Effects of thrombin on myometrial contractions in vitro and in vivo

The role of placental insufficiency in spontaneous preterm birth: A literature review

Preterm Birth (delivery before 37 weeks of gestation) is the leading cause of childhood mortality and is also associated with significant morbidity both in the neonatal period and beyond. The aetiology of spontaneous preterm birth is unclear and likely multifactorial incorporating factors such as infection/inflammation and cervical injury. Placental insufficiency is emerging as an additional contributor to spontaneous preterm delivery; however, the mechanisms by which this occurs are not fully understood. Serum biomarkers and imaging techniques have been investigated as potential predictors of placental insufficiency, however none have yet been found to have a sufficient predictive value. This review examines the evidence for the role of the placenta in preterm birth, preterm prelabour rupture of the membranes and abruption as well as highlighting areas where further research is required.

What do we know about why women bleed and what do we not know?

Women or people with a uterus are vulnerable to both normal and abnormal bleeding. During the reproductive years, the uterus is prepared physiologically to accept an embryo and support its growth and development during pregnancy, or in the absence of implantation of an embryo, recycle through the process of menstruation and accept an embryo a month or so later. If fertilization takes place and an embryo or embryos implant in the uterus, the fetal trophoblast, or outer cell layer of the embryo, invades and dilates the maternal spiral arteries and forms the placenta. No matter when in gestation a pregnancy ends, at the conclusion of pregnancy, the placenta should separate from the wall of the uterus and be expelled. Abnormal bleeding occurs during pregnancy or after delivery when the normal uteroplacental interface has not been established or is interrupted; during miscarriage; during ectopic pregnancy; during premature separation of the placenta; or during postpartum hemorrhage. Heavy menstrual bleeding, a subset of abnormal menstrual bleeding, can be quantitatively defined as >80 mL of blood loss per cycle. Unlike postpartum hemorrhage, heavy menstrual bleeding is significantly associated with an underlying bleeding disorder. While there is other reproductive tract bleeding in women, notably bleeding at the time of ovulation or with a life-threatening ruptured ectopic pregnancy, the unique bleeding that women experience is predominantly uterine in origin. Many of the unique aspects of uterine hemostasis, however, remain unknown.

The Role of Platelets in the Pathogenesis and Pathophysiology of Adenomyosis

Widely viewed as an enigmatic disease, adenomyosis is a common gynecological disease with bewildering pathogenesis and pathophysiology. One defining hallmark of adenomyotic lesions is cyclic bleeding as in eutopic endometrium, yet bleeding is a quintessential trademark of tissue injury, which is invariably followed by tissue repair. Consequently, adenomyotic lesions resemble wounds. Following each bleeding episode, adenomyotic lesions undergo tissue repair, and, as such, platelets are the first responder that heralds the subsequent tissue repair. This repeated tissue injury and repair (ReTIAR) would elicit several key molecular events crucial for lesional progression, eventually leading to lesional fibrosis. Platelets interact with adenomyotic cells and actively participate in these events, promoting the lesional progression and fibrogenesis. Lesional fibrosis may also be propagated into their neighboring endometrial-myometrial interface and then to eutopic endometrium, impairing endometrial repair and causing heavy menstrual bleeding. Moreover, lesional progression may result in hyperinnervation and an enlarged uterus. In this review, the role of platelets in the pathogenesis, progression, and pathophysiology is reviewed, along with the therapeutic implication. In addition, I shall demonstrate how the notion of ReTIAR provides a much needed framework to tether to and piece together many seemingly unrelated findings and how it helps to make useful predictions.

Relationship between unremoved cervical polyp in pregnancy and spontaneous preterm birth

BACKGROUND

Cervical polyps removed during pregnancy have been reported to be associated with preterm birth; however, the association between unremoved cervical polyps and preterm birth has not been elucidated.

OBJECTIVE

This study aimed to clarify the relationship between cervical polyps detected before 12 weeks of gestation managed expectantly and spontaneous preterm birth.

STUDY DESIGN

This retrospective cohort study included pregnant women who visited a tertiary perinatal center before 12 weeks of gestation between January 2015 and December 2019. The exclusion criteria were as follows: multiple gestations, loss or termination of pregnancy before 12 weeks of gestation, major fetal anomalies, fetal chromosomal abnormalities, fetal demise, having undergone removal of cervical polyps before the first visit to our hospital, and moving to other hospitals before delivery. A vaginal speculum examination was routinely performed during a prenatal visit before 12 weeks of gestation. When a cervical polyp was detected on speculum examination, it was managed expectantly, unless gynecologic malignancy was suspected. Relationships between cervical polyps and spontaneous preterm birth before 34 weeks of gestation were evaluated using logistic regression analysis and Cox proportional-hazards analysis adjusted for known confounders for spontaneous preterm birth.

RESULTS

A total of 4172 pregnant women were included, of whom 92 (2.2%) had a cervical polyp detected before 12 weeks of gestation. None of the women underwent polypectomy during pregnancy. The incidence of spontaneous preterm birth before 34 weeks of gestation was higher in pregnant women with cervical polyps than in those without them (5.4% vs 0.7%; P<.01). Logistic regression analysis revealed that cervical polyps were an independent risk factor for spontaneous preterm birth before 34 weeks of gestation (adjusted odds ratio, 4.09; 95% confidence interval, 1.70-9.81; P<.01). The adjusted hazard ratio for spontaneous preterm birth before 34 weeks of gestation among women with vs without cervical polyps was 2.95 (95% confidence interval, 1.32-6.62; P<.01).

CONCLUSION

Cervical polyps detected before 12 weeks of gestation managed expectantly are a significant risk factor for spontaneous preterm birth before 34 weeks of gestation.

Utility of the Levonorgestrel-Releasing Intrauterine System in the Treatment of Abnormal Uterine Bleeding and Dysmenorrhea: A Narrative Review

INTRODUCTION

We undertook a literature review of the use of levonorgestrel-releasing intrauterine devices when utilized for heavy menstrual bleeding and/or dysmenorrhea.

METHODS

A narrative review of articles in the Scopus and Medline databases was conducted.

RESULTS

A number of options exist for the management of both abnormal uterine bleeding (AUB) and dysmenorrhea, and evidence is accumulating that the insertion of a levonorgestrel-releasing intrauterine system (LNG-IUS) represents a useful option for their long-term treatment. The idea of using a progestogen released in utero was initially conceived to achieve long-term contraception, but it was quickly found that these systems could be utilized for a number of therapeutic applications. The first device to be made commercially available, Progestasert, was withdrawn from the market because, in the event of contraceptive failure, it caused a disproportionate percentage of extrauterine pregnancies. On the other hand, the LNG-IUS continues to be successfully utilized in its various variants, releasing 20, 13, or 8 μg/day. These devices have a respective duration of action of 7 (possibly 8), 5, and 3 years, and there exist versions of frameless systems affixed to the myometrium of the uterine fundus. In the present review, following a brief description of the major causes of AUB and dysmenorrhea, the molecular bases for the use of the LNG-IUS are summarized. This is followed by a compendium of its use in AUB and dysmenorrhea, concluding that the insertion of the system improves the quality of life, reduces menstrual blood loss better than other medical therapies, and decreases the extent of dysmenorrhea and pelvic pain. In addition, there is no evidence of a significant difference in these outcomes when the use of the LNG-IUS was compared with improvements offered by endometrial ablation or hysterectomy. Possibly, the most important mechanism of action of the system consists of its ability to induce amenorrhea, which effectively eliminates heavy bleeding and dysmenorrhea. However, no method is ideal for every woman, and, in the case of the LNG-IUS, younger age and severe dysmenorrhea seem to be associated with a higher risk of discontinuation.

CONCLUSION

The higher-dose LNG-IUS is a useful tool for HMB and dysmenorrhea in women of all ages. The low cost and ease of use make the LNG-IUS an attractive option, especially when contraception is also desired.

Proteomic identification of novel plasma biomarkers associated with spontaneous preterm birth in women with preterm labor without infection/inflammation

Objective

We sought to identify plasma biomarkers associated with spontaneous preterm birth (SPTB, delivery within 21 days of sampling) in women with preterm labor (PTL) without intra-amniotic infection/inflammation (IAI) using label-free quantitative proteomic analysis, as well as to elucidate specific protein pathways involved in these cases.

Methods

This was a retrospective cohort study comprising 104 singleton pregnant women with PTL (24–32 weeks) who underwent amniocentesis and demonstrated no evidence of IAI. Analysis of pooled plasma samples collected from SPTB cases and term birth (TB) controls (n = 10 for each group) was performed using label-free quantitative mass spectrometry for proteome profiling in a nested case-control study design. Eight candidate proteins of interest were validated by ELISA-based assay and a clot-based assay in the total cohort.

Results

Ninety-one proteins were differentially expressed (P < 0.05) in plasma samples obtained from SPTB cases, of which 53 (58.2%) were upregulated and 38 (41.8%) were downregulated when compared to TD controls. A validation study confirmed that plasma from women who delivered spontaneously within 21 days of sampling contained significantly higher levels of coagulation factor Ⅴ and lower levels of S100 calcium binding protein A9 (S100A9), especially the former which was independent of baseline variables. The top-ranked pathways related to the 91 differentially expressed proteins were liver-X-receptor/retinoid X receptor (RXR) activation, acute phase response signaling, farnesoid X receptor/RXR activation, coagulation system, and complement system.

Conclusions

Proteomic analyses in this study identified potential novel biomarkers (i.e., coagulation factor V and S100A9) and potential protein pathways in plasma associated with SPTB in the absence of IAI in women with PTL. The present findings provide novel insights into the molecular pathogenesis and therapeutic targets specific for idiopathic SPTB.

Prompt evaluation and treatment of third-trimester bleeding

ABSTRACT

Third-trimester bleeding is an obstetric emergency and is associated with significant maternal and fetal morbidity and mortality. The two most common causes for third-trimester bleeding are placental abruption and placenta previa, which account for about half of all cases. Clinicians should have a thorough understanding of the risk factors, clinical presentation, and appropriate management of these conditions. Timely management is necessary for the survival of mother and fetus and to reduce the incidence of neonatal complications.

Mechanisms of thrombin-Induced myometrial contractions: Potential targets of progesterone

Intrauterine bleeding during pregnancy is a major risk factor for preterm birth. Thrombin, the most abundant coagulation factor in blood, is associated with uterine myometrial contraction. Here, we investigated the molecular mechanism and signaling of thrombin-induced myometrial contraction. First, histologic studies of placental abruption, as a representative intrauterine bleeding, revealed that thrombin was expressed within the infiltrating hemorrhage and that thrombin receptor (protease-activated receptor 1, PAR1) was highly expressed in myometrial cells surrounding the hemorrhage. Treatment of human myometrial cells with thrombin resulted in augmented contraction via PAR1. Thrombin-induced signaling to myosin was then mediated by activation of myosin light chain kinase- and Rho-induced phosphorylation of myosin light chain-2. In addition, thrombin increased prostaglandin-endoperoxidase synthase-2 (PTGS2 or COX2) mRNA and prostaglandin E2 and F2α synthesis in human myometrial cells. Thrombin significantly increased the mRNA level of interleukine-1β, whereas it decreased the expressions of prostaglandin EP3 and F2α receptors. Progesterone partially blocked thrombin-induced myometrial contractions, which was accompanied by suppression of the thrombin-induced increase of PTGS2 and IL1B mRNA expressions as well as suppression of PAR1 expression. Collectively, thrombin induces myometrial contractions by two mechanisms, including direct activation of myosin and indirect increases in prostaglandin synthesis. The results suggest a therapeutic potential of progesterone for preterm labor complicated by intrauterine bleeding.

Matrix Metalloprotease-1 and Elastase Are Novel Uterotonic Agents Acting Through Protease-Activated Receptor 1

Matrix metalloproteinase-1 (MMP-1) and neutrophil elastase are proteolytic enzymes involved in tissue remodeling, but a role for them as uterotonic agents has not been considered. However, both these proteases activate protease-activated receptor 1 (PAR-1) that mediates thrombin-induced contractions. Matrix metalloproteinase-1 and elastase are products of neutrophils that infiltrate intrauterine tissues at the time of labor, so we tested the hypothesis that these proteases might be novel uterotonic agents acting via PAR-1. Decidual tissue was collected from fetal membranes of term not-in-labor (TNL), term labor (TL), and preterm labor (PTL) women and analyzed for gene and protein expression of MMP-1 and neutrophil elastase. Contractile effects of MMP-1 and elastase were tested with uterine strips of day 19 and 20 gestation rats. Expression of MMP-1 and neutrophil elastase was increased in TL and PTL as compared to TNL. Expression of both the pro- and active enzymes of MMP-1 increased progressively from TNL to TL to PTL. Tumor necrosis factor-α, a neutrophil product, increased MMP-1 in decidual and myometrial cells. Both MMP-1 and elastase stimulated strong contractions of myometrial strips, which were prevented by inhibition of PAR-1 and inhibition of inositol trisphosphate receptor or calcium channel blockade. Indomethacin did not prevent protease-induced contractions. These data suggest that MMP-1 and neutrophil elastase may be important but heretofore unrecognized players in stimulating uterine contractions at the time of labor, and they may explain why indomethacin delays, but does not prevent, PTL because indomethacin inhibits the prostaglandin component but not the protease component of labor.

The pattern and magnitude of "in vivo thrombin generation" differ in women with preeclampsia and in those with SGA fetuses without preeclampsia

OBJECTIVE

We aimed to determine the differences in the pattern and magnitude of thrombin generation between patients with preeclampsia (PE) and those with a small-for-gestational-age (SGA) fetus.

METHODS

This cross-sectional study included women in the following groups: (1) normal pregnancy (NP) (n = 49); (2) PE (n = 56); and (3) SGA (n = 28). Maternal plasma thrombin generation (TGA) was measured, calculating: (a) lag time (LT); (b) velocity index (VI); (c) peak thrombin concentration (PTC); (d) time-to-peak thrombin concentration (TPTC); and (e) endogenous thrombin potential (ETP).

RESULTS

(1) The median TPTC, VI, and ETP differed among the groups (p = .001, p = .006, p < .0001); 2) the median ETP was higher in the PE than in the NP (p < .0001) and SGA (p = .02) groups; 3) patients with SGA had a shorter median TPTC and a higher median VI than the NP (p = .002, p = .012) and PE (p < .0001, p = .006) groups.

CONCLUSIONS

(1) Patients with PE had higher in vivo thrombin generation than women with NP and those with an SGA fetus; (2) the difference in TGA patterns between PE and SGA suggests that the latter group had faster TGA, while patients with PE had a longer reaction, generating more thrombin. This observation is important for the identification of a subset of patients who might benefit from low molecular-weight heparin.

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.

Mechanistic Differences Leading to Infectious and Sterile Inflammation

Inflammation is a physiologic component of pregnancy and parturition. Overwhelming intrauterine inflammatory load promotes quiescent feto-maternal tissues into a contractile phenotype. Like inflammation, oxidative stress is an inevitable component of both pregnancy and parturition. Pathologic activation of host innate immune response to adverse pregnancy conditions can lead to premature activation of inflammatory and oxidative stress. Inflammation and oxidative stress markers seen with both sterile and infectious inflammation are often similar; therefore, it is difficult to understand causality of conditions like spontaneous preterm birth. This review demonstrates potential mechanistic pathways of activation of sterile and infectious inflammation. We demonstrate the activation of two unique pathways of inflammation by factors that are well-documented proxies for oxidative stress (cigarette smoke extract) and infection (lipopolysaccharide). Sterile inflammation seen after exposure to an oxidative stress inducer is due to cellular elemental damage resulting in p38 mitogen-activated protein kinase (MAPK) induced cellular senescence. Infectious inflammation is through activation of transcription factor NF-κB and independent of oxidative stress-associated damages and p38 MAPK-induced senescence. Understanding the differences in the inflammatory pathway activation by various risk factors is important to design better screening, diagnostic and intervention strategies to reduce the risks of adverse pregnancy outcomes.

Placental vascular pathology and increased thrombin generation as mechanisms of disease in obstetrical syndromes

Obstetrical complications including preeclampsia, fetal growth restriction, preterm labor, preterm prelabor rupture of membranes and fetal demise are all the clinical endpoint of several underlying mechanisms (i.e., infection, inflammation, thrombosis, endocrine disorder, immunologic rejection, genetic, and environmental), therefore, they may be regarded as syndromes. Placental vascular pathology and increased thrombin generation were reported in all of these obstetrical syndromes. Moreover, elevated concentrations of thrombin-anti thrombin III complexes and changes in the coagulation as well as anticoagulation factors can be detected in the maternal circulation prior to the clinical development of the disease in some of these syndromes. In this review, we will assess the changes in the hemostatic system during normal and complicated pregnancy in maternal blood, maternal–fetal interface and amniotic fluid, and describe the contribution of thrombosis and vascular pathology to the development of the great obstetrical syndromes.

Preterm labor: one syndrome, many causes

Preterm birth is associated with 5 to 18% of pregnancies and is a leading cause of infant morbidity and mortality. Spontaneous preterm labor, a syndrome caused by multiple pathologic processes, leads to 70% of preterm births. The prevention and the treatment of preterm labor have been long-standing challenges. We summarize the current understanding of the mechanisms of disease implicated in this condition and review advances relevant to intra-amniotic infection, decidual senescence, and breakdown of maternal-fetal tolerance. The success of progestogen treatment to prevent preterm birth in a subset of patients at risk is a cause for optimism. Solving the mystery of preterm labor, which compromises the health of future generations, is a formidable scientific challenge worthy of investment.

Effect of thrombin on human amnion mesenchymal cells, mouse fetal membranes, and preterm birth

Here, we investigated the effects of thrombin on matrix metalloproteinases (MMPs) and prostaglandin (PG) synthesis in fetal membranes. Thrombin activity was increased in human amnion from preterm deliveries. Treatment of mesenchymal, but not epithelial, cells with thrombin resulted in increased MMP-1 and MMP-9 mRNA and enzymatic activity. Thrombin also increased COX2 mRNA and PGE2 in these cells. Protease-activated receptor-1 (PAR-1) was localized to amnion mesenchymal and decidual cells. PAR-1-specific inhibitors and activating peptides indicated that thrombin-induced up-regulation of MMP-9 was mediated via PAR-1. In contrast, thrombin-induced up-regulation of MMP-1 and COX-2 was mediated through Toll-like receptor-4, possibly through thrombin-induced release of soluble fetal fibronectin. In vivo, thrombin-injected pregnant mice delivered preterm. Mmp8, Mmp9, and Mmp13, and PGE2 content was increased significantly in fetal membranes from thrombin-injected animals. These results indicate that thrombin acts through multiple mechanisms to activate MMPs and PGE2 synthesis in amnion.

Physiological functions and clinical implications of fibrinogen-like 2: A review

Fibrinogen-like 2 (FGL2) encompasses a transmembrane (mFGL2) and a soluble (sFGL2) form with differential tertiary structure and biological activities. Typically, mFGL2 functions as prothrombinase that is capable of initiating coagulation in tissue without activation of the blood clotting cascade, whereas sFGL2 largely acts as an immunosuppressor that can repress proliferation of alloreactive T lymphocytes and maturation of bone marrow dendritic cells. Protein sequences of FGL2 exhibit evolutionary conservation across wide variety of species, especially at the carboxyl terminus that contains fibrinogen related domain (FRED). The FRED of FGL2 confers specificity and complexity in the action of FGL2, including receptor recognition, calcium affiliation, and substrate binding. Constitutive expression of FGL2 during embryogenesis and in mature tissues suggests FGL2 might be physiologically important. However, excessive induction of FGL2 under certain medical conditions (e.g., pathogen invasion) could trigger complement activation, inflammatory response, cellular apoptosis, and immune dysfunctions. On the other hand, complete absence of FGL2 is also detrimental as lack of FGL2 can cause autoimmune glomerulonephritis and acute cellular rejection of xenografts. All these roles involve mFGL2, sFGL2, or their combination. Although it is not clear how mFGL2 is cleaved off its host cells and secreted into the blood, circulating sFGL2 has been found correlated with disease severity and viral loading among patients with human hepatitis B virus or hepatitis C virus infection. Further studies are warranted to understand how FGL2 expression is regulated under physiological and pathological conditions. Even more interesting is to determine whether mFGL2 can fulfill an immunoregulatory role through its FRED at carboxyl end of the molecule and, and vice versa, whether sFGL2 is procoagulant upon binding to a target cell. Knowledge in this area should shed light on development of sFGL2 as an alternative immunosuppressive agent for organ transplantation or as a biomarker for predicting disease progression, monitoring therapeutic effects, and targeting FGL2 for repression in ameliorating fulminant viral hepatitis.

Is thrombin activation predictive of subsequent preterm delivery?

OBJECTIVE

To determine the relation between thrombin generation (measured by thrombin-antithrombin [TAT] complexes) early in pregnancy and subsequent preterm delivery.

STUDY DESIGN

Select cohort of 731 women undergoing indicated second trimester amniocentesis prospectively followed to delivery. Primary outcome was preterm delivery. TAT levels were examined continuously and categorized by quartiles. Multivariable techniques were applied to adjust for potential confounders. Receiver operating characteristic curve analysis was used to determine a discriminatory cutoff level for TAT complexes.

RESULTS

TAT concentration was significantly higher in women who delivered preterm (median, 98.9 mcg/L) than in those who did not (median, 66.3 mcg/L; P < .001). This difference persisted when 55 spontaneous preterm deliveries (median, 87.6 mcg/L) and 34 indicated preterm deliveries (median, 117.7 mcg/L) were separately compared with controls (P = .04 and P < .001, respectively). Crude and adjusted odds ratio for preterm delivery in the upper 2 TAT quartiles relative to the uppermost quartile relative to the lowest quartile were 2.45 (95% confidence interval [CI], 1.36-4.72; P = .004) and 2.31 (95% CI, 1.18-4.65; P = .017), respectively. Despite these distinct differences, the area under the receiver operating characteristic curve was only 0.62 (95% CI, 0.56-0.69), indicating poor performance of TAT concentration as a risk discriminator.

CONCLUSION

Amniotic fluid levels of TAT complexes in the second trimester are elevated in women who subsequently deliver preterm, suggesting that thrombin generation may be involved in the various etiopathogenic mechanisms leading to preterm delivery.

Abruption-induced preterm delivery is associated with thrombin-mediated functional progesterone withdrawal in decidual cells

Plasma progesterone levels remain elevated throughout human pregnancy, suggesting that reduced reproductive-tract progesterone receptor (PR) initiates labor. Placental abruption and excess thrombin generation elicit preterm delivery (PTD). PR, glucocorticoid receptor (GR), and total and p-ERK1/2 in decidual cells (DCs) and interstitial trophoblasts (IT) were assessed via immunohistochemical staining in abruption-associated PTD versus gestational-age matched control placentas, and in cultured DCs incubated with estradiol (E2) ± medroxyprogesterone acetate (MPA) ± thrombin. Immunostaining for PR was lower in DC nuclei in abruption versus control decidua and was absent from ITs; GR was higher in IT than DCs, with no abruption-related changes in either cell type; p-ERK1/2 was higher in DCs in abruption than control decidua, with total ERK 1/2 unchanged. Immunoblotting of cultured DCs demonstrated strong E2, weak MPA, and intermediate E2+MPA mediated elevation of PR-A and PR-B levels, with constitutive GR expression. In cultured DCs, thrombin inhibited PR but not GR mRNA levels, reduced PR binding to DNA and [(3)H]progesterone binding to PR, and enhanced phosphorylated but not total ERK1/2 levels. Coincubation with a specific p-ERK1/2 inhibitor reversed thrombin-enhanced p-ERK1/2 and lowered PR levels. Thus, abruption-associated PTD is initiated by functional progesterone withdrawal, as indicated by significantly reduced DC nuclear expression of PR-A and PR-B. Functional withdrawal of progesterone results in increased p-ERK1/2, and is thus one pathway initiating abruption-associated PTD.

Early second trimester maternal plasma levels of thrombin-inhibitor complexes and subsequent spontaneous preterm delivery

OBJECTIVE

Increased thrombin generation has been implicated as a mechanism for several obstetric syndromes including preterm birth preceded by preterm labor (PTL) and preterm premature rupture of membranes (PPROM). In this study, we attempted to determine whether PTL or PPROM are associated with changes in the maternal plasma thrombin level during the early second trimester.

METHODS

This is a case-control study in which maternal thrombin-antithrombin (TAT) III complex concentrations at 15-21 weeks were compared between normal controls (n = 85) and women subsequently delivering preterm, due to either PTL with intact membranes (n = 21) or PPROM (n = 20). Statistical analysis was conducted using non-parametric statistics.

RESULTS

PTL patients with intact membranes showed non-significant differences in median plasma TAT level (110.1 µg/L) compared with the control group (107.9 µg/L). Similarly, women destined to deliver preterm because of PPROM had non-significantly higher plasma TAT level (134.3 µg/L) than those in the control group (107.9 µg/L) (p > 0.05). Logistic regression analysis demonstrated that after controlling for confounders including vaginal bleeding, TAT levels remained not significantly associated with subsequent spontaneous preterm birth (p = 0.27).

CONCLUSION

Maternal plasma TAT level is unsuitable as an early second trimester predictor of preterm birth preceded by PTL or PPROM.

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.

Prospective investigation of second-trimester thrombin activation and preterm birth

OBJECTIVE

We sought to determine if second-trimester amniotic fluid thrombin-antithrombin (TAT) complexes concentration correlates with subsequent preterm birth.

STUDY DESIGN

A cohort of 550 women with singleton nonanomalous pregnancies undergoing second-trimester genetic amniocentesis was followed up to delivery and analyzed as a nested case-control study. Cases of preterm birth (n = 52) were compared with 104 term control subjects. Amniotic fluid collected at amniocentesis was tested for TAT.

RESULTS

TAT concentrations were significantly higher in women who delivered preterm (median 115.9 µg/L) than in those who did not (median 62.2 µg/L; P < .001). This difference persisted when 31 spontaneous preterm births and 21 indicated preterm births were analyzed separately. The odds ratios for preterm birth in the highest TAT quartile relative to the lowest quartile was 4.98 (95% confidence interval, 1.17-22.01; P = .007).

CONCLUSION

We found a difference in the pattern of intraamniotic thrombin generation between women destined to deliver at term and those who deliver preterm, regardless of the type of preterm birth.

Abruption-associated prematurity

Chronic, subacute decidual hemorrhage (ie, abruptio placenta and retrochorionic hematoma formation) is an important contributor to preterm parturition. Such hemorrhage induces thrombin from decidual tissue factor, which plays a pivotal role in the development of preterm premature rupture of membranes and preterm delivery by acting through protease-activated receptors to promote the production of pro-inflammatory cytokines, and matrix-degrading metalloproteinases. Severe, acute abruption can lead to maternal and fetal mortality. Current management of abruption is individualized based on severity of disease, underlying etiology, and gestational age.

Placental bed disorders in preterm labor, preterm PROM, spontaneous abortion and abruptio placentae

Failure of physiologic transformation of the spiral arteries has been studied using placental bed biopsies in several obstetrical syndromes. Contrary to what was originally believed, this lesion is not restricted to preeclampsia and/or intrauterine growth restriction. A review of published evidence indicates that failure of physiologic transformation can be observed in women with spontaneous second trimester abortions, preterm labor with intact membranes, preterm prelabor rupture of membranes and abruptio placentae. Therefore, disorders of deep placentation are present in a wide range of complications of pregnancy, emphasizing the importance of understanding the physiology and pathology of transformation of the spiral arteries. We propose that changes in the population and function of immunocytes at the maternal-fetal interface can be part of the mechanism of disease of obstetrical disorders, and this requires further investigation.

Bleeding per vaginam is associated with funisitis in women with preterm prelabour rupture of the fetal membranes

OBJECTIVE

To evaluate the risk of funisitis among women with preterm prelabour rupture of the membranes (PPROM) and subsequent bleeding per vaginam.

DESIGN

Prospective cohort study.

SETTING

A University Hospital in the USA.

POPULATION

A total of 157 women with PPROM, divided into those with bleeding per vaginam during the hospital admission (n = 46) and those without bleeding per vaginam (n = 111).

METHODS

Pathologist blinded to bleeding status assessed placental pathology for funisitis.

MAIN OUTCOME MEASURES

Funisitis.

RESULTS

Women with bleeding per vaginam were more likely to have funisitis (67.4% versus 36%, P < 0.001) compared with those without bleeding. Logistic regression demonstrated that bleeding per vaginam predicted funisitis after controlling for gestational age at admission, latency period and gestational age at delivery.

CONCLUSIONS

Among women with PPROM, those with bleeding per vaginam are more likely to have funisitis than those without bleeding per vaginam.

A molecular signature of an arrest of descent in human parturition

OBJECTIVE

This study was undertaken to identify the molecular basis of an arrest of descent.

STUDY DESIGN

Human myometrium was obtained from women in term labor (TL; n = 29) and arrest of descent (AODes; n = 21). Gene expression was characterized using Illumina HumanHT-12 microarrays. A moderated Student t test and false discovery rate adjustment were applied for analysis. Confirmatory quantitative reverse transcription-polymerase chain reaction and immunoblot were performed in an independent sample set.

RESULTS

Four hundred genes were differentially expressed between women with an AODes compared with those with TL. Gene Ontology analysis indicated enrichment of biological processes and molecular functions related to inflammation and muscle function. Impacted pathways included inflammation and the actin cytoskeleton. Overexpression of hypoxia inducible factor-1a, interleukin -6, and prostaglandin-endoperoxide synthase 2 in AODes was confirmed.

CONCLUSION

We have identified a stereotypic pattern of gene expression in the myometrium of women with an arrest of descent. This represents the first study examining the molecular basis of an arrest of descent using a genome-wide approach.

Characterization of the myometrial transcriptome and biological pathways of spontaneous human labor at term

AIMS

to characterize the transcriptome of human myometrium during spontaneous labor at term.

METHODS

myometrium was obtained from women with (n=19) and without labor (n=20). Illumina HumanHT-12 microarrays were utilized. Moderated t-tests and false discovery rate adjustment of P-values were applied. Real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was performed for a select set of differentially expressed genes in a separate set of samples. Enzyme-linked immunosorbent assay and Western blot were utilized to confirm differential protein production in a third sample set.

RESULTS

1) Four hundred and seventy-one genes were differentially expressed; 2) gene ontology analysis indicated enrichment of 103 biological processes and 18 molecular functions including: a) inflammatory response; b) cytokine activity; and c) chemokine activity; 3) systems biology pathway analysis using signaling pathway impact analysis indicated six significant pathways: a) cytokine-cytokine receptor interaction; b) Jak-STAT signaling; and c) complement and coagulation cascades; d) NOD-like receptor signaling pathway; e) systemic lupus erythematosus; and f) chemokine signaling pathway; 4) qRT-PCR confirmed over-expression of prostaglandin-endoperoxide synthase-2, heparin binding epidermal growth factor (EGF)-like growth factor, chemokine C-C motif ligand 2 (CCL2/MCP1), leukocyte immunoglobulin-like receptor, subfamily A member 5, interleukin (IL)-8, IL-6, chemokine C-X-C motif ligand 6 (CXCL6/GCP2), nuclear factor of kappa light chain gene enhancer in B-cells inhibitor zeta, suppressor of cytokine signaling 3 (SOCS3) and decreased expression of FK506 binding-protein 5 and aldehyde dehydrogenase in labor; 5) IL-6, CXCL6, CCL2 and SOCS3 protein expression was significantly higher in the term labor group compared to the term not in labor group.

CONCLUSIONS

myometrium of women in spontaneous labor at term is characterized by a stereotypic gene expression pattern consistent with over-expression of the inflammatory response and leukocyte chemotaxis. Differential gene expression identified with microarray was confirmed with qRT-PCR using an independent set of samples. This study represents an unbiased description of the biological processes involved in spontaneous labor at term based on transcriptomics.

The frequency and clinical significance of intra-amniotic infection and/or inflammation in women with placenta previa and vaginal bleeding: an unexpected observation

OBJECTIVE

Idiopathic vaginal bleeding, a common complication of pregnancy, increases the risk of small-for-gestational age (SGA) neonate, preeclampsia and preterm delivery and can be the only clinical manifestation of intra-amniotic infection and/or inflammation (IAI). Placenta previa is thought to be protective against ascending intrauterine infection, yet an excess of histologic chorioamnionitis has been reported in this condition. The aim of this study was to determine the frequency and clinical significance of IAI in women with placenta previa and vaginal bleeding in the absence of preterm labor.

STUDY DESIGN

A retrospective cohort study including 35 women with placenta previa and vaginal bleeding <37 weeks of gestation who underwent amniocentesis was undertaken. Patients with multiple gestations were excluded. Intra-amniotic infection was defined as a positive culture for microorganisms, and intra-amniotic inflammation as an elevated amniotic fluid interleukin (IL)-6 concentration. IL-6 concentrations were determined by ELISA in 28 amniotic fluid samples available. Non-parametric statistics were used for analysis.

RESULTS

1) The prevalence of intra-amniotic infection was 5.7% (2/35), and that of IAI was 17.9% (5/28); 2) the gestational age at delivery was lower in patients with IAI than in those without IAI [29.4 weeks, interquartile range (IQR): 23.1-34.7 vs. 35.4 weeks, IQR: 33.9-36.9; P=0.028]; and 3) patients with placenta previa and IAI had a higher rate of delivery within 48 h (80% (4/5) vs. 19% (4/21); P=0.008) than those without IAI.

CONCLUSIONS

Patients with placenta previa presenting with vaginal bleeding have intra-amniotic infection in 5.7% of the cases, and IAI in 17.9%. IAI in patients with placenta previa and vaginal bleeding is a risk factor for preterm delivery within 48 h.

Changes in amniotic fluid concentration of thrombin-antithrombin III complexes in patients with preterm labor: evidence of an increased thrombin generation

OBJECTIVE

Preterm labor is associated with excessive maternal thrombin generation, as evidenced by increased circulating thrombin-antithrombin (TAT) III complexes concentration. In addition to its hemostatic functions, thrombin has uterotonic properties that may participate in the mechanism leading to preterm birth in cases of intrauterine bleeding. Thrombin also has a proinflammatory role, and inflammation is associated with increased thrombin generation. The aim of this study was to determine whether intra-amniotic infection/inflammation (IAI) is associated with increased amniotic fluid (AF) thrombin generation in women with preterm and term deliveries.

STUDY DESIGN

This cross-sectional study included the following groups: (1) mid-trimester (n = 74); (2) term not in labor (n = 39); (3) term in labor (n = 25); (4) term in labor with IAI (n = 22); (5) spontaneous preterm labor (PTL) who delivered at term (n = 62); (6) PTL without IAI who delivered preterm (n = 59); (7) PTL with IAI (n = 71). The AF TAT III complexes concentration was measured by enzyme linked immunosorbent assay (ELISA). Non-parametric statistics were used for analysis.

RESULTS

(1) TAT III complexes were identified in all AF samples; (2) patients with PTL who delivered preterm, with and without IAI, had a higher median AF TAT III complexes concentration than those with an episode of PTL who delivered at term (p < 0.001, p = 0.03, respectively); (3) among patients with PTL without IAI, elevated AF TAT III complexes concentration were independently associated with a shorter amniocentesis-to-delivery interval (hazard ratio, 1.5; 95% CI, 1.07-2.1); (4) among patients at term, those with IAI had a higher median AF TAT III complexes concentration than those without IAI, whether in labor or not in labor (p = 0.02); (5) there was no significant difference between the median AF TAT III complexes concentration of patients at term with and without labor; (6) patients who had a mid-trimester amniocentesis had a lower median AF TAT III complexes concentration than that of patients at term not in labor (p < 0.001).

CONCLUSIONS

We present herein a distinct difference in the pattern of intra-amniotic thrombin generation between term and preterm parturition. PTL leading to preterm delivery is associated with an increased intra-amniotic thrombin generation regardless of the presence of IAI. In contrast, term delivery is associated with an increased intra-amniotic thrombin generation only in patients with IAI.

Modulation of human uterine smooth muscle cell collagen contractility by thrombin, Y-27632, TNF alpha and indomethacin

BACKGROUND

Preterm labour occurs in approximately 10% of pregnancies and is a major cause of infant morbidity and mortality. However, the pathways involved in regulating contractility in normal and preterm labour are not fully elucidated. Our aim was to utilise a human myometrial contractility model to investigate the effect of a number of uterine specific contractility agents in this system. Therefore, we investigated the contractile response of human primary uterine smooth muscle cells or immortalised myometrial smooth muscle cells cultured within collagen lattices, to known mediators of uterine contractility, which included thrombin, the ROCK-1 inhibitor Y-27632, tumour necrosis factor alpha (TNF alpha) and the non-steroidal anti-inflammatory indomethacin.

METHODS

Cell contractility was calculated over time, with the collagen gel contraction assay, utilising human primary uterine smooth muscle cells (hUtSMCs) and immortalised myometrial smooth muscle cells (hTERT-HM): a decrease in collagen gel area equated to an increase in contractility. RNA was isolated from collagen embedded cells and gene expression changes were analysed by real time fluorescence reverse transcription polymerase chain reaction. Scanning electron and fluorescence microscopy were employed to observe cell morphology and cell collagen gel interactions. Statistical analysis was performed using ANOVA followed by Tukey's post hoc tests.

RESULTS

TNF alpha increased collagen contractility in comparison to the un-stimulated collagen embedded hUtSMC cells, which was inhibited by indomethacin, while indomethacin alone significantly inhibited contraction. Thrombin augmented the contractility of uterine smooth muscle cell and hTERT-HM collagen gels, this effect was inhibited by the thrombin specific inhibitor, hirudin. Y-27632 decreased both basal and thrombin-induced collagen contractility in the hTERT-HM embedded gels. mRNA expression of the thrombin receptor, F2R was up-regulated in hUtSMCs isolated from collagen gel lattices, following thrombin-stimulated contractility.

CONCLUSION

TNF alpha and thrombin increased uterine smooth muscle cell collagen contractility while indomethacin had the opposite effect. Thrombin-induced collagen contractility resulted in F2R activation which may in part be mediated by the ROCK-1 pathway. This study established the in vitro human myometrial model as a viable method to assess the effects of a range of uterotonic or uterorelaxant agents on contractility, and also permits investigation of the complex regulatory pathways involved in mediating myometrial contractility at labour.

A link between a hemostatic disorder and preterm PROM: a role for tissue factor and tissue factor pathway inhibitor

OBJECTIVE

Vaginal bleeding is a risk factor for preterm PROM (PPROM). A disorder of decidual hemostasis has been implicated in the genesis of PROM. Indeed, excessive thrombin generation has been demonstrated in PPROM both before and at the time of diagnosis. Decidua is a potent source of tissue factor (TF), the most powerful natural pro-coagulant. A decidual hemostatic disorder may link vaginal bleeding, PPROM and placental abruption. This study was conducted to determine the behaviour of maternal TF and its natural inhibitor, the tissue factor pathway inhibitor (TFPI) in PPROM.

METHODS

This cross-sectional study included women with PPROM (n = 123) and women with normal pregnancies (n = 86). Plasma concentrations of TF and TFPI were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) The median maternal plasma TF concentration was significantly higher in patients with PPROM than in women with normal pregnancies (median: 369.5 pg/mL; range: 3.27-2551 pg/mL vs. median: 291.5 pg/mL; range: 6.3-2662.2 pg/mL respectively, p = 0.001); (2) the median maternal TFPI plasma concentration was significantly lower in patients with PPROM than in women with normal pregnancies (median: 58.7 ng/mL; range: 26.3-116 ng/mL vs. median: 66.1 ng/mL; range: 14.3-86.5 ng/mL respectively, p = 0.019); (3) there was no correlation between the plasma concentration of TF and TFPI and the gestational age at sample collection; and (4) among patients with PPROM there was no association between the presence of intra-amniotic infection or inflammation and median plasma concentrations of TF and TFPI.

CONCLUSIONS

(1) Patients with PPROM have a higher median plasma concentration of TF and a lower median plasma concentration of TFPI than women with normal pregnancies. (2) These findings suggest that PPROM is associated with specific changes in the hemostatic/coagulation system.

Over-expression of the thrombin receptor (PAR-1) in the placenta in preeclampsia: a mechanism for the intersection of coagulation and inflammation

OBJECTIVE

Preeclampsia (PE) is characterized by excessive thrombin generation, which has been implicated in the multiple organ damage associated with the disease. The biological effects of thrombin on coagulation and inflammation are mediated by protease-activated receptor-1 (PAR-1), a G protein-coupled receptor. The aim of this study was to determine whether preterm PE is associated with changes in placental expression of PAR-1.

STUDY DESIGN

This cross-sectional study included two groups matched for gestational age at delivery: (1) patients with preterm PE (<37 weeks of gestation; n = 26) and (2) a control group of patients with preterm labor without intra-amniotic infection (n = 26). Placental tissue microarrays were immunostained for PAR-1. Immunoreactivity of PAR-1 in the villous trophoblasts was graded as negative, weak-positive, or strong-positive.

RESULTS

(1) The proportion of cases with strong PAR-1 immunoreactivity was significantly higher in placentas of patients with PE than in placentas from the control group (37.5% (9/24) vs. 8.7% (2/23); p = 0.036, respectively). (2) PAR-1 immunoreactivity was found in the cellular compartments of the placental villous tree, mainly in villous trophoblasts and stromal endothelial cells. (3) PAR-1 was detected in 92.3% (24/26) of the placentas of women with PE and in 88.5% (23/26) of the placentas from the control group.

CONCLUSION

Placentas from pregnancies complicated by preterm PE had a significantly higher frequency of strong PAR-1 expression than placentas from women with spontaneous preterm labor. This observation is consistent with a role for PAR-1 as a mediator of the effect of thrombin on coagulation and inflammation in PE. We propose that the effects of thrombin in PE are due to increased thrombin generation and higher expression of PAR-1, the major receptor for this enzyme.

Expression of prothrombin and protease activated receptors in human myometrium during pregnancy and labor

As thrombin is proposed to be involved in stimulating myometrial contractility during labor and preterm labor, we aimed to investigate the expression of prothrombin (F7), the precursor of thrombin, its receptors, the protease-activated receptor (PAR) family (F2R, F2RL1, F2RL2, and F2RL3), and prothrombinase FGL2 in human myometrium during pregnancy and labor. Messenger RNA and protein were isolated from human pregnant laboring and nonlaboring myometrial tissue and from human primary myometrial smooth muscle cells. Semiquantitative RT-PCR, real-time fluorescence RT-PCR, Western blotting, and fluorescence microscopy were performed to determine the expression levels of F7, FGL2, F2R, F2RL1, F2RL2, and F2RL3 in the myometrial tissues and cells. The expression of mRNA and protein for these molecules is reported for the first time in human myometrium at term pregnancy, at labor, and in the nonpregnant state. Importantly, an increase in F2R and a significant increase in F2RL3 mRNA expression at labor were demonstrated. Statistically significant increases in F2R and F2RL3 protein expression was also detected in human myometrium at labor. Furthermore, FGL2 mRNA expression at labor, and FGL2 protein expression at term pregnancy and at labor was observed in this tissue for the first time. The expression of F7, FGL2, F2R, F2RL1, F2RL2, and F2RL3 in human myometrium reveals that all the machinery necessary for thrombin activation and cellular activity is present in the myometrium during pregnancy and labor. These data, in conjunction with the demonstrated increase in F2R and F2RL3 expression at labor, suggest a principal role for these molecules in the regulation of myometrial function at labor, including preterm labor.

Plasma protein Z concentrations in pregnant women with idiopathic intrauterine bleeding and in women with spontaneous preterm labor

OBJECTIVES

Preterm parturition has been associated with decidual vascular disorders and excessive thrombin generation. The objective of this study was to examine maternal plasma concentrations of protein Z in normal pregnancies, as well as in those presenting with spontaneous preterm labor (PTL) and intrauterine bleeding during pregnancy.

STUDY DESIGN

A cross-sectional study was designed to include patients with preterm labor and intact membranes and those with idiopathic intrauterine bleeding during pregnancy. Protein Z plasma concentrations were measured in the following groups: (1) normal pregnant women (n = 71); (2) patients at term with (n = 67) and without labor (n = 88); (3) patients with spontaneous PTL before 34 weeks who were classified into: (a) PTL with intra-amniotic infection/inflammation (IAI; n = 35), (b) PTL without IAI (n = 54), and (c) patients with PTL who delivered at term (n = 49); and (4) patients with idiopathic intrauterine bleeding in the second and third trimester who were divided into: (a) subsequent spontaneous PTL and delivery, and (b) term delivery. Maternal plasma protein Z concentration was measured by a specific and sensitive immunoassay. Moreover, the amniotic fluid concentration of protein Z was determined in a subset of patients with preterm labor (n = 30).

RESULTS

(1) There was no correlation between maternal plasma protein Z concentration and gestational age in normal pregnant women. (2) The mean maternal plasma concentration of protein Z was significantly lower in women during spontaneous labor at term than in those not in labor (mean 2.15 microg/mL (95% CI 2.01-2.29) vs. mean 2.45+/-0.52 microg/mL (95% CI 2.34-2.56), respectively; p = 0.001). (3) Women with PTL without IAI who delivered preterm had a significantly lower mean protein Z concentration than normal pregnant women (mean 2.12 mug/mL (95% CI 1.98-2.26) vs. mean 2.39 microg/mL (95% CI 2.28-2.5); p = 0.008). (4) Of interest, PTL with IAI was not associated with lower plasma concentrations of protein Z, nor were those with PTL who delivered at term (p > 0.05 for each). (5) No differences were found in the maternal plasma concentrations of anti-protein Z antibodies between normal pregnancies and those with spontaneous PTL. (6) Patients with idiopathic intrauterine bleeding who had spontaneous PTL and delivery had a significantly lower mean plasma protein Z concentration than those who delivered at term (mean 1.24 microg/mL (95% CI 1.08-1.4) vs. mean 1.49+/-0.47 microg/mL (95% CI 1.33-1.65), respectively; p = 0.03). (7) Amniotic fluid was found to contain immunoreactive protein Z.

CONCLUSIONS

(1) Patients with PTL leading to preterm delivery in the absence of IAI had a significantly lower plasma concentration of protein Z than those with normal pregnancies. (2) Patients with idiopathic intrauterine bleeding and subsequently spontaneous PTL and delivery had a significantly lower plasma concentration of protein Z than those with idiopathic intrauterine bleeding who delivered at term. (3) Protein Z was present in the amniotic fluid of patients with PTL. Collectively, these observations suggest that a subgroup of patients with PTL have a hemostatic disorder that involves bleeding/thrombosis as a mechanism of disease.

Expression and function of protease-activated receptor 4 in human myometrium

OBJECTIVE

Little is known about the presence or functional effects of protease-activated receptor subtypes in human uterine tissues. The aims of this study were as follows: (1) to investigate for protease-activated receptor-4 messenger RNA and protein expression in human myometrium, (2) to evaluate the effects of a specific protease-activated receptor-4 activating peptide (AYPGKF-NH2) on spontaneous human myometrial contractility in vitro, and (3) to examine the effects of a protease-activated receptor-4 antagonist (tcYPGKF-NH2) on thrombin-mediated uterine contractility.

STUDY DESIGN

Reverse transcriptase-polymerase chain reaction and Immunofluorescence studies were used to investigate for protease-activated receptor-4 messenger RNA and protein expression, respectively. Isometric tension recordings were used to examine the functional effects on contractility.

RESULTS

Reverse transcriptase-polymerase chain reaction demonstrated messenger RNA expression for protease-activated receptor-4 in pregnant and non-pregnant myometrium. Immunofluorescence confocal microscopy demonstrated the presence of protease-activated receptor-4 protein in myometrial cells. With the use of isometric recordings, protease-activated receptor 4-activating peptide elicited a stimulatory effect on spontaneous human pregnant myometrial contractility (13.1% +/- 2.7 SEM; n = 6; P < .05). Protease-activated receptor-4 antagonism alone elicited a significant uterorelaxant effect (14.7% +/- 2.4; n = 6; P < .05). The observed thrombin-mediated uterotonic effect was similar in the absence (46.1% +/- 12.8; n = 6) and presence (48.8% +/- 12.6; n = 6) of the protease-activated receptor-4 antagonist (P = .91).

CONCLUSIONS

This study outlines protease-activated receptor-4 messenger RNA and protein expression in human myometrium. Protease-activated receptor-4 activation exerts a mild uterotonic effect, whereas protease-activated receptor-4 antagonism results in a mild uterorelaxant effect. The potent human uterotonic effect of thrombin is not apparently mediated to any great extent by protease-activated receptor-4.

The preterm parturition syndrome

The implicit paradigm that has governed the study and clinical management of preterm labour is that term and preterm parturition are the same processes, except for the gestational age at which they occur. Indeed, both share a common pathway composed of uterine contractility, cervical dilatation and activation of the membranes/decidua. This review explores the concept that while term labour results from physiological activation of the components of the common pathway, preterm labour arises from pathological signalling and activation of one or more components of the common pathway of parturition. The term "great obstetrical syndromes" has been coined to reframe the concept of obstetrical disease. Such syndromes are characterised by: (1) multiple aetiology; (2) long preclinical stage; (3) frequent fetal involvement; (4) clinical manifestations that are often adaptive in nature; and (5) gene-environment interactions that may predispose to the syndromes. This article reviews the evidence indicating that the pathological processes implicated in the preterm parturition syndrome include: (1) intrauterine infection/inflammation; (2) uterine ischaemia; (3) uterine overdistension; (4) abnormal allograft reaction; (5) allergy; (6) cervical insufficiency; and (7) hormonal disorders (progesterone related and corticotrophin-releasing factor related). The implications of this conceptual framework for the prevention, diagnosis, and treatment of preterm labour are discussed.

Inflammation in preterm and term labour and delivery

Inflammation has been implicated in the mechanisms responsible for preterm and term parturition, as well as fetal injury. Out of all of the suspected causes of preterm labour and delivery, infection and/or inflammation is the only pathological process for which both a firm causal link with preterm birth has been established and a molecular pathophysiology defined. Inflammation has also been implicated in the mechanism of spontaneous parturition at term. Most cases of histopathological inflammation and histological chorioamnionitis, both in preterm and term labour, are sub-clinical in nature. The isolation of bacteria in the amniotic fluid, known as microbial invasion of the amniotic cavity, is a pathological finding; the frequency of which is dependent upon the clinical presentation and gestational age. There is a window of time during which it may be possible to detect a 'molecular signature of inflammation' by analysis of the transcriptome before histological evidence is observed. This article reviews the role of inflammation in preterm and term parturition. It is possible that modulation of inflammation using anti-inflammatory cytokines, corticoids, antioxidants and/or other factors may complement antibiotic therapy and limit fetal injury.

A hemoglobin fragment found in cervicovaginal fluid from women in labor potentiates the action of agents that promote contraction of smooth muscle cells

We employed a proteomic approach to search for peptides that have a physiological role in labor. Cervicovaginal secretions were collected at term from women in labor and women at term not in labor. Samples were spotted onto weak cation exchange chips (WCX-2) and analyzed using Surface-Enhanced Laser Desorption Ionization Time-of-Flight Mass Spectrometry (SELDI-TOF-MS). Spectra were obtained for each sample and Biomarker Wizard analysis revealed 25 peaks that had significantly different peak intensity between the labor and non-laboring women. The sequences of five peaks that were significantly elevated in the labor cohort were determined using Protein Chip Interface Quadruple Time-of-Flight Mass Spectrometry (PCI-QTOF-MS). All of these peaks were identified as fragments of alpha or beta-hemoglobin (Hb). A 2.022 kDa fragment of alpha-Hb (amino acids 110-128, NH2-AAHLPAEFTPAVHASLDKF-COOH) was found to potentiate smooth muscle cell contraction in response to bradykinin, oxytocin and prostaglandin-F2alpha. This peptide may promote vasoconstriction and augment normal labor through enhancing the action of uterotonins.

Thrombin and interleukin-1beta regulate HOXA10 expression in human term decidual cells: implications for preterm labor

CONTEXT

Preterm delivery is commonly caused by intraamniotic infection with expression of proinflammatory cytokines (IL-1beta) or by abruption resulting in generation of decidual thrombin. Although human parturition is not preceded by overt progesterone withdrawal, progesterone resistance likely leads to labor. The uteri of Hoxa10(-/-) mice demonstrate progesterone resistance; several genes, including prostaglandin receptors, are inappropriately regulated in response to progesterone.

OBJECTIVE

We hypothesized that IL-1beta or thrombin would decrease HOXA10 expression, contributing to the progestin-resistant environment. We analyzed expression of HOX genes and their regulation by IL-1beta or thrombin in decidual cells.

DESIGN AND SETTING

We conducted an in vitro experiment at an academic medical center.

INTERVENTION

Term decidual cells were treated with estradiol (E(2)) or E(2) plus medroxyprogesterone acetate followed by addition of thrombin or IL-1beta.

MAIN OUTCOME MEASURE

HOX mRNA was evaluated by microarray and confirmed by quantitative RT-PCR. Protein expression was detected using immunohistochemistry and Western analysis.

RESULTS

HOXA9, HOXA10, and HOXA11 were expressed in decidual cells and regulated by IL-1beta and thrombin. HOXA10 was further analyzed because of its association with progesterone responsiveness. After E(2) treatment, IL-1beta and thrombin decreased HOXA10 mRNA by 94 and 81%, respectively. After E(2) plus medroxyprogesterone acetate treatment, IL-1beta and thrombin resulted in an 86 and 72% decrease in HOXA10 mRNA, respectively. A similar decrease was noted in HOXA10 protein expression.

CONCLUSION

The expression of HOXA10 protein at term indicates that it may have a role in maintaining decidual cell phenotype and pregnancy. The dramatic decrease of HOXA10 in response to IL-1beta or thrombin may contribute to progestin resistance in preterm labor, mimicking progesterone resistance seen in Hoxa10(-/-) mice.

Preconceptional antibiotic treatment to prevent preterm birth in women with a previous preterm delivery

This article addresses the question of whether the uterine cavity is normally sterile and reviews the difficulties in conducting microbiologic studies of the endometrium, the limitations of conventional microbiologic techniques (cultivation-dependent), and the potential contribution of molecular microbiology to examine microbial diversity and burden of the endometrium. Issues pertaining to the diagnosis of chronic endometritis and the need for information about the prognostic value of this finding in subsequent pregnancies are discussed. The results of a randomized clinical trial of antibiotic administration versus placebo in women with a previous preterm birth are reviewed and commentary is provided. The emerging picture is that microbial-host interactions in the endometrial cavity are important for reproductive success. This is a US government work. There are no restrictions on its use.

Idiopathic vaginal bleeding during pregnancy as the only clinical manifestation of intrauterine infection

OBJECTIVE

To determine the frequency and clinical significance of microbial invasion of the amniotic cavity (MIAC) in patients with vaginal bleeding in the absence of placenta previa, preterm labor or preterm premature rupture of membranes (PROM).

STUDY DESIGN

This retrospective cohort study included patients who presented with vaginal bleeding between 18 and 35 weeks, and underwent an amniocentesis shortly after admission for the assessment of the microbiologic status of the amniotic cavity and/or fetal lung maturity. Amniotic fluid was cultured for aerobic and anaerobic bacteria, as well as genital mycoplasmas. Patients presenting with preterm labor, preterm PROM, placenta previa, overt placental abruption, and an intrauterine device in situ were excluded, as well as those with local cervical bleeding. MIAC was defined as a positive amniotic fluid culture. Analysis was conducted with non-parametric statistics.

RESULTS

One hundred and fourteen patients met the entry criteria. MIAC was detected in 14% of cases (16/114). Patients with vaginal bleeding and a gestational age < 28 weeks at the time of amniocentesis had a significantly higher frequency of MIAC than those with a gestational age 28 weeks [25% (13/52) vs. 4.8% (3/62), respectively; p < 0.01]. Ureaplasma urealyticum was the microorganism most frequently isolated from the amniotic fluid. Except for one case admitted at 33 weeks, all patients with MIAC had an early preterm delivery 32 weeks. Patients with vaginal bleeding and MIAC had a shorter procedure-to-delivery interval than those without MIAC [MIAC, median survival 19 days (95% CI 10-27 days) vs. no MIAC, median survival 50 days (95% CI 37-62 days); p < 0.0001]. Patients with vaginal bleeding and MIAC had a significantly lower gestational age at delivery and lower birth weight than those with vaginal bleeding and negative amniotic fluid cultures (for gestational age, median 25 weeks, range 21-33 weeks vs. median 37 weeks, range 19-42 weeks, respectively; p < 0.01, and for birth weight, median 750 grams, range 520-1820 grams vs. 2800 grams, range 520-4880 grams, respectively; p < 0.01), as well as a higher frequency of subsequent preterm PROM [81.3% (13/16) vs. 9.2% (9/98); p < 0.01].

CONCLUSIONS

MIAC was detected in 14% of patients with 'idiopathic' vaginal bleeding and was associated with subsequent preterm PROM and early preterm delivery. Vaginal bleeding may be the only clinical manifestation of MIAC, and it predisposes to adverse outcome.

PAR-2 activating peptide-induced stimulation of pregnant rat myometrium contractile activity partly involves the other membrane receptors

OBJECTIVE

To study if spontaneous contractions augmented by proteinase-activated receptor-2 (PAR-2)-activating peptide serine-leucine-isoleucine-glycine-arginine-leucine (SLIGRL) involve coactivation of membrane chemoceptors and are associated with expression of PAR-2 mRNA in non-pregnant and pregnant rat myometrium.

MATERIALS AND METHODS

Non-pregnant, mid-pregnant, and late pregnant rat uterine horn and small intestine segments were snap-frozen in liquid nitrogen to determine PAR-2 mRNA levels by real time polymerase chain reaction (PCR). Uterine rings were used for isometric tension recording. Effect of SLIGRL (0.1 mM) on spontaneous contractions before and after exposure to ibuprofen (cyclooxygenase inhibitor, 1.0 microM), SQ-29548 (thromboxane A(2) receptor inhibitor, 1.0 microM), ketotifen (histamine 1 receptor inhibitor, 10 microM), WEB-2170BS (platelet-activating factor (PAF) receptor inhibitor, 10 microM), atropine (muscarinic receptor inhibitor, 0.1 microM), or ketanserin (serotonin receptor inhibitor, 10 microM) were compared. Paired t-test and one-way ANOVA followed by Dunnett's or Newman-Keuls post hoc tests were used for statistical analysis when appropriate.

SIGNIFICANCE

P<0.05.

RESULTS

The agents did not significantly affect time-associated decay in spontaneous contractile activity in any group of the tissues. Activation of spontaneous contractions induced by SLIGRL in non-pregnant rat myometrium did not involve coactivation of membrane chemoceptors, while in mid-pregnant rat myometrium coactivation of prostanoid, histamine, and serotonin receptors and in late pregnant rat myometrium coactivation of thromboxane receptors was noted. Expression of PAR-2 mRNA was similar in non-pregnant, mid-pregnant, and late pregnant rat myometrium.

CONCLUSIONS

Expression of PAR-2 in rat myometrium is not dependent on gestational age. Stimulation of PAR-2 is associated with production/release of cyclooxygenase pathway product(s) activating thromboxane/prostaglandin H2 receptors, partial involvement of histamine H1 receptors and serotonin receptors in midpregnancy and thromboxane A2/prostaglandin H2 receptors in late pregnancy.