Factors involved in the inflammatory events of cervical ripening in humans

Influence of pregnancy and labor on the occurrence of nerve fibers expressing the capsaicin receptor TRPV1 in human corpus and cervix uteri

BACKGROUND

Cervical ripening is a prerequisite for a normal obstetrical outcome. This process, including labor, is a painful event that shares features with inflammatory reactions where peripheral nociceptive pathways are involved. The capsaicin and heat receptor TRPV1 is a key molecule in sensory nerves involved in peripheral nociception, but little is known regarding its role in the pregnant uterus. Therefore, the aim of this study was to investigate human corpus and cervix uteri during pregnancy and labor and non-pregnant controls for the presence of TRPV1.

METHODS

We have investigated human uterine corpus and cervix biopsies at term pregnancy and parturition. Biopsies were taken from the upper edge of the hysterotomy during caesarean section at term (n = 8), in labor (n = 8) and from the corresponding area in the non-pregnant uterus after hysterectomy (n = 8). Cervical biopsies were obtained transvaginally from the anterior cervical lip. Serial frozen sections were examined immunohistochemically using specific antibodies to TRPV1 and nerve markers (neurofilaments/peripherin).

RESULTS

In cervix uteri, TRPV1-immunoreactive fibers were scattered throughout the stroma and around blood vessels, and appeared more frequent in the sub-epithelium. Counts of TRPV1-immunoreactive nerve fibers were not significantly different between the three groups. In contrast, few TRPV1-immunoreactive fibers were found in nerve fascicles in the non-pregnant corpus, and none in the pregnant corpus.

CONCLUSION

In this study, TRPV1 innervation in human uterus during pregnancy and labor is shown for the first time. During pregnancy and labor there was an almost complete disappearance of TRPV1 positive nerve fibers in the corpus. However, cervical innervation remained throughout pregnancy and labor. The difference in TRPV1 innervation between the corpus and the cervix is thus very marked. Our data suggest that TRPV1 may be involved in pain mechanisms associated with cervical ripening and labor. Furthermore, these data support the concept that cervix uteri may be the major site from which labor pain emanates. Our findings also support the possibility of developing alternative approaches to treat labor pain.

Nitric oxide in the human uterine cervix: endogenous ripening factor

The human uterine cervix can produce nitric oxide (NO), a free radical with an ultra-short half-life. The release of NO changes during pregnancy and is increased in early nonviable pregnancies compared to normal uncomplicated pregnancies. This review concentrates on the role of NO release in cervical ripening in pregnant women. Also some suggestions on future aspects are discussed.

Premature labor: a state of platelet activation?

OBJECTIVE

This study was undertaken to determine whether premature labor is associated with changes in the maternal plasma concentration of soluble CD40 ligand (sCD40L), a marker of platelet activation.

METHODS

A cross-sectional study included patients in the following groups: 1) non-pregnant (n=21); 2) normal pregnancy (n=71); 3) normal pregnancy at term with (n=67) and without labor (n=88); 4) preterm labor (PTL) with intact membranes (n=136) that was divided into the following sub-groups: 4a) PTL who delivered at term (n=49); 4b) PTL without intra-amniotic infection and/or inflammation (IAI) who delivered preterm (n=54); and 4c) PTL with IAI who delivered preterm (n=33). sCD40L concentrations were measured by ELISA.

RESULTS

The median maternal plasma sCD40L concentration was higher in pregnant than non-pregnant women (P=0.017). Patients with PTL had a higher median maternal plasma sCD40L concentration than women with normal pregnancies, regardless of the presence or absence of IAI and gestational age at delivery (P<0.001 for all comparisons). IAI was not associated with a higher median maternal plasma concentration of sCD40L.

CONCLUSIONS

Normal pregnancy is a state in which there is a physiologic increase of sCD40L. PTL was associated with an increased median maternal plasma sCD40L concentration that could not be accounted for by IAI. Thus, our findings suggest that platelet activation occurs during an episode of preterm labor.

Signature pathways identified from gene expression profiles in the human uterine cervix before and after spontaneous term parturition

OBJECTIVE

This study aimed to discover "signature pathways" that characterize biologic processes, based on genes differentially expressed in the uterine cervix before and after spontaneous labor.

STUDY DESIGN

The cervical transcriptome was characterized previously from biopsy specimens taken before and after term labor. Pathway analysis was used to study the differentially expressed genes, based on 2 gene-to-pathway annotation databases (Kyoto Encyclopedia of Genes and Genomes [Kanehisa Laboratories, Kyoto University, Kyoto, Japan] and Metacore software [GeneGo, Inc, St. Joseph, MI]). Overrepresented and highly impacted pathways and connectivity nodes were identified.

RESULTS

Fifty-two pathways in the Metacore database were enriched significantly in differentially expressed genes. Three of the top 5 pathways were known to be involved in cervical remodeling. Two novel pathways were plasmin signaling and plasminogen activator urokinase signaling. The same analysis with the Kyoto Encyclopedia of Genes and Genomes database identified 4 significant pathways that the impact analysis confirmed. Multiple nodes that provide connectivity within the plasmin and plasminogen activator urokinase signaling pathways were identified.

CONCLUSION

Three strategies for pathway analysis were consistent in their identification of novel, unexpected, and expected pathways, which suggests that this approach is both valid and effective for the elucidation of biologic mechanisms that are involved in cervical dilation and remodeling.

EMG activity of the muscular and stromal layer of the cervix in relation to EMG activity of the myometrium and cervical dilatation in PGF2α induced parturition in the cow

The goal of this study was to quantify and characterize the electromyographic (EMG) activities in the cervical outer muscular layer and in the cervical stromal layer, and to characterize their relationship with myometrial EMG activity and cervical dilatation during PGF2alpha-induced parturition in term pregnant cows. We continuously measured the EMG activity of the uterine myometrium and cervical outer muscular layer as well as the cervical stromal layer in five cows using bipolar electrodes while at the same time measuring changes in the cervical diameter with ultrasound cervimetry. This we did from the moment a prostaglandin analogue was injected until the expulsion of the calf. In contrast to the cervical stromal layer, the cervical outer muscular layer showed distinct EMG activity, which began to increase at about the same time as the EMG activity of the myometrium, i.e. some 12 h before the start of cervical dilatation. However, the rate of this increase was lower than in the myometrium and it was not characterized, like in the myometrium, by an increase in maximum EMG amplitude. Although the cervical outer muscular layer showed contracture and contraction like EMG activity in unison with in the myometrium, it was also characterized by a more irregular EMG activity, which occurred independently from the myometrium. These data suggest that while the outer muscular layer of the cervix may be considered to be a caudal continuation of the myometrium, it also displays activity independently from the myometrium. The physiological relevance of this activity remains to be explored.

Plasma membrane receptor mediated MAPK signaling pathways are activated in human uterine cervix at parturition

BACKGROUND

Cervical ripening resembles an inflammatory reaction. Estrogens induce leukocyte migration into tissue and factors promoting cervical remodeling and labor, although the mechanisms are only partially known. The aim of this study was to investigate whether plasma membrane receptor mediated pathways, known to be activated by estrogens and proinflammatory compounds, are involved in cervical ripening before labor.

METHODS

The expression and distribution of mitogen activated protein kinases (MAPK), which transduce extracellular signals into intracellular responses through phosphorylation, and their intracellular targets transcription factors c-Jun and c-Fos proteins (AP-1) were analysed in cervical biopsies from term pregnant women (TP), immediately after parturition (PP), and from non-pregnant women (NP). Immunohistochemistry and RT-PCR techniques were used.

RESULTS

Cell-specific alterations in the immunostaining pattern for MAPK were observed. The expressions of activated, phosphorylated MAPK forms pERK1/2, pJNK and p38MAPK were significantly increased in cervical stroma until TP and pERK1/2 expression was significantly enhanced in PP group. c-Jun was significantly increased in cervical stroma and smooth muscle in TP as compared to NP group. c-Fos was significantly increased in stroma, squamous epithelium and glandular epithelium in PP as compared to TP group.

CONCLUSION

We report, for the first time, cell-specific activation of pMAPKs and their targets transcription factors c-Fos and c-Jun (AP-1) proteins in human uterine cervix until term pregnancy, and immediately after parturition. These results suggest a role for MAPK activation in cervical ripening before labor.

Involvement of nuclear factor-kB activation through RhoA/Rho-kinase pathway in LPS-induced IL-8 production in human cervical stromal cells

Interleukin-8 (IL-8) is a chemokine that recruits and activates neutrophils in stromal tissue and plays an essential role in cervical ripening. Nuclear factor-kB (NF-kB) is known to be important for the up-regulation of IL-8 gene expression. We examined the molecular mechanisms responsible for NF-kB activation in IL-8 production in cervical stromal cells. Lipopolysaccharide (LPS) and IL-1beta stimulated IL-8 production by cervical stromal cells in a dose-dependent manner. Pretreatment of cervical stromal cells with inhibitors of RhoA (C3 transferase exoenzyme), Rho-kinase (Y-27632) or NF-kB (BAY11-7082) effectively blocked LPS-induced IL-8 release. In contrast, IL-1beta-induced IL-8 production was significantly blocked by BAY11-7082, but not by C3 transferase exoenzyme or Y-27632. Pull-down assays showed that LPS activated RhoA, but IL-1beta caused only a lower level of activation. Transfection of the cervical stromal cells with RhoA small interfering RNA (siRNA) inhibited LPS-stimulated IL-8 production, whereas IL-1beta-induced IL-8 production was not significantly inhibited by knockdown of RhoA with siRNA. Using an NF-kB transcription reporter vector, luciferase assays demonstrated that incubation with LPS or IL-1beta induced the activation of NF-kB in cervical stromal cells. Activation of NF-kB by LPS was inhibited by treatment with C3 exoenzyme, Y-27632 or RhoA siRNA. However, inhibition of the RhoA/Rho-kinase pathway did not attenuate the activation of NF-kB by IL-1beta. These results suggest that LPS-induced IL-8 production is accompanied by enhanced NF-kB activation through the RhoA/Rho-kinase pathway in human cervical cells.

The transcriptome of the uterine cervix before and after spontaneous term parturition

OBJECTIVE

This study was designed to identify genes differentially expressed in the human uterine cervix after spontaneous term labor.

STUDY DESIGN

The transcriptome of cervical tissue was characterized using Affymetrix HG-U133 plus 2 microarrays. Samples were collected from patients at term not in labor (n = 7) and after spontaneous labor (n = 9). Microarray statistical analysis included robust multiarray average, reduction of invariant probes, and permutation analysis for differential expression. Real-time quantitative reverse transcriptase-polymerase chain reaction assays of selected genes were performed on a new set of samples from term patients without labor (n = 10) and patients after spontaneous labor (n = 9).

RESULTS

(1) The cervical transcriptome of term patients without labor was dramatically different from that of patients who underwent labor; (2) unique genes (n = 1192) were differentially expressed in the cervical tissue from patients after spontaneous labor, compared with that of the term patients without labor (false discovery rate less than 0.05, absolute fold change greater than 2); (3) Gene Ontology analysis indicated that multiple "Biological Process" categories were enriched, including "response to biotic stimulus," "apoptosis," "epidermis development," and "steroid metabolism"; (4) of major interest, genes involved in neutrophil chemotaxis were dramatically up-regulated in specimens from women after spontaneous labor; (5) real-time quantitative reverse transcriptase-polymerase chain reaction confirmed the increased expression of interleukin-8, interleukin-6, and vascular endothelial growth factor in patients after spontaneous labor; and (6) Toll-like receptor-3 and Toll-like receptor-5 showed decreased gene expression in patients after spontaneous labor. This was confirmed by real-time quantitative reverse transcriptase-polymerase chain reaction.

CONCLUSION

(1) Cervical dilatation in term labor is associated with a stereotypic gene expression pattern determined by microarray, which is characterized by overexpression of genes involved in neutrophil chemotaxis, apoptosis, extracellular matrix regulation, and steroid metabolism; (2) Toll-like receptor-3 and Toll-like receptor-5 are differentially regulated during spontaneous parturition at term; and (3) this study provides an unbiased and comprehensive description of the changes in the cervical transcriptome before and after spontaneous term labor.

Mifepristone-induced nitric oxide release and expression of nitric oxide synthases in the human cervix during early pregnancy

BACKGROUND

Nitric oxide (NO) is a factor in cervical ripening, perhaps under the control of progesterone. We studied the effects of the antiprogesterone mifepristone on the release of NO and on the expression of inducible NO synthase (iNOS) and endothelial NO synthase (eNOS) in the uterine cervix of women in early pregnancy.

METHODS

Thirteen women were treated with oral mifepristone (200 mg), and 15 women were studied as controls. Cervical fluid samples were collected before treatment then hourly up to 3 h, and the samples were assayed for the concentration of nitric oxide metabolites (NOx). In addition, cervical biopsy samples from six women treated with mifepristone and from six controls were assessed for iNOS and eNOS by immunohistochemistry and Western blotting.

RESULTS

In 1-3 h, mifepristone induced 7.4- to 17.2-fold elevations in cervical fluid NOx concentrations; no change was seen in the controls. The expression of both iNOS and eNOS was detected in the cervical cells. The expression of cervical iNOS was strong in five of the six women treated with mifepristone but was not strong in any of the six control women.

CONCLUSION

This is the first study to show that mifepristone stimulates the release of NO and the expression of iNOS in cervical cells of women in early pregnancy. This may be one mechanism by which mifepristone initiates cervical ripening.

Isosorbide mononitrate induces increased cervical expression of cyclooxygenase-2, but not of cyclooxygenase-1, at term

OBJECTIVE

Prostaglandin and nitric oxide (NO) are both known to be involved in cervical ripening at term. The aim of the study was to investigate if NO has an effect on cervical expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), the two main isoenzymes involved in prostaglandin synthesis, and to localize these enzymes within the cervix.

STUDY DESIGN

Women with an unripe cervix scheduled for elective caesarean section at term were randomly selected to receive vaginally either the NO donor isosorbide mononitrate (IMN) or placebo 4h before surgery. At the operating theatre, cervical tissue specimens were obtained for immunoblotting and immunohistochemistry.

RESULTS

Increased expression of COX-2 was found in specimens exposed to IMN compared to specimens obtained from women in the placebo group. There was no difference in the expression of COX-1. Immunohistochemistry revealed similar localization of the two enzymes in treated and untreated women.

CONCLUSIONS

Vaginal administration of IMN induces increased cervical expression of COX-2, but not of COX-1. This pathway may be of importance in the process of cervical ripening at term.

The role of nuclear factor kappa B in human labour

Preterm birth remains the leading cause of perinatal mortality and morbidity, largely as a result of a poor understanding of the precise mechanisms controlling labour onset in humans. Inflammation has long been recognised as a key feature of both preterm and term labour, with an influx of inflammatory cells into the uterus and elevated levels of pro-inflammatory cytokines observed during parturition. Nuclear factor kappa B (NF-κB) is a transcription factor family classically associated with inflammation. Accumulating evidence points to a role for NF-κB in the physiology and pathophysiology of labour. NF-κB activity increases with labour onset and is central to multiple prolabour pathways. Premature or aberrant activation of NF-κB may thus contribute to preterm labour. The current understanding of NF-κB in the context of human labour is discussed here.