Whole transcriptome profiling of placental pathobiology in SARS-CoV-2 pregnancies identifies placental dysfunction signatures

The placental transcriptomic profile determined by maternal COVID-19 disease encompasses alterations reminiscent of preeclampsia

INTRODUCTION

During initial stages of the pandemic, SARS-CoV-2 infection during pregnancy was related to adverse pregnancy outcomes and alterations in the placenta. Whether placental abnormalities in pregnant women with COVID-19 still persist afterwards remains poorly studied. Here, we determined whether the absence of obstetric complications after maternal COVID-19 disease, including preeclampsia, is accompanied by a complete return to normalcy in terms of placental physiology.

METHODS

Placental RNA was purified from placental samples from SARS-CoV-2 positive mothers taken either in 2022, when Omicron was the predominant variant of concern (termed Omicron) (n = 21); or from healthy pregnancies predating the pandemic (termed preCOVID-19). Our cohort included samples from pregnant women who got infected weeks and even months before term. We performed RNA-seq, identified differentially expressed genes and examined to which biological, biochemical and cellular pathways they belong, using gene set enrichment analysis.

RESULTS

We identified 71 differentially expressed genes (DEGs) (defined by p-value ≤0.05 and fold change (FC) of ≤ -2 or ≥2). The alterations identified in placentas delivered by mothers who suffered an episode of COVID-19 disease could be mainly attributed to pathways related to organogenesis, extracellular matrix organization and oxygen transport. These alterations were also detected after exclusion of gestational diabetes mellitus (GDM) samples. Although none of the samples were taken from cases of preeclampsia, several of the relevant DEGs have been previously reported as dysregulated in hypertensive disorders of pregnancy including preeclampsia.

DISCUSSION

We propose that maternal SARS-CoV-2 infection causes alterations in gene expression that are indicative of vascular defects in the placenta.

Maternal Immune Activation: Implications for Congenital Heart Defects

Congenital heart defects (CHD) are the most common major birth defects and one of the leading causes of death from congenital defects after birth. CHD can arise in pregnancy from the combination of genetic and non-genetic factors. The maternal immune activation (MIA) hypothesis is widely implicated in embryonic neurodevelopmental abnormalities. MIA has been found to be associated with the development of asthma, diabetes mellitus, and other diseases in the offspring. Given the important role of cardiac immune cells and cytokines in embryonic heart development, it is hypothesized that MIA may play a significant role in embryonic heart development. This review aims to stimulate further investigation into the relationship between MIA and CHD and to highlight the gaps in the knowledge. It evaluates the impact of MIA on CHD in the context of pregnancy complications, immune-related diseases, infections, and environmental and lifestyle factors. The review outlines the mechanisms by which immune cells and their secretome indirectly regulate the immuno-microenvironment of the embryonic heart by influencing placental development. Furthermore, the inflammatory cytokines cross the placenta to induce related reactions including oxidative stress in the embryonic heart directly. This review delineates the role of MIA in CHD and underscores the impact of maternal factors, especially immune factors, as well as the embryonic cardiac immuno-microenvironment, on embryonic heart development. This review extends our understanding of the importance of MIA in the pathogenesis of CHD and provides important insights into prenatal prevention and treatment strategies for this congenital condition.

Extracellular Vesicles Alter Trophoblast Function in Pregnancies Complicated by COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and resulting coronavirus disease (COVID-19) cause placental dysfunction, which increases the risk of adverse pregnancy outcomes. While abnormal placental pathology resulting from COVID-19 is common, direct infection of the placenta is rare. This suggests that pathophysiology associated with maternal COVID-19, rather than direct placental infection, is responsible for placental dysfunction. We hypothesized that maternal circulating extracellular vesicles (EVs), altered by COVID-19 during pregnancy, contribute to placental dysfunction. To examine this hypothesis, we characterized circulating EVs from pregnancies complicated by COVID-19 and tested their effects on trophoblast cell physiology in vitro. Trophoblast exposure to EVs isolated from patients with an active infection (AI), but not controls, altered key trophoblast functions including hormone production and invasion. Thus, circulating EVs from participants with an AI, both symptomatic and asymptomatic cases, can disrupt vital trophoblast functions. EV cargo differed between participants with COVID-19, depending on the gestational timing of infection, and Controls, which may contribute to the disruption of the placental transcriptome and morphology. Our findings show that COVID-19 can have effects throughout pregnancy on circulating EVs, and circulating EVs are likely to participate in placental dysfunction induced by COVID-19.

Interferon-stimulated gene IFI27 as a multifaceted candidate target in precision medicine

IFI27, an interferon (IFN)-stimulated gene, is emerging as a crucial player in immune responses across various species, with significant implications for precision medicine. Commonly found among the most upregulated genes in infections, cancers, as well as inflammatory and autoimmune disorders, IFI27 is ready to be trialed in clinical practice for certain indications, and holds promise as an immunomodulatory target. We hypothesize that IFI27 plays a dual role, typically supporting immune defense but sometimes contributing to disease progression, which might render it a putative biomarker for diagnosis, prognosis, and treatment response. We advocate for focused research on IFI27 to unlock its potential in precision medicine and to contribute to a unifying framework of its mechanisms in the immune response. Our viewpoint is supported by numerous studies highlighting IFI27's involvement across various conditions and the possibilities for clinical application.

A novel combined oxidative stress and extracellular matrix related predictive gene signature for keratoconus

Keratoconus (KC) is an ectatic cornea disease with high prevalence and asymptomatic at early stage, leading to decreased visual acuity and even cornea transplantation. However, the etiology mechanism of keratoconus is still poorly understood. Oxidative stress (OS) and extracellular matrix (ECM) remodeling play critical roles in keratoconus development. Here, based on keratoconus datasets from GEO database, we obtained 454 differentially expressed genes (DEGs), which were further intersected with oxidative stress (OS) and extracellular matrix (ECM) genesets from MSigDB database. A total of 17 OS- and ECM-related DEGs (OEDEGs) were identified. Feature genes were screened by least absolute shrinkage and selection operator (LASSO) and support vector machine recursive feature elimination (SVM-RFE) algorithms, and a six-gene (COL1A1, CYP1B1, MMP3, HMOX1, FOS and GDF15) classification model was developed utilizing Logistic regression (LR), Support Vector Machine (SVM) and Naïve Bayes (NB) algorithms respectively, which was further verified in internal and external cohort. Subsequently, a predictive nomogram was constructed for KC patients. Six signature genes showed a strong correlation with the infiltration level of macrophages M1, neutrophils and eosinophils. Additionally, in vitro qRT-PCR validated the decreased expression of signature genes in either keratoconus clinical samples or human cornea epithelial (HCE) cells grown on soft hydrogel substrate. Finally, we revealed that CYP1B1 and GDF15 regulate cellular proliferation and response to oxidative stress. In conclusion, the developed combined OS and ECM gene signature showed excellent performance for keratoconus prediction, providing beneficial perspectives for keratoconus pathogenesis.

Similar Spatial Expression of Immune-Related Proteins in SARS-CoV-2 Placentitis and Chronic Histiocytic Intervillositis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in the placenta can lead to fetal distress and demise, characterized by severe trophoblast necrosis, chronic histiocytic intervillositis (CHI), and massive perivillous fibrin deposition. We aimed to uncover spatial immune-related protein changes in SARS-CoV-2 placentitis compared with CHI placentas and uncomplicated pregnancies to gain insight into the underlying pathophysiological mechanisms. Placentas were retrospectively collected from cases with SARS-CoV-2 placentitis resulting in fetal distress/demise (n = 9), CHI (n = 9), and uncomplicated term controls (n = 9). The expression of 53 immune-related proteins was quantified using GeoMx Digital Spatial Profiler in three separate compartments: villi (fetal compartment), intervillous space, and decidua (both maternal compartments). Compared with controls, SARS-CoV-2 placentitis and CHI both displayed differentially expressed proteins in the intervillous space only, including upregulation of myeloid markers (e.g., CD40, CD11c, CD68, CD163). Specifically, SARS-CoV-2 placentitis was associated with reduced expression of multiple apoptotic proteins (e.g., BAD, BIM, BLXL, BCL6). In conclusion, SARS-CoV-2 placentitis and CHI are associated with enhanced myeloid cell infiltration into the intervillous space, but not in the decidua and villi. The more prominently reduced apoptosis-related protein expression in SARS-CoV-2 placentitis may lead to an exaggerated immune response, causing acute placental dysfunction and fetal demise.

PD-L1 expression and characterization of its carrier macrophages in placentas with acute and specifically post-SARS-CoV-2 infection

At the beginning of the coronavirus disease 2019 (COVID-19) pandemic, uncertainties about the virus and its dangers during pregnancy caused great uncertainty and fear, especially among pregnant women. New data suggest an increased risk of obstetric complications, including maternal complications, preterm labor, intrauterine growth restriction, hypertensive disorders, stillbirths, gestational diabetes and risk, of neonatal developmental disorders. In addition, preeclampsia (PE)-like syndromes were also induced by severe COVID-19 infection. Therefore, the aim of this study was to investigate the expression of CD68 and CD163 and PD-L1 on placental tissues from acute covid patients, patients who survived a covid-19 infection and normal term controls that are known to be dysregulated in preeclampsia cases. We examined a total of 60 placentas from women that had given birth to female or male offspring in the University Hospital Augsburg. We investigated ten acute COVID-19 females, ten acute COVID-19 males, ten post-COVID-19 females, ten post-COVID-19 males, ten female term controls, and ten male term controls. Immunohistochemical staining against CD68, CD163, and PD-L1 was performed and the expression of the markers was evaluated with an immunoreactive score (percentage score). Identity of CD163- or PD-L1 expressing cells was analyzed by double immune fluorescence analyses. In opposite to PE, CD163 positive maternal macrophages are significantly upregulated in the decidua of male acute COVID-19 placentas. PD-L1 is significantly upregulated on male acute- and post-COVID-19 decidual immune cells and on male post-COVID-19 extravillous trophoblast cells. Surprisingly the observed effects are related to the fetal gender as they were not observed in female offsprings. Further investigation is necessary to analyze especially the imprinting effect of this infection.

Preeclampsia in the Context of COVID-19: Mechanisms, Pathophysiology, and Clinical Outcomes

The emergence of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to the global COVID-19 pandemic, significantly impacting the health of pregnant women. Obstetric populations, already vulnerable, face increased morbidity and mortality related to COVID-19, aggravated by preexisting comorbidities. Recent studies have shed light on the potential correlation between COVID-19 and preeclampsia (PE), a leading cause of maternal and perinatal morbidity worldwide, emphasizing the significance of exploring the relationship between these two conditions. Here, we review the pathophysiological similarities that PE shares with COVID-19, with a particular focus on severe COVID-19 cases and in PE-like syndrome cases related with SARS-CoV-2 infection. We highlight cellular and molecular mechanistic inter-connectivity between these two conditions, for example, regulation of renin-angiotensin system, tight junction and barrier integrity, and the complement system. Finally, we discuss how COVID-19 pandemic dynamics, including the emergence of variants and vaccination efforts, has shaped the clinical scenario and influenced the severity and management of both COVID-19 and PE. Continued research on the mechanisms of SARS-CoV-2 infection during pregnancy and the potential risk of developing PE from previous infections is warranted to delineate the complexities of COVID-19 and PE interactions and to improve clinical management of both conditions.

Implication of viruses in the etiology of preeclampsia

Preeclampsia is one of the most common disorders that poses threat to both mothers and neonates and a major contributor to perinatal morbidity and mortality worldwide. Viral infection during pregnancy is not typically considered to cause preeclampsia; however, syndromic nature of preeclampsia etiology and the immunomodulatory effects of viral infections suggest that microbes could trigger a subset of preeclampsia. Notably, SARS-CoV-2 infection is associated with an increased risk of preeclampsia. Herein, we review the potential role of viral infections in this great obstetrical syndrome. According to in vitro and in vivo experimental studies, viral infections can cause preeclampsia by introducing poor placentation, syncytiotrophoblast stress, and/or maternal systemic inflammation, which are all known to play a critical role in the development of preeclampsia. Moreover, clinical and experimental investigations have suggested a link between several viruses and the onset of preeclampsia via multiple pathways. However, the results of experimental and clinical research are not always consistent. Therefore, future studies should investigate the causal link between viral infections and preeclampsia to elucidate the mechanism behind this relationship and the etiology of preeclampsia itself.