A Pregnancy and Childhood Epigenetics Consortium (PACE) meta-analysis highlights potential relationships between birth order and neonatal blood DNA methylation

Higher birth order is associated with altered risk of many disease states. Changes in placentation and exposures to in utero growth factors with successive pregnancies may impact later life disease risk via persistent DNA methylation alterations. We investigated birth order with Illumina DNA methylation array data in each of 16 birth cohorts (8164 newborns) with European, African, and Latino ancestries from the Pregnancy and Childhood Epigenetics Consortium. Meta-analyzed data demonstrated systematic DNA methylation variation in 341 CpGs (FDR adjusted P < 0.05) and 1107 regions. Forty CpGs were located within known quantitative trait loci for gene expression traits in blood, and trait enrichment analysis suggested a strong association with immune-related, transcriptional control, and blood pressure regulation phenotypes. Decreasing fertility rates worldwide with the concomitant increased proportion of first-born children highlights a potential reflection of birth order-related epigenomic states on changing disease incidence trends.

Effect of blood loss during caesarean section on coagulation parameters

INTRODUCTION

Venous thrombosis is the leading cause of pregnancy-related maternal morbidity and mortality. The thrombosis risk is increased by caesarean section and blood loss, though underlying mechanisms of these prothrombotic changes remain unknown.

MATERIALS AND METHODS

This prospective study recruited 50 pregnant women at term undergoing elective caesarean section at University Hospital Magdeburg, Germany. Blood loss during surgery was correlated with the changes in total protein S, full length TFPI (TFPI_fl), prothrombin, the endogenous thrombin potential (ETP) and resistance to activated protein C (APCsr) determined via calibrated automated thrombography.

RESULTS

Mean blood loss was 506 ml (95%CI: 456 to 557 ml). Total protein S was 0.63 (95%CI: 0.60 to 0.67) U/ml preoperatively, decreased by 14.8% after caesarean section and almost normalised five days later. TFPI_fl was 0.47 (95%CI: 0.41 to 0.53) U/ml before, remained unchanged immediately after and increased by 11.5% five days after surgery. Prothormbin was 1.10 (95%CI: 1.03 to 1.16) U/ml preoperatively, reduced by 10.4% immediately after and increased again five days after caesarean section, exceeding the preoperative values by 4.4% (-0.7 to 9.6). The ETP decreased by 3.9%, whereas the APCsr increased by 37.0% immediately after caesarean section. The changes in total protein S, prothrombin, thrombin generation and APC resistance showed a trend to be more pronounced in the subgroups with higher blood loss.

DISCUSSION

Moderate blood loss during caesarean section hardly reduces thrombin generation but aggravates pregnancy-induced APC resistance and combined deficiency of TFPI and protein S, which can account for the increased thrombosis risk in early puerperium.

Human Chorionic Gonadotropin acts as a central regulator of adaptive immune responses during early pregnancy safeguarding fetal survival

A perfect interplay between the endocrine system and the maternal immune system is pivotal for early fetal tolerance induction. Particularly, the placenta-derived hormone human chorionic gonadotropin (hCG) that is secreted during early pregnancy stages and is suggested to regulate pro- and anti-inflammatory maternal immune responses. However, the precise mechanisms underlying hCG-driven immunoregulation are far from being understood. Thus, we performed several studies to illuminate the participation of hCG in immunomodulation with a specific focus on T and B cell responses.

We included human and mouse material in our studies to analyze the influence of hCG on the generation, plasticity and functionality of regulatory T (Treg) cells, Th17 cells and B cells using different in vitro assays. In vivo, we applied hCG during the peri-implantation period into abortion-prone mice and analyzed Treg proportions and activity.

Our in vitro results revealed that hCG attracts human Treg, promotes formation of human and mouse Treg and increases T cell suppressive activity in both species. Moreover, hCG inhibits mouse Th17 differentiation and induces Th17 cells with anti-inflammatory phenotypes in the mouse system. Human B cells adopt a regulatory phenotype and start to secrete fetal-protective asymmetric antibodies upon hCG stimulation in vitro. In vivo, hCG application into abortion-prone mice restored Treg levels, augmented Treg suppressive activity and rescued fetuses from rejection.

In summary, our findings suggest that hCG contributes to early fetal tolerance induction by shifting maternal adaptive immune responses towards an anti-inflammatory profile.

Chymase-Cre; Mcl-1fl/fl Mice Exhibit Reduced Numbers of Mucosal Mast Cells

Mast cells (MCs) are considered as key effector cells in the elicitation of allergic symptoms, and they are essential players in innate and adaptive immune responses. In mice, two main types of MCs have been described: connective tissue MCs (CTMCs) and mucosal MCs (MMCs). However, little is known about the biological functions of MMCs, which is due to the lack of suitable models to investigate MMCs in vivo. Here, we aimed to generate a mouse model selectively deficient in MMCs. It has been previously described that Cre expressed under the control of the baboon α-chymase promotor is predominantly localized in MMCs. Therefore, we mated α-chymase-Cre transgenic mice with mice bearing a floxed allele of the myeloid cell leukemia sequence 1 (Mcl-1). Mcl-1 encodes for an intracellular antiapoptotic factor in MCs; hence, a selective reduction in MMCs was expected. Our results show that this new mouse model contains markedly reduced numbers of MMCs in mucosal tissues, whereas numbers of CTMCs are normal. Thus, Chm-Cre; Mcl-1^fl/fl mice are a useful tool for the investigation of the pathophysiological functions of MMCs in vivo.

Simultaneous ablation of natural killer cells and mast cells leads to poor uterine vascularization that compromises fetal-well being

Once pregnancy is established, uterine spiral arteries (SA) need to undergo dramatic remodeling to ensure a consistent blood supply to the fetus.

Here, we studied the single and joint participation of natural killer cells (NKs) and mast cells (MCs) in SA remodeling and pregnancy outcome and investigated the underlying mechanisms. We show that NK deficiency or their depletion arrested SA remodeling without affecting pregnancy. MC absence resulted in abnormally remodeled SAs and intrauterine growth restriction (IUGR). Combined absence of NKs and MCs dramatically affected SA remodeling, and impaired fetal growth. Despite abnormal Doppler measurements and dramatic IUGR, maternal maternal blood pressure was not affected. We found that a-chymase mast cell protease (Mcpt) 5 mediates apoptosis of uterine smooth muscle cells, a key feature of SA remodeling. Additionally, we report a previously unknown source for Mcpt5: uterine (u) NKs. We confirmed the importance of Mcpt5 by employing mice with selective deletion of Mcpt5+ cells: pregnant females presented un-remodeled SAs and growth-restricted progeny. The human a-chymase CMA1, phylogenetic homolog of Mcpt5, stimulated the ex vivo migration of human trophoblasts, a pre-requisite for SA remodeling.

Our results show that chymases secreted by uMCs and uNKs are pivotal to the vascular changes required to support pregnancy. Understanding the mechanisms underlying pregnancy-induced vascular changes is essential for developing therapeutic options against pregnancy complications associated with poor vascular remodeling.

Myeloid and plasmacytoid dendritic cell subsets are differentially regulated by the pregnancy hormone human Chorionic Gonadotropin

Dendritic cells (DCs) are critically involved in the establishment and maintenance of fetal tolerance. However, the precise mechanisms underlying their regulation during pregnancy are still not defined. The placenta-derived hormone human Chorionic Gonadotropin (hCG) possesses immune modulatory properties and is commonly used in artificial reproductive techniques (ART). Here, we analyzed the effect of placenta-derived hCG and two hCG preparations on different DC subsets.

After isolation from peripheral blood of non pregnant women, DCs were stimulated with LPS to induce maturation. In parallel, DCs were co-cultured with placenta-derived hCG (JEG-3 cells), with urine-derived hCG or recombinant hCG. The total number and maturation state of two myeloid DC (MDC1; MDC2) and one plasmacytoid DC subset (PDC) was evaluated. Additionally, the levels of IL-6, IL-8, IL-10, IL-12 and TNF were determined in co-culture supernatants. In all experiments, unstimulated DCs and stimulated DCs cultured alone served as controls.

JEG-3 impaired the LPS-induced increase of total MDC1 while both hCG preparations hindered the increment of total MDC1 and MDC2. Moreover, JEG-3 interfered with PDC and MDC1 maturation while both hCG preparations hampered maturation of all DC subsets. However, significant effects could only be observed on the MDC1 subset. Cytokine assays revealed that JEG-3 and both hCG preparations impaired LPS-induced secretion of all analyzed cytokines.

Our results suggest that hCG from distinct sources regulates DC subsets in a different manner. This information does not only contribute to our understanding of a differential regulation of various DC subsets during pregnancy but is also relevant for the use of hCG preparations in ART.

Human chorionic gonadotropin supports human pregnancy by induction of regulatory T cells (MUC7P.766)

Regulatory T cells (Treg) are proposed to be involved in fetal tolerance induction. However, the precise mechanisms underlying their generation and function are still not defined. Recently, we proved that the pregnancy hormone human Chorionic Gonadotropin (hCG) efficiently attracts human Treg to trophoblasts favoring a local Treg accumulation. Here we analyzed whether hCG is also involved in Treg generation and activity. Naïve T cells were isolated from blood of pregnant women and co-cultured with either hCG-producing trophoblasts (JEG-3, primary cells) or non-hCG-producing trophoblasts (HTR8, Swan71) and keratinocytes (HaCat). To confirm hCG specificity, we either blocked hCG in JEG-3 co-cultures or used urine-purified or recombinant hCG as culture supplements. Treg induction was then assessed by the expression of specific Treg markers. Furthermore suppressive function of hCG-treated naïve T cells was evaluated in a mixed leukocyte reaction. Co-culture of naïve T cells with JEG-3, primary trophoblasts or supplemented hCG resulted in a statistically significant increase in the expression of specific Treg markers as compared to co-cultures with HTR8, Swan71 or HaCat cells. Moreover, blockage of hCG in JEG-3 co-cultures impaired the up-regulation of Treg markers. Interestingly, we further confirmed an increased suppressive activity of naïve T cells after hCG treatment. Our results strongly suggest a key role for hCG in Treg generation and induction of suppressive activity.

Uterine natural killer cells: their modulation by carbon monoxide and their impact on the remodeling of spiral arteries (MUC7P.768)

Pre-eclampsia (PE) and intrauterine growth restriction (IUGR) are linked to impaired remodeling of maternal spiral arteries (SA). We previously introduced Heme Oxygenase-1 (HO-1) as a positive modulator of pregnancy. Its main mediator, carbon monoxide, could mimic HO-1 protective effects in a mouse model of Hmox1 genetic deficiency. Here, we investigated whether HO-1 deficiency is related to gestational hypertension and if CO is able to prevent PE and IUGR through the modulation of uterine NK cells (uNK) that are necessary for initiation of SA remodeling. Hmox1+/- or Hmox1-/- implantations presented fewer uNK cell numbers and lower expression of uNK-related angiogeneic factors than Hmox1+/+ sites. Quantitative histology revealed that Hmox1+/- and Hmox1-/- implantations had shallow SA development. This was accompanied by IUGR and gestational hypertension. Application of CO at low dose during early to mid-gestation prevented IUGR in Hmox1+/- mothers, being this associated with enhanced in situ proliferation of uNKs and normalization of angiogenic parameters. Most importantly, CO improved SA remodeling and normalized blood pressure, ensuring a proper fetal growth. Thus, CO emerges as a key molecular player in pregnancy success by modulating uNKs, which results in promotion of SA remodeling, adequate fetal support/growth and prevention of gestational hypertension.

Human chorionic gonadotropin and luteinizing hormone, but not progesterone, contribute to the initiation of a tolerogenic immune response in pregnancy (P3216)

The survival of the fetus in the maternal uterus is ensured by both intensive hormonal changes and a protective maternal immune response towards the fetus. We have recently reported that human Chorionic Gonadotropin (hCG) facilitates the migration of Treg to the fetal-maternal interface and supports their tolerogenic function. The role of hormones in the establishment of an antigen-specific immune response is however not well understood. Here, we investigated the effect of pregnancy hormones on the maturation state of DCs and their functionality in a model of spontaneous abortion due to disturbed tolerance. Pregnant females were treated either with hCG, Luteinizing Hormone (LH), Progesterone (P) or PBS. Pregnancy outcome and the number of total and mature DCs was evaluated in the periphery and in the uterus. The effect of hCG on DC maturation and functionality was assessed in vitro. hCG and LH application totally prevented fetal rejection while P did not. The protective effect of hCG and LH was associated with a reduction in the number of total and mature DCs in the periphery and at the fetal maternal interface. By contrast, P did not affect DC phenotype. In vitro, hCG impaired the maturation process of DCs confirming our in vivo data. Our results highlights the importance of hormones in regulating the initiation of the adaptive immune response that allows the transient acceptance of paternal antigens and thus importantly contributes to pregnancy success.

Pregnancy establishment is influenced by CCR7 and CCR9 (P6360)

Pregnancy establishment and maintenance represents a challenge for the maternal immune system. It has to be alert against pathogens while tolerating paternal alloantigens in fetal structures. The maternal immune system is not only aware of these alloantigens, but it also actively tolerates them to ensure the survival of the fetus throughout pregnancy. Regulatory T cells (Treg) are reportedly involved in this process. They are known to act in both paracrine and cell-contact dependent ways and therefore their cellular localization is essential for their functional ability of suppressing specific immune responses. Chemokines are known coordinators of leukocyte migration and our aim was to understand how these molecules influence Treg recruitment at the feto-maternal interface and interfere with pregnancy success. We found that both CCL21 and CCL25 chemokine ligands are present in the uterus before and during pregnancy and their ligands CCR7 and CCR9 are expressed in Tregs from the uterus and lymph nodes draining the uterine region. CCR7 mediated the homing of Treg to the uterus while CCR9 determined the maturation state of uterine DCs and presence of T effector cells, and both critically interfered with implantation if genetically deleted. Our data provide new insights on the mechanisms of tolerance acquisition during pregnancy.

Pregnancy establishment depends on a pre-existent population of thymic-derived uterine Foxp3+ cells while pregnancy maintenance relies on de novo converted regulatory T cells (71.1)

Pregnancy represents a challenge for the maternal immune system; it has to be alert against pathogens while tolerating paternal alloantigens in fetal structures. The maternal immune system is aware of these alloantigens, actively tolerating them to ensure the survival of the fetus. Regulatory T cells (Treg) are reportedly involved in allotolerance towards paternal antigens. In mouse models, the transfer of antigen-specific Treg can protect from immunological rejection of the fetuses. However, Treg generation and indispensability for pregnancy remained unclear. Treg accumulate during the receptive phase of the estrous cycle as documented by in vivo imaging using a 2-photon microscope. Treg depletion prior to and during very early pregnancy (foxp3.DTR mice) leads to impaired implantation, while their depletion at later time points does not interfere with gestation. Helios+ cells leave the thymus and accumulate in blood and uterus-draining lymph nodes during early pregnancy. At later stages, Foxp3+ Treg are generated de novo in the periphery as we demonstrated in a Rag-model of cell transfer. While naturally occurring Treg are needed for pregnancy establishment, their absence at later stages is compensated by the generation of Foxp3+ cells from Foxp3- cells. Our data provides new insights in the generation/ function of Treg during pregnancy, which is essential to understand natural mechanisms of tolerance acquisition.

Novel role for inhibitor of differentiation 2 in the genesis of angiotensin II-induced hypertension

BACKGROUND

Angiotensin (Ang) II-induced target-organ damage involves innate and acquired immunity. Mice deficient for the helix-loop-helix transcription factor inhibitor of differentiation (Id2(-/-)) lack Langerhans and splenic CD8a+ dendritic cells, have reduced natural killer cells, and have altered CD8 T-cell memory. We tested the hypothesis that an alteration in the number and quality of circulating blood cells caused by Id2 deletion would ameliorate Ang II-induced target-organ damage.

METHODS AND RESULTS

We used gene-deleted and transgenic mice. We conducted kidney and bone marrow transplants. In contrast to Ang II-infused Id2(+/-), Id2(-/-) mice infused with Ang II remained normotensive and failed to develop albuminuria or renal damage. Bone marrow transplant of Id2(+/-) bone marrow to Id2(-/-) mice did not restore the blunted blood pressure response to Ang II. Transplantation of Id2(-/-) kidneys to Id2(+/-) mice also could not prevent Ang II-induced hypertension and renal damage. We verified the Ang II resistance in Id2(-/-) mice in a model of local tissue Ang II production by crossing hypertensive mice transgenic for rat angiotensinogen with Id2(-/-) or Id2(+/-) mice. Angiotensinogen-transgenic Id2(+/-) mice developed hypertension, albuminuria, and renal injury, whereas angiotensinogen-transgenic Id2(-/-) mice did not. We also found that vascular smooth muscle cells from Id2(-/-) mice showed an antisenescence phenotype.

CONCLUSIONS

Our bone marrow and kidney transplant experiments suggest that alterations in circulating immune cells or Id2 in the kidney are not responsible for Ang II resistance. The present studies identify a previously undefined role for Id2 in the pathogenesis of Ang II-induced hypertension.