The Local and Systemic Immune Response to Intrauterine LPS in the Prepartum Mouse

Immune Treatment Strategies in Unexplained Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is characterized by the occurrence of two or more consecutive pregnancy losses. Approximately half of these cases lack a clear etiology and are termed unexplained recurrent pregnancy loss (URPL). Maternal-fetal immune dysfunction is thought to be involved in causing URPL. Increased human leukocyte antigen compatibility, susceptibility genes, lack of blocking antibodies, and dysfunction of immune cells can all disrupt the immune tolerance environment of the maternal-fetal interface. To correct the maternal-fetal immune imbalances, some immunotherapies were recently tried to be used for patients with URPL. This review summarizes the characteristics and mechanisms of the immune microenvironment at the maternal-fetal interface of URPL patients, and the present immunotherapies for URPL patients, to serve as a reference for future research.

Lactobacillus crispatus S-layer proteins modulate innate immune response and inflammation in the lower female reproductive tract

Lactobacillus species dominance of the vaginal microbiome is a hallmark of vaginal health. Pathogen displacement of vaginal lactobacilli drives innate immune activation and mucosal barrier disruption, increasing the risks of STI acquisition and, in pregnancy, of preterm birth. We describe differential TLR mediated activation of the proinflammatory transcription factor NF-κB by vaginal pathogens and commensals. Vaginal Lactobacillus strains associated with optimal health selectively interact with anti-inflammatory innate immune receptors whereas species associated with suboptimal health including L. iners and Gardnerella vaginalis interact with both pro- and anti-inflammatory receptors. Anti-inflammatory action of L. crispatus is regulated by surface layer protein (SLPs)-mediated shielding of TLR ligands and selective interaction with the anti-inflammatory receptor DC-SIGN. Detection of SLPs within cervicovaginal fluid samples is associated with decreased concentrations of pro-inflammatory cytokines in Lactobacillus crispatus-dominated samples. These data offer mechanistic insights into how vaginal microbiota modulate host immune response and thus reproductive health and disease states.

A biomarker for bacteremia in pregnant women with acute pyelonephritis: soluble suppressor of tumorigenicity 2 or sST2

Objective: Sepsis is a leading cause of maternal death, and its diagnosis during the golden hour is critical to improve survival. Acute pyelonephritis in pregnancy is a risk factor for obstetrical and medical complications, and it is a major cause of sepsis, as bacteremia complicates 15-20% of pyelonephritis episodes in pregnancy. The diagnosis of bacteremia currently relies on blood cultures, whereas a rapid test could allow timely management and improved outcomes. Soluble suppression of tumorigenicity 2 (sST2) was previously proposed as a biomarker for sepsis in non-pregnant adults and children. This study was designed to determine whether maternal plasma concentrations of sST2 in pregnant patients with pyelonephritis can help to identify those at risk for bacteremia.Study design: This cross-sectional study included women with normal pregnancy (n = 131) and pregnant women with acute pyelonephritis (n = 36). Acute pyelonephritis was diagnosed based on a combination of clinical findings and a positive urine culture. Patients were further classified according to the results of blood cultures into those with and without bacteremia. Plasma concentrations of sST2 were determined by a sensitive immunoassay. Non-parametric statistics were used for analysis.Results: The maternal plasma sST2 concentration increased with gestational age in normal pregnancies. Pregnant patients with acute pyelonephritis had a higher median (interquartile range) plasma sST2 concentration than those with a normal pregnancy [85 (47-239) ng/mL vs. 31 (14-52) ng/mL, p < .001]. Among patients with pyelonephritis, those with a positive blood culture had a median plasma concentration of sST2 higher than that of patients with a negative blood culture [258 (IQR: 75-305) ng/mL vs. 83 (IQR: 46-153) ng/mL; p = .03]. An elevated plasma concentration of sST2 ≥ 215 ng/mL had a sensitivity of 73% and a specificity of 95% (area under the receiver operating characteristic curve, 0.74; p = .003) with a positive likelihood ratio of 13.8 and a negative likelihood ratio of 0.3 for the identification of patients who had a positive blood culture.Conclusion: sST2 is a candidate biomarker to identify bacteremia in pregnant women with pyelonephritis. Rapid identification of these patients may optimize patient care.

Sex-Specific Dysconnective Brain Injuries and Neuropsychiatric Conditions such as Autism Spectrum Disorder Caused by Group B Streptococcus-Induced Chorioamnionitis

Global health efforts have increased against infectious diseases, but issues persist with pathogens like Group B Streptococcus (GBS). Preclinical studies have elaborated on the mechanistic process of GBS-induced chorioamnionitis and its impact on the fetal programming of chronic neuropsychiatric diseases. GBS inoculation in rodents demonstrated the following: (i) silent and self-limited placental infection, similar to human chorioamnionitis; (ii) placental expression of chemokines attracting polymorphonuclear (PMN) cells; (iii) in vitro cytokine production; (iv) PMN infiltration in the placenta (histologic hallmark of human chorioamnionitis), linked to neurobehavioral impairments like cerebral palsy and autism spectrum disorders (ASD); (v) upregulation of interleukin-1β (IL-1β) in the placenta and fetal blood, associated with higher ASD risk in humans; (vi) sex-specific effects, with higher IL-1β release and PMN recruitment in male placenta; (vii) male offspring exhibiting ASD-like traits, while female offspring displayed attention deficit and hyperactivity disorder (ADHD)-like traits; (viii) IL-1 and/or NF-kB blockade alleviate placental and fetal inflammation, as well as subsequent neurobehavioral impairments. These findings offer potential therapeutic avenues, including sex-adapted anti-inflammatory treatment (e.g., blocking IL-1; repurposing of FDA-approved IL-1 receptor antagonist (IL-1Ra) treatment). Blocking the IL-1 pathway offers therapeutic potential to alleviate chorioamnionitis-related disabilities, presenting an opportunity for a human phase II RCT that uses IL-1 blockade added to the classic antibiotic treatment of chorioamnionitis.

Lipid Polysaccharides have a Detrimental Effect on the Function of the Ovaries and Uterus in Mice through Increased Pro-Inflammatory Cytokines

As the number of coronavirus disease 2019 (COVID-19) vaccinations increases, various side effects are being reported, and menstrual abnormalities have been reported as a side effect in women. However, it is still unclear whether the COVID-19 vaccine has detrimental effects on the female reproductive system. Therefore, we investigated the effect of excessive immune response on reproductive function by administering Lipopolysaccharides (LPS) instead of the COVID-19 vaccine. The immune response in mice was induced by injection of LPS. Mice injected with saline 5 times were used as a control group, and mice injected with LPS 5 times were used as an experimental group. Repeated administration of LPS significantly reduced the number of corpus luteum (CL). On the other hand, the injection of LPS did not affect the development of follicles leading before the CL. The expression of the apoptosis-related genes Fas and Fas-L increased in the experimental group. In addition, the expression of the inflammation-related genes increased in the experimental group. In this study, we confirmed that LPS had detrimental effects on the uterus and ovaries in mice. These results suggest that injection of LPS can cause immune reactions within the uterus and ovaries and cause hormonal changes, which can have adverse effects such as abnormal operation or bleeding of the menstrual cycle. These results are expected to help determine the cause of decreased reproductive function, infertility, or physiological disorders caused by the COVID-19 vaccine.

The Efficacy and Safety of the Zhuyun Formula and Auricular Acupressure for the Infertile Women with Recurrent Implantation Failure: A Randomized Controlled Trial

Background

Recurrent implantation failure (RIF), a clinical disorder characterized by failure to achieve pregnancy after repeated (≥3) embryo transfer, is a challenge for reproductive demands worldwide. In our preliminary work, the Zhuyun formula (ZYF) with auricular acupressure, a complementary and alternative medicine (CAM) with a small sample size for RIF, can improve the clinical pregnancy rate (41.2% vs. 26.7%, treatment group vs. control group, p < 0.05). Based on the toxicological and pregnancy-related pharmacological analysis of ZYF for RIF, the T-cell receptor signaling pathway might be involved in the pharmacological activity. This study aimed at evaluating the efficacy and safety of the CAM therapy according to pregnancy outcomes and maternal and child health and investigating the changes of T-helper (Th) cells in the peripheral blood of unexplained RIF women.

Materials and Methods

We conducted a prospective, two-arms, randomized, nonblinded study. All eligible women were randomly assigned to the treatment group (TG) and the control group (CG) according to a computer-generated randomization list in sealed opaque envelopes. Blood samples were collected from the two groups, and serum Th1, Th2, and Treg were detected by flow cytometry. The cytokines were detected by an enzyme-linked immunosorbent assay (ELISA). The TG was administrated with ZYF and auricular acupressure for three months before ovarian stimulation, while the control group was on a waiting list for the same period. The primary outcome was CPR. The second outcomes were the serum levels of immune parameters. For the safety evaluation, the perinatal outcomes of maternal and child were obtained by follow-up. Post-hoc sensitivity analyses were performed to assess the effect of missing data.

Results

One hundred and twenty-three women were randomized into the TG (n = 62) and CG (n = 61). The CPR was increased significantly in the TG (45.2%) than CG (26.2%) (p = 0.029). Twenty blood samples were collected, and the Th2/Th1 and Treg expression level was significantly higher in the TG than in the CG. IL-2, IL-10, and Foxp3 were higher significantly in the TG than in the CG. The maternal and child perinatal outcomes were not significantly different between the two groups.

Conclusions

The ZYF with auricular acupressure was effective and safe in improving the pregnancy outcomes of RIF. It might be related to balancing the level of cytokines related to the immune tolerance of the maternal-fetal interface to protect the embryo from the maternal immune system. Clinical Trial Registration: Clinical Trial Registry; date: 14/Dec/2013; no. NCT03078205.

Myometrial-derived CXCL12 promotes lipopolysaccharide induced preterm labour by regulating macrophage migration, polarization and function in mice

Preterm birth is a major contributor to neonatal mortality and morbidity. Infection results in elevation of inflammation-related cytokines followed by infiltration of immune cells into gestational tissue. CXCL12 levels are elevated in preterm birth indicating it may have a role in preterm labour (PTL); however, the pathophysiological correlations between CXCL12/CXCR4 signalling and premature labour are poorly understood. In this study, PTL was induced using lipopolysaccharide (LPS) in a murine model. LPS induced CXCL12 RNA and protein levels significantly and specifically in myometrium compared with controls (3-fold and 3.5-fold respectively). Highest levels were found just before the start of labour. LPS also enhanced the infiltration of neutrophils, macrophages and T cells, and induced macrophage M1 polarization. In vitro studies showed that condition medium from LPS-treated primary smooth muscle cells (SMC) induced macrophage migration, M1 polarization and upregulated inflammation-related cytokines such as interleukin (IL)-1, IL-6 and tumor necrosis factor alpha (TNF-α). AMD3100 treatment in pregnant mice led to a significant decrease in the rate of PTL (70%), prolonged pregnancy duration and suppressed macrophage infiltration into gestation tissue by 2.5-fold. Further, in-vitro treatment of SMC by AMD3100 suppressed the macrophage migration, decreased polarization and downregulated IL-1, IL-6 and TNF-α expression. LPS treatment in pregnant mice induced PTL by increasing myometrial CXCL12, which recruits immune cells that in turn produce inflammation-related cytokines. These effects stimulated by LPS were completely reversed by AMD3100 through blocking of CXCL12/CXCR4 signalling. Thus, the CXCL12/CXCR4 axis presents an excellent target for preventing infection and inflammation-related PTL.

Fetal inflammatory response at the fetomaternal interface: A requirement for labor at term and preterm

Human parturition at term and preterm is an inflammatory process synchronously executed by both fetomaternal tissues to transition them from a quiescent state t an active state of labor to ensure delivery. The initiators of the inflammatory signaling mechanism can be both maternal and fetal. The placental (fetal)-maternal immune and endocrine mediated homeostatic imbalances and inflammation are well reported. However, the fetal inflammatory response (FIR) theories initiated by the fetal membranes (amniochorion) at the choriodecidual interface are not well established. Although immune cell migration, activation, and production of proparturition cytokines to the fetal membranes are reported, cellular level events that can generate a unique set of inflammation are not well discussed. This review discusses derangements to fetal membrane cells (physiologically and pathologically at term and preterm, respectively) in response to both endogenous and exogenous factors to generate inflammatory signals. In addition, the mechanisms of inflammatory signal propagation (fetal signaling of parturition) and how these signals cause immune imbalances at the choriodecidual interface are discussed. In addition to maternal inflammation, this review projects FIR as an additional mediator of inflammatory overload required to promote parturition.

IFNγ-Producing γ/δ T Cells Accumulate in the Fetal Brain Following Intrauterine Inflammation

Intrauterine inflammation impacts prenatal neurodevelopment and is linked to adverse neurobehavioral outcomes ranging from cerebral palsy to autism spectrum disorder. However, the mechanism by which a prenatal exposure to intrauterine inflammation contributes to life-long neurobehavioral consequences is unknown. To address this gap in knowledge, this study investigates how inflammation transverses across multiple anatomic compartments from the maternal reproductive tract to the fetal brain and what specific cell types in the fetal brain may cause long-term neuronal injury. Utilizing a well-established mouse model, we found that mid-gestation intrauterine inflammation resulted in a lasting neutrophil influx to the decidua in the absence of maternal systemic inflammation. Fetal immunologic changes were observed at 72-hours post-intrauterine inflammation, including elevated neutrophils and macrophages in the fetal liver, and increased granulocytes and activated microglia in the fetal brain. Through unbiased clustering, a population of Gr-1+ γ/δ T cells was identified as the earliest immune cell shift in the fetal brain of fetuses exposed to intrauterine inflammation and determined to be producing high levels of IFNγ when compared to γ/δ T cells in other compartments. In a case-control study of term infants, IFNγ was found to be elevated in the cord blood of term infants exposed to intrauterine inflammation compared to those without this exposure. Collectively, these data identify a novel cellular immune mechanism for fetal brain injury in the setting of intrauterine inflammation.

CCR2 mediates the adverse effects of LPS in the pregnant mouse

In our earlier work, we found that intrauterine (i.u.) and intraperitoneal (i.p.) injection of LPS (10-μg serotype 0111:B4) induced preterm labor (PTL) with high pup mortality, marked systemic inflammatory response and hypotension. Here, we used both i.u. and i.p. LPS models in pregnant wild-type (wt) and CCR2 knockout (CCR2-/-) mice on E16 to investigate the role played by the CCL2/CCR2 system in the response to LPS. Basally, lower numbers of monocytes and macrophages and higher numbers of neutrophils were found in the myometrium, placenta, and blood of CCR2-/- vs. wt mice. After i.u. LPS, parturition occurred at 14 h in both groups of mice. At 7 h post-injection, 70% of wt pups were dead vs. 10% of CCR2-/- pups, but at delivery 100% of wt and 90% of CCR2-/- pups were dead. Myometrial and placental monocytes and macrophages were generally lower in CCR2-/- mice, but this was less consistent in the circulation, lung, and liver. At 7 h post-LPS, myometrial ERK activation was greater and JNK and p65 lower and the mRNA levels of chemokines were higher and of inflammatory cytokines lower in CCR2-/- vs. wt mice. Pup brain and placental inflammation were similar. Using the IP LPS model, we found that all measures of arterial pressure increased in CCR2-/- but declined in wt mice. These data suggest that the CCL2/CCR2 system plays a critical role in the cardiovascular response to LPS and contributes to pup death but does not influence the onset of inflammation-induced PTL.

Characterizing the immune cell population in the human fetal membrane

PROBLEM

This study localized CD45⁺ immune cells and compared changes in their numbers between term, not in labor (TNIL) and term, labor (TL) human fetal membranes.

METHOD OF STUDY

Fetal membranes (amniochorion) from normal TNIL and TL subjects were analyzed by immunohistochemistry (IHC), immunofluorescence (IF), and flow cytometry for evidence of total (CD45⁺ ) immune cells as well as innate immune cells (neutrophils, macrophages and NK cells) using specific markers. Fetal origin of immune cells was determined using polymerase chain reaction (PCR) for SRY gene in Y chromosome.

RESULTS

CD45⁺ cells were localized in human fetal membranes for both TNIL and TL. A threefold increase in CD45⁺ cells was seen in TL fetal membranes of (7.73% ± 2.35) compared to TNIL (2.36% ± 0.78). This increase is primarily contributed by neutrophils. Macrophages and NK cells did not change in the membranes between TNIL and TL. Leukocytes of fetal origin are present in the fetal membranes.

CONCLUSION

The fetal membranes without decidua contain a small proportion of immune cells. Some of these immune cells in the fetal membrane are fetal in origin. There is a moderate increase of immune cells in the fetal membranes at term labor; however, it is unclear whether this is a cause or consequence of labor. Further functional studies are needed to determine their contribution to membrane inflammation associated with parturition.

Verbascoside-Rich Abeliophyllum distichum Nakai Leaf Extracts Prevent LPS-Induced Preterm Birth Through Inhibiting the Expression of Proinflammatory Cytokines from Macrophages and the Cell Death of Trophoblasts Induced by TNF-α

Background: Preterm birth is a known leading cause of neonatal mortality and morbidity. The underlying causes of pregnancy-associated complications are numerous, but infection and inflammation are the essential high-risk factors. However, there are no safe and effective preventive drugs that can be applied to pregnant women. Objective: The objectives of the study were to investigate a natural product, Abeliophyllum distichum leaf (ADL) extract, to examine the possibility of preventing preterm birth caused by inflammation. Methods: We used a mouse preterm birth model by intraperitoneally injecting lipopolysaccharides (LPS). ELISA, Western blot, real-time PCR and immunofluorescence staining analyses were performed to confirm the anti-inflammatory efficacy and related mechanisms of the ADL extracts. Cytotoxicity and cell death were measured using Cell Counting Kit-8 (CCK-8) analysis and flow cytometer. Results: A daily administration of ADL extract significantly reduced preterm birth, fetal loss, and fetal growth restriction after an intraperitoneal injection of LPS in mice. The ADL extract prevented the LPS-induced expression of TNF-α in maternal serum and amniotic fluid and attenuated the LPS-induced upregulation of placental proinflammatory genes, including IL-1β, IL-6, IL-12p40, and TNF-α and the chemokine gene CXCL-1, CCL-2, CCL3, and CCL-4. LPS-treated THP-1 cell-conditioned medium accelerated trophoblast cell death, and TNF-α played an essential role in this effect. The ADL extract reduced LPS-treated THP-1 cell-conditioned medium-induced trophoblast cell death by inhibiting MAPKs and the NF-κB pathway in macrophages. ADL extract prevented exogenous TNF-α-induced increased trophoblast cell death and decreased cell viability. Conclusions: We have demonstrated that the inhibition of LPS-induced inflammation by ADL extract can prevent preterm birth, fetal loss, and fetal growth restriction.

Maternal inflammation leads to different mTORC1 activity varied by anatomic locations in mouse placenta†

Maternal inflammation (MI) is associated with many adverse perinatal outcomes. The placenta plays a vital role in mediating maternal-fetal resource allocation. Studies have shown that MI contributes to placental dysfunction, which then leads to adverse birth outcomes and high health risks throughout childhood. Placental mammalian target of rapamycin complex 1 (mTORC1) signaling pathway links maternal nutrient availability to fetal growth; however, the impact of MI on mTORC1 signaling in the placenta remains unclear. In this study, we sought to explore the changes of mTORC1 signaling in the mouse placenta at late gestation by using two models of MI employing lipopolysaccharide (LPS) and interleukin-1β (IL-1β) to mimic acute (aMI) and sub-chronic (cMI) inflammatory states, respectively. We determined placental mTORC1 activity by measuring the activity of mTORC1 downstream molecules, including S6k, 4Ebp1, and rpS6. In the aMI model, we found that mTORC1 activity was significantly decreased in the placental decidual and junctional zone at 2 and 6 h after LPS surgery, respectively; however, mTORC1 activity was significantly increased in the placental labyrinth zone at 2, 6, and 24 h after LPS treatment, respectively. In the cMI model, we observed that mTORC1 activity was increased only in the placental labyrinth zone after consecutive IL-1β exposure. Our study reveals that different parts of the mouse placenta react differently to MI, leading to variable mTORC1 activity throughout the placenta. This suggests that different downstream molecules of mTORC1 from different parts of the mouse placenta may be used in clinical research to monitor the fetal well-being during MI.

Gestational diabetes mellitus in women increased the risk of neonatal infection via inflammation and autophagy in the placenta

BACKGROUND

Gestational diabetes mellitus (GDM) produces numerous problems for maternal and fetal outcomes. However, the precise molecular mechanisms of GDM are not clear.

METHODS

In our study, we randomly assigned 22 pregnant women with fasting glucose concentrations, 1 hour oral glucose tolerance test (1H-OGTT) and 2 hour oral glucose tolerance test (2H-OGTT), different than 28 normal pregnant women from a sample of 107 pregnant women at the First Affiliated Hospital of Jinan University in China. Lipopolysaccharide (LPS), interleukin 1 alpha (IL-1α), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α) were measured from blood plasma of pregnant women and umbilical arteries using ultraviolet spectrophotometry. Hematoxylin & Eosin (H&E), Periodic acid-Schiff (PAS) or Masson staining were performed to examine whether diabetes mellitus altered the morphology of placenta. Quantitative PCR (Q-PCR), western blotting and immunofluorescent staining were performed to examine whether diabetes mellitus and autophagy altered the gene expressions of the placental tissue.

RESULTS

We found that women with GDM exhibited increased placental weight and risk of neonatal infection. The concentrations of IL-6 protein and IL-8 protein in GDM were increased in both maternal and umbilical arterial blood. H&E, Masson and PAS staining results showed an increased number of placental villi and glycogen deposition in patients with GDM, but no placental sclerosis was found. Q-PCR results suggested that the expression levels of HIF-1α and the toll like receptor 4 (TLR4)/ myeloid differential protein-88 (MyD88)/ nuclear factor kappa-B (NF-κB) pathway were increased in the GDM placenta. Through Western Blotting, we found that the expression of NF-kappa-B inhibitor alpha (IKBα) and Nuclear factor-κB p65 (NF-κB p65) in GDM placenta was significantly enhanced. We also showed that the key autophagy-related genes, autophagy-related 7 (ATG7) and microtubule-associated protein 1A/1B-light chain 3 (LC3), were increased in GDM compared with normal pregnant women.

CONCLUSIONS

Our results suggest that women with GDM exhibit an increased risk of neonatal infection via inflammation and autophagy in the placenta.

Aminophylline and progesterone prevent inflammation-induced preterm parturition in the mouse†

Although progesterone (P4) supplementation is the most widely used therapy for the prevention of preterm labor (PTL), reports of its clinical efficacy have been conflicting. We have previously shown that the anti-inflammatory effects of P4 can be enhanced by increasing intracellular cyclic adenosine monophosphate (cAMP) levels in primary human myometrial cells. Here, we have examined whether adding aminophylline (Am), a non-specific phosphodiesterase inhibitor that increases intracellular cAMP levels, to P4 might improve its efficacy using in vivo and in vitro models of PTL. In a mouse model of lipopolysaccharide (LPS)-induced PTL, we found that the combination of P4 and Am delayed the onset of LPS-induced PTL, while the same dose of P4 and Am alone had no effect. Pup survival was not improved by either agent alone or in combination. Myometrial prolabor and inflammatory cytokine gene expression was reduced, but the reduction was similar in P4 and P4/Am treated mice. There was no effect of the combination of P4 and Am on an ex vivo assessment of myometrial contractility. In human myometrial cells and myometrial tissue explants, we found that the combination had marked anti-inflammatory effects, reducing cytokine and COX-2 mRNA and protein levels to a greater extent than either agent alone. These data suggest that the combination of P4 and Am has a more potent anti-inflammatory effect than either agent alone and may be an effective combination in women at high-risk of PTL.

Novel pathways of inflammation in human fetal membranes associated with preterm birth and preterm pre-labor rupture of the membranes

Spontaneous preterm birth (PTB) and preterm pre-labor rupture of the membranes (pPROM) are major pregnancy complications. Although PTB and pPROM have common etiologies, they arise from distinct pathophysiologic pathways. Inflammation is a common underlying mechanism in both conditions. Balanced inflammation is required for fetoplacental growth; however, overwhelming inflammation (physiologic at term and pathologic at preterm) can lead to term and preterm parturition. A lack of effective strategies to control inflammation and reduce the risk of PTB and pPROM suggests that there are several modes of the generation of inflammation which may be dependent on the type of uterine tissue. The avascular fetal membrane (amniochorion), which provides structure, support, and protection to the intrauterine cavity, is one of the key contributors of inflammation. Localized membrane inflammation helps tissue remodeling during pregnancy. Two unique mechanisms that generate balanced inflammation are the progressive development of senescence (aging) and cyclic cellular transitions: epithelial to mesenchymal (EMT) and mesenchymal to epithelial (MET). The intrauterine build-up of oxidative stress at term or in response to risk factors (preterm) can accelerate senescence and promote a terminal state of EMT, resulting in the accumulation of inflammation. Inflammation degrades the matrix and destabilizes membrane function. Inflammatory mediators from damaged membranes are propagated via extracellular vesicles (EV) to maternal uterine tissues and transition quiescent maternal uterine tissues into an active state of labor. Membrane inflammation and its propagation are fetal signals that may promote parturition. This review summarizes the mechanisms of fetal membrane cellular senescence, transitions, and the generation of inflammation that contributes to term and preterm parturitions.

Intra-amniotic inflammation induces preterm birth by activating the NLRP3 inflammasome†

Intra-amniotic inflammation is strongly associated with spontaneous preterm labor and birth, the leading cause of perinatal mortality and morbidity worldwide. Previous studies have suggested a role for the NLRP3 (NLR family pyrin domain-containing protein 3) inflammasome in the mechanisms that lead to preterm labor and birth. However, a causal link between the NLRP3 inflammasome and preterm labor/birth induced by intra-amniotic inflammation has not been established. Herein, using an animal model of lipopolysaccharide-induced intra-amniotic inflammation (IAI), we demonstrated that there was priming of the NLRP3 inflammasome (1) at the transcriptional level, indicated by enhanced mRNA expression of inflammasome-related genes (Nlrp3, Casp1, Il1b); and (2) at the protein level, indicated by greater protein concentrations of NLRP3, in both the fetal membranes and decidua basalis prior to preterm birth. Additionally, we showed that there was canonical activation of the NLRP3 inflammasome in the fetal membranes, but not in the decidua basalis, prior to IAI-induced preterm birth as evidenced by increased protein levels of active caspase-1. Protein concentrations of released IL1β were also increased in both the fetal membranes and decidua basalis, as well as in the amniotic fluid, prior to IAI-induced preterm birth. Finally, using the specific NLRP3 inhibitor, MCC950, we showed that in vivo inhibition of the NLRP3 inflammasome reduced IAI-induced preterm birth and neonatal mortality. Collectively, these results provide a causal link between NLRP3 inflammasome activation and spontaneous preterm labor and birth in the context of intra-amniotic inflammation. We also showed that, by targeting the NLRP3 inflammasome, adverse pregnancy and neonatal outcomes can be significantly reduced.

Role of Regulatory T Cells in Regulating Fetal-Maternal Immune Tolerance in Healthy Pregnancies and Reproductive Diseases

Regulatory T cells (Tregs) are a specialized subset of T lymphocytes that function as suppressive immune cells and inhibit various elements of immune response in vitro and in vivo. While there are constraints on the number or function of Tregs which can be exploited to evoke an effective anti-tumor response, sufficient expansion of Tregs is essential for successful organ transplantation and for promoting tolerance of self and foreign antigens. The immune-suppressive property of Tregs equips this T lymphocyte subpopulation with a pivotal role in the establishment and maintenance of maternal tolerance to fetal alloantigens, which is necessary for successful pregnancy. Elevation in the level of pregnancy-related hormones including estrogen, progesterone and human chorionic gonadotropin promotes the recruitment and expansion of Tregs, directly implicating these cells in the regulation of fetal-maternal immune tolerance. Current studies have provided evidence that a defect in the number or function of Tregs contributes to the etiology of several reproductive diseases, such as recurrent spontaneous abortion, endometriosis, and pre-eclampsia. In this review, we provide insight into the underlying mechanism through which Tregs contribute to pregnancy-related immune tolerance and demonstrate the association between deficiencies in Tregs and the development of reproductive diseases.

IRAK1 Is a Critical Mediator of Inflammation-Induced Preterm Birth

Preterm birth (PTB) is a major cause of neonatal mortality and morbidity, often triggered by chorioamnionitis or intrauterine inflammation (IUI) with or without infection. Recently, there has been a strong association of IL-1 with PTB. We hypothesized that IL-1R-associated kinase 1 (IRAK1), a key signaling mediator in the TLR/IL-1 pathway, plays a critical role in PTB. In human fetal membranes (FM) collected immediately after birth from women delivering preterm, p-IRAK1 was significantly increased in all the layers of FM with chorioamnionitis, compared with no-chorioamnionitis subjects. In a preterm rhesus macaque model of IUI given intra-amniotic LPS, induction of p-IRAK1 and downstream proinflammatory signaling mediators were seen in the FM. In a C57BL/6J wild-type PTB mouse model of IUI given intrauterine LPS, an IRAK1 inhibitor significantly decreased PTB and increased live birth in a dose-dependent manner. Furthermore, IRAK1 knockout mice were protected from LPS-induced PTB, which was seen in wild-type controls. Activation of IRAK1 was maintained by K63-mediated ubiquitination in preterm FM of humans with chorioamnionitis and rhesus and mouse IUI models. Mechanistically, IRAK1 induced PTB in the mouse model of IUI by upregulating expression of COX-2. Thus, our data from human, rhesus, and mouse demonstrates a critical role IRAK1 in IUI and inflammation-associated PTB and suggest it as potential therapeutic target in IUI-induced PTB.

Rapid onset of severe septic shock in the pregnant mouse†

AIMS

Globally, sepsis is a major cause of mortality through the combination of cardiovascular collapse and multiorgan dysfunction. Pregnancy appears to increase the risk of death in sepsis, but the exact reason for the greater severity is unclear. In this study, we used polymicrobial sepsis induced by cecal ligation and puncture (CLP) and high-dose intraperitoneal lipopolysaccharide (LPS; 10 or 40 mg, serotype 0111: B4) to test the hypotheses that pregnant mice are more susceptible to sepsis and that this susceptibility was mediated through an excessive innate response causing a more severe cardiovascular collapse rather than a reduction in microbe killing.

METHODS AND RESULTS

Initial studies found that mortality rates were greater, and that death occurred sooner in pregnant mice exposed to CLP and LPS. In pregnant and nonpregnant CD1 mice monitored with radiotelemetry probes, cardiovascular collapse occurred sooner in pregnant mice, but once initiated, occurred over a similar timescale. In a separate study, tissue, serum, and peritoneal fluid (for protein, flow cytometry, nitric oxide, and bacterial load studies) were collected. At baseline, there was no apparent Th1/Th2 bias in pregnant mice. Post CLP, the circulating cytokine response was the same, but leukocyte infiltration in the lung was greater in pregnant mice, but only TNFα levels were greater in lung tissue. The bacterial load in blood and peritoneal fluid was similar in both groups.

CONCLUSION

Sepsis-related mortality was markedly greater in pregnant mice. Cardiovascular collapse and organ dysfunction occurred sooner in pregnancy, but bacterial killing was similar. Circulating and tissue cytokine levels were similar, but immune cell extravasation into other organs was greater in pregnant mice. These data suggest that an excessive innate immune system response as shown by the exaggerated lung infiltration of leukocytes may be responsible for the greater mortality. Approaches that reduce off-site trafficking may improve the prognosis of sepsis in pregnancy.

Nodal is required to maintain the uterine environment in an anti-inflammatory state during pregnancy†

Preterm birth remains the major cause of perinatal mortality and morbidity worldwide, affecting up to 12% of pregnancies and accounting for ~75% of neonatal deaths. However, the mechanisms and causes that underlie it are still largely unknown. One of the major causes of preterm birth is infection or inflammation within the maternal-fetal interface. Our lab has previously shown that a uterine specific deletion of Nodal results in mutant females delivering 2 days prior to term demonstrating an important role for this factor in the maintenance of pregnancy. Here, we have addressed the function of Nodal in the uterus during pregnancy. We demonstrate that Nodal heterozygous mice have an increase in basal levels of pro-inflammatory cytokines IL-1β, IL-6, IL-12p, TNF-α, and IFN-γ as well as an increase in the number of macrophages in response to the inflammatory agent, lipopolysaccharide (LPS). Using bone marrow-derived macrophages, we demonstrated that pretreatment with recombinant Nodal reduces pro-inflammatory gene expression when these cells are challenged with LPS. Our results demonstrate that Nodal is required to maintain the uterine environment in an anti-inflammatory state by preventing proinflammatory cytokine expression.

Quercetin Prevents Lipopolysaccharide-Induced Experimental Preterm Labor in Mice and Increases Offspring Survival Rate

Premature labor is still a worldwide problem, causing serious social economic burden and family burden. Currently, there is no effective way to prevent preterm labor. Since inflammation increases the risk of preterm birth and quercetin is reported to have anti-inflammation, immune-enhancement, and antioxidative effects, this study aims to explore whether quercetin exerts inhibitory effect on preterm labor in mice and increases offspring survival. Lipopolysaccharide (LPS) is one of the commonly used drugs in the inflammatory animal model of preterm birth. On day 15 of pregnancy, mice received a dose of vehicle phosphate-buffered saline (PBS) or a dose of quercetin (low concentration, 30 mg/kg; medium concentration, 90 mg/kg; high concentrations, 150 mg/kg) via oral gavage. After 2 h, mice received a dose of LPS (50 μg/kg) or vehicle intraperitoneally (i.p.). In the absence of quercetin, a 100% incidence of preterm labor was observed in LPS-treated mice, and the fetuses were all died. Medium concentration of quercetin significantly prevented 63.5% of LPS-induced inflammatory preterm labor, and the survival rate of pups on day 22 was 83.76%. Specifically, quercetin significantly inhibited LPS-induced upregulation of NF-kappa-B/P65(RELA), AP-1/C-JUN(JUN), cyclooxygenase-2(PTGS2), and interleukin 6(IL6) in mice myometrium on mRNA level and inhibited the upregulation of P65 and C-JUN on protein level. Based on these observations, we concluded that quercetin exerts inhibitory effect on LPS-induced experimental mice preterm labor and increases offspring survival through a mechanism involving NF-κB/AP-1 pathway.

Mechanistic insights into the action of probiotics against bacterial vaginosis and its mediated preterm birth: An overview

The human body is a reservoir of numerous micro-creatures; whose role is substantial and indispensable in the overall development of human beings. The advances in omic approaches have offered powerful means to decipher the core microbiome and metabolome diversities in a specific organ system. The establishment of lactobacilli in the female reproductive tract is thought to be a paramount prerequisite that maintains homeostatic conditions for a sustainable and healthy pregnancy. Nevertheless, a plethora of such Lactobacillus strains of vaginal source revealed probiotic phenotypes. The plummeting in the occurrence of lactobacilli in the vaginal ecosystem is associated with several adverse pregnancy outcomes (APOs). One such pathological condition is "Bacterial Vaginosis" (BV), a pathogen dominated gynecological threat. In this scenario, the ascending traffic of notorious Gram-negative/variable BV pathogens to the uterus is one of the proposed pathways that give rise to inflammation-related APOs like preterm birth. Since antibiotic resistance is aggravating among urogenital pathogens, the probiotics intervention remains one of the alternative biotherapeutic strategies to overcome BV and its associated APOs. Perhaps, the increased inclination towards the safer and natural biotherapeutic strategies rather than pharmaceutical drugs for maintaining gestational and reproductive health resulted in the use of probiotics in pregnancy diets. In this context, the current review is an attempt to highlight the microbiome and metabolites signatures of BV and non-BV vaginal ecosystem, inflammation or infection-related preterm birth, host-microbial interactions, role and effectiveness of probiotics to fight against aforesaid diseased conditions.

Characterization of an Adapted Murine Model of Intrauterine Inflammation-Induced Preterm Birth

Preterm birth (PTB) affects nearly 15 million infants each year. Of these PTBs, >25% are a result of inflammation or infection. Animal models have improved our understanding of the mechanisms leading to PTB. Prior work has described induction of intrauterine inflammation in mice with a single injection of lipopolysaccharide (LPS). Herein, we have improved the reproducibility and potency of LPS in the model using two injections distal to the cervix. An in vivo imaging system revealed more uniform distribution of Evans Blue Dye using a double distal injection (DDI) approach compared with a single proximal injection (SPI). Endotoxin concentrations in vaginal lavage fluid from SPI dams were significantly higher than from DDI dams. At equivalent LPS doses, DDI consistently induced more PTB than SPI, and DDI showed a linear dose-response, whereas SPI did not. Gene expression in myometrial tissue revealed increased levels of inflammatory markers in dams that received LPS DDI compared with LPS SPI. The SPI group showed more significant overexpression in cervical remodeling genes, likely due to the leakage of LPS from the uterine horns through the cervix. The more reliable PTB induction and uniform uterine exposure provided by this new model will be useful for further studying fetal outcomes and potential therapeutics for the prevention of inflammation-induced PTB.

Cyclic-recombinase-reporter mouse model to determine exosome communication and function during pregnancy

BACKGROUND

During pregnancy, feto-maternal communication can be mediated through extracellular vesicles, specifically exosomes, 30- to 150-nm particles released from each cell. Exosomes carry cellular signals, and traffic between fetal and maternal tissues to produce functional changes in recipient cells. Exosomes may function as a biomarker indicative of the physiologic status of their tissue of origin. These properties of exosomes during pregnancy are not well studied.

OBJECTIVE

To test exosome trafficking and function, we used a transgenic mouse model containing membrane-targeted, red fluorescent protein tdTomato and enhanced green fluorescent protein cyclic recombinase-reporter construct expressed only in fetal tissues. This model allows fetal tissues and their exosomes to express tdTomato under normal conditions or green fluorescent protein if fetal tissues are exposed to cyclic recombinase that will excise tdTomato. As maternal tissue remains negative for this construct, tdTomato/green fluorescent protein expression and their switching can be used to determine fetal-specific cell and exosome trafficking.

MATERIALS AND METHODS

tdTomato/green fluorescent protein-homozygous male mice were mated with wild-type females to have all fetal tissues express the tdTomato/green fluorescent protein allele. Red fluorescence due to tdTomato expression of the tdTomato/green fluorescent protein allele in fetal tissues (placenta, fetal membranes) was confirmed by confocal microscopy on embryonic day 16. Localization of fetal exosomes in maternal uterine tissues were performed by immunostaining for exosome marker CD81 and tdTomato expression followed by confocal microscopy. Fetal exosomes (tdTomato-positive) in maternal plasma were immunoprecipitated using anti-red fluorescent protein tdTomato, followed by confirmation with flow cytometry. To further illustrate the fidelity of fetal exosomes in maternal samples, exosomes bioengineered to contain cyclic recombinase (1.0 × 1010 exosomes) were injected intraperitoneally on embryonic day 13. On embryonic day 16, fetal (placenta and fetal membranes) tissues were imaged to show tdTomato-to-green fluorescent protein transition. The green fluorescent protein-expressing exomes were localized in maternal tissues (confocal microscopy) and plasma (flow cytometry).

RESULTS

Mating between a male with the tdTomato/green fluorescent protein construct and a null female resulted in fetal tissues and their exosomes expressing tdTomato positivity. Total fetal exosomes in maternal plasma was about 35%. tdTomato-positive exosomes were isolated from maternal plasma and immunostaining localized tdTomato-positive exosomes in maternal uterine tissues. Maternal intraperitoneal injection of cyclic recombinase-enriched exosomes crossed placenta, excised tdTomato from the tdTomato/green fluorescent protein construct in the fetal tissues, and caused green fluorescent protein expression in fetal cells. Furthermore, green fluorescent protein-positive exosomes released from fetal cells were isolated from maternal blood.

CONCLUSION

In this pilot study, we report feto-maternal and maternal-fetal trafficking of exosomes indicative of paracrine signaling during pregnancy. Exosomes from the maternal side can produce functional changes in fetal tissues. Trafficking of exosomes suggests their potential role in pregnancy as biomarkers of fetal functions and usefulness as a carrier of drugs and other cargo to the fetal side during pregnancy. Isolation and characterization of fetal exosomes can advance fetal research without performing invasive procedures.

Mouse models of preterm birth: suggested assessment and reporting guidelines

Preterm birth affects approximately 1 out of every 10 births in the United States, leading to high rates of mortality and long-term negative health consequences. To investigate the mechanisms leading to preterm birth so as to develop prevention strategies, researchers have developed numerous mouse models of preterm birth. However, the lack of standard definitions for preterm birth in mice limits our field's ability to compare models and make inferences about preterm birth in humans. In this review, we discuss numerous mouse preterm birth models, propose guidelines for experiments and reporting, and suggest markers that can be used to assess whether pups are premature or mature. We argue that adoption of these recommendations will enhance the utility of mice as models for preterm birth.

The role of maternal T cell and macrophage activation in preterm birth: Cause or consequence?

The role of the immune system in term (TL) and preterm labor (PTL) is unknown. Despite the fact that globally, PTL remains the most important cause of childhood mortality. Infection, typically of the fetal membranes, termed chorioamnionitis, is the best-understood driver of PTL, but the mechanisms underpinning other causes, including idiopathic and stretch-induced PTL, are unclear, but may well involve activation of the maternal immune system. The final common pathway of placental dysfunction, fetal membrane rupture, cervical dilation and uterine contractions are highly complex processes. At term, choriodecidual rather than myometrial inflammation is thought to drive the onset of labor and similar findings are present in different types of PTL including idiopathic PTL. Although accumulated data has confirmed an association between the immune response and preterm birth, there is yet a need to understand if this response is an initiator or a consequence of tissue-level dysregulation. This review focuses on the potential role of macrophages and T cells in innate and adaptive immunity relevant to preterm birth in humans and animal models.

Ascending Vaginal Infection Using Bioluminescent Bacteria Evokes Intrauterine Inflammation, Preterm Birth, and Neonatal Brain Injury in Pregnant Mice

Preterm birth is a serious global health problem and the leading cause of infant death before 5 years of age. At least 40% of cases are associated with infection. The most common way for pathogens to access the uterine cavity is by ascending from the vagina. Bioluminescent pathogens have revolutionized the understanding of infectious diseases. We hypothesized that bioluminescent Escherichia coli can be used to track and monitor ascending vaginal infections. Two bioluminescent strains were studied: E. coli K12 MG1655-lux, a nonpathogenic laboratory strain, and E. coli K1 A192PP-lux2, a pathogenic strain capable of causing neonatal meningitis and sepsis in neonatal rats. On embryonic day 16, mice received intravaginal E. coli K12, E. coli K1, or phosphate-buffered saline followed by whole-body bioluminescent imaging. In both cases, intravaginal delivery of E. coli K12 or E. coli K1 led to bacterial ascension into the uterine cavity, but only E. coli K1 induced preterm parturition. Intravaginal administration of E. coli K1 significantly reduced the proportion of pups born alive compared with E. coli K12 and phosphate-buffered saline controls. However, in both groups of viable pups born after bacterial inoculation, there was evidence of comparable brain inflammation by postnatal day 6. This study ascribes specific mechanisms by which exposure to intrauterine bacteria leads to premature delivery and neurologic inflammation in neonates.

Inflammation induced preterm labor and birth

Preterm birth which occurs before 37 weeks gestation is one of the most common obstetrical complication in humans. After many studies, it appears that "not one answer fits all" regarding the risk factors, causes and the treatments for this syndrome. However, it is becoming more evident that one of the major risk factors is inflammation and/or infection in the fetoplacental unit. In animal models (usually consisting of mice injected with lipopolysaccharide at 14 days of gestation), IL-22 and IL-6 have been identified as factors related to preterm birth. There are some clinical tests available to determine the risk for preterm labor and delivery, which can be identified before, during early, or at mid-gestation. However, treatment of preterm birth with antibiotics so far has not been "curable" and studies using anti-inflammatory treatments are not readily available. More studies regarding causes and treatments for preterm labor and delivery in humans are necessary to prevent neonatal deaths and/or developmental abnormalities associated with this common syndrome.

The response of the innate immune and cardiovascular systems to LPS in pregnant and nonpregnant mice

Sepsis is the leading cause of direct maternal mortality, but there are no data directly comparing the response to sepsis in pregnant and nonpregnant (NP) individuals. This study uses a mouse model of sepsis to test the hypothesis that the cardiovascular response to sepsis is more marked during pregnancy. Female CD1 mice had radiotelemetry probes implanted and were time mated. NP and day 16 pregnant CD-1 mice received intraperitoneal lipopolysaccharide (LPS; 10 μg, serotype 0111: B4). In a separate study, tissue and serum (for RNA, protein and flow cytometry studies), aorta and uterine vessels (for wire myography) were collected after LPS or vehicle control administration. Administration of LPS resulted in a greater fall in blood pressure in pregnant mice compared to NP mice. This occurred with similar changes in the circulating levels of cytokines, vasoactive factors, and circulating leukocytes, but with a greater monocyte and lesser neutrophil margination in the lungs of pregnant mice. Baseline markers of cardiac dysfunction and apoptosis as well as cytokine expression were higher in pregnant mice, but the response to LPS was similar in both groups as was the ex vivo assessment of vascular function. In pregnant mice, nonfatal sepsis is associated with a more marked hypotensive response but not a greater immune response. We conclude that endotoxemia induces a more marked hypotensive response in pregnant compared to NP mice. These changes were not associated with a more marked systemic inflammatory response in pregnant mice, although monocyte lung margination was greater. The more marked hypotensive response to LPS may explain the greater vulnerability to some infections exhibited by pregnant women.

Sinomenine inhibits lipopolysaccharide-induced inflammatory injury by regulation of miR-101/MKP-1/JNK pathway in keratinocyte cells

OBJECTIVE

Recent studies have demonstrated that Sinomenine (SIN) exerted anti-inflammatory effect in various immune-related diseases. However, the effect of SIN on glucocorticoids dermatitis has not been investigated. In our study, we aimed to explore the effect of SIN on lipopolysaccharide (LPS)-induced inflammatory injury in HaCaT cells.

MATERIALS AND METHODS

We constructed an inflammatory injury model of LPS-induced HaCaT cells, then SIN was added to LPS-treated cells, cell viability, apoptosis, apoptosis-associated factors and inflammatory cytokines were detected by CCK-8, flow cytometry, western blot, qRT-PCR and ELISA. Subsequently, miR-101 mimic and mimic control were transfected into HaCaT cells to investigate the effect of SIN and miR-101 on LPS-induced cells injury. Furthermore, MKP-1 and JNK signal pathways were measured by qRT-PCR and western blot. Finally, the animal experiment was performed to further clarify the effect of SIN on inflammatoty injury.

RESULTS

LPS suppressed cell viability, promoted apoptosis and increased IL-6, IL-8 and TNF-α expressions and secretions in HaCaT cells. SIN significantly alleviated LPS-induced HaCaT cells injury. Additionally, SIN down-regulated miR-101 expression, and the protective effect of SIN on LPS-induced inflammatory injury was abolished by miR-101 overexpression. Besides, SIN promoted MKP-1 expression by down-regulation of miR-101, and SIN inhibited JNK signal pathway by up-regulation of MKP-1 expression in LPS-treated HaCaT cells. Animal experiments revealed that SIN exhibited anti-inflammatory effects in vivo.

CONCLUSIONS

The data indicated that SIN attenuated LPS-induced inflammatory injury by regulation of miR-101, MKP-1 and JNK pathway. These findings might provide a novel method for treatment of glucocorticoids dermatitis.

Interleukin 22 prevents lipopolysaccharide- induced preterm labor in mice

Preterm birth is widespread and causes 35% of all neonatal deaths. Infants who survive face potential long-term complications. A major contributing factor of preterm birth is infection. We investigated the role of interleukin 22 (IL22) as a potential clinically relevant cytokine during gestational infection. IL22 is an effector molecule secreted by immune cells. While the expression of IL22 was reported in normal nonpregnant endometrium and early pregnancy decidua, little is known about uterine IL22 expression during mid or late gestational stages of pregnancy. Since IL22 has been shown to be an essential mediator in epithelial regeneration and wound repair, we investigated the potential role of IL22 during defense against an inflammatory response at the maternal-fetal interface. We used a well-established model to study infection and infection-associated inflammation during preterm birth in the mouse. We have shown that IL22 is upregulated to respond to an intrauterine lipopolysaccharide administration and plays an important role in controlling the risk of inflammation-induced preterm birth. This paper proposes IL22 as a treatment method to combat infection and prevent preterm birth in susceptible patients.

Fetal and Placental DNA Stimulation of TLR9: A Mechanism Possibly Contributing to the Pro-inflammatory Events During Parturition

INTRODUCTION

While there is evidence for a relationship between cell-free fetal DNA (cffDNA) and parturition, questions remain regarding whether cffDNA could trigger a pro-inflammatory response on the pathway to parturition. We hypothesized that placental and/or fetal DNA stimulates toll-like receptor 9 (TLR9) leading to secretion of pro-inflammatory cytokines by macrophage cells.

METHODS

Four in vitro DNA stimulation studies were performed using RAW 264.7 mouse peritoneal macrophage cells incubated in media containing the following DNA particles: an oligodeoxynucleotide (ODN2395), intact genomic DNA (from mouse placentas, fetuses and adult liver), mouse DNA complexed with DOTAP (a cationic liposome forming compound), and telomere-depleted mouse DNA. Interleukin 6 (IL6) secretion was measured in the media by enzyme-linked immunosorbent assay; and the cell pellet was homogenized for protein content (picograms IL6/mg protein).

RESULTS

Robust IL6 secretion was observed in response to ODN2395 (a CpG-rich TLR9 agonist), mouse DNA-DOTAP complexes, and telomere-depleted mouse DNA in concentrations of 5 to 15 μg/mL. In contrast, ODN A151 (containing telomere sequence motifs), intact genomic mouse DNA, and restriction enzyme-digested DNA had no effect on IL6 secretion. The IL6 response was significantly inhibited by chloroquine (10 μg/mL), thereby confirming the important role for TLR9 in the response by macrophage cells.

CONCLUSIONS

DNA derived from mouse placentas and fetuses, and depleted of telomeric sequences, stimulates a robust pro-inflammatory response by macrophage cells, thereby supporting the hypothesis that cffDNA is able to stimulate an innate immune response that could trigger the onset of parturition. These findings are of clinical importance, as we search for effective treatment/prevention of preterm parturition.

The unique immunological and microbial aspects of pregnancy

The comparison of the immunological state of pregnancy to an immunosuppressed host-graft model continues to lead research and clinical practice to ill-defined approaches. This Review discusses recent evidence that supports the idea that immunological responses at the receptive maternal-fetal interface are not simply suppressed but are instead highly dynamic. We discuss the crucial role of trophoblast cells in shaping not only the way in which immune cells respond to the invading blastocyst but also how they collectively react to external stimuli. We also discuss the role of the microbiota in promoting a tolerogenic maternal immune system and highlight how subclinical viral infections can disrupt this status quo, leading to pregnancy complications.