What are the roles of macrophages and monocytes in human pregnancy?

Monocyte profile in peripheral blood of gestational diabetes mellitus patients

OBJECTIVE

Gestational diabetes Mellitus has been considered an inflammatory disease involving different cells and mediators in its development. The role of innate immune cells in GDM physiopathology remains unclear, therefore this study was conducted to assess monocyte profile in GDM patients.

DESIGN

This was a case-control study including 20 glucose-tolerant pregnant women (controls) and 18 GDM patients.

METHODS

Flow cytometry was used to assess peripheral blood monocytes subsets (classical, intermediate, non-classical), the expression of TLR4 and CCR2 chemokine receptor (CD192) and cytokines (TNFA, IL6, IL10) secretion by monocytes subsets. In addition, sCD14 serum levels were evaluated by ELISA.

RESULTS

We observed increased percentage of CD14⁺ cells, decreased frequency of intermediate monocytes (CD14⁺CD16⁺), and lower percentage of circulating monocytes (classical, intermediate and non-classical) that express TLR4 in the diabetic group compared to controls. Soluble CD14⁺ serum levels were higher in GDM patients compared to controls. There were no differences in the expression of the CCR2 chemokine receptor and cytokines (TNFA, IL6 and IL10) secretion between the studied groups.

CONCLUSIONS

Our results demonstrated that GDM patients present impaired monocyte profile in the peripheral blood, suggesting that these cells are involved in GDM physiopathology.

Whole-transcriptome analysis delineates the human placenta gene network and its associations with fetal growth

BACKGROUND

The placenta is the principal organ regulating intrauterine growth and development, performing critical functions on behalf of the developing fetus. The delineation of functional networks and pathways driving placental processes has the potential to provide key insight into intrauterine perturbations that result in adverse birth as well as later life health outcomes.

RESULTS

We generated the transcriptome-wide profile of 200 term human placenta using the Illumina HiSeq 2500 platform and characterized the functional placental gene network using weighted gene coexpression network analysis (WGCNA). We identified 17 placental coexpression network modules that were dominated by functional processes including growth, organ development, gas exchange and immune response. Five network modules, enriched for processes including cellular respiration, amino acid transport, hormone signaling, histone modifications and gene expression, were associated with birth weight; hub genes of all five modules (CREB3, DDX3X, DNAJC14, GRHL1 and C21orf91) were significantly associated with fetal growth restriction, and one hub gene (CREB3) was additionally associated with fetal overgrowth.

CONCLUSIONS

In this largest RNA-Seq based transcriptome-wide profiling study of human term placenta conducted to date, we delineated a placental gene network with functional relevance to fetal growth using a network-based approach with superior scale reduction capacity. Our study findings not only implicate potential molecular mechanisms underlying fetal growth but also provide a reference placenta gene network to inform future studies investigating placental dysfunction as a route to future disease endpoints.

PlGF enhances TLR-dependent inflammatory responses in human mononuclear phagocytes

PROBLEM

Levels of placental growth factor (PlGF) peak during third trimester of pregnancy, a time when women are at increased risk of virus-induced morbidity. We hypothesized PlGF might contribute to an exaggerated inflammatory response to Toll-like receptor (TLR) activation.

METHOD OF STUDY

Primary human adult and cord blood CD14⁺ cells were cultured in the presence of TLR ligands and/or PlGF.

RESULTS

PlGF significantly enhanced the magnitude and duration of TNF messenger RNA and protein production by TLR-7/8-activated monocytes, and increased subsequent production of TNF-independent inflammatory cytokines. This PlGF/TLR effect involved multiple inflammatory cytokines/chemokines and was seen with the majority of TLR agonists. PlGF enhanced phosphorylation of IkappaB kinase (IKK) in monocytes stimulated with the TLR-7/8 agonist R848, and IKK inhibition completely suppressed the PlGF effect.

CONCLUSION

PlGF enhances TLR-signaling upstream of IKK and contributes to an exaggerated pathologic pro-inflammatory state in response to activation of maternal and fetal mononuclear phagocytes by specific TLR agonists.

Immunosuppressive macrophages induced by IDO1 promote the growth of endometrial stromal cells in endometriosis

It was previously demonstrated that anomalous expression of indoleamine 2,3-dioxygenase-1 (IDO1) in endometrial stromal cells (ESCs) stimulated an inflammatory response that subsequently initiated the activation of immunosuppressive macrophages in endometriosis. The aim of the present study was to clarify the effect of IDO1‑induced macrophages on the growth of ESCs in endometriosis. Normal ESCs, ectopic ESCs and normal ESCs treated with plasmid pEGFP‑N1‑IDO1 or SD11‑IDO1 short hairpin RNA were co‑cultured with peripheral blood‑derived monocyte (PBMC)‑driven macrophages directly for 48 h. Compared with normal ESCs, the PBMC‑driven macrophages that were co‑cultured with ectopic ESCs displayed a lower phagocytic ability. pEGFP‑N1‑IDO1 transfection of normal ESCs also decreased the phagocytic ability of co‑cultured macrophages. Additionally, pEGFP‑N1‑IDO1‑transfected ESC‑induced macrophages significantly increased the viability and proliferation of ESCs, while ESC apoptosis was decreased, compared with control ESCs. In conclusion, IDO1 educated-macrophages may facilitate the survival of retrograde endometrial tissues, and be involved in the pathogenesis of endometriosis.

Myometrial cytokines and their role in the onset of labour

Human labour is an inflammatory event, physiologically driven by an interaction between hormonal and mechanical factors and pathologically associated with infection, bleeding and excessive uterine stretch. The initiation and communicators of inflammation is still not completely understood; however, a key role for cytokines has been implicated. We summarise the current understanding of the nature and role of cytokines, chemokines and hormones and their involvement in signalling within the myometrium particularly during labour.

Coordinated expression of TNFα- and VEGF-mediated signaling components by placental macrophages in early and late pregnancy

INTRODUCTION

Mononuclear phagocytes are thought to significantly contribute to cytokine regulation at the maternal-foetal interface, but the role of placental macrophages has been poorly investigated. TNFα and VEGF were demonstrated to have regulatory effects on basic structures of the placenta, particularly the trophoblast and blood vessels. The aims of this study were to determine the expression of TNFα, VEGF and related receptors in placental macrophages, and how does the participation of placental macrophages alter with gestational age in TNFα- and VEGF-mediated signaling.

METHODS

Macrophages were isolated from placental villous tissue from normal pregnancies at either 9-12 or 38-40 weeks gestation. Cell surface receptors (TNFR1, TNFR2, VEGFR1, and VEGFR2) and intracellular TNFα and VEGF were quantified by flow cytometry after antibody staining. Basal and stimulated secretion of both cytokines and soluble TNF receptors was quantified by cytometric bead arrays. Secreted VEGFR1 was measured by ELISA.

RESULTS

The expression of TNFR1 and VEGFR1 was remarkably variable and did not change from first to third trimester. There was minimal basal TNFα production in the placental macrophages, but nearly all cells in the population produced VEGF. TNFα and VEGF secretion increased with gestational age accompanied by decreased secretion of the antagonists sTNFR1 and sVEGFR. Macrophages isolated from early term placentas were less effective in responding to bacterial endotoxin. Lipopolysaccharide induced increases in the secretion of TNFα, TNFR1, TNFR2, and VEGFR1 but did not affect the production of VEGF. In late pregnancy, a significant correlation was observed between TNFR1 and VEGFR1.

DISCUSSION

The progression of pregnancy is accompanied by the concerted increase in TNFα and VEGF secretion and decrease in the production of their soluble receptors, but the expression of cell surface receptors does not depend on gestational age. The observed patterns of basal and stimulated expression of TNFα and VEGF may reflect the dual immune and morphogenetic roles of placental macrophages in gestation. Compatible patterns of TNFR1 and VEGFR1 expression suggest common regulatory pathways for these receptors.

The role of decidual cells in uterine hemostasis, menstruation, inflammation, adverse pregnancy outcomes and abnormal uterine bleeding

BACKGROUND

Human pregnancy requires robust hemostasis to prevent hemorrhage during extravillous trophoblast (EVT) invasion of the decidualized endometrium, modification of spiral arteries and post-partum processes. However, decidual hemorrhage (abruption) can occur throughout pregnancy from poorly transformed spiral arteries, causing fetal death or spontaneous preterm birth (PTB), or it can promote the aberrant placentation observed in intrauterine growth restriction (IUGR) and pre-eclampsia; all leading causes of perinatal or maternal morbidity and mortality. In non-fertile cycles, the decidua undergoes controlled menstrual bleeding. Abnormal uterine bleeding (AUB) accompanying progestin-only, long-acting, reversible contraception (pLARC) accounts for most discontinuations of these safe and highly effective agents, thereby contributing to unwanted pregnancies and abortion. The aim of this study was to investigate the role of decidual cells in uterine hemostasis, menstruation, inflammation, adverse pregnancy outcomes and abnormal uterine bleeding.

METHODS

We conducted a critical review of the literature arising from PubMed searches up to December 2015, regarding in situ and in vitro expression and regulation of several specific proteins involved in uterine hemostasis in decidua and cycling endometrium. In addition, we discussed clinical and molecular mechanisms associated with pLARC-induced AUB and pregnancy complications with abruptions, chorioamnionitis or pre-eclampsia.

RESULTS

Progestin-induced decidualization of estradiol-primed human endometrial stromal cells (HESCs) increases in vivo and in vitro expression of tissue factor (TF) and type-1 plasminogen activator inhibitor (PAI-1) while inhibiting plasminogen activators (PAs), matrix metalloproteinases (MMPs), and the vasoconstrictor, endothelin-1 (ET-1). These changes in decidual cell-derived regulators of hemostasis, fibrinolysis, extracellular matrix (ECM) turnover, and vascular tone prevent hemorrhage during EVT invasion and vascular remodeling. In non-fertile cycles, progesterone withdrawal reduces TF and PAI-1 while increasing PA, MMPs and ET-1, causing menstrual-associated bleeding, fibrinolysis, ECM degradation and ischemia. First trimester decidual hemorrhage elicits later adverse outcomes including pregnancy loss, pre-eclampsia, abruption, IUGR and PTB. Decidual hemorrhage generates excess thrombin that binds to decidual cell-expressed protease-activated receptors (PARs) to induce chemokines promoting shallow placentation; such bleeding later in pregnancy generates thrombin to down-regulate decidual cell progesterone receptors and up-regulate cytokines and MMPs linked to PTB. Endometria of pLARC users display ischemia-induced excess vasculogenesis and progestin inhibition of spiral artery vascular smooth muscle cell proliferation and migration leading to dilated fragile vessels prone to bleeding. Moreover, aberrant TF-derived thrombin signaling also contributes to the pathogenesis of endometriosis via induction of angiogenesis, inflammation and cell survival.

CONCLUSION

Perivascular decidualized HESCs promote endometrial hemostasis during placentation yet facilitate menstruation through progestational regulation of hemostatic, proteolytic, and vasoactive proteins. Pathological endometrial hemorrhage elicits excess local thrombin generation, which contributes to pLARC associated AUB, endometriosis and adverse pregnancy outcomes through several biochemical mechanisms.