Maternal hybrid immunity and risk of infant COVID-19 hospitalizations: national case-control study in Israel.

Hybrid immunity, acquired through vaccination followed or preceded by a COVID-19 infection, elicits robust antibody augmentation. We hypothesize that maternal hybrid immunity will provide greater infant protection than other forms of COVID-19 immunity in the first 6 months of life. We conducted a case-control study in Israel, enrolling 661 infants up to 6 months of age, hospitalized with COVID-19 (cases) and 59,460 age-matched non-hospitalized infants (controls) between August 24, 2021, and March 15, 2022. Infants were grouped by maternal immunity status at delivery: Naïve (never vaccinated or tested positive, reference group), Hybrid-immunity (vaccinated and tested positive), Natural-immunity (tested positive before or during the study period), Full-vaccination (two-shot regimen plus 1 booster), and Partial-vaccination (less than full three shot regimen). Applying Cox proportional hazards models to estimate the hazard ratios, which was then converted to percent vaccine effectiveness, and using the Naïve group as the reference, maternal hybrid-immunity provided the highest protection (84% [95% CI 75-90]), followed by full-vaccination (66% [95% CI 56-74]), natural-immunity (56% [95% CI 39-68]), and partial-vaccination (29% [95% CI 15-41]). Maternal hybrid-immunity was associated with a reduced risk of infant hospitalization for Covid-19, as compared to natural-immunity, regardless of exposure timing or sequence. These findings emphasize the benefits of vaccinating previously infected individuals during pregnancy to reduce COVID-19 hospitalizations in early infancy.

Pregnancy trained decidual NK cells protect pregnancies from harmful Fusobacterium nucleatum infection.

Natural killer cells (NKs) found during pregnancy at the maternal-fetal interface named decidual (d)NKs, show signs of education following first pregnancy, resulting in better placentation and fetus-growth, hence termed pregnancy trained dNKs (PTdNKs). Here we show that PTdNKs provide increased protection of the fetus from Fusobacterium nucleatum (FN) infection. We demonstrate that PTdNKs secrete elevated amounts of the bacteriocidal protein granulysin (GNLY) upon incubation with FN compared to dNKs derived from first pregnancies, which leads to increased killing of FN. Furthermore, we showed mechanistically that the GNLY secretion is mediated through the interaction of the FN's Fap2 protein with Gal-GalNAc present on PTdNKs. Finally, we show in vivo, using GNLY-tg mice that enhanced protection of the fetuses from FN infection is observed, as compared to wild type and that this enhance protection is NK cell dependent. Altogether, we show a new function for PTdNKs as protectors of the fetus from bacterial infection.

Expert review: preeclampsia Type I and Type II.

Pregnancy involves an interplay between maternal and fetal factors affecting changes to maternal anatomy and physiology to support the developing fetus and ensure the well-being of both the mother and offspring. A century of research has provided evidence of the imperative role of the placenta in the development of preeclampsia. Recently, a growing body of evidence has supported the adaptations of the maternal cardiovascular system during normal pregnancy and its maladaptation in preeclampsia. Debate surrounds the roles of the placenta vs the maternal cardiovascular system in the pathophysiology of preeclampsia. We proposed an integrated model of the maternal cardiac-placental-fetal array and the development of preeclampsia, which reconciles the disease phenotypes and their proposed origins, whether placenta-dominant or maternal cardiovascular system-dominant. These phenotypes are sufficiently diverse to define 2 distinct types: preeclampsia Type I and Type II. Type I preeclampsia may present earlier, characterized by placental dysfunction or malperfusion, shallow trophoblast invasion, inadequate spiral artery conversion, profound syncytiotrophoblast stress, elevated soluble fms-like tyrosine kinase-1 levels, reduced placental growth factor levels, high peripheral vascular resistance, and low cardiac output. Type I is more often accompanied by fetal growth restriction, and low placental growth factor levels have a measurable impact on maternal cardiac remodeling and function. Type II preeclampsia typically occurs in the later stages of pregnancy and entails an evolving maternal cardiovascular intolerance to the demands of pregnancy, with a moderately dysfunctional placenta and inadequate blood supply. The soluble fms-like tyrosine kinase-1-placental growth factor ratio may be normal or slightly disturbed, peripheral vascular resistance is low, and cardiac output is high, but these adaptations still fail to meet demand. Emergent placental dysfunction, coupled with an increasing inability to meet demand, more often appears with fetal macrosomia, multiple pregnancies, or prolonged pregnancy. Support for the notion of 2 types of preeclampsia observable on the molecular level is provided by single-cell transcriptomic survey of gene expression patterns across different cell classes. This revealed widespread dysregulation of gene expression across all cell types, and significant imbalance in fms-like tyrosine kinase-1 (FLT1) and placental growth factor, particularly marked in the syncytium of early preeclampsia cases. Classification of preeclampsia into Type I and Type II can inform future research to develop targeted screening, prevention, and treatment approaches.

Pluripotency-independent induction of human trophoblast stem cells from fibroblasts.

Human trophoblast stem cells (hTSCs) can be derived from embryonic stem cells (hESCs) or be induced from somatic cells by OCT4, SOX2, KLF4 and MYC (OSKM). Here we explore whether the hTSC state can be induced independently of pluripotency, and what are the mechanisms underlying its acquisition. We identify GATA3, OCT4, KLF4 and MYC (GOKM) as a combination of factors that can generate functional hiTSCs from fibroblasts. Transcriptomic analysis of stable GOKM- and OSKM-hiTSCs reveals 94 hTSC-specific genes that are aberrant specifically in OSKM-derived hiTSCs. Through time-course-RNA-seq analysis, H3K4me2 deposition and chromatin accessibility, we demonstrate that GOKM exert greater chromatin opening activity than OSKM. While GOKM primarily target hTSC-specific loci, OSKM mainly induce the hTSC state via targeting hESC and hTSC shared loci. Finally, we show that GOKM efficiently generate hiTSCs from fibroblasts that harbor knockout for pluripotency genes, further emphasizing that pluripotency is dispensable for hTSC state acquisition.

Maternal third dose of BNT162b2 mRNA vaccine and risk of infant COVID-19 hospitalization.

Infants are at a higher risk of Coronavirus Disease 2019 (COVID-19)-related hospitalizations compared to older children. In this study, we investigated the effect of the recommended third maternal dose of BNT162b2 COVID-19 vaccine during pregnancy on rates of infant COVID-19-related hospitalizations. We conducted a nationwide cohort study of all live-born infants delivered in Israel between 24 August 2021 and 15 March 2022 to estimate the effectiveness of the third booster dose versus the second dose against infant COVID-19-related hospitalizations. Data were analyzed for the overall study period, and the Delta and Omicron periods were analyzed separately. Cox proportional hazard regression models estimated hazard ratios and 95% confidence intervals (CIs) for infant hospitalizations according to maternal vaccination status at delivery. Among 48,868 live-born infants included in the analysis, rates of COVID-19 hospitalization were 0.4%, 0.6% and 0.7% in the third-dose, second-dose and unvaccinated groups, respectively. Compared to the second dose, the third dose was associated with reduced infant hospitalization with estimated effectiveness of 53% (95% CI: 36-65%). Greater protection was associated with a shorter interval between vaccination and delivery. A third maternal dose during pregnancy reduced the risk of infant hospitalization for COVID-19 during the first 4 months of life, supporting clinical and public health guidance for maternal booster vaccination to prevent infant COVID-19 hospitalization.

Boosting maternal and neonatal anti-SARS-CoV-2 humoral immunity using a third mRNA vaccine dose.

BACKGROUND: To minimize COVID-19 pandemic burden and spread, 3-dose vaccination campaigns commenced worldwide. Since patients who are pregnant are at increased risk for severe disease, they were recently included in that policy, despite the lack of available evidence regarding the impact of a third boosting dose during pregnancy, underscoring the urgent need for relevant data. We aimed to characterize the effect of the third boosting dose of mRNA Pfizer BNT162b2 vaccine in pregnancy. METHODS: We performed a prospective cohort study of anti-SARS-CoV-2 antibody titers (n = 213) upon delivery in maternal and cord blood of naive fully vaccinated parturients who received a third dose (n = 86) as compared with 2-dose recipients (n = 127). RESULTS: We found a robust surge in maternal and cord blood levels of anti-SARS-CoV-2 titers at the time of delivery, when comparing pregnancies in which the mother received a third boosting dose with 2-dose recipients. The effect of the third boosting dose remained significant when controlling for the trimester of last exposure, suggesting additive immunity extends beyond that obtained after the second dose. Milder side effects were reported following the third dose, as compared with the second vaccine dose, among the fully vaccinated group. CONCLUSION: The third boosting dose of mRNA Pfizer BNT162b2 vaccine augmented maternal and neonatal immunity with mild side effects. These data provide evidence to bolster clinical and public health guidance, reassure patients, and increase vaccine uptake among patients who are pregnant. FUNDING: Israel Science Foundation KillCorona grant 3777/19; Research grant from the "Ofek" Program of the Hadassah Medical Center.

Effectiveness of a third BNT162b2 mRNA COVID-19 vaccination during pregnancy: a national observational study in Israel.

The Centers for Disease Control (CDC) recommend a third dose of COVID-19 vaccine for pregnant women, although data regarding effectiveness during pregnancy are lacking. This national, population-based, historical cohort study of pregnant women in Israel, delivering between August 1, 2021 and March 22, 2022, aims to analyze and compare the third and second doses' vaccine effectiveness in preventing COVID-19-related hospitalizations during pregnancy during two COVID-19 waves (Delta variant in the summer of 2021 and Omicron, BA.1, variant in the winter of 2022). Time-dependent Cox proportional-hazards regression models estimate the hazard ratios (HR) and 95% confidence intervals (CI) for COVID-related outcomes according to vaccine dose, and vaccine effectiveness as 1-HR. Study includes 82,659 and 33,303 pregnant women from the Delta and Omicron waves, respectively. Compared with the second dose, the third dose effectively prevents overall hospitalizations with SARS-CoV-2 infections, with estimated effectiveness of 92% (95% CI 83-96%) during Delta, and enhances protection against significant disease during Omicron, with effectiveness of 92% (95% CI 26-99%), and 48% (95% CI 37-57%) effectiveness against hospitalization overall. A third dose of the BNT162b2 mRNA COVID-19 vaccine during pregnancy, given at least 5 months after the second vaccine dose, enhances protection against adverse COVID-19-related outcomes.

Boosting maternal and neonatal humoral immunity following SARS-CoV-2 infection using a single messenger RNA vaccine dose.

BACKGROUND: Post-COVID-19 vaccine boosting is a potent tool in the ongoing pandemic. Relevant data regarding this approach during pregnancy are lacking, which affects vaccination policy guidance, public acceptance, and vaccine uptake during pregnancy. We aimed to investigate the dynamics of anti-SARS-CoV-2 antibody levels following SARS-CoV-2 infection during pregnancy and to characterize the effect of a single postinfection vaccine booster dose on the anti-SARS-CoV-2 antibody levels in parturients in comparison with the levels in naïve vaccinated and convalescent, nonboosted parturients. STUDY DESIGN: Serum samples prospectively collected from parturients and umbilical cords at delivery at our university-affiliated urban medical center in Jerusalem, Israel, from May to October 2021, were selected and analyzed in a case-control manner. Study groups comprised the following participants: a consecutive sample of parturients with a polymerase chain reaction-confirmed history of COVID-19 during any stage of pregnancy; and comparison groups selected according to time of exposure comprising (1) convalescent, nonboosted parturients with polymerase chain reaction-confirmed COVID-19; (2) convalescent parturients with polymerase chain reaction-confirmed COVID-19 who received a single booster dose of the BNT162b2 messenger RNA vaccine; and (3) infection-naïve, fully vaccinated parturients who received 2 doses of the BNT162b2 messenger RNA vaccine. Outcomes that were determined included maternal and umbilical cord blood anti-SARS-CoV-2 antibody levels detected at delivery, the reported side effects, and pregnancy outcomes. RESULTS: A total of 228 parturients aged 18 to 45 years were included. Of those, samples from 64 were studied to characterize the titer dynamics following COVID-19 at all stages of pregnancy. The boosting effect was determined by comparing (1) convalescent (n=54), (2) boosted convalescent (n=60), and (3) naïve, fully vaccinated (n=114) parturients. Anti-SARS-CoV-2 antibody levels detected on delivery showed a gradual and significant decline over time from infection to delivery (r=0.4371; P=.0003). Of the gravidae infected during the first trimester, 34.6% (9/26) tested negative at delivery, compared with 9.1% (3/33) of those infected during the second trimester (P=.023). Significantly higher anti-SARS-CoV-2 antibody levels were observed among boosted convalescent than among nonboosted convalescent (17.6-fold; P<.001) and naïve vaccinated parturients (3.2-fold; P<.001). Similar patterns were observed in umbilical cord blood. Side effects in convalescent gravidae resembled those in previous reports of mild symptoms following COVID-19 vaccination during pregnancy. CONCLUSION: Postinfection maternal humoral immunity wanes during pregnancy, leading to low or undetectable protective titers for a marked proportion of patients. A single boosting dose of the BNT162b2 messenger RNA vaccine induced a robust increase in protective titers for both the mother and newborn with moderate reported side effects.

Placental colonization by Fusobacterium nucleatum is mediated by binding of the Fap2 lectin to placentally displayed Gal-GalNAc.

While the existence of an indigenous placental microbiota remains controversial, several pathogens are known to be involved in adverse pregnancy outcomes. Fusobacterium nucleatum is an oral bacterium that is one of several bacteria associated with preterm birth. Oral fusobacteria translocate to the placenta hematogenously; however, the mechanisms localizing them to the placenta remain unclear. Here, using peanut agglutinin, we demonstrate that the level of Gal-GalNAc (Galß1-3GalNAc; Thomsen Friedenreich antigen) found on trophoblasts facing entering maternal blood rises during gestation and is recognized by the fusobacterial Fap2 Gal-GalNAc lectin. F. nucleatum binding to human and mouse placenta correlates with Gal-GalNAc levels and is reduced upon O-glycanase treatment or with soluble Gal-GalNAc. Fap2-inactivated F. nucleatum shows reduced binding to Gal-GalNAc-displaying placental sections. In a mouse model, intravenously injected Fap2-expressing F. nucleatum, but not a Fap2 mutant, reduces mouse fetal survival by 70%.

An integrated model of preeclampsia: a multifaceted syndrome of the maternal cardiovascular-placental-fetal array.

Maternal tolerance of the semiallogenic fetus necessitates conciliation of competing interests. Viviparity evolved with a placenta to mediate the needs of the fetus and maternal adaptation to the demands of pregnancy and to ensure optimal survival for both entities. The maternal-fetal interface is imagined as a 2-dimensional porous barrier between the mother and fetus, when in fact it is an intricate multidimensional array of tissues and resident and circulating factors at play, encompassing the developing fetus, the growing placenta, the changing decidua, and the dynamic maternal cardiovascular system. Pregnancy triggers dramatic changes to maternal hemodynamics to meet the growing demands of the developing fetus. Nearly a century of extensive research into the development and function of the placenta has revealed the role of placental dysfunction in the great obstetrical syndromes, among them preeclampsia. Recently, a debate has arisen questioning the primacy of the placenta in the etiology of preeclampsia, asserting that the maternal cardiovascular system is the instigator of the disorder. It was the clinical observation of the high rate of preeclampsia in hydatidiform mole that initiated the focus on the placenta in the etiology of the disease. Over many years of research, shallow trophoblast invasion with deficient remodeling of the maternal spiral arteries into vessels of higher capacitance and lower resistance has been recognized as hallmarks of the preeclamptic milieu. The lack of the normal decrease in uterine artery resistance is likewise predictive of preeclampsia. In abdominal pregnancies, however, an extrauterine pregnancy develops without remodeling of the spiral arteries, yet there is reduced resistance in the uterine arteries and distant vessels, such as the maternal ophthalmic arteries. Proponents of the maternal cardiovascular model of preeclampsia point to the observed maternal hemodynamic adaptations to pregnancy and maladaptation in gestational hypertension and preeclampsia and how the latter resembles the changes associated with cardiac disease states. Recognition of the importance of the angiogenic-antiangiogenic balance between placental-derived growth factor and its receptor soluble fms-like tyrosine kinase-1 and disturbance in this balance by an excess of a circulating isoform, soluble fms-like tyrosine kinase-1, which competes for and disrupts the proangiogenic receptor binding of the vascular endothelial growth factor and placental-derived growth factor, opened new avenues of research into the pathways to normal adaptation of the maternal cardiovascular and other systems to pregnancy and maladaptation in preeclampsia. The significance of the "placenta vs heart" debate goes beyond the academic: understanding the mutuality of placental and maternal cardiac etiologies of preeclampsia has far-reaching clinical implications for designing prevention strategies, such as aspirin therapy, prediction and surveillance through maternal hemodynamic studies or serum placental-derived growth factor and soluble fms-like tyrosine kinase-1 testing, and possible treatments to attenuate the effects of insipient preeclampsia on women and their fetuses, such as RNAi therapy to counteract excess soluble fms-like tyrosine kinase-1 produced by the placenta. In this review, we will present an integrated model of the maternal-placental-fetal array that delineates the commensality among the constituent parts, showing how a disruption in any component or nexus may lead to the multifaceted syndrome of preeclampsia.

Efficient maternal to neonatal transfer of antibodies against SARS-CoV-2 and BNT162b2 mRNA COVID-19 vaccine.

BACKGROUNDThe significant risks posed to mothers and fetuses by COVID-19 in pregnancy have sparked a worldwide debate surrounding the pros and cons of antenatal SARS-CoV-2 inoculation, as we lack sufficient evidence regarding vaccine effectiveness in pregnant women and their offspring. We aimed to provide substantial evidence for the effect of the BNT162b2 mRNA vaccine versus native infection on maternal humoral, as well as transplacentally acquired fetal immune response, potentially providing newborn protection.METHODSA multicenter study where parturients presenting for delivery were recruited at 8 medical centers across Israel and assigned to 3 study groups: vaccinated (n = 86); PCR-confirmed SARS-CoV-2 infected during pregnancy (n = 65), and unvaccinated noninfected controls (n = 62). Maternal and fetal blood samples were collected from parturients prior to delivery and from the umbilical cord following delivery, respectively. Sera IgG and IgM titers were measured using the Milliplex MAP SARS-CoV-2 Antigen Panel (for S1, S2, RBD, and N).RESULTSThe BNT162b2 mRNA vaccine elicits strong maternal humoral IgG response (anti-S and RBD) that crosses the placenta barrier and approaches maternal titers in the fetus within 15 days following the first dose. Maternal to neonatal anti-COVID-19 antibodies ratio did not differ when comparing sensitization (vaccine vs. infection). IgG transfer ratio at birth was significantly lower for third-trimester as compared with second trimester infection. Lastly, fetal IgM response was detected in 5 neonates, all in the infected group.CONCLUSIONAntenatal BNT162b2 mRNA vaccination induces a robust maternal humoral response that effectively transfers to the fetus, supporting the role of vaccination during pregnancy.FUNDINGIsrael Science Foundation and the Weizmann Institute Fondazione Henry Krenter.

Trophoblast lineage specific expression of the alternative splicing factor RBFOX2 suggests a role in placental development.

INTRODUCTION: RBFOX2, an RNA-binding protein, controls tissue-specific alternative splicing of exons in diverse processes of development. The progenitor cytotrophoblast of the human placenta differentiates into either the syncytiotrophoblast, formed via cell fusion, or the invasive extravillous trophoblast lineage. The placenta affords a singular system where a role for RBFOX2 in both cell invasion and cell fusion may be studied. We investigated a role for RBFOX2 in trophoblast cell differentiation, as a foundation for investigations of RBFOX2 in embryo implantation and placental development. METHODS: Immunohistochemistry of RBFOX2 was performed on placental tissue sections from three trimesters of pregnancy and from pathological pregnancies. Primary trophoblast cell culture and immunofluorescence were employed to determine RBFOX2 expression upon cell fusion. Knockdown of RBFOX2 expression was performed with ßhCG and syncytin-1 as molecular indicators of fusion. RESULTS: In both normal and pathological placentas, RBFOX2 expression was confined to the cytotrophoblast and the extravillous trophoblast, but absent from the syncytiotrophoblast. Additionally, we showed that primary trophoblasts that spontaneously fused in cell culture downregulated RBFOX2 expression. In functional experiments, knockdown expression of RBFOX2 significantly upregulated ßhCG, while the upregulation of syncytin-1 did not reach statistical significance. DISCUSSION: RBFOX2, by conferring mRNA diversity, may act as a regulator switch in trophoblast differentiation to either the fusion or invasive pathways. By studying alternative splicing we further our understanding of placental development, yielding possible insights into preeclampsia, where expression of antiangiogenic isoforms produced through alternative splicing play a critical role in disease development and severity.

The chimera-type galectin-3 is a positive modulator of trophoblast functions with dysregulated expression in gestational diabetes mellitus.

PROBLEM: From conception, a delicate regulation of galectins, a family of carbohydrate-binding proteins, is established to ensure maternal immune tolerance in pregnancy. Though galectin-3 (gal-3), the only chimera-type galectin, is abundantly expressed at the feto-maternal interface; the physiological role of this lectin during pregnancy remains to be fully elucidated and requires further investigation. METHOD OF STUDY: In this study, we analyzed serum gal-3 levels during the course of healthy gestation. Trophoblast functions were evaluated upon gal-3 exogenous stimulation using trophoblastic cell lines (e.g. , HIPEC65, SGHPL-4, and BeWo cells). Finally, we investigated variations in peripheral gal-3 levels associated with the development of spontaneous abortion and gestational diabetes mellitus (GDM). RESULTS: Gal-3 circulating levels increased as normal pregnancy progressed. In vitro experiments showed that exogenous gal-3 positively regulated trophoblast functions inducing invasion, tube formation, and fusion. Compared with normal pregnant women, circulating gal-3 levels were significantly decreased in patients who developed GDM. CONCLUSION: Our results reveal a physiological role for gal-3 during pregnancy, promoting proper trophoblast functions associated with healthy gestation. GDM is associated with a failure to increase circulating gal-3 levels late in gestation. Thus, dysregulation of gal-3 may indicate a contribution of the chimera-type lectin to this adverse pregnancy outcome.

Vaginal microbiome transplantation in women with intractable bacterial vaginosis.

We report the results of a first exploratory study testing the use of vaginal microbiome transplantation (VMT) from healthy donors as a therapeutic alternative for patients suffering from symptomatic, intractable and recurrent bacterial vaginosis (ClinicalTrials.gov NCT02236429 ). In our case series, five patients were treated, and in four of them VMT was associated with full long-term remission until the end of follow-up at 5-21 months after VMT, defined as marked improvement of symptoms, Amsel criteria, microscopic vaginal fluid appearance and reconstitution of a Lactobacillus-dominated vaginal microbiome. One patient presented with incomplete remission in clinical and laboratory features. No adverse effects were observed in any of the five women. Notably, remission in three patients necessitated repeated VMT, including a donor change in one patient, to elicit a long-standing clinical response. The therapeutic efficacy of VMT in women with intractable and recurrent bacterial vaginosis should be further determined in randomized, placebo-controlled clinical trials.

Learning from experience: cellular and molecular bases for improved outcome in subsequent pregnancies.

The frequencies of preeclampsia, fetal growth restriction, fetal demise, and low birthweight are lower in subsequent pregnancies. Enhanced maternal cardiovascular adaptation, shorter first and second stages of labor, and more robust lactation also have been observed in subsequent as compared with first pregnancies. We sought to investigate the cellular and molecular bases for better outcomes in subsequent pregnancies. Based on the knowledge that specialized immune cells at the maternal-fetal interface, decidual natural killer cells, promote development of the placental bed and conversion of the spiral arteries by secreting a myriad of angiogenic and growth factors, we asked whether decidual natural killer cells differ in subsequent as compared with first pregnancies. This idea stemmed from recent studies suggesting that natural killer cells, although part of the innate immune system, possess some features of adaptive immunity, including a certain type of immune cell memory, termed trained immunity. We found that decidual natural killer cells from parous women "remember pregnancy" and differ from decidual natural killer cells of primigravidae. Compared with the decidual natural killer cells of first pregnancy, these cells, that we termed pregnancy-trained decidual natural killer cells, express greater levels of the natural killer receptors NKG2C and leukocyte immunoglobulin-like receptor B1, which interact with ligands expressed on invasive trophoblasts. Furthermore, they secrete greater levels of several growth factors, including vascular endothelial growth factor α as well as interferon-γ, augmenting remodeling of the placental bed. We propose that this pregnancy-trained memory dwells in the epigenome, where memory of stimuli is known to persist even when the stimulus is no longer present. This epigenetic memory apparently resides in endometrial natural killer cells between pregnancies. We suggest that this trained memory, which we coined pregnancy-trained decidual natural killer cells, may be the missing link in the immune basis for enhanced subsequent pregnancy. Epigenetic memory (chromatin modification) also may afford a global explanation for additional findings of enhanced maternal cardiovascular adaptation, shorter first and second stages of labor, and more robust lactation. Understanding the molecular and cellular bases of improved outcomes of subsequent pregnancy may lead to the development of treatment modalities designed for women at high risk for pregnancy disorders originating at the maternal-fetal interface.

Trained Memory of Human Uterine NK Cells Enhances Their Function in Subsequent Pregnancies.

Natural killer cells (NKs) are abundant in the human decidua, regulating trophoblast invasion and angiogenesis. Several diseases of poor placental development are associated with first pregnancies, so we thus looked to characterize differences in decidual NKs (dNKs) in first versus repeated pregnancies. We discovered a population found in repeated pregnancies, which has a unique transcriptome and epigenetic signature, and is characterized by high expression of the receptors NKG2C and LILRB1. We named these cells Pregnancy Trained decidual NK cells (PTdNKs). PTdNKs have open chromatin around the enhancers of IFNG and VEGFA. Activation of PTdNKs led to increased production and secretion of IFN-γ and VEGFα, with the latter supporting vascular sprouting and tumor growth. The precursors of PTdNKs seem to be found in the endometrium. Because repeated pregnancies are associated with improved placentation, we propose that PTdNKs, which are present primarily in repeated pregnancies, might be involved in proper placentation.

Elevated circulating micro-ribonucleic acid (miRNA)-200b and miRNA-429 levels in anovulatory women.

OBJECTIVE: To study the role of micro-RNA (miRNA)-200b and miRNA-429 in human ovulation and to measure their expression levels in ovulatory and anovulatory patients. DESIGN: Micro-RNA-200b and miRNA-429 expression analysis in human serum and granulosa cells at different phases of the ovulation cycle in normal cycling women and women undergoing assisted reproductive technology cycles. SETTING: University-affiliated hospital and academic research laboratory. PATIENT(S): Forty women (7 normally ovulating, 15 normally ovulating with pure male infertility factor, and 18 with polycystic ovary syndrome) were included in this study. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The expression profile of circulating miRNAs and granulosa cells was assessed by means of real-time quantitative reverse transcription-polymerase chain reaction analysis. RESULT(S): We identified miRNA-200b and miRNA-429 in the sera of all women tested. These miRNA expression levels were elevated during the early follicular phase of the cycle compared with serum levels during the early luteal phase. Anovulatory women, diagnosed with polycystic ovary syndrome, expressed significantly higher levels of miRNA-200b and miRNA-429 compared with spontaneously ovulating women. Ovulation induction with exogenous gonadotropins during an IVF cycle reduced these levels to the levels measured in normal ovulating women. CONCLUSION(S): Our findings suggest an involvement of miRNA-200b and miRNA-429 in the pituitary regulation of human ovulation. Although it is unclear whether this altered miRNA expression profile is a cause or a result of anovulation, the levels of these molecules in the serum of anovulatory women may serve as serum biomarkers for the ovulation process.

microRNA in Human Reproduction.

microRNAs constitute a large family of approximately 21-nucleotide-long, noncoding RNAs. They emerged more than 20 years ago as key posttranscriptional regulators of gene expression. The regulatory role of these small RNA molecules has recently begun to be explored in the human reproductive system. microRNAs have been shown to play an important role in control of reproductive functions, especially in the processes of oocyte maturation, folliculogenesis, corpus luteum function, implantation, and early embryonic development. Knockout of Dicer, the cytoplasmic enzyme that cleaves the pre-miRNA to its mature form, results in postimplantation embryonic lethality in several animal models, attributing to these small RNA vital functions in reproduction and development. Another intriguing characteristic of microRNAs is their presence in body fluids in a remarkably stable form that is protected from endogenous RNase activity. In this chapter we will describe the current knowledge on microRNAs, specifically relating to human gonadal cells. We will focus on their role in the ovarian physiologic process and ovulation dysfunction, regulation of spermatogenesis and male fertility, and putative involvement in human normal and aberrant trophoblast differentiation and invasion through the process of placentation.