Pregnancy and preeclampsia affect monocyte subsets in humans and rats

Effects of parity and early pregnancy on peripheral blood leukocytes in dairy cattle

Subfertility remains a major problem in the dairy industry. Only 35-40% of high-yielding dairy cows and 55-65% of nonlactating heifers become pregnant after their first service. The immune system plays a critical role in the establishment of pregnancy. However, it can also create challenges for embryo survival and contribute to reduced fertility. We conducted 2 separate experiments to characterize changes in subsets of peripheral blood leukocytes (PBL) and their phenotype over the estrous cycle and early pregnancy in heifers and cows. We used flow cytometry and RT-qPCR to assess protein and mRNA expression of molecules important for immune function. We observed that CD14+ monocytes and CD3+ T cells tended to be affected by pregnancy status in heifers, whereas CD8B+ lymphocytes and NCR1+ natural killer (NK) cells were affected during early pregnancy in cows. Changes in expression of immune function proteins appeared to be greater in heifers than cows. To compare the most striking differences between heifers and cows observed in the initial experiments, we conducted a third experiment where PBL sampled from heifers and cows were simultaneously collected and analyzed under the same experimental conditions. Our results indicate that, compared with heifers, cows had greater mRNA expression of proinflammatory cytokines (IFNG and IL6) and AHR protein along with greater percentage of MM20A+ neutrophils and myeloid cells expressing SIRPA, ITGAM and ITGAX. Moreover, animals that failed to become pregnant showed altered expression of anti-inflammatory molecules compared with cyclic and pregnant animals. Overall, these findings support the hypothesis that early pregnancy signaling alters the phenotype of immune cells in the peripheral blood and that there are differences in the peripheral immune response to pregnancy between cows and heifers. Because cows have lower conception rates than heifers, it is possible that a more proinflammatory immune status in peripheral blood may play a role in embryo loss.

Diet-Induced Obesity in Mice Affects the Maternal Gut Microbiota and Immune Response in Mid-Pregnancy

Maternal obesity during pregnancy is associated with adverse pregnancy outcomes. This might be due to undesired obesity-induced changes in the maternal gut microbiota and related changes in the maternal immune adaptations during pregnancy. The current study examines how obesity affects gut microbiota and immunity in pregnant obese and lean mice during mid-pregnancy (gestational day 12 (GD12)). C57BL/6 mice were fed a high-fat diet or low-fat diet from 8 weeks before mating and during pregnancy. At GD12, we analyzed the gut microbiota composition in the feces and immune responses in the intestine (Peyer's patches, mesenteric lymph nodes) and the peripheral circulation (spleen and peripheral blood). Maternal obesity reduced beneficial bacteria (e.g., Bifidobacterium and Akkermansia) and changed intestinal and peripheral immune responses (e.g., dendritic cells, Th1/Th2/Th17/Treg axis, monocytes). Numerous correlations were found between obesity-associated bacterial genera and intestinal/peripheral immune anomalies. This study shows that maternal obesity impacts the abundance of specific bacterial gut genera as compared to lean mice and deranges maternal intestinal immune responses that subsequently change peripheral maternal immune responses in mid-pregnancy. Our findings underscore the opportunities for early intervention strategies targeting maternal obesity, ideally starting in the periconceptional period, to mitigate these obesity-related pregnancy effects.

Obesity and diet independently affect maternal immunity, maternal gut microbiota and pregnancy outcome in mice

Introduction

Maternal obesity poses risks for both mother and offspring during pregnancy, with underlying mechanisms remaining largely unexplored. Obesity is associated with microbial gut dysbiosis and low-grade inflammation, and also the diet has a major impact on these parameters. This study aimed to investigate how maternal obesity and diet contribute to changes in immune responses, exploring potential associations with gut microbiota dysbiosis and adverse pregnancy outcomes in mice.

Methods

Before mating, C57BL/6 mice were assigned to either a high-fat-diet (HFD) or low-fat-diet (LFD) to obtain obese (n=17) and lean (n=10) mice. To distinguish between the effects of obesity and diet, 7 obese mice were switched from the HFD to the LFD from day 7 until day 18 of pregnancy ("switch group"), which was the endpoint of the study. T helper (Th) cell subsets were studied in the spleen, mesenteric lymph nodes (MLN) and Peyer's patches (PP), while monocyte subsets and activation status were determined in maternal blood (flow cytometry). Feces were collected before and during pregnancy (day 7,14,18) for microbiota analysis (16S rRNA sequencing). Pregnancy outcome included determination of fetal and placental weight.

Results

Obesity increased splenic Th1 and regulatory T cells, MLN Th1 and PP Th17 cells and enhanced IFN-γ and IL-17A production by splenic Th cells upon ex vivo stimulation. Switching diet decreased splenic and PP Th2 cells and classical monocytes, increased intermediate monocytes and activation of intermediate/nonclassical monocytes. Obesity and diet independently induced changes in the gut microbiota. Various bacterial genera were increased or decreased by obesity or the diet switch. These changes correlated with the immunological changes. Fetal weight was lower in the obese than the lean group, while placental weight was lower in the switch than the obese group.

Discussion

This study demonstrates that obesity and diet independently impact peripheral and intestinal immune responses at the end of pregnancy. Simultaneously, both factors affect specific bacterial gut genera and lead to reduced fetal or placental weight. Our data suggest that switching diet during pregnancy to improve maternal health is not advisable and it supports pre/probiotic treatment of maternal obesity-induced gut dysbiosis to improve maternal immune responses and pregnancy outcome.

Immunometabolic adaptation in monocytes underpins functional changes during pregnancy

Metabolic heterogeneity is a determinant of immune cell function. The normal physiological metabolic reprogramming of pregnancy that ensures the fuel requirements of mother and baby are met, might also underpin changes in immunity that occur with pregnancy and manifest as altered responses to pathogens and changes to autoimmune disease symptoms. Using peripheral blood from pregnant women at term, we reveal that monocytes lose M2-like and gain M1-like properties accompanied by reductions in mitochondrial mass, maximal respiration, and cardiolipin content in pregnancy; glycolysis is unperturbed. We establish that muramyl dipeptide (MDP)-stimulated cytokine production relies on oxidative metabolism, then show in pregnancy reduced cytokine production in response to MDP but not LPS. Overall, mitochondrially centered metabolic capabilities of late gestation monocytes are down-regulated revealing natural plasticity in monocyte phenotype and function that could reveal targets for improving pregnancy outcomes but also yield alternative therapeutic approaches to diverse metabolic and/or immune-mediated diseases beyond pregnancy.

Placental Drug Delivery to Treat Pre-Eclampsia and Fetal Growth Restriction

Pre-eclampsia and fetal growth restriction (FGR) continue to cause unacceptably high levels of morbidity and mortality, despite significant pharmaceutical and technological advances in other disease areas. The recent pandemic has also impacted obstetric care, as COVID-19 infection increases the risk of poor pregnancy outcomes. This review explores the reasons why it lacks effective drug treatments for the placental dysfunction that underlies many common obstetric conditions and describes how nanomedicines and targeted drug delivery approaches may provide the solution to the current drug drought. The ever-increasing range of biocompatible nanoparticle formulations available is now making it possible to selectively deliver drugs to uterine and placental tissues and dramatically limit fetal drug transfer. Formulations that are refractory to placental uptake offer the possibility of retaining drugs within the maternal circulation, allowing pregnant individuals to take medicines previously considered too harmful to the developing baby. Liposomes, ionizable lipid nanoparticles, polymeric nanoparticles, and adenoviral vectors have all been used to create efficacious drug delivery systems for use in pregnancy, although each approach offers distinct advantages and limitations. It is imperative that recent advances continue to be built upon and that there is an overdue investment of intellectual and financial capital in this field.

Effects of parity and early pregnancy on peripheral blood leukocytes in dairy cattle

Subfertility remains a major problem in the dairy industry. Only 35-40% of high-yielding dairy cows and 55-65% of nonlactating heifers become pregnant after their first service. The immune system plays a critical role in the establishment of pregnancy. However, it can also create challenges for embryo survival and contribute to reduced fertility. We conducted 2 separate experiments to characterize changes in subsets of peripheral blood leukocytes (PBL) and their phenotype over the estrous cycle and early pregnancy in heifers and cows. We used flow cytometry and RT-qPCR to assess protein and mRNA expression of molecules important for immune function. We observed that monocytes and T cells were most affected by pregnancy status in heifers, whereas, CD8+ lymphocytes and natural killer (NK) cells were most affected during early pregnancy in cows. Changes in immune parameters measured appeared to be greater in heifers than cows including changes in expression of numerous immune function molecules. To test the hypothesis, we conducted a third experiment to simultaneously analyze the immunological responses to pregnancy between cows and heifers. We observed that cows had greater expression of proinflammatory cytokines and molecules associated with leukocyte migration and phagocytosis compared to heifers. Moreover, animals that failed to become pregnant showed altered expression of anti-inflammatory molecules. Overall, these findings support the hypothesis that early pregnancy signaling alters the proportions and functions of peripheral blood immune cells and differences between cows and heifers may yield insight into the reduced fertility of mature lactating dairy cows.

The causal role of circulating immunity-inflammation in preeclampsia: A Mendelian randomization

Patients with systemic autoimmune diseases, such as systemic lupus erythematosus, were at a higher risk for preeclampsia. The causal relationship between immunological inflammation and preeclampsia (PE) remains uncertain. We aimed to investigate the causal relationship between circulating immune inflammation and PE. Genetically predicted blood immune cells and circulating inflammatory proteins were identified using two genome-wide association studies (GWAS). We used a two-sample Mendelian randomization (MR) method to determine whether circulating immunological inflammation causes PE. Our findings indicated that ten immunophenotypes were identified to be significantly associated with PE risk: CD62L- Dendritic Cell Absolute Count, CD86+ myeloid Dendritic Cell %Dendritic Cell, CD62L- myeloid Dendritic Cell Absolute Count, CD86+ myeloid Dendritic Cell Absolute Count, CD62L- myeloid Dendritic Cell %Dendritic Cell, CD62L- CD86+ myeloid Dendritic Cell %Dendritic Cell, CD62L- CD86+ myeloid Dendritic Cell Absolute Count, CD16 on CD14+ CD16+ monocyte, HLA DR+ Natural Killer Absolute Count, and T cell Absolute Count. Ninety-one inflammation-related proteins had no statistically significant effect on PE following false discovery rate (FDR) correction. Certain proteins exhibited unadjusted low p-values that merited mention. These proteins include interleukin-10 (OR = 0.76, 95%CI = 0.63-0.93, p = .006), fibroblast growth factor 21 (OR = 1.23, 95%CI = 1.01-1.47, p = .035), and Caspase 8 (OR = 0.65, 95%CI = 0.50-0.85, p = .001). The ELISA analysis demonstrated elevated levels of FGF-21 and decreased levels of IL-10 and Caspase-8 in the plasma of patients with PE. These findings reveal that immunophenotypes and circulating inflammatory proteins may induce PE, confirming the importance of peripheral Immunity-Inflammation in PE. The discovery has the potential to lead to earlier detection and more effective treatment techniques.

Interferon-stimulated gene 15 polymorphisms are associated with spontaneous preterm birth in Taiwanese women

PROBLEM

Immune and inflammatory responses are known to be major causes of preterm birth (PTB). The maternal genetic background plays an important role in the development of PTB. Interferon-stimulated gene 15 (ISG15) is an interferon-induced protein which can modulate immune cell activation and function. We aim to study if polymorphisms in the ISG15 gene are associated with spontaneous PTB (sPTB) risk in Taiwanese women.

METHOD OF STUDY

ISG15 rs4615788 C/G, rs1921 G/A, and rs8997 A/G polymorphisms were genotyped in a hospital-based study of 112 women with sPTB and 1120 term controls. The plasma concentrations of ISG15 were determined by enzyme-linked immunosorbent assay.

RESULTS

We found the ISG15 rs1921 G-rs8997 A haplotype was associated with decreased risk for PTB (χ2  = 6.26, p = .01, pc  = .04). The A/G genotype of ISG15 rs8997 polymorphism might have the potential to confer reduced risk of PTB women (χ2  = 4.09, p = .04, pc  = .08). Spontaneous PTB women displayed higher plasma ISG15 levels compared to term controls (p < .001). The plasma ISG15 levels among pregnant women with rs8997 A/G genotype were found significantly lower compared to G/G genotype (p = .03).

CONCLUSIONS

Women with the ISG15 rs1921 G-rs8997 A haplotype may associate with spontaneous PTB. These findings provide new insights into the etiology of preterm birth.

Effects of different obesogenic diets on joint integrity, inflammation and intermediate monocyte levels in a rat groove model of osteoarthritis

Introduction: Obesogenic diets aggravate osteoarthritis (OA) by inducing low-grade systemic inflammation, and diet composition may affect OA severity. Here, we investigated the effect of diet on joint damage and inflammation in an OA rat model. Methods: Wistar-Han rats (n = 24) were fed a chow, a high-fat (HF) diet, or a high-fat/high-sucrose (HFS) for 24 weeks. OA was induced unilaterally 12 weeks after the diet onset by groove surgery, and compared to sham surgery or no surgical intervention (contralateral limb). Knee OA severity was determined by OARSI histopathology scoring system. At several timepoints monocyte populations were measured using flow cytometry, and joint macrophage response was determined via CD68 immunohistochemistry staining. Results: Groove surgery combined with HF or HFS diet resulted in higher OARSI scores, and both HF and HFS diet showed increased circulating intermediate monocytes compared to chow fed rats. Additionally, in the HFS group, minimal damage by sham surgery resulted in an increased OARSI score. HFS diet resulted in the largest metabolic dysregulation, synovial inflammation and increased CD68 staining in tibia epiphysis bone marrow. Conclusion: Obesogenic diets resulted in aggravated OA development, even with very minimal joint damage when combined with the sucrose/fat-rich diet. We hypothesize that diet-induced low-grade inflammation primes monocytes and macrophages in the blood, bone marrow, and synovium, resulting in joint damage when triggered by groove OA inducing surgery. When the metabolic dysregulation is larger, as observed here for the HFS diet, the surgical trigger required to induce joint damage may be smaller, or even redundant.

The Effect of Antibiotics Treatment on the Maternal Immune Response and Gut Microbiome in Pregnant and Non-Pregnant Mice

The gut microbiota are involved in adaptations of the maternal immune response to pregnancy. We therefore hypothesized that inducing gut dysbiosis during pregnancy alters the maternal immune response. Thus, pregnant mice received antibiotics from day 9 to day 16 to disturb the maternal gut microbiome. Feces were collected before, during and after antibiotic treatment, and microbiota were measured using 16S RNA sequencing. Mice were sacrificed at day 18 of pregnancy and intestinal (Peyer's patches (PP) and mesenteric lymph nodes (MLN)) and peripheral immune responses (blood and spleen) were measured using flow cytometry. Antibiotic treatment decreased fetal and placental weight. The bacterial count and the Shannon index were significantly decreased (Friedman, followed by Dunn's test, p < 0.05) and the bacterial genera abundance was significantly changed (Permanova, p < 0.05) following antibiotics treatment as compared with before treatment. Splenic Th1 cells and activated blood monocytes were increased, while Th2, Th17 and FoxP3/RoRgT double-positive cells in the PP and MLNs were decreased in pregnant antibiotics-treated mice as compared with untreated pregnant mice. In addition, intestinal dendritic cell subsets were affected by antibiotics. Correlation of immune cells with bacterial genera showed various correlations between immune cells in the PP, MLN and peripheral circulation (blood and spleen). We conclude the disturbed gut microbiota after antibiotics treatment disturbed the maternal immune response. This disturbed maternal immune response may affect fetal and placental weight.

Immune profiling of SARS-CoV-2 infection during pregnancy reveals NK cell and γδ T cell perturbations

Pregnancy poses a greater risk for severe COVID-19; however, underlying immunological changes associated with SARS-CoV-2 during pregnancy are poorly understood. We defined immune responses to SARS-CoV-2 in unvaccinated pregnant and nonpregnant women with acute and convalescent COVID-19, quantifying 217 immunological parameters. Humoral responses to SARS-CoV-2 were similar in pregnant and nonpregnant women, although our systems serology approach revealed distinct antibody and FcγR profiles between pregnant and nonpregnant women. Cellular analyses demonstrated marked differences in NK cell and unconventional T cell activation dynamics in pregnant women. Healthy pregnant women displayed preactivated NK cells and γδ T cells when compared with healthy nonpregnant women, which remained unchanged during acute and convalescent COVID-19. Conversely, nonpregnant women had prototypical activation of NK and γδ T cells. Activation of CD4+ and CD8+ T cells and T follicular helper cells was similar in SARS-CoV-2-infected pregnant and nonpregnant women, while antibody-secreting B cells were increased in pregnant women during acute COVID-19. Elevated levels of IL-8, IL-10, and IL-18 were found in pregnant women in their healthy state, and these cytokine levels remained elevated during acute and convalescent COVID-19. Collectively, we demonstrate perturbations in NK cell and γδ T cell activation in unvaccinated pregnant women with COVID-19, which may impact disease progression and severity during pregnancy.

The imbalance of circulating monocyte subgroups with a higher proportion of the CD14+CD16+CD163+ phenotype in patients with preeclampsia

BACKGROUND

Preeclampsia is a major cause of increased maternal and fetal morbidity and mortality, which is closely related to the abnormal maternal immune response. The skew of decidual macrophage polarization toward M1 phenotype has been proved to promote the pathogenesis of preeclampsia. However, it's not easy to monitor the change of decidual macrophage subtypes. The current study aims to examine the distribution of different circulating monocyte subtypes and analyze whether certain monocyte subtypes act as potential clinical indicators for preeclampsia.

METHODS

A total of 50 pregnant women [mild preeclampsia (n = 20); severe preeclampsia (n = 15); healthy pregnancy (n = 15)] and 15 healthy donors were included in the study. Medical information such as BMI, blood pressure, ALT, creatinine, thrombocyte, etc., were recorded. The frequency of different monocyte subtypes in venous blood were measured by flow cytometry. Serum level of IL-6 was detected using Roche-Hitachi cobas 8000. Serum concentration of inflammatory cytokines (IL-1β, IL-4, IL-10 and TNF-α) were measured by ELISA.

RESULTS

A circulating monocyte subset with both M1 and M2 markers (CD14+CD16+CD163+) was found to occupy an obvious higher proportion in the preeclampsia group than in the normal pregnancy group. The ratio of CD206+/CD206- M2-like monocytes was also increased in the preeclampsia group, and meanwhile, it had statistic difference between the mild- and the severe-preeclampsia group. Furthermore, the serum levels of IL-1β and TNF-α were positively correlated with the frequency of CD14+CD16+CD163+ intermediate monocytes in the preeclampsia group.

CONCLUSIONS

The increased proportion of CD14+C16+CD163+ circulating monocytes and the high ratio of CD206+/CD206- M2-like monocytes may act as potential clinical indicators for preeclampsia, with the superiority of convenience and dynamic monitoring.

Placental macrophage responses to viral and bacterial ligands and the influence of fetal sex

Bacterial and viral infections of the placenta are associated with inflammation and adverse pregnancy outcomes. Hofbauer cells (HBCs) are fetal-origin macrophages in the placenta, proposed to protect the fetus from vertical pathogen transmission. We performed quantitative proteomics on term HBCs under resting conditions and following exposure to bacterial and viral pathogen-associated molecular patterns (PAMPs), and investigated the contribution of fetal sex. Resting HBCs expressed proteins pertinent to macrophage function, including chemokines, cytokines, Toll-like receptors, and major histocompatibility complex class I and II molecules. HBCs mounted divergent responses to bacterial versus viral PAMPs but exhibited protein expression changes suggestive of a more pro-inflammatory phenotype. A comparison between male and female HBCs showed that the latter mounted a stronger and wider response. Here, we provide a comprehensive understanding of the sex-dependent responses of placental macrophages to infectious triggers, which were primarily associated with lipid metabolism in males and cytoskeleton organization in females.

Cross-Generational Impact of Innate Immune Memory Following Pregnancy Complications

Pregnancy complications can have long-term negative effects on the health of the affected mothers and their children. In this review, we highlight the underlying inflammatory etiologies of common pregnancy complications and discuss how aberrant inflammation may lead to the acquisition of innate immune memory. The latter can be described as a functional epigenetic reprogramming of innate immune cells following an initial exposure to an inflammatory stimulus, ultimately resulting in an altered response following re-exposure to a similar inflammatory stimulus. We propose that aberrant maternal inflammation associated with complications of pregnancy increases the cross-generational risk of developing noncommunicable diseases (i.e., pregnancy complications, cardiovascular disease, and metabolic disease) through a process mediated by innate immune memory. Elucidating a role for innate immune memory in the cross-generational health consequences of pregnancy complications may lead to the development of novel strategies aimed at reducing the long-term risk of disease.

Immune-metabolic adaptations in pregnancy: A potential stepping-stone to sepsis

Physiological shifts during pregnancy predispose women to a higher risk of developing sepsis resulting from a maladapted host-response to infection. Insightful studies have delineated subtle point-changes to the immune system during pregnancy. Here, we present an overlay of these point-changes, asking what changes and when, at a physiological, cellular, and molecular systems-level in the context of sepsis. We identify distinct immune phases in pregnancy delineated by placental hormone-driven changes in homeostasis setpoints of the immune and metabolic systems that subtly mirrors changes observed in sepsis. We propose that pregnancy immune-metabolic setpoint changes impact feedback thresholds that increase risk for a maladapted host-response to infection and thus act as a stepping-stone to sepsis. Defining maternal immune-metabolic setpoint changes is not only vital for tailoring the right diagnostic tools for early management of maternal sepsis but will facilitate an unravelling of the pathophysiological pathways that predispose an individual to sepsis.

Immune cell profiling of preeclamptic pregnant and postpartum women by single-cell RNA sequencing

Preeclampsia (PE), a leading cause of maternal and fetal morbidity and mortality, is closely related to the immune system alterations. However, little is known about the landscape and heterogeneity of maternal immune system at single-cell level among PE patients. In this study, peripheral blood mononuclear cells (PBMCs) were isolated from three early-onset preeclamptic pregnant women and two healthy control, respectively. Single-cell RNA sequencing was performed on 10× genomics platform and single-cell transcriptomes were obtained to characterize immune cell subgroups at the pregnant and postpartum stages. In total, 80,429 single-cell transcriptomes were obtained. 19 cellular compositions were identified, which were categorized into six cell types including T cells, natural killer (NK) cells, B cells, monocytes, plasmacytoid dendritic cells and conventional dendritic cells. There were excessive activation of B cells, monocytes and NK cells in PE patients at the pregnant stage based on comparative analysis. Lower immune response activation was noticed in CD4+ and CD8+ T cells in PE patients, especially the low-activation of memory T cells at the pregnant and postpartum stages. PE patients showed high activation of B cells in pregnancy persisted postpartum and lower activation of memory T cells, indicating their persistent effects on the pathogenesis and recurrence risk of PE. This study provide a broad characterization of the single-cell transcriptome of PBMCs in PE, which contributes to identification of immune imbalance for its monitoring and treatment.

Placental Therapeutic Targets and Nanodelivery Systems

Pregnancy complications affect millions of women each year. Some of these diseases have high morbidity and mortality such as preeclampsia. At present, there is no safe and effective treatment for pregnancy complications, so it is still a difficult clinical problem. As many pregnancy complications are closely related to placental dysplasia, placenta-specific therapy, as an important method, is expected to be a safe, effective, and specific therapeutic strategy. This review explains in detail the placenta physiological structure, characteristics, and action mechanism of some biomolecules and signaling pathways that play roles in normal development and disorders of the development of the placenta, and how to use these biomolecules as therapeutic targets when the placenta disorder causes disease, combining the latest progress in the field of nanodelivery systems, so as to lay a foundation for the development of placenta-specific therapy of pregnancy complications.

Distinct gene expression patterns for CD14++ and CD16++ monocytes in preeclampsia

Preeclampsia (PE) is a serious gestational complication affecting the life of a mother and child. The immunophenotype and gene expression profile of isolated blood monocyte subpopulations of pregnant women with PE have not been studied before. In this work, we assessed changes in CD14++ and CD16++ monocyte subpopulations in PE and physiological pregnancy (n = 33). Immunophenotyping, immunomagnetic sorting of monocytes and analysis of the transcriptional profile of their genes were carried out. The percentage of classical monocytes was significantly lower, while the intermediate fraction of monocytes was significantly higher in late-onset PE compared to control. Transcriptome analysis of late-onset PE classical CD14++ monocytes revealed significant activation of inflammation mediated by chemokine and cytokine signalling pathways; apoptosis; regulation of transcription from RNA polymerase II promoter in response to stress and others. The most suppressed signalling pathways were associated with T cell activation and selection. In CD16++ monocytes of late-onset PE cases, positive regulation of cell-cell adhesion, integrin signalling pathway, blood coagulation cascade were the most activated ones. The inflammation mediated by chemokine and cytokine signalling pathway and p53 pathway were the most down-regulated in CD16++ monocytes. The obtained results indicate profound changes occurring to two most polar monocyte subpopulations in PE and their different roles in the pathogenesis of this disease.

Monocytes are increased in pregnancy after gestational hypertensive disease

Monocytes derive from bone marrow and circulate in the blood. They phagocytose, produce cytokines and present antigens. Individual monocyte subsets play distinct roles in the pathogenesis of cardiovascular disease, but their implications in gestational hypertensive disease are unclear. Our objective was to examine the difference in monocyte subsets between pregnant women with or without previous hypertension in pregnancy. Women were enrolled in a prospective observational study in which monoclonal antibodies against cell surface receptors were used to detect monocytes in the peripheral blood by flow cytometry. We compared 17 pregnant women with previous hypertension in pregnancy (Group 1) and 42 pregnant women without previous gestational hypertensive disease (Group 2) with 27 healthy, non-pregnant controls (Group 3). The pregnant women were studied at 13 ± 1 weeks gestation. Monocyte subsets were quantified by flow cytometry: Mon1 (CD14++CD16-CCR2+), Mon2 (CD14++CD16+CCR2+), Mon3 (CD14+CD16+CCR2-), their aggregates with platelets and expression of the surface markers. The groups were well-matched for age, body mass index and ethnicity (P > 0.05 for all). Mon1 counts were higher in women with a history of gestational hypertension or preeclampsia compared to other groups (Group 1 = 441 per µl (376-512); Group 2 = 357 (309-457); Group 3 = 323 (277-397); P < 0.001). Mon3 was higher in both groups of pregnant women compared to non-pregnant controls (Group 1 = 51 (38-62); Group 2 = 38 (29-58); Group 3 = 26 (20-40), P = 0.002). Increased monocytes in women with a previous hypertensive pregnancy generates a hypothesis that these cells may link hypertension in pregnancy, chronic inflammation and future cardiovascular risk.

Placental dysfunction influences fetal monocyte subpopulation gene expression in preterm birth

The placenta is the primary organ for immune regulation, nutrient delivery, gas exchange, protection against environmental toxins, and physiologic perturbations during pregnancy. Placental inflammation and vascular dysfunction during pregnancy are associated with a growing list of prematurity-related complications. The goal of this study was to identify differences in gene expression profiles in fetal monocytes - cells that persist and differentiate postnatally - according to distinct placental histologic domains. Here, by using bulk RNA-Seq, we report that placental lesions are associated with gene expression changes in fetal monocyte subsets. Specifically, we found that fetal monocytes exposed to acute placental inflammation upregulate biological processes related to monocyte activation, monocyte chemotaxis, and platelet function, while monocytes exposed to maternal vascular malperfusion lesions downregulate these processes. Additionally, we show that intermediate monocytes might be a source of mitogens, such as HBEGF, NRG1, and VEGFA, implicated in different outcomes related to prematurity. This is the first study to our knowledge to show that placental lesions are associated with unique changes in fetal monocytes and monocyte subsets. As fetal monocytes persist and differentiate into various phagocytic cells following birth, our study may provide insight into morbidity related to prematurity and ultimately potential therapeutic targets.

Maternal body mass index is associated with an altered immunological profile at 28 weeks of gestation

Healthy pregnancy is accompanied by various immunological and metabolic adaptations. Maternal obesity has been implicated in adverse pregnancy outcomes such as miscarriage, preeclampsia, and gestational diabetes mellitus (GDM), while posing a risk to the neonate. There is a lack of knowledge surrounding obesity and the maternal immune system. The objective of this study was to consider if immunological changes in pregnancy are influenced by maternal obesity. Peripheral blood was collected from fasted GDM-negative pregnant women at 26-28 weeks of gestation. Analysis was done using immunoassay, flow cytometry, bioenergetics analysis, and cell culture. The plasma profile was significantly altered with increasing BMI, specifically leptin (r = 0.7635), MCP-1 (r = 0.3024), and IL-6 (r = 0.4985). Circulating leukocyte populations were also affected with changes in the relative abundance of intermediate monocytes (r = -0.2394), CD4:CD8 T-cell ratios (r = 0.2789), and NKT cells (r = -0.2842). Monocytes analysed in more detail revealed elevated CCR2 expression and decreased mitochondrial content with increased BMI. However, LPS-stimulated cytokine production and bioenergetic profile of PBMCs were not affected by maternal BMI. The Th profile skews towards Th17 with increasing BMI; Th2 (r = -0.3202) and Th9 (r = -0.3205) cells were diminished in maternal obesity, and CytoStim™-stimulation exacerbates IL-6 (r = 0.4166), IL-17A (r = 0.2753), IL-17F (r = 0.2973), and IL-22 (r = 0.2257) production with BMI, while decreasing IL-4 (r = -0.2806). Maternal obesity during pregnancy creates an inflammatory microenvironment. Successful pregnancy requires Th2-biased responses yet increasing maternal BMI favours a Th17 response that could be detrimental to pregnancy. Further research should investigate key populations of cells identified here to further understand the immunological challenges that beset pregnant women with obesity.

Single-cell atlas of peripheral blood mononuclear cells from pregnant women

Background

During pregnancy, mother–child interactions trigger a variety of subtle changes in the maternal body, which may be reflected in the status of peripheral blood mononuclear cells (PBMCs). Although these cells are easy to access and monitor, a PBMC atlas for pregnant women has not yet been constructed.

Methods

We applied single‐cell RNA sequencing (scRNA‐seq) to profile 198,356 PBMCs derived from 136 pregnant women (gestation weeks 6 to 40) and a control cohort. We also used scRNA‐seq data to establish a transcriptomic clock and thereby predicted the gestational age of normal pregnancy.

Results

We identified reconfiguration of the peripheral immune cell phenotype during pregnancy, including interferon‐stimulated gene upregulation, activation of RNA splicing‐related pathways and immune activity of cell subpopulations. We also developed a cell‐type‐specific model to predict gestational age of normal pregnancy.

Conclusions

We constructed a single‐cell atlas of PBMCs in pregnant women spanning the entire gestation period, which should help improve our understanding of PBMC composition turnover in pregnant women.

Pregnancy tailors endotoxin-induced monocyte and neutrophil responses in the maternal circulation

Objective

To comprehensively characterize monocyte and neutrophil responses to E. coli and its product [lipopolysaccharide (LPS) or endotoxin] in vitro during pregnancy.

Material or subjects

Peripheral blood was collected from pregnant women during the third trimester (n = 20) and from non-pregnant women (n = 20).

Methods

The number, phagocytic activity, and reactive oxygen species (ROS) production of peripheral monocytes and neutrophils were investigated using flow cytometry. The phenotypes of peripheral monocytes and neutrophils after acute or chronic LPS stimulation were also determined using flow cytometry. Cytokine profiles were quantified for LPS-stimulated peripheral blood mononuclear cells (PBMCs) and a whole blood TruCulture^® system using a multiplex immunoassay.

Results

Increased number, phagocytic activity, and ROS production capacity of monocytes and neutrophils were found in pregnant compared to non-pregnant women. Additionally, specific subsets of pro-inflammatory monocytes (IL-6⁺CD14⁺ or MIP-1α⁺CD14⁺ cells) and neutrophils (IL-1β⁺CD15⁺ or MIP-1β⁺CD15⁺ cells) were increased in pregnant women in response to acute LPS stimulation. Moreover, distinct subsets of intermediate-activated monocytes expressing CD142, IL-6, and IL-1RA were increased in pregnant women upon chronic LPS stimulation. Last, pregnant women displayed a different cytokine profile than non-pregnant women in LPS-stimulated PBMCs and in whole blood.

Conclusions

Pregnancy tailors the immune responses of circulating monocytes and neutrophils to endotoxin, a Gram-negative bacterial product.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00011-022-01569-z.

Serum Cortisol and Its Correlation with Leucocyte Profile and Circulating Lipids in Donkeys (Equus asinus)

The values for basal serum cortisol concentrations of horses are available in many studies. However, there are limited data about serum cortisol in donkeys. The present study aimed to determine the baseline values for serum cortisol, to evaluate the influence of age and pregnancy on its levels, and to correlate its values with leucocyte profile, serum cholesterol, and triglycerides. Serum samples were collected from 97 healthy donkeys. Cortisol was analyzed by chemo-luminescent assay. The median and the 2.5th and 97.5th percentiles of serum cortisol measured and calculated in all donkeys were 5.64, 3.40, and 10.54 µg/dL, respectively. Females (n.91) were divided into three groups: Group A (young), Group B (adult), and Group C (pregnant at the 9th−11th months). The effect of age and physiological status was investigated by the Mann−Whitney test. Group C showed significantly higher levels than Group B (p < 0.05). Significant correlations were found in Group B with monocytes (r = 0.37, p < 0.01) and triglycerides (r = 0.30, p < 0.05), and in Group C with monocytes (r = 0.79, p < 0.01), basophils (r = 0.6, p < 0.05), and neutrophil/lymphocyte ratio (r = −0.63, p < 0.05). Higher cortisol values related to late pregnancy are also found in this species. These preliminary results provide evidence for a relationship between cortisol and the immune system as well as cortisol and lipid metabolism modulated by age and pregnancy when parameters are within normal values.

Systemic and local innate immune responses to surgical co-transplantation of mesenchymal stromal cells and biphasic calcium phosphate for bone regeneration

Bone regeneration from mesenchymal stromal cells (MSC) is attributed to comprehensive immune modulation mediated by the MSC. However, the temporal and spatial regulation of these immune responses has not yet been described. The aim of the present study was to assess the local and systemic innate immune responses to implantation of biphasic calcium phosphate biomaterial (BCP) alone, or with bone marrow derived MSC (BCP+MSC), in critical-sized calvarial bone defects of Lewis rats. Four weeks after implantation, flow cytometry analysis of innate immune cells revealed increased numbers of circulating classical monocyte-macrophages (MM) and decreased non-classical MM in the BCP+MSC group. At week 8, this differential systemic MM response was associated with an increased presence of local tissue anti-inflammatory macrophages expressing CD68 and CD163 markers (M2-like). In the BCP group without MSC, NK cells increased at weeks 1 and 4, and neutrophils increased in circulation at weeks 2 and 8. At week 8, the increase in number of neutrophils in circulation was associated with decreased local tissue neutrophils, in the BCP+MSC group. Gene expression analysis of tissue biopsies from defects implanted with BCP+MSC, in comparison to BCP alone, revealed upregulated expression of early osteogenesis genes along with macrophage differentiation-related genes at weeks 1 and 8 and neutrophil chemotaxis-related genes at week 1. This study is the first to demonstrate that surgical implantation of BCP or BCP+MSC grafts differentially regulate both systemic and local tissue innate immune responses which enhance bone formation. The results provide new insights into immune mechanisms underlying MSC-mediated bone regeneration. STATEMENT OF SIGNIFICANCE: The suitability of biphasic calcium phosphate and mesenchymal stromal cell construct (BCP+MSC) transplantation is evident from their progress in clinical trials for treating challenging maxillofacial bone defects. But less is known about the overall immune response generated by this surgical process and how it later impacts the bone formation. To this end, it is crucial to understand for both clinicians and researchers, the systemic immune response to transplanting MSC in patients for ensuring both the safety and efficacy of cell therapies. In this study, we used rat calvarial bone defect model and showed that both systemic and local innate immunes responses (monocyte-macrophages and neutrophils) are favorably directed towards enhanced bone formation in BCP+MSC implanted defects, as compared to BCP alone.

Modeling Trophoblast Cell-Guided Uterine Spiral Artery Transformation in the Rat

The rat possesses hemochorial placentation with deep intrauterine trophoblast cell invasion and trophoblast-guided uterine spiral artery remodeling, which resembles human placentation. Uterine spiral arteries are extensively remodeled to deliver sufficient supply of maternal blood and nutrients to the developing fetus. Inadequacies in these key processes negatively impact fetal growth and development. Recent innovations in genome editing combined with effective phenotyping strategies have provided new insights into placental development. Application of these research approaches has highlighted both conserved and species-specific features of hemochorial placentation. The review provides foundational information on rat hemochorial placental development and function during physiological and pathological states, especially as related to the invasive trophoblast cell-guided transformation of uterine spiral arteries. Our goal is to showcase the utility of the rat as a model for in vivo mechanistic investigations targeting regulatory events within the uterine-placental interface.

Immunometabolic adaptation and immune plasticity in pregnancy and the bi-directional effects of obesity

Mandatory maternal metabolic and immunological changes are essential to pregnancy success. Parallel changes in metabolism and immune function make immunometabolism an attractive mechanism to enable dynamic immune adaptation during pregnancy. Immunometabolism is a burgeoning field with the underlying principle being that cellular metabolism underpins immune cell function. With whole body changes to the metabolism of carbohydrates, protein and lipids well recognised to occur in pregnancy and our growing understanding of immunometabolism as a determinant of immunoinflammatory effector responses, it would seem reasonable to expect immune plasticity during pregnancy to be linked to changes in the availability and handling of multiple nutrient energy sources by immune cells. While studies of immunometabolism in pregnancy are only just beginning, the recognised bi-directional interaction between metabolism and immune function in the metabolic disorder obesity might provide some of the earliest insights into the role of immunometabolism in immune plasticity in pregnancy. Characterised by chronic low-grade inflammation including in pregnant women, obesity is associated with numerous adverse outcomes during pregnancy and beyond for both mother and child. Concurrent changes in metabolism and immunoinflammation are consistently described but any causative link is not well established. Here we provide an overview of the metabolic and immunological changes that occur in pregnancy and how these might contribute to healthy versus adverse pregnancy outcomes with special consideration of possible interactions with obesity.

Cellular immune responses in the pathophysiology of preeclampsia

Preeclampsia, defined as new-onset hypertension accompanied by proteinuria occurring at 20 weeks of gestation or later, is a leading cause of perinatal morbidity and mortality worldwide. The pathophysiology of this major multi-systemic syndrome includes defective deep placentation, oxidative stress, endothelial dysfunction, the presence of an anti-angiogenic state, and intravascular inflammation, among others. In this review, we provide a comprehensive overview of the cellular immune responses involved in the pathogenesis of preeclampsia. Specifically, we summarize the role of innate and adaptive immune cells in the maternal circulation, reproductive tissues, and at the maternal-fetal interface of women affected by this pregnancy complication. The major cellular subsets involved in the pathogenesis of preeclampsia are regulatory T cells, effector T cells, NK cells, monocytes, macrophages, and neutrophils. We also summarize the literature on those immune cells that have been less characterized in this clinical condition, such as γδ T cells, invariant natural killer T cells, dendritic cells, mast cells, and B cells. Moreover, we discuss in vivo studies utilizing a variety of animal models of preeclampsia to further support the role of immune cells in this disease. Finally, we highlight the existing gaps in knowledge of the immunobiology of preeclampsia that require further investigation. The goal of this review is to promote translational research leading to clinically relevant strategies that can improve adverse perinatal outcomes resulting from the obstetrical syndrome of preeclampsia.

Obesity and Maternal-Placental-Fetal Immunology and Health

Obesity rates in women of childbearing age is now at 29%, according to recent CDC reports. It is known that obesity is associated with oxidative stress and inflammation, including disruptions in cellular function and cytokine levels. In pregnant women who are obese, associated placental dysfunction can lead to small for gestational age (SGA) infants. More frequently, however, maternal obesity is associated with large for gestational age (LGA) newborns, who also have higher incidence of metabolic disease and asthma due to elevated levels of inflammation. In addition, anthropogenic environmental exposures to "endocrine disrupting" and "forever" chemicals affect obesity, as well as maternal physiology, the placenta, and fetal development. Placental function is intimately associated with the control of inflammation during pregnancy. There is a large amount of literature examining the relationship of placental immunology, both cellular and humoral, with pregnancy and neonatal outcomes. Cells such as placental macrophages and NK cells have been implicated in spontaneous miscarriage, preeclampsia, preterm birth, perinatal neuroinflammation, and other post-natal conditions. Differing levels of placental cytokines and molecular inflammatory mediators also have known associations with preeclampsia and developmental outcomes. In this review, we will specifically examine the literature regarding maternal, placental, and fetal immunology and how it is altered by maternal obesity and environmental chemicals. We will additionally describe the relationship between placental immune function and clinical outcomes, including neonatal conditions, autoimmune disease, allergies, immunodeficiency, metabolic and endocrine conditions, neurodevelopment, and psychiatric disorders.

Total Th1/Th2 cytokines profile from peripheral blood lymphocytes in normal pregnancy and preeclampsia syndrome

To evaluate total Th1/Th2 cytokines in CD3⁺ cells (immunocompetent T-lymphocytes) and peripheral blood lymphocytes, mostly CD4+ (T helper cells) and CD8+ (T-cytotoxic cells) subpopulations in preeclampsia. Total blood leukocytes and lymphocytes counts, percent cells: CD3⁺, INF-g⁺/CD3⁺, IL-4⁺/CD3⁺, and IL-10⁺/CD3⁺, CD4⁺/CD8⁺ were determined by flow-cytometry. Preeclampsia (n= 26) and normal pregnancy (n= 25) participants were age and gestational age matched. CD4⁺ lymphocytes count was higher in preeclampsia, compared with normal pregnancy (43.6 ± 5.8 vs 37.6 ± 5.6%; P< 0.001). CD3⁺ cells Th1/Th2 shift was not detected in preeclampsia, yet may be present in other cell types, such as CD4⁺ and CD3 - lymphocytes.

The implications of the purinergic signaling throughout pregnancy

Purinergic signaling is a necessary mechanism to trigger or even amplify cell communication. Its ligands, notably adenosine triphosphate (ATP) and adenosine, modulate specific membrane-bound receptors in virtually all human cells. Regardless of the stage of the pregnancy, cellular communication between maternal, placental, and fetal cells is the paramount mechanism to sustain its optimal status. In this review, we describe the crucial role of purinergic signaling on the regulation of the maternal-fetal trophic exchanges, immune control, and endocrine exchanges throughout pregnancy. The nature of the modulation of both ATP and adenosine on the embryo-maternal interface, going through placental invasion until birth delivery depends on the general maternal-fetal health state and consequently on the selective activation of their specific receptors. In addition, an increasing number of studies have been demonstrating the pivotal role of ATP and adenosine in modulating deleterious effects of suboptimal conditions of pregnancy. Here, we discuss the role of purinergic signaling on the balance that coordinates the embryo-maternal exchanges and a promising therapeutic venue in the context of pregnancy disorders.

Immunological comparison of pregnant Dahl salt-sensitive and Sprague-Dawley rats commonly used to model characteristics of preeclampsia

The pregnant Dahl salt-sensitive (S) rat is an established preclinical model of superimposed spontaneous preeclampsia characterized by exacerbated hypertension, increased urinary protein excretion, and increased fetal demise. Because of the underlying immune system dysfunction present in preeclamptic pregnancies in humans, we hypothesized that the pregnant Dahl S rat would also have an altered immune status. Immune system activation was assessed during late pregnancy in the Dahl S model and compared with healthy pregnant Sprague-Dawley (SD) rats subjected to either a sham procedure or a procedure to reduce uterine perfusion pressure (RUPP). Circulating immunoglobulin and cytokine levels were measured by enzyme-linked immunosorbent assay (ELISA) and Milliplex bead assay, respectively, and percentages of circulating, splenic, and placental immune cells were determined using flow cytometry. The pregnant Dahl S rat exhibited an increase in CD4+ T cells, and specifically TNFα+CD4+ T cells, in the spleen compared with virgin Dahl S rats. The Dahl also had increased neutrophils and decreased B cells in the peripheral blood as compared with Dahl virgin rats. SD rats that received the RUPP procedure had increases in circulating monocytes and increased IFN-ɣ+CD4+ splenic T cells. Together these findings suggest that dysregulated T cell activity is an important factor in both the pregnant Dahl S rats and SD rats after the RUPP procedure.

Gap junction-mediated cell-cell interaction between transplanted mesenchymal stem cells and vascular endothelium in stroke

We have shown previously that transplanted bone marrow mononuclear cells (BM-MNC), which are a cell fraction rich in hematopoietic stem cells, can activate cerebral endothelial cells via gap junction-mediated cell-cell interaction. In the present study, we investigated such cell-cell interaction between mesenchymal stem cells (MSC) and cerebral endothelial cells. In contrast to BM-MNC, for MSC we observed suppression of vascular endothelial growth factor uptake into endothelial cells and transfer of glucose from endothelial cells to MSC in vitro. The transfer of such a small molecule from MSC to vascular endothelium was subsequently confirmed in vivo and was followed by suppressed activation of macrophage/microglia in stroke mice. The suppressive effect was absent by blockade of gap junction at MSC. Furthermore, gap junction-mediated cell-cell interaction was observed between circulating white blood cells and MSC. Our findings indicate that gap junction-mediated cell-cell interaction is one of the major pathways for MSC-mediated suppression of inflammation in the brain following stroke and provides a novel strategy to maintain the blood-brain barrier in injured brain. Furthermore, our current results have the potential to provide a novel insight for other ongoing clinical trials that make use of MSC transplantation aiming to suppress excess inflammation, as well as other diseases such as COVID-19 (coronavirus disease 2019).

Gestational Diabetes Mellitus and Maternal Immune Dysregulation: What We Know So Far

Gestational diabetes mellitus (GDM) is an obstetric complication that affects approximately 5-10% of all pregnancies worldwide. GDM is defined as any degree of glucose intolerance with onset or first recognition during pregnancy, and is characterized by exaggerated insulin resistance, a condition which is already pronounced in healthy pregnancies. Maternal hyperglycaemia ensues, instigating a 'glucose stress' response and concurrent systemic inflammation. Previous findings have proposed that both placental and visceral adipose tissue play a part in instigating and mediating this low-grade inflammatory response which involves altered infiltration, differentiation and activation of maternal innate and adaptive immune cells. The resulting maternal immune dysregulation is responsible for exacerbation of the condition and a further reduction in maternal insulin sensitivity. GDM pathology results in maternal and foetal adverse outcomes such as increased susceptibility to diabetes mellitus development and foetal neurological conditions. A clearer understanding of how these pathways originate and evolve will improve therapeutic targeting. In this review, we will explore the existing findings describing maternal immunological adaption in GDM in an attempt to highlight our current understanding of GDM-mediated immune dysregulation and identify areas where further research is required.

The Role of B Cells in PE Pathophysiology: A Potential Target for Perinatal Cell-Based Therapy?

The pathophysiology of preeclampsia (PE) is poorly understood; however, there is a large body of evidence that suggests a role of immune cells in the development of PE. Amongst these, B cells are a dominant element in the pathogenesis of PE, and they have been shown to play an important role in various immune-mediated diseases, both as pro-inflammatory and regulatory cells. Perinatal cells are defined as cells from birth-associated tissues isolated from term placentas and fetal annexes and more specifically from the amniotic membrane, chorionic membrane, chorionic villi, umbilical cord (including Wharton's jelly), the basal plate, and the amniotic fluid. They have drawn particular attention in recent years due to their ability to modulate several aspects of immunity, making them promising candidates for the prevention and treatment of various immune-mediated diseases. In this review we describe main findings regarding the multifaceted in vitro and in vivo immunomodulatory properties of perinatal cells, with a focus on B lymphocytes. Indeed, we discuss evidence on the ability of perinatal cells to inhibit B cell proliferation, impair B cell differentiation, and promote regulatory B cell formation. Therefore, the findings discussed herein unveil the possibility to modulate B cell activation and function by exploiting perinatal immunomodulatory properties, thus possibly representing a novel therapeutic strategy in PE.

Transcriptomic Profiling of Human Placenta in Gestational Diabetes Mellitus at the Single-Cell Level

Gestational diabetes mellitus (GDM) is associated with an increased risk of adverse pregnancy outcomes. Increasing evidence shows that placentation defects may play important roles in GDM. However, our understanding of the human placenta remains limited. In this study, we generated a comprehensive transcriptomic profile of cellular signatures and transcriptomes in the human placenta in GDM using single-cell RNA sequencing (scRNA-seq), constructed a comprehensive cell atlas, and identified cell subtypes and subtype-specific marker genes. In addition, we investigated the placental cellular function and intercellular interactions in GDM. These findings help to elucidate the molecular mechanisms of GDM, and may facilitate the development of new approaches to GDM treatment and prevention.

Immunological Changes in Pregnancy and Its Relation to COVID-19 Infection

This chapter describes the immunological adaptation to pregnancy. A special focus is drawn on the susceptibility to viral infections, especially COVID-19. Older literature refers to the pregnancy as an immunosuppressive state, while recent studies show an immunomodulation to adapt to the growing semiallograftic fetus. Despite this, pregnant women are not susceptible to all viral infections. Regarding influenza, pregnant women are not more susceptible to the infection, but more severe maternal courses. To prevent this, influenza vaccination is recommended for pregnant women. Based on the available evidence, pregnant patients are also not more susceptible to infection with regard to COVID-19 infection. Yet, more severe courses are described throughout gestation with the onset of obstetrical complications.

NLRP3 inflammasome: a new therapeutic target for high-risk reproductive disorders?

ABSTRACT

The NOD-like receptor protein 3 (NLRP3) inflammasome is a key regulator of the host's immune response, and many immune and metabolic disorders are linked to its activation. This review aimed to investigate and clarify the relationship between this inflammasome and high-risk reproductive disorders. Papers cited here were retrieved from PubMed up to August 2020 using the keywords "NLRP3" or "NALP3", "caspase-1", "endometriosis", "gestational diabetes", "interleukin (IL)-18", "IL-1β", "pre-eclampsia (PE)", "preterm birth", "polycystic ovarian syndrome (PCOS)", "recurrent spontaneous abortion (RSA)", and combinations of these terms. The results show that NLRP3 inflammasome is associated with various high-risk reproductive disorders and many inflammatory factors are secreted during its activation, such as IL-1β induced during the development of endometriosis. PCOS is also associated with activation of the NLRP3 inflammasome, especially in overweight patients. It also participates in the pathogenesis of RSA and is activated in fetal membranes before preterm birth. The placentas of pregnant women with PE show higher expression of the NLRP3 inflammasome, and gestational diabetes mellitus occurs simultaneously with its activation. Current evidence suggest that the NLRP3 inflammasome plays an important role in female reproductive disorders. New treatment and management methods targeting it might help reduce the incidence of such disorders and improve neonatal outcomes.

Maternal Immunological Adaptation During Normal Pregnancy

The risk and severity of specific infections are increased during pregnancy due to a combination of physiological and immunological changes. Characterizing the maternal immune system during pregnancy is important to understand how the maternal immune system maintains tolerance towards the allogeneic fetus. This may also inform strategies to prevent maternal fatalities due to infections and optimize maternal vaccination to best protect the mother-fetus dyad and the infant after birth. In this review, we describe what is known about the immunological changes that occur during a normal pregnancy.

Extracellular vesicles: Mediators of embryo-maternal crosstalk during pregnancy and a new weapon to fight against infertility

In modern-day life, infertility is one of the major issues that can affect an individual, both physically and psychologically. Several anatomical, physiological, and genetic factors might contribute to the infertility of an individual. Intercellular communication between trophectoderm and endometrial epithelium triggers successful embryo implantation and thereby establishes pregnancy. Recent studies demonstrate that Extracellular vesicles (EVs) are emerging as one of the crucial components that are involved in embryo-maternal communication and promote pregnancy. Membrane-bound EVs release several secreted factors within the uterine fluid, which mediates an intermolecular transfer of EVs' cargos between blastocysts and endometrium. Emerging evidences indicate that several events like imbalance in the release of endometrial or placenta-derived EVs (exosomes/MVs), uptake of their content, failure of embryo selection might lead to implantation failure. Here in this review, we have discussed the current knowledge of the involvement of EVs in maternal-fetal communications during implantation and also highlighted the EVs' rejuvenating ability to overcome infertility-related issues. We also discussed the alteration of the EVs' cargo in different pathological conditions that lead to infertility. Therefore, this review would give a better understanding of EVs' contribution in successful embryo implantation, which could help in the development of new diagnostic tools and cell-free biologics to improve the in vivo reproductive process and to treat infertility by restoring normal reproductive functions.

In-depth characterization of monocyte subsets during the course of healthy pregnancy

Pregnancy represents an immunological challenge for the maternal immune system. Pregnancy augments innate immune responses, and particularly monocytes contribute to maintaining the balance between pro- and anti-inflammatory immune responses required for the successful sequence of distinct immunological phases throughout pregnancy. Nonetheless, studies that focus on the heterogeneity of monocytes and analyze the alteration of monocyte subsets in a longitudinal approach throughout healthy pregnancies have remained scarce. In this study, we characterized the gradual phenotypic changes of monocyte subsets and the secretory potential of bulk monocytes in peripheral blood mononuclear cells of healthy pregnant women from a population-based prospective birth cohort study. Blood samples at predefined time points were analyzed using flow cytometry for in-depth characterization of monocyte subsets, which confirmed a shift from classical towards intermediate monocytes throughout pregnancy. Principal component analysis revealed characteristic phenotypic changes on monocyte subsets, especially on the intermediate monocyte subset, throughout pregnancy. Pregnancy-related hormones were measured in serum and β-human chorionic gonadotropin levels were significantly associated with expression of CD11b, CD116 and CCR2 on monocyte subsets. TLR4 and TLR7/8 stimulation of monocytes furthermore showed reduced polycytokine production towards the end of pregnancy. These data provide a comprehensive overview of phenotypic changes and secretory potential of monocytes in healthy pregnant women and establish a selective contribution of different monocyte subsets to healthy pregnancy. The results from this study therefore build a basis for future comparisons and evaluation of women with adverse pregnancy outcomes.

Microbiota Induced Changes in the Immune Response in Pregnant Mice

Pregnancy is associated with adaptations of the immune response and with changes in the gutmicrobiota. We hypothesized the gut microbiota are involved in inducing (part of) the immunological adaptations during pregnancy. To test this hypothesis, we collected feces from pregnant conventional mice before and during pregnancy (days 7, 14, and 18) and microbiota were measured using 16S RNA sequencing. At day 18, mice were sacrificed and splenic (various Th cell populations) and blood immune cells (monocyte subsets) were measured by flow cytometry. The data were compared with splenic and blood immune cell populations from pregnant (day 18) germfree mice and non-pregnant conventional and germfree mice. Finally, the abundances of the individual gut bacteria in the microbiota of each conventional pregnant mouse were correlated to the parameters of the immune response of the same mouse. The microbiota of conventional mice were significantly different at the end of pregnancy (day 18) as compared with pre-pregnancy (Permanova, p < 0.05). The Shannon index was decreased and the Firmicutes/Bacteroidetes ratio was increased (Friedman followed by Dunn's test, p < 0.05), while abundances of various species (such as Allobaculum stercoricanis, Barnesiella intestihominis, and Roseburia faecis) were significantly different at day 18 compared with pre-pregnancy. In pregnant conventional mice, the percentage of Th1 cells was decreased, while the percentages of Treg cells and Th2 cells were or tended to be increased vs. non-pregnant mice. In germfree mice, only the percentage of Th1 cells was decreased in pregnant vs. non-pregnant mice, with no effect of pregnancy on Treg and Th2 cells. The percentages of monocyte subsets were affected by pregnancy similarly in conventional and germfree mice. However, the activation status of monocytes (expression of CD80 and MHCII) was affected by pregnancy mainly in conventional mice, and not in germfree mice. Correlation (Spearman's coefficient) of pregnancy affected microbiota with pregnancy affected immune cells, i.e., immune cells that were only affected differently in conventional mice and germfree mice, showed 4 clusters of bacteria and 4 clusters of immune cells, some of these clusters were correlated with each other. For instance, the microbiota in cluster 1 and 2 (in which there were various short chain fatty acid producing microbiota) are positively correlated with immune cells in cluster B, containing Treg cells and Th2 cells. Microbiota and immune cells are affected by pregnancy in mice. The different immunological adaptations to pregnancy between conventional and germfree mice, such as the increase in Treg and tendency to an increase in Th2 cells in conventional pregnant mice only, may suggest that the microbiota may play a role in adapting the maternal immune response to pregnancy.

Role of the NLRP3 Inflammasome in Preeclampsia

Reproduction involves tightly regulated series of events and the immune system is involved in an array of reproductive processes. Disruption of well-controlled immune functions leads to infertility, placental inflammation, and numerous pregnancy complications, including preeclampsia (PE). Inflammasomes are involved in the process of pathogen clearance and sterile inflammation. They are large multi-protein complexes that are located in the cytosol and play key roles in the production of the pivotal inflammatory cytokines, interleukin (IL)-1β and IL-18, and pyroptosis. The nucleotide-binding oligomerization domain, leucine-rich repeat-, and pyrin domain-containing 3 (NLRP3) inflammasome is a key mediator of sterile inflammation induced by various types of damage-associated molecular patterns (DAMPs). Recent evidence indicates that the NLRP3 inflammasome is involved in pregnancy dysfunction, including PE. Many DAMPs (uric acid, palmitic acid, high-mobility group box 1, advanced glycation end products, extracellular vesicles, cell-free DNA, and free fatty acids) are increased and associated with pregnancy complications, especially PE. This review focuses on the role of the NLRP3 inflammasome in the pathophysiology of PE.

Human labour is associated with altered regulatory T cell function and maternal immune activation

During human pregnancy, regulatory T cell (T_reg ) function is enhanced and immune activation is repressed allowing the growth and development of the feto-placental unit. Here, we have investigated whether human labour is associated with a reversal of the pregnancy-induced changes in the maternal immune system. We tested the hypothesis that human labour is associated with a decline in T_reg function, specifically their ability to modulate Toll-like receptor (TLR)-induced immune responses. We studied the changes in cell number, activation status and functional behaviour of peripheral blood, myometrial (myoMC) and cord blood mononuclear cells (CBMC) with the onset of labour. We found that T_reg function declines and that T_reg cellular targets change with labour onset. The changes in T_reg function were associated with increased activation of myoMC, assessed by their expression of major histocompatibility complex (MHC) class II molecules and CBMC inflammatory cells. The innate immune system showed increased activation, as shown by altered monocyte and neutrophil cell phenotypes, possibly to be ready to respond to microbial invasion after birth or to contribute to tissue remodelling. Our results highlight changes in the function of the adaptive and innate immune systems that may have important roles in the onset of human labour.

Role of the Monocyte-Macrophage System in Normal Pregnancy and Preeclampsia

The proper functioning of the monocyte-macrophage system, an important unit of innate immunity, ensures the normal course of pregnancy. In this review, we present the current data on the origin of the monocyte-macrophage system and its functioning in the female reproductive system during the ovarian cycle, and over the course of both normal and complicated pregnancy. Preeclampsia is a crucial gestation disorder characterized by pronounced inflammation in the maternal body that affects the work of the monocyte-macrophage system. The effects of inflammation at preeclampsia manifest in changes in monocyte counts and their subset composition, and changes in placental macrophage counts and their polarization. Here we summarize the recent data on this issue for both the maternal organism and the fetus. The influence of estrogen on macrophages and their altered levels in preeclampsia are also discussed.

The role of autoimmunity in women with type 1 diabetes and adverse pregnancy outcome: A missing link

The incidence of pregnancy complications in women with type 1 Diabetes Mellitus (T1D) is greater than in healthy pregnant women. This has mostly been attributed to hyperglycemia. However, despite the implementation of stricter guidelines regarding glycemic control, pregnancy complications remain more common in women with T1D. This may suggest that other etiological factors are involved. We suggest that the immune response may play a role, since the immune response has to adapt during pregnancy in order to facilitate implantation, placental and fetal development, and aberrant immunological adaptations to pregnancy are involved in various pregnancy complications. Since T1D is an autoimmune disorder, the question rises whether the immune response of women with T1D is able to adapt properly during pregnancy. Here we review the current proof and views on the role of aberrant immunological adaptations in pregnancy complications and whether such aberrant adaptations could be involved in the pregnancy complications of T1D patients.

Placental CX3CL1 is Deregulated by Angiotensin II and Contributes to a Pro-Inflammatory Trophoblast-Monocyte Interaction

CX3CL1, which is a chemokine involved in many aspects of human pregnancy, is a membrane-bound chemokine shed into circulation as a soluble isoform. Placental CX3CL1 is induced by inflammatory cytokines and is upregulated in severe early-onset preeclampsia. In this study, the hypothesis was addressed whether angiotensin II can deregulate placental CX3CL1 expression, and whether CX3CL1 can promote a pro-inflammatory status of monocytes. qPCR analysis of human placenta samples (n = 45) showed stable expression of CX3CL1 and the angiotensin II receptor AGTR1 throughout the first trimester, but did not show a correlation between both or any influence of maternal age, BMI, and gestational age. Angiotensin II incubation of placental explants transiently deregulated CX3CL1 expression, while the angiotensin II receptor antagonist candesartan reversed this effect. Overexpression of recombinant human CX3CL1 in SGHPL-4 trophoblasts increased adhesion of THP-1 monocytes and significantly increased IL8, CCL19, and CCL13 in co-cultures with human primary monocytes. Incubation of primary monocytes with CX3CL1 and subsequent global transcriptome analysis of CD16⁺ subsets revealed 81 upregulated genes, including clusterin, lipocalin-2, and the leptin receptor. Aldosterone synthase, osteopontin, and cortisone reductase were some of the 66 downregulated genes present. These data suggest that maternal angiotensin II levels influence placental CX3CL1 expression, which, in turn, can affect monocyte to trophoblast adhesion. Release of placental CX3CL1 could promote the pro-inflammatory status of the CD16⁺ subset of maternal monocytes.

Roles of microRNAs in preeclampsia

Preeclampsia (PE) is a complex disorder that is characterized by hypertension and proteinuria after the 20th week of pregnancy, and it causes most neonatal morbidity and perinatal mortality. Most studies suggest that placental dysfunction is the main cause of PE. However, genetic factors, immune factors, and systemic inflammation are also related to the pathophysiology of this syndrome. Thus far, the exact pathogenesis of PE is not yet fully understood, and intense research efforts are focused on PE to elucidate the pathophysiological mechanisms. MicroRNAs (miRNAs) refer to small single-stranded and noncoding molecules that can negatively regulate gene expression, and miRNA regulatory networks play an important role in diverse pathological processes. Many studies have confirmed deregulated miRNA in pregnant patients with PE, and the function and mechanism of these differentially expressed miRNA are gradually being revealed. In this review, we summarize the current research about miRNA involved in PE, including placenta-specific miRNA, their predictive value, and their function in the development of PE. This review will provide fundamental evidence of miRNA in PE, and further studies are necessary to explore the roles of miRNA in the early diagnosis and treatment of PE.