Novel insights into molecular mechanisms of abruption-induced preterm birth

Correlation Between Maternal-Fetus Interface and Placenta-Mediated Complications

Pregnancy is a highly regulated biological phenomenon that involves the development of a semi-allogeneic fetus inside the uterus of the mother. The maternal-fetal interface is a critical junction where communication takes place between the fetal and maternal immune systems, which determine the outcome of the pregnancy. The interface is composed of the decidua and placenta. The main cells present at the maternal-fetal interface include invading trophoblasts, maternal immune cells, and decidual stromal cells. Although maternal tolerance is crucial for maintaining a successful pregnancy, the role of the placenta in pregnancy is also important. Dysregulation of the placenta leads to various placenta-mediated complications, such as preeclampsia, intrauterine growth restriction, and placental abruption. Although the exact mechanism involving these complications is unclear, research has elucidated various factors involved in these pregnancy disorders. This review aimed to provide a summary of the maternal-fetal interface and immune mechanisms involved in placenta-mediated complications.

Placenta accreta spectrum conservative management and coagulopathy: case series and systematic review

OBJECTIVE

Management of placenta accreta spectrum (PAS) with the placenta kept in situ aims to preserve fertility and minimize blood loss. However, this method is associated with a risk of coagulopathy and subsequent bleeding. The aim of this study was to evaluate the occurrence and pathophysiology of coagulopathy in cases of PAS managed conservatively.

METHODS

We reviewed our database for cases of PAS in which the placenta was kept in situ. In addition, we performed a systematic review of articles on PAS in which the placenta was left in situ and was complicated by coagulopathy. PubMed was searched for publications between 1980 and 2023. Our eligibility criteria included studies in which no additional interventions were performed other than keeping the placenta entirely in situ, and in which coagulopathy was reported.

RESULTS

After screening and selection of full-text articles, 10 studies were included in the review. A review of our databases yielded a case series of PAS managed conservatively with the placenta kept in situ. When adding our case series to the results of our systematic review, a total of 87 cases were found to have been managed conservatively, with 28 cases of coagulopathy. Of these, the time at which coagulopathy developed was known in 11 cases. The median time at development of coagulopathy was 58 (interquartile range, 50-67) days postpartum.

CONCLUSIONS

Our findings highlight that conservative management of PAS with the placenta in situ poses a risk of coagulopathy. Keeping the placenta in situ after delivery prolongs the risk factors that are integral to PAS. The pathophysiology behind coagulopathy is comparable with that of concealed placental abruption, due to the disrupted uteroplacental interface and the collection of blood in the placenta. Therefore, the presence of large placental lakes could be an indicator of developing coagulopathy. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Challenges in Using Progestin to Prevent Singleton Preterm Births: Current Knowledge and Clinical Advice

Preterm birth is the leading cause of infant morbidity and mortality in children younger than 5 years old and accounts for approximately 35% of newborn deaths worldwide. The use of progestogen therapy for prevention of preterm birth has been one of the most controversial topics in modern obstetrics. Progestogens can be classified as natural or synthetic. Progesterone is a natural progestogen while progestins such as 17-alpha-hydroxyprogesterone caproate (17OHP-C) are synthetic steroid hormones. Evidence supporting the use of progestogens varies by formulation and populations studied. After more than a decade, the US Food and Drug Administration has withdrawn accelerated approval of 17OHP-C for the prevention of recurrent preterm birth in pregnant individuals with a singleton gestation. With this decision, there is no current FDA-approved treatment for prevention of spontaneous preterm birth. In this review, we provide a historical context behind the rise and fall of 17OHP-C clinical application, highlight the challenges behind the data supporting progestogen use, and offer suggestions on how to make an impact on preterm birth moving forward.

Decreased level of TREM like Transcript 1 (TLT-1) is associated with prematurity and promotes the in-utero inflammatory response to maternal lipopolysaccharide (LPS) exposure

PROBLEM

The occurrence of preterm birth is associated with multiple factors including bleeding, infection and inflammation. Platelets are mediators of hemostasis and can modulate inflammation through interactions with leukocytes. TREM like Transcript 1 (TLT-1) is a type 1 single Ig domain receptor on activated platelets. In adults, it plays a protective role by dampening the inflammatory response and facilitating platelet aggregation at sites of vascular injury. TLT-1 is expressed in human placenta and found in cord blood. We thus hypothesized that TLT-1 deficiency is associated with prematurity and fetal inflammation.

METHOD OF STUDY

To test this hypothesis, we examined cord blood levels of soluble TLT-1 (sTLT) in premature and term infants and compared the inflammatory response in C57BL/6 (WT) and TLT-1-/- (treml1-/- , KO) mice given intraperitoneal LPS mid-gestation RESULTS: The preterm infant cord blood level of sTLT was significantly lower than that found at term. On exposure to LPS, histology of KO (as compared to WT) placenta and decidua showed increased hemorrhage, and KO decidual RNA expression of IL-10 was significantly lower. KO fetal interface tissues (placenta, membranes, amniotic fluid) over time showed increased expression of inflammatory cytokines such as IL-6, IFN-γ, and TNF, but not MCP-1. However, fetal organs showed similar levels.

CONCLUSION

There is a potential association between insufficient TLT-1 expression and increased fetal inflammatory responses in the setting of prematurity. The data support further study of TLT-1 in the mechanistic link between bleeding, inflammation and preterm birth, and perhaps as a biomarker in human pregnancy.

Risk factors for blood component therapy in parturients-Case-control study

OBJECTIVE

Postpartum hemorrhage is a major cause of maternal morbidity and mortality, so early identification of patients at risk is crucial. In this study, we aim to assess the risk factors for major transfusion in parturients.

METHODS

A case-control study was conducted between 2011 and 2019. The cases included women who were treated with postpartum major transfusion compared with two control groups, one of which was treated with 1-2 packed red blood cells and one of which was not treated with packed red blood cells. Cases were matched with controls based on two variables: multiple pregnancies and previous history of three or more cesarean sections. A multivariable conditional logistic regression model was used to determine the role of the independent risk factors.

RESULTS

Of the 187 424 deliveries included in the present study, 246 (0.3%) women were treated with major transfusions. After applying a multivariate analysis, maternal age (odds ratio [OR] 1.07, 95% confidence interval [CI] 0.996-1.16), antenatal anemia with hemoglobin less than 10 g/dL (OR 12.58, 95% CI 2.86-55.25), retained placenta (OR 5.5, 95% CI 2.15-13.78), and cesarean delivery (OR 10.12, 95% CI 0.93-1.95) remained independent risk factors for major transfusions.

DISCUSSION

Retained placenta and antenatal anemia (hemoglobin < 10 g/dL) are independent risk factors for major transfusion. Of these, anemia was found to be the most significant.

Bloody Amniotic Fluid and Neonatal Outcomes

Information on the effect of bloody amniotic fluid during labor at term is scarce. This study assessed risk factors and adverse outcomes in labors with bloody amniotic fluid. During the six years of this study, all nulliparas in our institution, with a trial of labor, were included. Multiple pregnancies and preterm deliveries were excluded. Outcomes were compared between the bloody amniotic fluid group and the clear amniotic fluid group. Overall, 11,252 women were included. Among them, 364 (3.2%) had bloody amniotic fluid and 10,888 (96.7%) had clear amniotic fluid. Women in the bloody amniotic fluid group were characterized by shorter duration of the second stage and higher rate of cesarean section due to non-reassuring fetal heart rate. In addition, there were higher rates of low cord pH (<7.1) and NICU admissions in the bloody amniotic fluid group. In multivariate logistic regression analysis, cesarean delivery, cord blood pH < 7.1, and NICU admission were independently associated with increased odds ratio for bloody amniotic fluid. Bloody amniotic fluid at term is associated with adverse outcomes and must be considered during labor.

Placental abruption at near-term and term gestations: pathophysiology, epidemiology, diagnosis, and management

Placental abruption is the premature separation of the placenta from its uterine attachment before the delivery of a fetus. The clinical manifestations of abruption typically include vaginal bleeding and abdominal pain with a wide variety of abnormal fetal heart rate patterns. Clinical challenges arise when pregnant people with this condition present with profound vaginal bleeding, necessitating urgent delivery, especially when there is a concern for maternal and fetal compromise and coagulopathy. Abruption occurs in 0.6% to 1.2% of all pregnancies, with nearly half of abruption occurring at term gestations. An exposition of abruption at near-term (defined as the late preterm period from 34 0/7 to 36 6/7 weeks of gestation) and term (defined as ≥37 weeks of gestation) provides unique insights into its direct effects, as risks associated with preterm birth do not impact outcomes. Here, we explore the pathophysiology, epidemiology, and diagnosis of abruption. We discuss the interaction of chronic processes (decidual and uteroplacental vasculopathy) and acute processes (shearing forces applied to the abdomen) that underlie the pathophysiology. Risk factors for abruption and strengths of association are summarized. Sonographic findings of abruption and fetal heart rate tracings are presented. In addition, we propose a management algorithm for acute abruption that incorporates blood loss, vital signs, and urine output, among other factors. Lastly, we discuss blood component therapy, viscoelastic point-of-care testing, disseminated intravascular coagulopathy, and management of abruption complicated by fetal death. The review seeks to provide comprehensive, clinically focused guidance during a gestational age range when neonatal outcomes can often be favorable if rapid and evidence-based care is optimized.

Iron deficiency anaemia associated with increased placenta praevia and placental abruption: a retrospective case-control study

BACKGROUND/OBJECTIVES

A few studies reported association between placenta praevia (PP) and placental abruption (PA) with maternal iron deficiency anaemia (IDA), which is not an established risk factor for these conditions. This retrospective case-control study was performed to determine the relationship between IDA with PP and PA.

METHODS

Maternal characteristics, risk factors for and incidence of antepartum haemorrhage overall, and PP and PA, were compared between women with IDA only and controls without IDA or haemoglobinopathies matched for exact age and parity (four controls to each index case), who carried singleton pregnancy to ≥22 weeks and managed under our care from 1997 to 2019.

RESULTS

There were 1,176 women (0.8% of eligible women in the database) with IDA only, who exhibited slightly but significantly different maternal characteristics, and increased antepartum haemorrhage overall (3.4% versus 2.2%, p = 0.031, OR 1.522, 95% CI 1.037-2.234) and PP (1.8% versus 0.9%, p = 0.010, OR 1.953, 95% CI 1.164-3.279), but not PA (1.2% versus 1.1%, p = 0.804, OR 1.077, 95% CI 0.599-1.936). When stratified by parity status, increased PP was found in nulliparous women only. On multivariate analysis adjusting for parity, previous abortion history, overweight and obesity, short stature, other antenatal complications as a composite factor, preterm (<37) delivery, previous caesarean delivery, and infant gender, IDA was associated with PP (aOR 3.485, 95% CI 1.959-6.200) and PA (aOR 2.181, 95% CI 1.145-4.155).

CONCLUSIONS

Both PP and PA are increased in women with IDA, the prevention of which could be a means to reduce the occurrence of both PP and PA.

Molecular Changes on Maternal-Fetal Interface in Placental Abruption-A Systematic Review

Placental abruption is the separation of the placenta from the lining of the uterus before childbirth. It is an infrequent perinatal complication with serious after-effects and a marked risk of maternal and fetal mortality. Despite the fact that numerous placental abruption risk factors are known, the pathophysiology of this issue is multifactorial and not entirely clear. The aim of this review was to examine the current state of knowledge concerning the molecular changes on the maternal–fetal interface occurring in placental abruption. Only original research articles describing studies published in English until the 15 March 2021 were considered eligible. Reviews, book chapters, case studies, conference papers and opinions were excluded. The systematic literature search of PubMed/MEDLINE and Scopus databases identified 708 articles, 22 of which were analyzed. The available evidence indicates that the disruption of the immunological processes on the maternal–fetal interface plays a crucial role in the pathophysiology of placental abruption. The features of chronic non-infectious inflammation and augmented immunological cytotoxic response were found to be present in placental abruption samples in the reviewed studies. Various molecules participate in this process, with only a few being examined. More advanced research is needed to fully explain this complicated process.

Pyoderma gangrenosum following an unplanned caesarean section: a patient revisited

A 35-year-old woman was referred urgently to the dermatology department because of significant wound breakdown 3 weeks following an emergency caesarean section. Examination revealed a full thickness, undermined ulcer spanning the width of the patient's caesarean scar, exposing the patient's uterus. Clinical appearances were consistent with pyoderma gangrenosum. The patient has a history of complicated pyoderma gangrenosum, having undergone skin grafts 14 years prior, for ulcers on her lower legs. That episode was the subject of a case report, published in the BMJ, in 2007. On this occasion, the patient was treated with oral corticosteroids, and ciclosporin based on its efficacy during her previous episode, which in conjunction with negative pressure wound therapy, resulted in complete re-epithelialisation of her ulcer within 6 months.

GIT2 deficiency attenuates inflammation-induced expression of pro-labor mediators in human amnion and myometrial cells†

Untimely activation of the inflammatory response by sterile or infective insults in uterine tissues can result in preterm birth. Pro-inflammatory cytokines and pathogenic activation of toll-like receptors (TLRs) initiate a biochemical cascade of events leading to myometrial activation and contractility, cervical dilatation, and rupture of the chorioamniotic membranes. GIT2 is a signaling protein known to play a role in innate and adaptive immunity; however, its role in the inflammatory pathways of human labor is not known. In this article, we report that GIT2 expression is lower in human myometrium and fetal membranes with term labor, and in preterm amnion with histological chorioamnionitis. GIT2 knockdown by siRNA in primary myometrial and amnion cells exhibited reduced expression of pro-inflammatory cytokines and chemokines in response to inflammatory challenge by cytokines or TLR ligands. In addition, the pro-inflammatory cytokines IL1B and TNF could not induce the expression of extracellular matrix degrading enzymes in GIT2-deficient amnion cells. Myometrial activation in response to pro-inflammatory cytokines was also significantly suppressed in GIT2-deficient cells as evidenced by decreased prostaglandin release and expression of contraction-associated proteins. Further to this, collagen gel assays demonstrated that TNF had a reduced ability to induce myometrial contractility in situ in GIT2-deficient myometrial cells compared to control-transfected cells. In summary, the loss of GIT2 diminishes the effects inflammatory mediators have in promoting myometrial contraction and fetal membrane rupture in vitro, suggesting that GIT2 could be a possible target for preterm birth therapies.

Exposure to Asian dust within a few days of delivery is associated with placental abruption in Japan: a case-crossover study

OBJECTIVE

Asian dust is a natural phenomenon in which dust particles are transported from desert areas in China and Mongolia to East Asia. Short-term exposure to Asian dust has been associated with cardiovascular disease through mechanisms such as systemic inflammation. Because inflammation is a potential trigger of placental abruption, exposure may also lead to abruption. We examined whether exposure to Asian dust was associated with abruption.

DESIGN

A bi-directional, time-stratified case-crossover design.

SETTING AND POPULATION

From the Japan Perinatal Registry Network database, we identified 3014 patients who delivered singleton births in hospitals in nine Japanese prefectures from 2009 to 2014 with a diagnosis of placental abruption.

METHODS

Asian dust levels were measured at Light Detection and Ranging monitoring stations, and these measurements were used to define the Asian dust days. As there was no information on the onset day of abruption, we assumed this day was the day before delivery (lag1).

MAIN OUTCOME MEASURES

Placental abruption.

RESULTS

During the study period, the Asian dust days ranged from 15 to 71 days, depending on the prefecture. The adjusted odds ratio of placental abruption associated with exposure to Asian dust was 1.4 (95% confidence interval = 1.0, 2.0) for cumulative lags of 1-2 days. Even after adjustment for co-pollutant exposures, this association did not change substantially.

CONCLUSIONS

In this Japanese multi-area study, exposure to Asian dust was associated with an increased risk of placental abruption.

TWEETABLE ABSTRACT

Exposure to environmental factors such as Asian dust may be a trigger of placental abruption.

The role of the obstetrician in the prevention of retinopathy of prematurity

This review underlines the important role that obstetricians play in the prevention of retinopathy of prematurity. Efforts predominately focus on predicting which pregnant women are at highest risk of preterm birth, instigating treatments to prevent pre-eclampsia, fetal growth restriction and maternal infection which could lead to iatrogenic or spontaneous preterm birth, and optimizing care when preterm birth is inevitable. More broadly, optimizing maternal health pre-conception through stopping smoking, improving diet, reducing obesity with its associated gestational diabetes, and treating hypertension may reduce preterm birth and other pregnancy complications. This is a message that all healthcare professionals including obstetricians, neonatologists and GPs, nursing and midwifery staff need to communicate all women and men who are contemplating having a baby.

Maternal blood biomarkers and adverse pregnancy outcomes: a systematic review and meta-analysis

Background: Pregnancy is a vulnerable period for the mother and the infant and exposures to environmental chemicals in utero can influence neonatal morbidity and mortality. There is a momentum toward understanding and exploring the current maternal biological mechanisms specific to in utero effects, to improve birth outcomes. This study aims to examine the current understanding of the role of biomarkers that may be associated with term of pregnancy, infant birth weights and infant development in utero.Methods: Electronic searches were conducted in PubMed, Embase, OvidMD, and Scopus databases; and all relevant research articles in English were retrieved. Studies were selected if they evaluated maternal blood plasma/serum biomarkers proposed to influence adverse birth outcomes in the neonate. Data were extracted on characteristics, quality, and odds ratios from each study and meta-analysis was conducted.Results: A total of 54 studies (35 for meta-analysis), including 43,702 women, 50 plasma markers and six descriptors of birth outcomes were included in the present study. The random effect point estimates for risk of adverse birth outcomes were 1.61(95%CI: 1.39-1.85, p < 0.0001) for inflammation-related biomarkers and 1.65(95%CI: 1.22-2.25, p = 0.0013) for growth factor/hormone-related biomarkers. All subgroups of plasma markers showed significant associations with adverse birth outcomes with no apparent study bias.Conclusions: The two subsets of plasma markers identified in this study (inflammation-related and growth factor/hormone-related) may serve as potentially valuable tools in the investigation of maternal molecular mechanisms, especially select pathways underlying inflammatory and immunological mediation in terms of modulating adverse infant outcomes. Future large, prospective cohort studies are needed to validate the promising plasma biomarkers, and to examine other maternal biological matrices such as cervicovaginal fluid and urine.

Double-blind randomized trial of progesterone to prevent preterm birth in second-trimester bleeding

INTRODUCTION

Second-trimester vaginal bleeding increases the risk of spontaneous preterm birth. We aimed to examine the efficacy of vaginal progesterone to reduce preterm birth rate in women with second-trimester vaginal bleeding.

MATERIAL AND METHODS

Two-center, double-blind, placebo-controlled trial involving pregnant women with second-trimester vaginal bleeding. Women with documented uterine bleeding were randomly assigned in a 1:1 ratio to receive 200 mg of micronized vaginal progesterone or placebo once daily at 16-26 weeks until 36 weeks of gestation. Women who had prior preterm birth or short cervix diagnosed before recruitment were not eligible. The primary outcome was spontaneous delivery <37 weeks.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01269450.

RESULTS

Between March 2011 and January 2017, 128 women gave consent and were randomized; 16 withdrew consent and 3 had a second-trimester termination of pregnancy. The final analysis included 109 women: 60 in the progesterone group and 49 in the placebo group. Demographic and obstetric characteristics did not differ between the groups. Primary outcome occurred in 19 (31.7%) and 12 (24.5%) in the progesterone and placebo groups, respectively (odds ratio [OR] 1.32; 95% confidence interval [CI] 0.55-3.16; P = 0.53). The proportion of births <34 weeks was similar between the groups (OR 1.19; 95% CI 0.47-3.02; P = 0.72), as were the survival curves from randomization to delivery (hazard ratio, 1.24; 95% CI, 0.60-2.56; P = 0.57). There were no significant differences in neonatal morbidities between the groups. The study was ended prematurely because of slow recruitment.

CONCLUSIONS

Antepartum vaginal progesterone does not seem to reduce the incidence of preterm birth in women with second-trimester bleeding.

Expression and regulation of metallothioneins in myometrium and fetal membranes

PROBLEM

Metallothioneins (MTs) play important roles in regulating oxidative stress, inflammation, and hormone signaling. These processes play a major role in labor at term and preterm. The aims of this study were to characterize (a) temporal- and labor-associated changes and (b) the effect of pro-inflammatory and pro-labor insults on the expression of MT1 isoforms, MT2A, MT3, and MT4 in fetal membranes and myometrium.

METHOD OF STUDY

The expression of MTs was assessed in fetal membranes and myometrium from nonlaboring and laboring women at preterm and term by RT-qPCR. Tissue explants were used to assess the effect of pro-inflammatory cytokines and Toll-like receptor (TLR) ligands on the expression of MTs in fetal membranes and myometrium.

RESULTS

In fetal membranes, the expression of MT1A, MT1E, MT1F, MT1X, and MT2A was higher at term compared with preterm. Preterm labor and preterm histological chorioamnionitis were associated with increased expression of MT1A, MT1G, MT1M, MT1X, MT2A, and MT3. Term labor was associated with increased expression of MT1A, MT1F, MT1X, MT2A, and MT3 in fetal membranes and expression of MT1A, MT1E, MT1F, MT1G, MT1M, MT1X, MT2A, and MT3 in myometrium. Pro-inflammatory cytokines and TLR ligands increased the expression of MT1A, MT1E, MT1F, MT1G, MT1H, MT1X, and MT2A in fetal membranes and myometrium.

CONCLUSION

Temporal-, labor-, and infection-associated increases in MT1 isoforms, MT2A, and MT3 have been observed in fetal membranes and/or myometrium. Furthermore, pro-inflammatory cytokines and bacterial and viral products increased the expression of MT1 isoforms, MT2A, MT3, and MT4 mRNA expression in fetal membranes and myometrium.

SMAD7 regulates proinflammatory and prolabor mediators in amnion and myometrium

Preterm birth continues to be a significant public health problem. Infection (bacterial and or viral) and inflammation, by stimulating proinflammatory cytokines, adhesion molecules, and matrix metalloproteinase 9 (MMP9), play a central role in the rupture of membranes and myometrial contractions. SMAD7 has been implicated in regulating the inflammatory response; however, no studies have been performed with regard to human labor. In this study, we determined the effect of spontaneous human labor and prolabor mediators on SMAD7 expression in myometrium and fetal membranes. Functional studies were employed to investigate the effect of siRNA knockdown of SMAD7 (siSMAD7) in regulating infection and inflammation-induced prolabor mediators. SMAD7 mRNA and protein expression were significantly higher with spontaneous term labor, compared to no labor, in myometrium and fetal membranes. SMAD7 expression was also significantly higher in amnion from women with preterm chorioamnionitis. The proinflammatory cytokines IL1B and TNF, the bacterial product fsl-1, and the viral dsRNA analog poly(I:C) significantly increased SMAD7 in myometrial cells and amnion cells. In myometrial cells, siSMAD7 cells significantly decreased cytokine (IL6) and chemokine (CXCL1, CXCL8, CCL2 are also known as GRO-alpha, interleukin (IL)-8 and monocyte chemotactic protein-1 (MCP-1)) production induced by IL1B, TNF, and fsl-1. There was also a decrease in the expression of adhesion molecules intercellular adhesion molecule 1 (ICAM1) and vascular cell adhesion molecule 1 (VCAM1) in siSMAD7 cells, and MMP9 expression. In amnion, siSMAD7 cells treated with IL1B also decreased cytokine and chemokine production, ICAM1 and MMP9 expression. In conclusion, we report a proinflammatory role for SMAD7 in human gestational tissues, with SMAD7 silencing attenuating the inflammatory response.

Thrombin Alters Human Endometrial Stromal Cell Differentiation During Decidualization

Vaginal bleeding and subchorionic hematomas are associated with increased risk of both early and late pregnancy loss. Thrombin generation may play a pivotal role in the development of these complications. To determine the effects of thrombin on human endometrial stromal cells (hESCs), cells were treated with thrombin at baseline or during decidualization with cyclic adenosine monophosphate (cAMP)+medroxyprogesterone acetate (MPA). Next-generation RNA sequencing revealed that markers of decidualization (IGF-1, IGFBP-1, and prolactin [PRL]) were induced after the initiation of decidualization, whereas thrombin suppressed insulin-like growth factor ( IGF)-1, Insulin-like growth factor binding protein ( IGFBP)-1, and PRL gene expression at baseline and during decidualization. These effects were mediated through protease activated receptor (PAR)-1- and PAR-1-independent pathways. Thrombin decreased the secretion of a key marker of decidualization (PRL), altered the morphological transformation of decidualizing hESCs, and activated genes involved in matrix degradation and proinflammatory chemokines ( Interleukin-8 and Interleukin-6). Genes encoding factors important for matrix stability ( Col1α1, LOX) were suppressed. We suggest that intrauterine bleeding and generation of thrombin accentuates leukocyte extravasation and endometrial inflammation, impairs decidualization, and endometrial support of early pregnancy.

Pellino 1 is a novel regulator of TNF and TLR signalling in human myometrial and amnion cells

Preterm birth is the primary cause of neonatal deaths and morbidities. Pathological processes causally linked to preterm birth are inflammation and infection. Pellino-1 (Peli1) has previously been found to regulate the inflammatory response in non-gestational tissues in response to toll-like receptor (TLR) ligands and pro-inflammatory cytokines. The aims of this study were to determine the effect of labor on Peli1 expression in myometrium and fetal membranes, and the effect of Peli1 silencing by siRNA (siPELI1) on the production of pro-inflammatory and pro-labor mediators. The expression of Peli1 was found to be higher in myometrium and fetal membranes with term labor, compared to non-laboring samples. Peli1 mRNA and protein expression was also higher in amnion from women with preterm histological chorioamnionitis. In human primary myometrial cells, siPELI1 transfected cells showed a decrease in pro-inflammatory cytokine IL6, chemokines (CXCL8, CCL2) and adhesion molecule ICAM1 when in the presence of pro-inflammatory cytokine TNF, TLR2/6 ligand fsl-1, TLR5 ligand flagellin, and TLR3 ligand poly(I:C). Similarly in primary amnion cells, siPELI1 transfected cells decreased IL1B-induced expression and secretion of IL6 and CXCL8. In siPELI1 transfected myometrial cells, there was a decrease in prostaglandin PGF_2α and its receptor, PTGFR mRNA expression when treated with TNF. There was a decrease in NF-κB RELA transcriptional activity in siPELI1 transfected cells in the presence of TNF, fsl-1 and flagellin, but not poly(I:C). Our study suggests a novel role for Peli1 in regulating pro-inflammatory and pro-labor mediators through TNF and TLR signalling.

Inhibition of PIM1 kinase attenuates inflammation-induced pro-labour mediators in human foetal membranes in vitro

STUDY QUESTION

Does proviral integration site for Moloney murine leukaemic virus (PIM)1 kinase play a role in regulating the inflammatory processes of human labour and delivery?

SUMMARY ANSWER

PIM1 kinase plays a critical role in foetal membranes in regulating pro-inflammatory and pro-labour mediators.

WHAT IS KNOWN ALREADY

Infection and inflammation have strong causal links to preterm delivery by stimulating pro-inflammatory cytokines and collagen degrading enzymes, which can lead to rupture of membranes. PIM1 has been shown to have a role in immune regulation and inflammation in non-gestational tissues; however, its role has not been explored in the field of human labour.

STUDY DESIGN, SIZE, DURATION

PIM1 expression was analysed in myometrium and/or foetal membranes obtained at term and preterm (n = 8-9 patients per group). Foetal membranes, freshly isolated amnion cells and primary myometrial cells were used to investigate the effect of PIM1 inhibition on pro-labour mediators (n = 5 patients per treatment group).

PARTICIPANTS/MATERIALS, SETTING AND METHODS

Foetal membranes, from term and preterm, were obtained from non-labouring and labouring women, and from preterm pre-labour rupture of membranes (PPROM) (n = 9 per group). Amnion was collected from women with and without preterm chorioamnionitis (n = 8 per group). Expression of PIM1 kinase was determined by qRT-PCR and western blotting. To determine the effect of PIM1 kinase inhibition on the expression of pro-inflammatory and pro-labour mediators induced by bacterial products lipopolysaccharide (LPS) (10 μg/ml) and flagellin (1 μg/ml) and pro-inflammatory cytokine tumour necrosis factor (TNF) (10 ng/ml), chemical inhibitors SMI-4a (20 μM) and AZD1208 (50 μM) were used in foetal membrane explants and siRNA against PIM1 was used in primary amnion cells. Statistical significance was set at P < 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

PIM1 expression was significantly increased in foetal membranes after spontaneous term labour compared to no labour at term and in amnion with preterm chorioamnionitis compared to preterm with no chorioamnionitis. There was no change in PIM1 expression with preterm labour or PPROM compared to preterm with no labour or PPROM. In human foetal membranes, PIM1 inhibitors SMI-4a and AZD1208 significantly decreased the expression of pro-inflammatory cytokine interleukin-6 (IL6) and chemokines CXCL8 and CCL2 mRNA and release, prostaglandin prostaglandin F2α (PGF2α) release, adhesion molecule intercellular adhesion molecule 1 mRNA expression and release, and oxidative stress marker 8-isoprostane release after stimulation with either LPS or flagellin. Primary amnion cells transfected with PIM1 siRNA also showed decreased expression of IL6, CXCL8 and CCL2, PTGS2 mRNA and PGF2α release, and matrix metalloproteinase-9 (MMP9) expression, when stimulated with TNF.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

The conclusions were drawn from in vitro experiments using foetal membrane explants and primary cells isolated from amnion. Animal models are necessary to determine whether PIM1 kinase inhibitors can prevent spontaneous preterm birth in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

PIM1 kinase inhibitors may provide a novel therapeutic approach for preventing spontaneous preterm birth.

STUDY FUNDING/COMPETING INTEREST(S)

Associate Professor Martha Lappas is supported by a Career Development Fellowship from the National Health and Medical Research Council (NHMRC; grant no. 1047025). Funding for this study was provided by the NHMRC (grant no. 1058786), Norman Beischer Medical Research Foundation and the Mercy Research Foundation. The authors have no conflict of interest.

Air Pollutant Exposure Within a Few Days of Delivery and Placental Abruption in Japan

BACKGROUND

Placental abruption is an emergency obstetric complication. Although the etiology of abruption is not fully understood, acute stimuli, such as ischemia and/or inflammation, are associated with rupture of the decidual artery, resulting in placental separation. Ischemia and inflammation are acute biologic effects of air pollution. Using a case-crossover design, we tested the hypothesis that a short-term increase in exposure to air pollutants is a potential trigger of placental abruption.

METHODS

We received data for western Japan (Kyushu-Okinawa Districts) from the Japan Perinatal Registry Network database. From 2005 to 2010, 821 singleton pregnant women with placental abruption were identified. We assigned daily concentrations of air pollutants, including nitrogen dioxide (NO2), suspended particulate matter, ozone, and sulfur dioxide (SO2), from the nearest monitoring station to the respective delivery hospital of each woman. Because information on the onset day of abruption was not obtained, we assumed the case day to be 1 day before the day of delivery.

RESULTS

Exposure to NO2 at 2 days' lag was associated with placental abruption (temperature adjusted odds ratio per 10 ppb increase = 1.4; 95% confidence interval = 1.1, 1.8). The association patterns were similar, when we restricted to participants who delivered by emergency cesarean (1.4, 1.1, 1.9), or who delivered after 35 weeks of gestation (1.4, 1.0, 2.0). There was no association with suspended particulate matter, ozone, or SO2.

CONCLUSIONS

We observed an association between NO2 exposure at 2 days before the day of delivery and placental abruption in pregnant Japanese women.

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.

Optineurin suppression activates the mediators involved in the terminal effector pathways of human labour and delivery

Spontaneous preterm birth remains the major cause of neonatal death and morbidity. Studies in non-gestational tissues report that optineurin (OPTN) is critical in the termination of NFKB1 activity and control of inflammation, central features of spontaneous preterm birth. The aims of the present study were to determine: (1) OPTN expression in fetal membranes and the myometrium during labour; (2) the effects of IL1B on OPTN expression in primary myometrial cells; and (3) the effects of OPTN short interference (si) RNA on IL1B-stimulated proinflammatory and prolabour mediators. OPTN mRNA and protein expression was significantly decreased with spontaneous term labour in fetal membranes and the myometrium. Although there was no effect of spontaneous preterm labour on OPTN expression in fetal membranes, there was decreased OPTN expression in membranes with chorioamnionitis and myometrial cells treated with 1ng mL^-1 IL1B for 1 or 6h. In cells transfected with OPTN siRNA, significant increases were seen in IL1B-stimulated IL6, tumour necrosis factor, CXCL8 and monocyte chemoattractant protein-1 mRNA expression and release, cyclo-oxygenase-2 and prostanoid PTGFR receptor mRNA expression and the release of prostaglandin F_2α. There was no change in IL1B-stimulated NFKBIA expression; however, there was increased NFKB1 p65 DNA-binding activity. The results of the present study suggest that OPTN is a negative regulator of inflammation-induced prolabour mediators.

Thrombin Augments LPS-Induced Human Endometrial Endothelial Cell Inflammation via PAR1 Activation

PROBLEM

Risk factors for preterm birth include placental abruption, giving rise to excessive decidual thrombin, and intrauterine bacterial infection. Human endometrial endothelial cells (HEECs) express Toll-like receptors (TLRs), and infection-derived agonists trigger HEECs to generate specific inflammatory responses. As thrombin, in addition to inducing coagulation, can contribute to inflammation, its effect on HEEC inflammatory responses to the TLR4 agonist, bacterial lipopolysaccharide (LPS), was investigated.

METHOD OF STUDY

HEECs were pre-treated with or without thrombin or specific protease-activated receptor (PAR) agonists, followed by treatment with or without LPS. Supernatants were measured for cytokines and chemokines by ELISA and multiplex analysis.

RESULTS

Thrombin significantly and synergistically augmented LPS-induced HEEC secretion of interleukin (IL)-6, IL-8, granulocyte colony-stimulating factor (G-CSF), and growth-regulated oncogene-alpha (GRO-α), and significantly augmented monocyte chemotactic protein (MCP)-1, tumor necrosis factor-alpha (TNF-α), and vascular endothelial growth factor (VEGF) secretion additively. Similar to thrombin, a PAR1 agonist synergistically augmented the LPS-induced HEEC secretion of inflammatory IL-6, IL-8, G-CSF, and GRO-α.

CONCLUSION

Thrombin, via PAR1 activation, synergistically augments LPS-induced HEEC production of chemokines involved in immune cell recruitment and survival, suggesting a mechanism by which intrauterine abruption and bacterial infection may together be associated with an aggravated uterine inflammatory response.

Pyoderma gangrenosum and pregnancy: an example of abnormal inflammation and challenging treatment

Pyoderma gangrenosum (PG) is a neutrophil-predominant inflammatory disease that initially presents as a sterile pustule and may progress to ulcerations. Its root cause is unknown, but the presentation is commonly associated with systemic inflammatory conditions such as inflammatory bowel disease, arthritis and haematological abnormalities. On the other hand, pregnant women show a progressive neutrophilia during gestation, which culminates in a major inflammatory event to help drive labour. Although uncommonly, PG has been associated with pregnancy, which provides an additional link to systemic inflammation as an underlying cause of PG. We reviewed documented presentations of PG in gravid and post-partum patients, and have speculated on the possible pathogenesis based on their clinical presentations. Also, we summarize the reported treatments and their outcomes in these patients.

Autophagy, which is decreased in labouring fetal membranes, regulates IL-1β production via the inflammasome

INTRODUCTION

IL-1β plays a vital role in the terminal processes of human labour and delivery. Inflammasome activation is required to process pro IL-1β to an active, secreted molecule. Recent studies have shown that autophagy regulates IL-1β via the inflammasome. The aims were to determine the effect of (i) human spontaneous term and preterm labour on the expression of autophagy proteins in fetal membranes; and (ii) autophagy inhibition on IL-1β release.

METHODS

Fetal membranes, from term and preterm, were obtained from non-labouring and labouring women. Tissue explants were used to determine the effect of inhibition of autophagy on IL-1β secretion.

RESULTS

Expression of the autophagy proteins Beclin-1, Atg3, Atg5, Atg7, Atg12, Atg16L1 were lower after spontaneous term labour. Beclin-1 and Atg7 expression were lower after spontaneous preterm labour. Beclin-1, Atg3, and Atg7 expression were lower after preterm pre-labour rupture of membranes (PPROM) compared to preterm with intact membranes. LC3B-I expression was higher after spontaneous term and preterm labour and with PPROM; there was no difference in LC3B-II expression between the two groups. The autophagy inhibitor LY290042 increased IL-1β secretion in the presence of bacterial endotoxin LPS; IL-1β secretion was ameliorated in the presence inflammasome inhibitors.

DISCUSSION

Autophagy is decreased in fetal membranes after spontaneous labour and delivery, and PPROM. Inhibition of autophagy regulates the secretion of IL-1β via inflammasome activation. IL-1β is a major contributor to the pathophysiology of spontaneous preterm birth. Therefore activation of autophagy may be a potential therapeutic mechanism to delay or prevent infection-induced preterm birth.

Mechanisms of chorioamnionitis-associated preterm birth: interleukin-1β inhibits progesterone receptor expression in decidual cells

In chorioamnionitis (CAM), a major cause of preterm birth (PTB), maternal-fetal inflammation of the decidua and amniochorion cause the release of cytokines that elicit cervical ripening, fetal membrane rupture and myometrial activation. We posit that this inflammatory milieu triggers PTB by inhibiting progesterone receptor (PR) expression and increasing decidual prostaglandin (PG) production. Immunohistochemical staining of decidua detected significantly lower PR levels in decidual cells (DCs) from CAM-complicated PTB. Incubation of DCs with IL-1β decreased PR expression and significantly increased PGE2 and PGF2α production and COX-2 expression. The addition of PGF2α to DC cultures also suppressed PR expression. However, the COX inhibitor, indomethacin, did not reverse IL-1β suppression of PR expression in DC cultures. Although IL-1β treatment activated the NF-KB, ERK1/2 and p38 MAPK signalling cascades in DCs, inhibition of ERK1/2 MAPK signalling alone was sufficient to completely reverse the suppression of PR levels by IL-1β. These findings suggest that CAM-associated PTB is induced at least in part by IL-1β-mediated functional progesterone withdrawal.

Activation of AMPK in human fetal membranes alleviates infection-induced expression of pro-inflammatory and pro-labour mediators

INTRODUCTION

In non-gestational tissues, the activation of adenosine monophosphate (AMP)-activated kinase (AMPK) is associated with potent anti-inflammatory actions. Infection and/or inflammation, by stimulating pro-inflammatory cytokines and matrix metalloproteinase (MMP)-9, play a central role in the rupture of fetal membranes. However, no studies have examined the role of AMPK in human labour.

METHODS

Fetal membranes, from term and preterm, were obtained from non-labouring and labouring women, and after preterm pre-labour rupture of membranes (PPROM). AMPK activity was assessed by Western blotting of phosphorylated AMPK expression. To determine the effect of AMPK activators on pro-inflammatory cytokines, fetal membranes were pre-treated with AMPK activators then stimulated with bacterial products LPS and flagellin or viral dsDNA analogue poly(I:C). Primary amnion cells were used to determine the effect of AMPK activators on IL-1β-stimulated MMP-9 expression.

RESULTS

AMPK activity was decreased with term labour. There was no effect of preterm labour. AMPK activity was also decreased in preterm fetal membranes, in the absence of labour, with PROM compared to intact membranes. AMPK activators AICAR, phenformin and A769662 significantly decreased IL-6 and IL-8 stimulated by LPS, flagellin and poly(I:C). Primary amnion cells treated with AMPK activators significantly decreased IL-1β-induced MMP-9 expression.

DISCUSSION

The decrease in AMPK activity in fetal membranes after spontaneous term labour and PPROM indicates an anti-inflammatory role for AMPK in human labour and delivery. The use of AMPK activators as possible therapeutics for threatened preterm labour would be an exciting future avenue of research.

Amniotic fluid infection, inflammation, and colonization in preterm labor with intact membranes

OBJECTIVE

The purpose of this study was to compare intraamniotic inflammation vs microbial invasion of the amniotic cavity (MIAC) as predictors of adverse outcome in preterm labor with intact membranes.

STUDY DESIGN

Interleukin-6 (IL-6) was measured in prospectively collected amniotic fluid from 305 women with preterm labor. MIAC was defined by amniotic fluid culture and/or detection of microbial 16S ribosomal DNA. Cases were categorized into 5 groups: infection (MIAC; IL-6, ≥11.3 ng/mL); severe inflammation (no MIAC; IL-6, ≥11.3 ng/mL); mild inflammation (no MIAC; IL-6, 2.6-11.2 ng/mL); colonization (MIAC; IL-6, <2.6 ng/mL); negative (no MIAC; IL-6, <2.6 ng/mL).

RESULTS

The infection (n = 27) and severe inflammation (n = 36) groups had similar latency (median, <1 day and 2 days, respectively) and similar rates of composite perinatal morbidity and mortality (81% and 72%, respectively). The colonization (n = 4) and negative (n = 195) groups had similar outcomes (median latency, 23.5 and 25 days; composite morbidity and mortality rates, 21% and 25%, respectively). The mild inflammation (n = 47) groups had outcomes that were intermediate to the severe inflammation and negative groups (median latency, 7 days; composite morbidity and mortality rates, 53%). In logistic regression adjusting for gestational age at enrollment, IL-6 ≥11.3 and 2.6-11.2 ng/mL, but not MIAC, were associated significantly with composite morbidity and mortality rates (odds ratio [OR], 4.9; 95% confidence interval [CI], 2.2-11.2, OR, 3.1; 95% CI, 1.5-6.4, and OR, 1.8; 95% CI, 0.6-5.5, respectively).

CONCLUSION

We confirmed previous reports that intraamniotic inflammation is associated with adverse perinatal outcomes whether or not intraamniotic microbes are detected. Colonization without inflammation appears relatively benign. Intraamniotic inflammation is not simply present or absent but also has degrees of severity that correlate with adverse outcomes. We propose the designation amniotic inflammatory response syndrome to denote the adverse outcomes that are associated with intraamniotic inflammation.

Complications from inflammatory bowel disease during pregnancy and delivery

BACKGROUND & AIMS

Little is known about complications from ulcerative colitis (UC) or Crohn's disease (CD) during pregnancy and delivery. We assessed complications by using data from a large, population-based cohort.

METHODS

We analyzed data from 1209 women with UC, 787 women with CD, and 10,773 women without these diseases (the comparison group) by using the Medical Birth, Patient, and Prescribed Drug Registers of all residents in Sweden. All the women included in the analysis gave birth to a single infant between October 2006 and December 2009. We used data on medical treatment, surgery, and hospital admissions to assess disease activity. Risks of pregnancy and delivery complications were determined from adjusted odds ratios (aORs) with 95% confidence intervals (CIs).

RESULTS

The risk of venous thromboembolism was increased among women with UC (aOR, 3.78; 95% CI, 1.52-9.38), particularly for those with flaring disease. Women with CD had a higher risk of antepartum hemorrhage (aOR, 1.66; 95% CI, 1.12-2.45), with the highest risks among those with no disease activity. Risks of elective cesarean delivery were more than doubled among women with UC (aOR, 2.44; 95% CI, 2.06-2.88) or CD (aOR, 2.31; 95% CI, 1.89-2.83). Women with UC (aOR, 1.39; 95% CI, 1.13-1.70) or CD (aOR, 1.50; 95% CI, 1.17-1.92) had increased risk for emergency cesarean delivery. Women with an inactive UC or flaring CD had the highest risks of cesarean delivery.

CONCLUSIONS

Women with UC or CD have more complications during pregnancy and delivery than women without these diseases. Disease activity affects mode of delivery, and thrombophilic events present differently in women with UC vs CD.

Advances in medical diagnosis of intra-amniotic infection

INTRODUCTION

Intrauterine infection is a global problem and a significant contributor to morbidity and perinatal death. The host response to infection causes an inflammatory state that acts synergistically with microbial insult to induce preterm birth and fetal damage. Prompt and accurate diagnosis of intra-amniotic infection in the asymptomatic stage of the disease is critical for improved maternal and neonatal outcomes.

AREAS COVERED

This article provides an overview of the most recent progress, challenges, and opportunities for discovery and clinical implementation of various maternal serum, cervicovaginal, and amniotic fluid biomarkers in pregnancies complicated by intra-amniotic infection.

EXPERT OPINION

Clinically relevant biomarkers are critical to the accurate diagnostic of intrauterine infection. Front-end implementation of such biomarkers will also translate in lower incidence of early-onset neonatal sepsis (EONS) which is an important determinant of neonatal morbidity and mortality associated with prematurity. However, of the hundreds of differentially expressed proteins, only few may have clinical utility and thus function as biomarkers. The small number of validation studies along with barriers to implementation of technological innovations in the clinical setting are current limitations.

Tissue factor-dependent thrombin generation across pregnancy

OBJECTIVE

Normal pregnancy results in a prothrombotic state. Studies that have investigated the capacity of pregnant women to generate thrombin are limited. Our aim was to evaluate thrombin generation longitudinally from the preconception period, through pregnancy, and after pregnancy.

STUDY DESIGN

We evaluated young, healthy nulligravid women (n = 20) at 4 time points and compared the data with 10 control women at 2 time points. Coagulation was initiated with tissue factor in contact pathway inhibited plasma, and thrombin generation was determined in the presence of a fluorogenic substrate.

RESULTS

The maximum level and rate of thrombin generation increased during pregnancy; the highest level and rate occurred in late pregnancy compared with prepregnancy (P < .001). Subsequently, thrombin generation decreased in the postpregnancy samples that included maximum level, rate, and area under the curve (P < .001).

CONCLUSION

Our data provide evidence for an increase in tissue factor-dependent thrombin generation with pregnancy progression, followed by a return to prepregnancy thrombin levels.

Phospholipid scramblase expression in the pregnant mouse uterus in LPS-induced preterm delivery

Phospholipid scramblases (PLSCR), stimulated by proinflammatory cytokines, are thought to mediate the loss of lipid asymmetry in cell membranes, allowing for specific reactions in the coagulation cascade. The PLSCR may therefore provide a link between inflammation, coagulation, and, because thrombin is a uterotonic, preterm birth (PTB). To explore the relationship between PLSCR expression and inflammation-related PTB, we utilized reverse transcriptase-polymerase chain reaction and Western blot studies to quantify messenger RNA (mRNA) and protein expression for the 4 PLSCR homologues (PLSCR 1-4). Uteri from day 15 pregnant mice were harvested at several time points after intrauterine lipopolysaccharide (LPS) injection (or normal saline, for controls). Expression of mRNA in all 4 Plscr isoforms was demonstrated. Lipopolysaccharide treatment resulted in increased expression of PLSCR-1 and a decrease in Plscr4 mRNA, thereby demonstrating modulation of PLSCR-1 and PLSCR-4 in LPS-induced PTB. Additionally, protein expression was confirmed for all except PLSCR-4, with increased expression of PLSCR-1 after LPS treatment.

Proteomics/diagnosis of chorioamnionitis and of relationships with the fetal exposome

Proteomics, a relatively young science, originally emerged as a complement to genomics research. By definition, the goal of proteomics is to provide a snapshot of all the proteins within an organism, tissue or biological sample at a given moment. Proteomics has the ability to single out one or more proteins (biomarkers) that change consistently in affected subjects as compared to those disease-free. From a proteomics perspective, chorioamnionitis poses both challenges and opportunities. Challenges relate to the dynamic course of the inflammatory process, and compartmentalization of the gestational sac in relation to the maternal compartment. An inability to evaluate the amniotic fluid non-invasively and repeatedly for meaningful changes in its proteome, and lack of a true gold standard for diagnosis of inflammation and/or infection, represent additional challenges. On the other hand, the unbiased and holistic nature of proteomics offers a real opportunity to improve the current diagnostic and prognostic algorithms for chorioamnionitis. Even at this current stage there are reasons to believe that proteomic biomarkers will improve the understanding of how chorioamnionitis programs or affects the fetus in utero, thus defining its exposome (sum of interactions between genetic make-up of the fetus and the intrauterine environment) of pregnancies affected by infection and/or inflammation. This review summarizes the results of proteomics studies that have aimed or reached these goals.

Heparin elevates circulating soluble fms-like tyrosine kinase-1 immunoreactivity in pregnant women receiving anticoagulation therapy

BACKGROUND

Alterations in circulating levels of pro- and antiangiogenic factors have been associated with adverse pregnancy outcomes. Heparin is routinely administered to pregnant women, but without clear knowledge of its impact on these factors.

METHODS AND RESULTS

We conducted a longitudinal study of 42 pregnant women. Twenty-one women received prophylactic heparin anticoagulation, and 21 healthy pregnant women served as controls. Compared with gestational age-matched controls, heparin treatment was associated with increased circulating levels of soluble fms-like tyrosine kinase-1 (sFlt-1) in the third trimester (P<0.05), in the absence of preeclampsia, placental abruption, or fetal growth restriction. Heparin had no effect on circulating levels of vascular endothelial growth factor, placenta growth factor, or soluble endoglin as assessed by ELISA. In vitro, low-molecular weight and unfractionated heparins stimulated sFlt-1 release from placental villous explants, in a dose- and time-dependent manner. This effect was not due to placental apoptosis, necrosis, alteration in protein secretion, or increased transcription. Western blot analysis demonstrated that heparin induced shedding of the N-terminus of Flt-1 both in vivo and in vitro as indicated by a predominant band of 100-112 kDa. By using an in vitro angiogenesis assay, we demonstrated that serum of heparin-treated cases inhibited both basal and vascular endothelial growth factor-induced capillary-like tube formation.

CONCLUSIONS

Heparin likely increases the maternal sFlt-1 through shedding of the extracellular domain of Flt-1 receptor. Our results imply that upregulation of circulating sFlt-1 immunoreactivity in pregnancy is not always associated with adverse outcomes, and that heparin's protective effects, if any, cannot be explained by promotion of angiogenesis.