast, chronic GC treatment potentiated U46619 constriction in a dose-dependent manner, which was partially abolished by mifepristone cotreatment. Similar effects were observed using a novel nonsteroidal glucocorticoid receptor-specific agonist. Chronic treatment with GCs altered the expression of several vasoactive factors, including thromboxane and bradykinin receptors, prokineticin-1, cyclooxygenase-2, and endothelial NOS. In summary, acute and chronic GC treatment exerts contrasting effects on CPA vasoreactivity. These opposing effects are consistent with temporal actions in other vascular beds and reflect activation of distinct nongenomic and genomic pathways. Chronic exposure to elevated GCs may contribute to the raised vascular resistance observed in the fetoplacental circulation in FGR.

The fetal cardiovascular response to increased placental vascular impedance to flow determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis

OBJECTIVE

We sought to determine if increased placental vascular impedance to flow is associated with changes in fetal cardiac function using spatiotemporal image correlation and virtual organ computer-aided analysis.

STUDY DESIGN

A cross-sectional study was performed in fetuses with umbilical artery pulsatility index >95th percentile (abnormal [ABN]). Ventricular volume (end-systole, end-diastole), stroke volume, cardiac output (CO), adjusted CO, and ejection fraction were compared to those of 184 normal fetuses.

RESULTS

A total of 34 fetuses were evaluated at a median gestational age of 28.3 (range, 20.6-36.9) weeks. Mean ventricular volumes were lower for ABN than normal cases (end-systole, end-diastole) with a proportionally greater decrease for left ventricular volume (vs right). Mean left and right stroke volume, CO, and adjusted CO were lower for ABN (vs normal) cases. Right ventricular volume, stroke volume, CO, and adjusted CO exceeded the left in ABN fetuses. Mean ejection fraction was greater for ABN than normal cases. Median left ejection fraction was greater (vs right) in ABN fetuses.

CONCLUSION

Increased placental vascular impedance to flow is associated with changes in fetal cardiac function.

HSP70 is associated with endothelial activation in placental vascular diseases

Endothelial cell injury and activation in the placenta are features of placental vascular disease (PVD). While advances in PVD have been made, the pathogenesis of this disease is still unknown. The objective of this study was to pursue potential risk factors and signal transcription pathways involved in PVD pathogenesis. Gene expression in subjects with PVD and with normal pregnancies was compared using a two-channel microarray technique. Higher expression of HSPA6 and HSPA1A was exhibited in PVD subjects. HSPA6 and HSPA1A both encode HSP70, and, therefore, we localized HSP70 expression in placental tissue. Using quantitative polymerase chain reaction (PCR) and Western blot, we observed a significant upregulation of HSP70 in both mRNA and protein levels in placental tissue and microvascular endothelial cells of PVD subjects when compared with normal pregnancies (P< 0.05). HSP70 mRNA and protein expression also correlated negatively with infant birth weight (P< 0.05). HSP70 was expressed mainly in endothelial cells and smooth muscle cells in the placental microvessels. We therefore conclude that HSP70 may mediate endothelial activation and play a role in pathogenesis of PVD.

Placenta and fetal growth restriction

The placenta, as the vector for all maternal-fetal oxygen and nutrient exchange, is a principal influence on birthweight. Placental weight summarizes laterally expanding growth of the chorionic disc, and villous arborization yielding the nutrient exchange surface. These different growth dimensions alter fetoplacental weight ratio and ponderal index, and thus may modify placental functional efficiency. The placenta may show a range of histopathologies, some of which are also associated with fetal growth restriction. Different fetal intrinsic abilities to compensate for gross and histo-pathology may clarify the imperfect relationships between fetal growth and both intrauterine pathology, and the long-term health risks associated with poor fetal growth.

Egr-1 transcription activation exists in placental endothelium when vascular disease is present

OBJECTIVE

To seek evidence of early vascular injury in the placental villous microcirculation in placental insufficiency identified by a high-resistance umbilical Doppler study by examining for expression of fibroblast growth factor receptor-1 (FGFR-1), its transcription factor, early growth response factor-1 (Egr-1) and plasma fibroblast growth factor-2 (FGF-2).

DESIGN

Case-control study.

SETTING

University teaching hospital.

SAMPLE

Placentas and umbilical vein blood were collected at delivery from 12 women with normal pregnancy delivered at term and 14 with placental vascular disease defined by an abnormal umbilical artery Doppler study.

METHODS

Microvascular endothelial cells were isolated from fresh human placentas using collagenase digestion and Dynabeads coated with monoclonal antibody against CD31. RNA was extracted from the isolated endothelial cells. The messenger RNA (mRNA) expression of FGFR-1 and Egr-1 production were assessed by reverse transcription polymerase chain reaction and factored relative to 18S ribosomal RNA. To confirm that FGF-2 was playing a significant role in this microvascular endothelial cell injury in the placenta, we also measured the soluble fraction of FGF-2 in fetal plasma from same groups of pregnancies using an enzyme-linked immunosorbent assay.

MAIN OUTCOME MEASURES

Microvascular endothelial cells expression of Egr-1mRNA, FGFR-1 mRNA and presence of soluble FGF-2 in fetal plasma.

RESULTS

The soluble level of FGF-2 in the fetal placental circulation from pregnancy with placental vascular disease was increased when compared with normal pregnancy (median 10.15 pg/ml and interquartile range 5.34-21.83 pg/ml versus 4.46 pg/ml and 3.69-5.66 pg/ml; P < 0.05). Microvascular endothelial cells from the placental villi with placental vascular disease showed upregulation of both FGFR-1 mRNA expression (median 0.72 and interquartile range 0.40-1.64 versus 0.34 and 0.19-0.71; P<0.05) and Egr-1 expression (median 0.79 and interquartile range 0.27-1.86 versus 0.23 and 0.17-0.67; P<0.05) in comparison with normal pregnancy.

CONCLUSIONS

Endothelial cells from the placental villi are upregulated for expression of Egr-1 transcription factor gene in placental vascular disease. The FGFR-1 activation and increase in FGF-2 in the fetal circulation are known to be very early features of the response of endothelium to injury. Egr-1 is a promoter of many key pathophysiologically relevant target genes, which influence the development of subsequent vascular lesions. This change may occur before the pathological features recognised on microscopy.

Homeobox genes are differentially expressed in macrovascular human umbilical vein endothelial cells and microvascular placental endothelial cells

Angiogenesis is fundamental to normal placental development. Aberrant angiogenesis within the placental terminal villi is a characteristic of significant placental pathologies and includes structural and vascular abnormalities as well as altered endothelial cell function, which substantially impacts on maternal-fetal exchange. Homeobox gene transcription factors regulate vascular development in embryonic and adult tissues, but their role in the placental microvasculature is not well known. In this study, we isolated and enriched human placental microvascular endothelial cells (PLEC) by a perfusion-based method and compared homeobox gene expression between PLEC and macrovascular human umbilical vein endothelial cells (HUVEC). Reverse transcriptase PCR detected mRNA expression of homeobox genes DLX3, DLX4, MSX2, GAX and HLX1 in both PLEC and HUVEC. DLX4 and HLX1 have not been previously detected in PLEC and with the exception of GAX, none of these homeobox genes have been previously identified in HUVEC. There was lower expression of HLX1 mRNA in HUVEC compared with PLEC. Using real-time PCR analysis PLEC HLX1 mRNA expression relative to housekeeping gene GAPDH was 0.9+/-0.06 fold of the calibrator (n=6) versus 0.2+/-0.06 (n=6) for HUVEC, p<0.001. These data provided evidence of heterogeneity in homeobox gene expression between microvascular PLEC and macrovascular HUVEC that most likely reflects significant differences in endothelial cell function in the two different cellular environments.

Placental vascular disease and toll-like receptor 4 gene expression

OBJECTIVE

Vascular disease in the placenta, which is identified by the study of umbilical artery Doppler flow velocity waveforms, is associated with endothelial cell activation and a proinflammatory cytokine response in the villous placental circulation. We studied toll-like receptor 4 expression (the ligand is lipopolysaccharide) to examine whether infection may cause these inflammatory components of placental vascular disease through an innate immune response.

STUDY DESIGN

Microvessel endothelial cells were isolated from human placentae with collagenase digestion and then extracted with Dynabeads that were coated with monoclonal antibody against CD31. We studied 13 placentae from normal pregnancies that were delivered at term and 15 pregnancies with umbilical placental vascular disease that was defined by an abnormal umbilical artery Doppler study. We extracted RNA from the isolated endothelial cells. The messenger RNA expression of toll-like receptor 4 production was assessed by reverse transcriptase-polymerase chain reaction and factored relative to the glyceraldehyde-3-phosphate dehydrogenase and 18S ribosomal RNA genes.

RESULTS

Microvessel endothelial cells from placental villi with placental vascular disease showed up-regulation of toll-like receptor 4 expression (toll-like receptor 4/18S, 1.92 +/- 0.37 vs 0.99 +/- 0.19; P < .05; toll-like receptor 4/glyceraldehyde-3-phosphate dehydrogenase, 2.20 +/- 0.36 vs 1.25 +/- 0.22; P < .05) in comparison with normal pregnancy.

CONCLUSION

Up-regulation of toll-like receptor 4 gene in the endothelium of the placental villi is present in placental vascular disease, which may result from exposure of this endothelium to the toll-like receptor 4 ligand lipopolysaccharide in vivo. Directly extracted endothelial cells were used to avoid the possibility for change in behavior in tissue culture. We conclude that Gram-negative infection and lipopolysaccharide stimulation may cause placental vascular disease.