Preterm Cervical Ripening Research Articles

Diffusion-Weighted and Intravoxel Incoherent Motion MRI of the pregnant cervix as a tool to monitor cervical ripening

Background and Hypothesis: Preterm delivery is a major source of infant morbidity and mortality and is difficult to predict. The process of cervical ripening prior to delivery has known histologic changes including breakdown of collagen and increasing water content. It is hypothesized that the diffusion of water, which can be measured on MRI, will increase as the cervical water content increases. Diffusion weighted imaging (DWI) is a form of MRI that measures the random Brownian motion of water molecules (represented as the apparent diffusion coefficient (ADC)). Intravoxel incoherent motion (IVIM) MRI further subdivides the ADC into microcapillary perfusion (D*) and diffusion (D). We hypothesize that as the pregnant cervix ripens near delivery, diffusion of water within the cervix (ADC and D) will increase without changes in the capillary perfusion (D*). We sought to determine the relationship between ADC, D*, D, gestational age, and time to delivery in a cohort of volunteer pregnant females.
 Experimental Design or Project Methods: DWI and IVIM MR studies from a cohort of 45 volunteer pregnant females with no known underlying fetal anomalies were examined. Subglandular and stromal cervix thickness and cervical length were measured along with the ADC, D*, and D of the subglandular and stromal cervix. Gestational history and delivery information was documented.
 Results: Subglandular ADC inversely correlated with time to delivery (r=-0.393, p=0.052). Although not significant, subglandular D revealed a trend of increasing with increased gestation age (r=0.261, p=0.149). Subglandular ADC also varied inversely with thickness of the subglandular cervix (r=-0.352, p=0.047). Subglandular D* varied inversely with maternal age (r=-0.380, p=0.028).
 Conclusion and Potential Impact: Our data support the hypothesized trend of increased diffusion of water within the cervix with unchanged capillary perfusion as a normal pregnancy progressed throughout the second and third trimesters. This study suggests that diffusion measures (ADC and D) follow a predictable progression during the course of a normal pregnancy and have the potential to provide a means of predicting preterm labor in the setting of preterm cervical ripening.

RhoA and Rho-kinase inhibitors modulate cervical resistance: The possible role of RhoA/Rho-kinase signalling pathway in cervical ripening and contractility

Improper cervical function may lead premature or late-term birth. The RhoA/Rho-kinase (ROCK) signalling pathway takes part in cellular functions including smooth muscle contraction. No information is available about the cervical expression of the RhoA/ROCK system during pregnancy. Our aim was to detect the mRNA and protein expression of ROCK enzymes in rat cervices and to evaluate the effects of RhoA/ROCK inhibitors on cervical resistance.The mRNA and protein expressions of RhoA, ROCK I and II were measured in non-pregnant, pregnant and postpartum rat cervices and during parturition by Real-time qPCR and Western blot. The cervical resistance modifying effects of RhoA (simvastatin) and ROCK (fasudil, Y-27632) (10−6M) were investigated in tissue bath experiments.RhoA mRNA was increased on post-partum day 3, while the RhoA protein expression was decreased near and during parturition. ROCK I mRNA and protein expressions were fluctuating with a decrease in protein expression during parturition. ROCK II mRNA and protein expressions were sharply reduced during parturition. Simvastatin increased the cervical resistance on pregnancy days 20 and 22 while Y-27632 and fasudil reduced the resistance on pregnancy days 20.The decrease in RhoA/ROCK expression near parturition may take part in cervical ripening, especially in the final processes leading to delivery. ROCK inhibitors might be potential drug candidates to treat insufficient cervical ripening late-term pregnancies. The effect of simvastatin possibly due to its unique smooth muscle contracting activity in pregnant cervix. Compounds with simvastatin-like action might be new drug candidates for preterm cervical ripening.

Distinct reorganization of collagen architecture in lipopolysaccharide-mediated premature cervical remodeling.

Previous work has identified divergent mechanisms by which cervical remodeling is achieved in preterm birth (PTB) induced by hormone withdrawal (mifepristone) or lipopolysaccharide (LPS). Our current study aims to document how collagen architecture is modified to achieve premature cervical remodeling in mice treated with LPS as a model of infection-induced inflammation. Cervices were collected on gestation day (d) 15 from mice with premature cervical ripening induced by LPS and compared to d15 and d18 controls as well as a hormone withdrawal PTB model. Second harmonic generation (SHG) and electron microscopy were utilized for visualization of collagen morphology and ultrastructure. LPS-mediated premature cervical ripening is characterized by unique structural changes in collagen fiber morphology. LPS treatment increased the interfibrillar spacing of collagen fibrils. A preferential disruption of collagen fiber architecture in the subepithelial region compared to midstroma region was evidenced by increased pores lacking collagen signal in SHG images in the LPS-treated mice. Coinciding with this alteration, the infiltration of neutrophils was concentrated in the subepithelial stromal region as compared to midstromal region implicating the potential role of immune cells to extracellular matrix reorganization in inflammation-induced preterm cervical ripening. The current study demonstrates a preferential disorganization of collagen interfibrillar spacing and collagen fiber structure in LPS-mediated ripening.

Prostaglandin dehydrogenase is a target for successful induction of cervical ripening

The cervix represents a formidable structural barrier for successful induction of labor. Approximately 10% of pregnancies undergo induction of cervical ripening and labor with prostaglandin (PG) E2 or PGE analogs, often requiring many hours of hospitalization and monitoring. On the other hand, preterm cervical ripening in the second trimester predicts preterm birth. The regulatory mechanisms of this paradoxical function of the cervix are unknown. Here, we show that PGE2 uses cell-specific EP2 receptor-mediated increases in Ca2+ to dephosphorylate and translocate histone deacetylase 4 (HDAC4) to the nucleus for repression of 15-hydroxy prostaglandin dehydrogenase (15-PGDH). The crucial role of 15-PGDH in cervical ripening was confirmed in vivo. Although PGE2 or 15-PGDH inhibitor alone did not alter gestational length, treatment with 15-PGDH inhibitor + PGE2 or metabolism-resistant dimethyl-PGE2 resulted in preterm cervical ripening and delivery in mice. The ability of PGE2 to selectively autoamplify its own synthesis in stromal cells by signaling transcriptional repression of 15-PGDH elucidates long sought-after molecular mechanisms that govern PG action in the cervix. This report details unique mechanisms of action in the cervix and serves as a catalyst for (i) the use of 15-PGDH inhibitors to initiate or amplify low-dose PGE2-mediated cervical ripening or (ii) EP2 receptor antagonists, HDAC4 inhibitors, and 15-PGDH activators to prevent preterm cervical ripening and preterm birth.

Prostaglandin E2 Regulates Its Own Inactivating Enzyme, 15-PGDH, by EP2 Receptor-Mediated Cervical Cell-Specific Mechanisms

Prostaglandins play important roles in parturition and have been used to induce cervical ripening and labor. Prior to cervical ripening at term, 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is highly expressed in the cervix and metabolizes cyclooxygenase-2-mediated increases in active prostaglandin E2 (PGE2) to inactive 15-keto PGE2. At term, 15-PGDH gene expression decreases and PGE2 accumulates, leading to cervical ripening and labor. Previously, we found that the cervical isoform of microphthalmia-associated transcription factor (MiTF-CX) serves as a progestational transcription factor that represses IL-8 and hypoxia-mediated increases in cyclooxygenase-2. We tested the hypothesis that PGE2 regulates its own inactivation through MiTF-CX. We used human cervical stromal cells to investigate the regulation of 15-PGDH. This was a laboratory-based study using cells from clinical tissue samples. We evaluated the mechanisms by which PGE2 regulates 15-PGDH in human cervical stromal cells. PGE2 repressed MiTF-CX and 15-PGDH, whereas ectopic overexpression of MiTF-CX induced 15-PGDH expression levels. Stabilization of HIF-1α by deferoxamine resulted in concomitant down-regulation of MiTF-CX and 15-PGDH. Ectopic overexpression of MiTF-CX abrogated PGE2- and deferoxamine-mediated loss of MiTF-CX and 15-PGDH. PGE2-induced loss of MiTF-CX and 15-PGDH was mediated through prostaglandin E2 receptor (EP2) receptors (PTGER2), but not cAMP. The 15-PGDH gene is a MiTF-CX target gene in cervical stromal cells and is down-regulated by PGE2 through EP2 receptors. The findings suggest that EP2 receptor-specific antagonists may be used as an adjunct to present clinical management for the prevention of preterm cervical ripening and preterm labor.

Cervical remodeling in term and preterm birth: insights from an animal model

Proper cervical function is essential for a normal pregnancy and birth to occur. Understanding the mechanisms that take place in normal pregnancy will allow a better comprehension of the complications involved in premature cervical remodeling and lead to better methods of diagnostics and prevention for preterm birth. Unfortunately, human samples are not easily available, and samples that are collected are often confounded by variations in timing and region of cervix from which sample is collected. Animal models, specifically the mouse, have facilitated a great deal of exploration into the mechanisms of cervical function and pathways of preterm birth. This review highlights some of the groundbreaking discoveries that have arisen from murine research including 1) the identification of early pregnancy changes in collagen fibril processing and assembly that result in progressive modifications to collagen architecture with subsequent loss of tissue stiffness during pregnancy, 2) the determination that immune cells are not key to cervical ripening at term but have diverse phenotypes and functions in postpartum repair, and 3) the finding that the process of preterm cervical ripening can differ from term ripening and is dependent on the etiology of prematurity. These findings, which are relevant to human cervical biology, provide new insights that will allow targeted studies on the human cervix as well as identify potential biomarkers for early detection of premature cervical ripening and development of improved therapies to prevent premature ripening of the cervix and subsequent preterm birth.

Preterm and Term Cervical Ripening in CD1 Mice (Mus musculus): Similar or Divergent Molecular Mechanisms?1

Premature cervical ripening is believed to contribute to preterm birth (PTB). Preterm cervical ripening may be due to an aberrant regulation in timing of the same processes that occur at term, or may result from unique molecular mechanisms. Using mouse models of PTB, this study sought to investigate if the molecular mechanisms that govern cervical ripening were similar between preterm and term. Lipopolysaccharide (LPS) is infused into the uterine horn to create a mouse model of inflammation-induced PTB. For a noninfectious model of PTB, RU486 was administered. Both models result in delivery of pups in 8-24 h. Cervical tissues were collected from these models, as well as throughout gestation. Cervical tissues from E15 (preterm), E15 LPS (preterm inflammation), and E18.5 (term) were used for microarray analysis (n = 18). Additional experiments using gestational time course specimens were performed to confirm microarray results. Specific gene pathways were differentially expressed between the groups. Genes involved in immunity and inflammation were increased in the cervix in inflammation-induced PTB; term labor was not associated with differential expression of immune pathways. Cytokine expression was not increased in cervices during term labor, but was increased in the pospartum period. Epithelial cell differentiation pathway was significantly altered in term, but not preterm, labor. Activation of immune pathways may be sufficient for cervical ripening, but does not appear necessary. Differential expression of the epithelial cell differentiation pathway appears necessary in the process of cervical repair. Our results indicate that the molecular mechanisms governing preterm and term cervical ripening are distinctly different.

Medroxyprogesterone Acetate Modulates Remodeling, Immune Cell Census, and Nerve Fibers in the Cervix of a Mouse Model for Inflammation-induced Preterm Birth

To determine whether a progestational agent can modify inflammation-induced preterm cervical ripening, mice on day 15 of gestation were given an intrauterine injection of (1) saline, (2) lipopolysaccharide, (3) an intramuscular injection of medroxyprogesterone acetate alone prior to lipopolysaccharide, or (4) medroxyprogesterone acetate alone. Cervices were obtained 6 hours later, then fixed, sectioned, and processed to stain collagen structure or to identify immune cells or nerve fibers. Cervical remodeling was induced by lipopolysaccharide treatment compared with that in saline controls, an effect blocked by medroxyprogesterone acetate pretreatment. Moreover, lipopolysaccharide reduced macrophages and enhanced neutrophils in the cervix, effects also forestalled by medroxyprogesterone acetate pretreatment. Although the density of nerve fibers was not altered by lipopolysaccharide, medroxyprogesterone acetate reduced innervation in the cervix. Thus, progestational treatment forestalls the inflammation-induced reduction in collagen structure and immune cell traffic through a mechanism that is independent of nerve fiber density. These findings raise the possibility that progestational treatment may regulate ripening of the cervix early in the process leading to preterm birth.

136: Heat shock proteins and inflammation-induced preterm birth

Heat shock proteins (HSP) have been suggested to be critical players in inflammatory disease states by binding to Toll-like receptor-4(TLR-4) as endogenous ligands. HSPs are released from cells in response to stress and function as regulators of the innate immune response. Limited obstetrical studies suggest that HSPs may have a mechanistic role in preterm birth (PTB) or may be promising biomarkers. These studies sought to determine 1) the regulation of HSP during pregnancy and in the setting of inflammation-induced PTB and 2) the validity of HSP as a potential non-invasive biomarker using a mouse model of PTB. 2 sets of experiments were performed. 1) Cervical (CX) and uterine (UT) tissue was harvested from CD-1 non-pregnant (NP) and pregnant mice on E15, E17, E19 (n=3-6 mice/group). 2) On E15, dams were randomized to intrauterine infusion of saline or lipopolysaccharide (LPS)(N=5-6/group). 6 hrs later, maternal serum (MS), CX and UT were collected for QPCR and ELISA for evaluatoin of HSP 70. HSP 70 levels were undetectable in saline-exposed dams in maternal serum. While HSP 70 was increased in LPS-exposed, variability between dams was pronounced. SEE TABLETabled 1E15 / NPE15 / NPE15 LPS / E15E15 LPS / E15CervixUterusCervixUterusHSP60−9.4−1.5−1.61.6HSP70−10.22.1−2.51.1HSP90−5.91.7−1.61.3 Open table in a new tab HSPs do not appear to be critically involved in the pathogenesis of PTB. Down-regulation of HSPs in the CX during normal pregnancy could be a protective mechanism against preterm cervical ripening by preventing endogenous ligands from activating TLRs.

Cervical length changes during preterm cervical ripening: effects of 17-α-hydroxyprogesterone caproate

Cervical length changes during preterm cervical ripening: effects of 17-α-hydroxyprogesterone caproate

Cervical length changes during preterm cervical ripening: effects of 17-α-hydroxyprogesterone caproate

The purpose of this study was to evaluate whether 17-alpha-hydroxyprogesterone caproate (17P) treatment affect changes in cervical length. Women with singleton pregnancy, between 25 and 33 + 6 weeks of gestation, who were hospitalized for preterm labor were included. Patients with rupture of membranes and/or signs of chorioamnionitis were excluded. Sixty undelivered patients were allocated randomly to either observation or to receive 341 mg of 17P intramuscularly, twice each week until gestational week 36. Cervical length was measured by transvaginal ultrasound scanning at discharge and at day 7 and 21 after discharge. Statistical comparisons were done with analysis of variance and chi-square test. Shortening of the cervix in the observation group (30 cases) was higher than in the 17P group (30 cases) both at day 7 (2.37 +/- 2.0 mm vs 0.83 +/- 1.74 mm; P = .002) and day 21 (4.60 +/- 2.73 mm vs 2.40 +/- 2.46 mm; P = .002). Treatment with 17P was associated with both a reduction in the risk of cervical shortening of > or = 4 mm (odds ratio, 0.18; 95% CI, 0.04-0.66) and in the risk of preterm delivery (odds ratio, 0.15; 95% CI, 0.04-0.58). Undelivered patients after preterm labor undergo progressive shortening of the cervix, which is attenuated by 17P treatment.

Non-infected preterm parturition is related to increased concentrations of IL-6, IL-8 and MCP-1 in human cervix

BackgroundHuman cervical ripening is an inflammatory process. In labour at term the mRNA-levels and protein concentrations for interleukin-6 (IL-6) and IL-8 in cervix significantly increase. The aim of this study was to investigate if there are differences in the inflammatory process of preterm and term cervical ripening.MethodsCervical biopsies from 50 singleton pregnant women without clinical signs of infection were allocated to four groups: preterm labour, term labour, preterm not in labour and term not in labour. The protein levels of IL-8, IL-6, monocyte chemotactic protein-1 (MCP-1), regulated upon activation normal t cells expressed and secreted (RANTES) and tumour necrosis factor-alpha (TNF-alpha) were quantified in tissue homogenates by ELISA or Immulite. The mRNA expression of IL-8, MCP-1 and RANTES was studied using RT-PCR. White blood cell count (WBC) and C-reactive protein (CRP) in the blood were determined. For determination of statistically significant differences between study groups Mann-Whitney U test or Kruskal-Wallis test were applied.ResultsProtein concentrations of IL-8, IL-6, and MCP-1 were significantly increased during labour compared to non-labouring groups, whereas no changes were observed for RANTES and TNF-alpha. The mRNA levels of representative cytokines such as IL-8 and MCP-1 increased significantly during labour whereas RANTES mRNA expression remained unchanged. WBC and CRP were significantly higher in the labouring groups as compared to groups not in labour. For neither of the analysed cytokines, WBC or CRP levels were there any changes between preterm and term respective groups.ConclusionOur findings indicate that non-infected preterm cervical ripening is an inflammatory process, just as cervical ripening at term, with cytokines as important mediators.

Platelet-activating factor antagonist WEB-2170 inhibits lipopolysaccharide-induced, but not antiprogestin-induced, preterm cervical ripening in timed-pregnant rats

Objective The purpose of this study was to determine whether the platelet-activating factor antagonist WEB-2170 inhibits preterm cervical ripening induced by lipopolysaccharide or by antiprogestin RU 486. Study design Timed-pregnant rats were killed on day 16 after treatment with (1) WEB-2170, lipopolysaccharide, lipopolysaccharide plus WEB-2170, or vehicle control and (2) with WEB-2170, RU 486, RU 486 plus WEB-2170, or vehicle control. Cervical ripening was assessed by light-induced fluorescence and resistance to stretch. Statistics were assessed by 1-way analysis of variance followed by Tukey-test ( P < .05). Results Light-induced fluorescence and resistance to stretch were significantly lower in the lipopolysaccharide-treated and in the RU486-treated animals compared with vehicle control (lipopolysaccharide:light-induced fluorescence, 7.0±0.6 vs 12.8±0.8 [ P = .001]; resistance to stretch, 0.41±0.03 N/mm vs 0.54±0.04 N/mm [ P < .05]; RU486:light-induced fluorescence, 9.6±0.6 vs 11.7±0.6 [ P < .05]; resistance to stretch, 0.28±0.06 N/mm vs 0.61±0.02 N/mm [ P < .001]). Compared with vehicle control, WEB-2170 alone did not alter cervical light-induced fluorescence or resistance to stretch. Although WEB-2170 significantly blocked cervical ripening after lipopolysaccharide administration (light-induced fluorescence, 11.3±1.3 [ P < .05]; resistance to stretch, 0.61±0.04 [ P < .01]), WEB-2170 did not inhibit the RU 486–induced cervical ripening. Conclusion Although infection-related cervical ripening is inhibited by platelet-activating factor antagonists, the physiologic process of cervical ripening appears to be unaffected. Platelet-activating factor inhibition may be of clinical value in the infection-related pathologic processes that are responsible for premature cervical ripening.

Expression of adhesion molecules in the lower uterine segment during term and preterm parturition.

Term and preterm cervical ripening and dilatation have similarities with an inflammatory reaction. Since cell adhesion molecules are involved in this process, investigations on the expression of intercellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, vascular cell adhesion molecule-1, and platelet endothelial cell adhesion molecule in the lower uterine segment and in vitro experiments on human umbilical vein endothelial cells were performed. In addition, current reports on expression of endothelial adhesion molecules by the uterine cervix were summarized. Cell adhesion molecule expression by lower uterine segment and uterine cervix in term and preterm parturition was measured using immunohistochemistry, enzyme immunoassay, and Northern blot analysis. Regulation of adhesion molecule expression was evaluated in vitro by indirect immunofluorescence and flow cytometry using human umbilical vein endothelial cells. Investigations in term parturition revealed that intercellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, and vascular cell adhesion molecule-1 expression increases during parturition. In preterm labor, the expression of endothelial leukocyte adhesion molecule-1 and intercellular adhesion molecule-1 in the lower uterine segment increased. Expression of platelet endothelial cell adhesion molecule did not change in term and preterm parturition. Expression of adhesion molecules was localized mainly on lower uterine segment vascular endothelial cells and to a smaller extent on leukocytes. In vitro experiments showed that expression of adhesion molecules by human umbilical vein endothelial cells can be stimulated by tumor necrosis factor-alpha, 17beta-estradiol, prostaglandin E(2), and the antigestagen onapristone. Progesterone exerted no stimulatory effect. Cervical ripening and dilatation during term and preterm parturition are associated with an increased expression of endothelial cell adhesion molecules by lower uterine segment and uterine cervix. The expression can be modulated by pro-inflammatory cytokines, sex hormones, and prostaglandin E(2). Mechanisms controlling the extravasation of leukocytes may play a fundamental role in term and preterm parturition.

Pre-term cervical ripening and labor induction

Objective: To evaluate retrospectively pre-term induction; with Prostaglandin (PG) E 2-gel and i.v. oxtytocin, respectively. Methods: Fifty pre-term women with a gestational age between 28+0 and 36+6 and medical indications for labor induction were compared with the two next induced at term and post-term. The obstetric end points were numbers of PGE 2-gel applications, failed inductions, instrumental delivery and heavy bleeding after partus (>1000 ml). The neonatal outcome was registered as operative delivery for fetal distress (ODFD) or Apgar score <7 at 5′. Results: The number of PGE 2-gel applications did not differ. The duration of labor was shorter in the pre-term group ( P=0.043). A five-fold higher risk of heavy postpartum bleeding (>1000 ml) was noticed in the post-term group compared to the pre-term. The incidence of low Apgar scores were similar in the three groups. Conclusions: Safe vaginal labor induction and delivery can be anticipated pre-term with PGE 2-gel.

Mast cells in cervical ripening—an immunohistochemical and biomechanical study in rats

Cervical ripening purportedly involves different cell types and mediators normally associated with inflammatory reactions. The purpose of the present study was to determine the presence of mast cells in rat cervices during spontaneous and antigestagen induced ripening and to test whether a mast cell stabilizer was able to inhibit the antigestagen induced cervical ripening. Immunohistochemical examinations demonstrated an increased number of mast cells in pregnant and intrapartum rats. Furthermore, mast cell degranulation was found to be prominent after antigestagen treatment. The degranulation was completely abolished by co-treatment with the mast cell stabilizer. Biomechanical analysis showed that the mast cell stabilizer also inhibited the antigestagen induced cervical ripening to some extent. Thus, it is concluded that mast cell stabilizers might constitute a new approach in the treatment of preterm cervical ripening.