Placental inflammation in a fetal demise of a SARS-CoV-2-asymptomatic, COVID-19-unvaccinated pregnant woman: a case-report

BACKGROUND

Intrauterine fetal demise is a recognized complication of coronavirus disease 2019 in pregnant women and is associated with histopathological placental lesions. The pathological mechanism and virus-induced immune response in the placenta are not fully understood. A detailed description of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced inflammation in the placenta during fetal demise is crucial for improved clinical management.

CASE PRESENTATION

We report the case of a 27-week gestation SARS-CoV-2-asymptomatic unvaccinated pregnant woman without comorbidities or other risk factors for negative pregnancy outcomes with a diagnosis of intrauterine fetal demise. Histopathological findings corresponded to patterns of subacute inflammation throughout the anatomic compartments of the placenta, showing severe chorioamnionitis, chronic villitis and deciduitis, accompanied by maternal and fetal vascular malperfusion. Our immunohistochemistry results revealed infiltration of CD68+ macrophages, CD56+ Natural Killer cells and scarce CD8+ T cytotoxic lymphocytes at the site of placental inflammation, with the SARS-CoV-2 nucleocapsid located in stromal cells of the chorion and chorionic villi, and in decidual cells.

CONCLUSION

This case describes novel histopathological lesions of inflammation with infiltration of plasma cells, neutrophils, macrophages, and natural killer cells associated with malperfusion in the placenta of a SARS-CoV-2-infected asymptomatic woman with intrauterine fetal demise. A better understanding of the inflammatory effects exerted by SARS-CoV-2 in the placenta will enable strategies for better clinical management of pregnant women unvaccinated for SARS-CoV-2 to avoid fatal fetal outcomes during future transmission waves.

Sex-specific mediation of placental inflammatory biomarkers in the effects of prenatal phthalate coexposure on preschooler cognitive development

The objective of this study is to investigate the mediating effect of placental inflammatory biomarkers on the relationship between prenatal phthalate coexposure and cognitive development in preschoolers. A subgroup of 1660 mother-child pairs from the Ma'anshan Birth Cohort study were included. We measured the levels of phthalate metabolites of dibutyl phthalate (DBP), butyl benzyl phthalate (BBzP), and di (2-ethylhexyl) phthalate (DEHP) in all the women included in the study from three urine samples collected in each of the trimesters. A potency-weighted sum of coexposure to DBP, BBzP, and DEHP (indicator: ∑PAE) was calculated. The mRNA of the proinflammatory cytokine IL-6 and the classically activated macrophage (M1) biomarker CD68 was analyzed using placental tissues. The Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition-Chinese was used to evaluate the full-scale intelligence quotient (FSIQ) of children aged 2.5-6 years. Average ∑PAEs and ∑PAEs in each trimester were associated with IL-6 and CD68. ∑PAE in the first trimester was positively associated with IL-6 (β = 0.11, 95% CIs = 0.03-0.19) and CD68 (β = 0.16, 95% CIs = 0.04-0.28), and negatively associated with FSIQ (β =-0.06, 95% CIs = -0.11 to -0.02), verbal comprehension (β =-0.06, 95% CIs = -0.11 to -0.01), and processing speed (β =-0.07, 95% CIs = -0.12 to -0.01). Additionally, sex discrepancies were observed for the mediating effects of placental inflammation on the relationships between ∑PAE and children's cognitive development. For instance, the association between ∑PAE in early pregnancy and FSIQ was partially mediated by IL-6 (estimated proportion mediated: 21.85%) and CD68 (estimated proportion mediated: 16.2%). Gender-specific associations and trimester-specific relationships of prenatal multiple phthalate coexposure were revealed. ∑PAE in the first trimester of pregnancy was associated with increased of placental inflammation, and a decrease in preschoolers' cognitive development. In boys, placental IL-6 and CD68 elevation resulting from phthalates might be potential mechanisms of poor cognitive development.

Significance of inhibitory maternal killer-cell immunoglobulin-like receptor (KIR) and fetal KIR ligand genotype combinations in placenta related obstetric complications

Some maternal killer-cell immunoglobulin-like receptor (KIR) and fetal KIR ligand genotypes are associated with obstetric complications, such as recurrent miscarriage, fetal growth restriction, preeclampsia, and preterm birth. However, how KIR/KIR ligand genotypes affect these placenta-related obstetric complications has not been fully understood. We aimed to demonstrate the association of maternal KIR-fetal KIR ligand genotype combinations with immunological/metabolic risk factor associated placenta-related obstetric complications. This study consisted of three groups of pregnant women: 1) Miscarriage group (n = 30), 2) Complicated Pregnancy (CP) group (n = 30), and 3) Control group (n = 30). The observed maternal genotype frequencies of all inhibitory and activating KIRs were similar in all groups (p > 0.05). However, inhibitory 2DL3 was quite frequent in the miscarriage group (p = 0.052). There was no difference between groups in terms of centromeric and telomeric maternal haplotypes (p > 0.05). The fetal group 1 HLA-C genotype was frequently detected in the miscarriage and CP groups with rates of 83.3 % and 93.3 % respectively, while the observed frequency was 70 % in the control group. The fetal group 2 HLA-C genotype was the same in all groups. The results demonstrated significantly less fetal group 2 HLA-C homozygosity in the CP groups when compared to the control group (p = 0.020). The fetal HLA-Bw4 genotype was detected more frequently in the miscarriage and CP groups (p = 0.028 and p = 0.001, respectively). The inhibitory KIR/KIR ligand genotype combinations of 2DL3-C1 and 3DL1-Bw4 were more frequent in the miscarriage and CP groups (p = 0.045 and p = 0.002, respectively). Enhanced NK cell inhibition may be one of the mechanisms underlying placenta-related obstetric complications.

The natural compound puerarin alleviates inflammation and apoptosis in experimental cell and rat preeclampsia models

Puerarin (Pue), an isoflavone derived from Radix puerariae, exerts anti-apoptosis and anti-inflammatory effects. However, the protective effect of Pue on PE is still unknown. The present study aimed to investigate whether Pue alleviates symptoms of PE and suppresses inflammation and apoptosis in vitro and in vivo. A cell model of PE was established by exposing HTR8/SVneo cells to LPS and an RNA-SEQ study was performed in LPS-stimulated HTR8/SVneo cells. We also established a rat model of PE by injecting pregnant rats with LPS and the basic preeclamptic symptoms were evaluated. Additionally, the placental histology, placental inflammation cytokines, and apoptosis markers were also measured. Pue protected HTR8/SVneo cells from LPS-evoked cytotoxicity, decreased the levels of sFlt-1, ET-1, and tPA in HTR8/SVneo cells. RNA-SEQ results revealed the significant changes in the expression levels of hub genes (TNF, IL-6, Jun, and NFKBIA) related to multiple inflammatory pathways, including the TNF signaling pathway, IL-17 signaling pathway, inflammatory disease, and NF-κB signaling pathway. After administration of Pue, we observed that LPS-evoked PE symptoms (hypertension, proteinuria, and fetal growth restriction), were reversed. Besides, Pue improved placental pathology change and reducing placental sFlt-1, ET-1, and tPA mRNA expression. Abnormal placental inflammatory cytokines (TNF, IL-6, IFN-γ, and IL-4) and apoptosis markers (Bcl-2, Bax, caspase-3, caspase-8, and caspase-9) expressions in the LPS-treated group were reversed after Pue treatment. Our findings revealed that Pue plays beneficial roles in PE models, and therefore possesses the therapeutic potential for prevention and treatment of PE.

Prenatal pregnancy-related anxiety predicts boys' ADHD symptoms via placental C-reactive protein

Many modes of stress (i.e. life events, catastrophic events) during pregnancy have been found to increase the risk of externalizing behaviors, and probably in a sex-specific way. Maternal immune activation may be the sex-difference mechanism, but direct evidence that assess three factors in conjunction -- maternal stress, maternal immune activation, and offspring neurodevelopment --from human beings is lacking. This prospective study followed 2926 pregnant women from early pregnancy to 36 months after delivery. Pregnancy-related anxiety symptoms assessment was completed three times using the Pregnancy-Related Anxiety Questionnaire; child attention deficit hyperactivity disorder (ADHD) symptoms were assessed by the parent version of the Conners' Hyperactivity Index. More importantly, nine inflammatory cytokines were detected in placental tissues for the sex-difference mechanism investigation. Our results showed that after controlling for confounding factors, pregnancy-related anxiety during at least two trimesters of pregnancy increased the risk of ADHD for boys (adjusted odds ratio (aOR) = 3.37, 95 % confidence interval (95 % CI) = 1.78-6.38), but not for girls (aOR = 1.02, 95 %CI = 0.44-2.38), which confirmed previous findings. Besides, the structural equation models revealed that placental C-reactive protein (CRP) mRNA expression significantly mediated the association between pregnancy-related anxiety and ADHD for boys (indirect effect: β = 0.025, P = 0.022), but not for girls (indirect effect: β = 0.005, P = 0.589). This prospective study suggested that frequent pregnancy-related anxiety during pregnancy and its induced-placental inflammation partially contributed to the sex-bias of ADHD symptoms.

Effect of nicotine on placental inflammation and apoptosis in preeclampsia-like model

AIMS

Placental tissues from patients with preeclampsia (PE) and in the lipopolysaccharide (LPS)-induced PE-like model were used to investigate the implication of placental inflammation and apoptosis in PE. Whether the beneficial effects of nicotine are related to inhibition of placental inflammation and apoptosis in the PE-like model were investigated.

MAIN METHODS

Placental apoptosis was detected in PE patients and the PE-like rat model by TUNEL staining. Changes in the number of CD68⁺ macrophages in placental tissues from PE patients were detected by immunofluorescent staining. The mRNA expression of the pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin (IL-1β), MCP-1, and proteins involved in extrinsic or intrinsic apoptosis signaling in the PE-like model was determined by qRT-PCR; immunofluorescent staining was used to detect the expression of TNF-α receptor (TNFR1), MCP-1 and apoptosis-related proteins.

KEY FINDINGS

Placental apoptosis was increased in both PE patients and the PE-like model, more macrophages infiltrated into placenta in PE patients. A significant upregulation in mRNA expression of TNF-α, IL-1β, MCP-1, and caspase 3, caspase 8, caspase 9 was found in the PE-like rats compared to the control animals, the immunoreactivity of placental MCP-1, TNFR1, and apoptosis-related proteins (caspase 3, caspase 8, caspase 9, Bax) was also enhanced; nicotine treatment significantly reversed those changes.

SIGNIFICANCE

Our data suggests that the protective effects of nicotine are associated with inhibiting placenta inflammation and apoptosis, and nicotine might be a potentially therapeutic candidate for preventing preeclampsia.

Inflammation-mediated generation and inflammatory potential of human placental cell-free fetal DNA

Introduction

Circulating DNA can be pro-inflammatory when detected by leukocytes via toll-like receptor 9 (TLR9). Cell-free fetal DNA (cff-DNA) of placental origin, circulates in pregnancy, and increased concentrations are seen in conditions associated with placental and maternal inflammation such as pre-eclampsia. However, whether cff-DNA is directly pro-inflammatory in pregnant women and what regulates cff-DNA levels in pregnancy are unknown.

Methods

Using a human term placental explant model, we examined whether induction of placental inflammation can promote cff-DNA release, and the capacity of this cff-DNA to stimulate peripheral blood mononuclear cells (PBMCs) from pregnant women.

Results

We demonstrate lipopolysaccharide (LPS)-mediated inflammation in placental explants and induced apoptosis after 24 h. However, this did not increase levels of cff-DNA generation compared to controls. Furthermore, the methylation status of the cff-DNA, was not altered by LPS-induced inflammation. Cff-DNA did not elicit production of inflammatory cytokines from PBMCs, in contrast to exposure to LPS or the TLR9 agonist CpG-ODN. Finally, we demonstrate that cff-DNA acquired directly from pregnant women did not differ in methylation status from placental extracted DNA, or from placental explant generated cell-free DNA, and that, unlike Escherichia coli DNA, this cff-DNA has a low level of unmethylated CpG sequences.

Discussion

Our data suggest that placental inflammation does not increase release of cff-DNA and that placental cff-DNA is not pro-inflammatory to circulating PBMCs. It thus seems unlikely that high levels of cff-DNA are either a direct consequence or cause of inflammation observed in obstetric complications.

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Cell-free fetal DNA was generated using a human placental explant model.

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Lipopolysaccharide causes inflammation and cell death in placental explants.

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Inflammation does not increase cell-free fetal DNA release from placental explants.

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Generated DNA does not elicit inflammation from blood cells from pregnant women.

Placental and intra-amniotic inflammation are associated with altered fetal immune responses at birth

INTRODUCTION

High-grade placental inflammation is associated with preterm birth and poor neonatal outcomes. Recent reports suggest that low-grade placental inflammation is common in uncomplicated pregnancies. The relationship between placental inflammation and innate immune anti-microbial responses is unknown. In this study we sought to identify any association between placental inflammation and fetal immune responses.

METHODS

Cord blood samples collected from late preterm and full-term Caesarean section deliveries (n = 44) were exposed to various immune challenges (resiquimod, LPS, PGN, poly (I:C), cGAMP, and 5'ppp-dsRNA) and production of inflammatory mediators (G-CSF, IFN-γ, IL-1β, IL-6, IL-8, IL-10, and TNF-α) was measured by multiplex assay. Hospital histology reports were used to assess the extent of inflammation in the placenta.

RESULTS

Almost half (47.7%) of placentae examined here showed histological evidence of inflammation. Resiquimod, LPS, and PGN elicited strong inflammatory responses in neonatal cord blood, while poly (I:C), cGAMP, and 5'ppp-dsRNA elicited weaker responses. Fetuses with evidence of chorioamnionitis and fetal inflammatory reaction in their placentae had significantly increased immune responses to cGAMP and 5'ppp-dsRNA (ligands for STING and RIG-I, respectively) and significantly decreased immune responses to poly (I:C) (a TLR3 agonist). Interestingly, STING, RIG-I, and TLR3 are all involved in viral response pathways, suggesting that fetuses exposed to chorioamnionitis or fetal inflammatory reaction might respond differently to viruses postnatally.

CONCLUSION

Our data suggest that low-level placental inflammation is associated with altered innate cytokine responses at birth.

Placental inflammation, lifestyle, maternal and early child sensitisation to allergens - the assessment of lifestyle and allergic disease during infancy birth cohort

AIM

To investigate (i) whether maternal sensitisation to allergens, and lifestyle can influence the risk of acute and chronic inflammation of the placenta, in the forms of chorioamnionitis and villitis, respectively, and (ii) whether these placental inflammations are associated with the outcome of sensitisation for the child during preschool age.

METHODS

Placentas from term uncomplicated pregnancies (n = 275) in the assessment of lifestyle and allergic disease during infancy study were analysed for the presence of acute chorioamnionitis and chronic villitis. Stepwise logistic regression was performed to estimate the relative risk of placental inflammation in relation to maternal allergic sensitisation and lifestyle, and the association between placental inflammation and sensitisation of the child up to five years of age.

RESULTS

Parity and delivery at home were independently associated with chorioamnionitis, home delivery only with the low grade. Maternal allergic sensitisation was associated with increased risk of villitis in the bivariable model, however, not in the multivariable model. No significant associations were detected between placental inflammation and the outcome of sensitisation to allergens at five years of age.

CONCLUSION

Our data do not support the hypothesis that the increased risk for sensitisation of a child when the mother is allergic is mediated via placental inflammation.

Severe vitamin D deficiency in the first trimester is associated with placental inflammation in high-risk singleton pregnancy

BACKGROUND & AIMS

Vitamin D deficiency during pregnancy is a worldwide epidemic. This study aimed to identify whether vitamin D deficiency in early pregnancy is associated with placental inflammation in high-risk pregnancy.

METHODS

This study comprised 23,396 women who provided serum samples in the first trimester for vitamin D analysis from January 2015 to December 2016. Among them, 2648 women with high-risk pregnancy underwent placental pathologic examination. Women were divided into placental inflammation positive (PIP) and placental inflammation negative (PIN) groups based on placental pathology. Multivariate logistic regression was used to evaluate the relationship between vitamin D levels and placental inflammation.

RESULTS

We found that severe vitamin D deficiency in early pregnancy was associated with placental inflammation. Maternal vitamin D levels were significantly lower in the PIP group than those in the PIN group (P = 0.025). Compared with the highest quartile of vitamin D levels, risk for placental inflammation was significantly higher in women with extremely low vitamin D levels (<5th percentile; P = 0.012). The effect estimate was slightly decreased but still significant (P = 0.027) after adjusting for maternal age, gestational age at birth, birth weight, infant sex, and sample collection season. In addition, compared with the PIN group, the incidences of adverse neonatal outcomes, including sepsis (0.5% vs 2.4%) and fetal intrauterine infection (5.7% vs 15.6%), were significantly higher in the PIP group than that in the PIN group (P < 0.001).

CONCLUSIONS

Severe vitamin D deficiency in the first trimester is a risk factor for placental inflammation in high-risk pregnancy.

Hyperactive behavior in female rats in utero-exposed to group B Streptococcus-induced inflammation

Group B Streptococcus (GBS) is one the most common bacterium responsible of maternal infections during pregnancy. Offspring in utero-exposed to GBS-induced placental inflammation displayed sex-specific forebrain injuries. Sex differences have been reported in several neuropsychiatric disorders. Hence, we hypothesized that female rats in utero-exposed to GBS may present sex-specific neurobehavioral impairments. Lewis rats were injected intraperitoneally every 12 h from gestational day (G) 19 to G22 with either saline (controls) or inactivated serotype Ia GBS (10⁹ CFU). Before puberty, no difference in terms of spontaneous motor activity, exploratory or anxiety-related behaviors was noticed between experimental conditions. During puberty, GBS-exposed females - but not males - performed worse than same-sex controls in a forced motor task. During adulthood, GBS-exposed females - but not males - displayed increased spontaneous locomotor activity and decreased inhibition. In conclusion, our findings show for the first time that adult females - but not males - in utero-exposed to GBS-induced inflammation presented a hyperactive and disinhibited phenotype emerging after puberty.

The contribution of Toll-like receptors to placental inflammation in diet-induced maternal obesity

Toll-like receptor (TLR)-regulated protein kinases and inflammatory cytokines were activated in fetal vascular smooth muscle cells (VSMC) treated with palmitate. Tumor necrosis factor (TNFα) and interleukin-6 (IL6) were increased and correlated with expression of TLRs in the labyrinth placentae of high fat (HF)-fed rats with increased plasma lipids and visceral adiposity. Thus, local induction of TLR signaling via saturated fatty acids (SFA) may in part contribute to placental inflammation in diet-induced maternal obesity.

Increased expression of perforin, granzyme B, and C5b-9 in villitis of unknown etiology

INTRODUCTION

Villitis of unknown etiology (VUE) is associated with fetal growth restriction. However, the underlying mechanisms of villous injury in placentas with VUE are still largely unknown. We aimed to verify whether apoptosis-related factors are increased in VUE placentas. Furthermore, we determined apoptosis of villous cells.

METHODS

Six placentas with VUE and 3 control placentas were stained using immunohistochemistry with antibodies for CD3, CD4, CD8, CD68, CD163, perforin, granzyme B, granzyme K, and C5b-9. TUNEL assay analysis was also performed with these placentas. The percentage of cells that stained positive, CD163/CD68 ratio, percentage of C5b-9 positive area, and apoptosis index were quantified and compared between the inflammatory lesions of the VUE placentas, non-VUE inflammatory lesions of the VUE placentas, and control placentas.

RESULTS

The percentages of CD3, CD4, CD8 CD68, CD163, perforin, and granzyme B positive cells were significantly higher in the inflammatory lesions of the VUE placentas (p < 0.05). The intravillous CD163/CD68 ratio was higher in the inflammatory lesions compared with the non-inflammatory lesion of the VUE placentas (p < 0.05). The percentage of granzyme K-positive cells was not significantly different between the groups. C5b-9 deposition was higher in the inflammatory lesions of the VUE placentas (p < 0.05). TUNEL-positive cells were significantly higher in the inflammatory lesions of the VUE placentas (p < 0.05).

DISCUSSION

To the best of our knowledge, this is the first report to assess villous injury, especially from a viewpoint of villous apoptosis in VUE placentas. An activated perforin/granzyme pathway and C5b-9 are suggested as possible mechanisms of apoptosis.

Hepatocyte growth factor is elevated in amniotic fluid from obese women and regulates placental glucose and fatty acid metabolism

INTRODUCTION

To evaluate the impact of the pro-inflammatory cytokine hepatocyte growth factor (HGF) on the regulation of glucose and lipid placental metabolism.

METHODS

HGF levels were quantified in amniotic fluid and placenta from control and obese women. 2-deoxy-glucose (2-DOG) uptake, glycolysis, fatty acid oxidation (FAO), fatty acid esterification, de novo fatty acid synthesis, triglyceride levels and carnitine palmitoyltransferase activities (CPT) were measured in placental explants upon addition of pathophysiological HGF levels.

RESULTS

In obese women, total- and -activated-HGF levels in amniotic fluid were elevated ∼24%, and placental HGF levels were ∼3-fold higher than in control women. At a similar dose to that present in amniotic fluid of obese women, HGF (30 ng/mL) increased Glut-1 levels and 2-DOG uptake by ∼25-30% in placental explants. HGF-mediated effect on 2-DOG uptake was dependent on the activation of phosphatidylinositol 3-kinase signaling pathway. In addition, HGF decreased ∼20% FAO, whereas esterification and de novo fatty acid synthesis increased ∼15% and ∼25% respectively, leading to 2-fold triglyceride accumulation in placental explants. In parallel, HGF reduced CPT-I activity ∼70%.

DISCUSSION

HGF is a cytokine elevated in amniotic fluid and placental tissue of obese women, which through its ability to stimulate 2-DOG uptake and metabolism impairs FAO and enhances esterification and de novo fatty acid synthesis, leading to accumulation of placental triglycerides.

The immunological basis of villitis of unknown etiology - review

Villitis of unknown etiology (VUE) represents a common placental inflammatory lesion, primarily, but not exclusively, identifiable T lymphocytes at term. Despite considerable evidence to contest that this simply represents a benign pathological finding, VUE remains a significantly undervalued diagnosis. Given its association with adverse pregnancy outcomes; including fetal growth restriction, preterm birth, and recurrent pregnancy loss, an increased awareness amongst clinician obstetricians is certainly warranted. The underlying immunopathogenesis of VUE remains uncertain. Despite initial theories that this represents an infectious placental lesion of undiagnosed pathogenic source, a more complex sequence of events involving the "breakdown" of maternal-fetal tolerance is emerging. Characterization of a unique inflammatory phenomenon in which both maternal and fetal T lymphocytes and Höfbauer cells interact has captivated particular research interest and has generated analogies to both the problems of allograft rejection and graft-versus-host disease (GvHD). Within the context of VUE, this review evaluates how disruption of the multidimensional immunological mechanisms underlying feto-maternal tolerance may permit abnormal lymphocyte infiltration into placental villi. We shall review the existing evidence for these events in VUE and outline areas of certain future interest.