Onapristone and prostaglandin E2 induction of delivery in the rat in late pregnancy: a model for the analysis of cervical softening

Effect of preterm birth in rats on proliferation and hyperplasia of cardiomyocytes

Aim. To identify the effect of preterm birth on proliferation and hyperplasia of cardiomyocytes in the early postnatal period of ontogenesis in rats.

Materials and methods. Preterm birth (on day 21 and 21.5 of gestation) in Wistar rats was induced by subcutaneous administration of mifepristone. Immunohistochemistry was used to identify and calculate the number of Ki67-positive and Mklp2-positive cardiomyocytes in the left ventricle of preterm and full-term rats on days 1, 2, 3, 4, 5, and 6 of postnatal ontogenesis. Statistical analysis of morphometric parameters was performed using the Shapiro – Wilk test and Mann – Whitney test with the Bonferroni correction.

Results. We revealed an increase in the number of Ki67-positive cardiomyocytes in the left ventricle of the rats: on day 1 of postnatal ontogenesis (in the rats born on day 21 of gestation) and on days 3–5 of postnatal ontogenesis (in the rats born on day 21.5 of gestation). Preterm birth in rats did not result in a change in the number of Mklp2-positive cardiomyocytes in the left ventricular wall.

Conclusion. A change in the pattern of Ki67 expression by cardiomyocytes in the rats born 12 or 24 hours before full term was demonstrated in the early postnatal period of ontogenesis. An isolated increase in Ki67 expression without a change in Mklp2 expression by cardiomyocytes in the left ventricular wall of preterm rats indicates acceleration of cardiomyocyte hypertrophy. Shorter duration of prenatal development is associated with more pronounced morphological and functional rearrangements in the rat myocardium.

Maternal gut microbiota reflecting poor diet quality is associated with spontaneous preterm birth in a prospective cohort study

BACKGROUND

A processed diet, high in fat and low in fiber, is associated with differences in the gut microbiota and adverse health outcomes in humans; however, little is known about the diet-microbiota relation and its impact on pregnancy. Spontaneous preterm birth (SPTB), a pregnancy outcome with serious short- and long-term consequences, occurs more frequently in black and in obese women in the United States.

OBJECTIVES

In a prospective, case-control sample matched for race and obesity (cases = 16, controls = 32), we compared the fecal gut microbiota, fecal and plasma metabolites, and diet in the late second trimester. We hypothesized that a Western diet would be associated with reduced microbiota richness and a metabolic signature predicting incidence of SPTB.

METHODS

The fecal microbiota was characterized by 16S-tagged sequencing and untargeted metabolomics was used to analyze both plasma and fecal metabolites. Wilcoxon's rank-sum test was used for the comparison of microbiota genera, α-diversity, fecal and plasma metabolites, and dietary variables between term and SPTB. β-Diversity was analyzed using permutational multivariate ANOVA, and metabolite associations were assessed by module analysis.

RESULTS

A decrease in α-diversity was strongly associated with the development of SPTB, especially in the taxonomic class of Betaproteobacteria. Of 824 fecal metabolites, 22 metabolites (mostly lipids) differed between cases and controls (P < 0.01), with greater DHA (22:6n-3) and EPA (20:5n-3) in cases [false discovery rate (FDR) < 0.2]. The most significant fecal metabolite module (FDR-adjusted P = 0.008) was dominated by DHA and EPA. Dietary saturated fat (primarily palmitate) intake was greater in cases (31.38 ± 7.37 compared with 26.08 ± 8.62 g, P = 0.045) and was positively correlated with fecal DHA and EPA (P < 0.05).

CONCLUSIONS

Reduced α-diversity of the gut microbiota and higher excretion of omega-3 (n-3) fatty acids in stool may provide a novel biomarker signature predicting SPTB in women with a low-fiber, high-fat diet. Further investigation of these markers in a larger sample is needed for validation.

In vivo characterization of connective tissue remodeling using infrared photoacoustic spectra

Premature cervical remodeling is a critical precursor of spontaneous preterm birth, and the remodeling process is characterized by an increase in tissue hydration. Nevertheless, current clinical measurements of cervical remodeling are subjective and detect only late events, such as cervical effacement and dilation. Here, we present a photoacoustic endoscope that can quantify tissue hydration by measuring near-infrared cervical spectra. We quantify the water contents of tissue-mimicking hydrogel phantoms as an analog of cervical connective tissue. Applying this method to pregnant women in vivo, we observed an increase in the water content of the cervix throughout pregnancy. The application of this technique in maternal healthcare may advance our understanding of cervical remodeling and provide a sensitive method for predicting preterm birth.

Functional and morphological development of the womb throughout life

The uterus undergoes changes throughout a woman's life, beginning with her own embryonic development when she is still in the womb, commencing a monthly cycle at the onset of adulthood, and undergoing dramatic changes during pregnancy and parturition. The impact of preterm labour and other perinatal health problems is significant, both in human and financial terms; therefore the study of the physiological and regulatory changes which the uterus undergoes can be of enormous potential benefit. Here we briefly review the current state of knowledge, with an emphasis on the importance of changes in connectivity in the uterine smooth muscle cell network and on recent mathematical modelling work aimed at elucidating the role of spatial heterogeneity in this connected network.

Estimation of shear wave speed in the human uterine cervix

OBJECTIVES

To explore spatial variability within the cervix and the sensitivity of shear wave speed (SWS) to assess softness/stiffness differences in ripened (softened) vs unripened tissue.

METHODS

We obtained SWS estimates from hysterectomy specimens (n = 22), a subset of which were ripened (n = 13). Multiple measurements were made longitudinally along the cervical canal on both the anterior and posterior sides of the cervix. Statistical tests of differences in the proximal vs distal, anterior vs posterior and ripened vs unripened cervix were performed with individual two-sample t-tests and a linear mixed model.

RESULTS

Estimates of SWS increase monotonically from distal to proximal longitudinally along the cervix, they vary in the anterior compared to the posterior cervix and they are significantly different in ripened vs unripened cervical tissue. Specifically, the mid position SWS estimates for the unripened group were 3.45 ± 0.95 m/s (anterior; mean ± SD) and 3.56 ± 0.92 m/s (posterior), and 2.11 ± 0.45 m/s (anterior) and 2.68 ± 0.57 m/s (posterior) for the ripened group (P < 0.001).

CONCLUSIONS

We propose that SWS estimation may be a valuable research and, ultimately, diagnostic tool for objective quantification of cervical stiffness/softness.

Nonlinear optical microscopy and ultrasound imaging of human cervical structure

The cervix softens and shortens as its collagen microstructure rearranges in preparation for birth, but premature change may lead to premature birth. The global preterm birth rate has not decreased despite decades of research, likely because cervical microstructure is poorly understood. Our group has developed a multilevel approach to evaluating the human cervix. We are developing quantitative ultrasound (QUS) techniques for noninvasive interrogation of cervical microstructure and corroborating those results with high-resolution images of microstructure from second harmonic generation imaging (SHG) microscopy. We obtain ultrasound measurements from hysterectomy specimens, prepare the tissue for SHG, and stitch together several hundred images to create a comprehensive view of large areas of cervix. The images are analyzed for collagen orientation and alignment with curvelet transform, and registered with QUS data, facilitating multiscale analysis in which the micron-scale SHG images and millimeter-scale ultrasound data interpretation inform each other. This novel combination of modalities allows comprehensive characterization of cervical microstructure in high resolution. Through a detailed comparative study, we demonstrate that SHG imaging both corroborates the quantitative ultrasound measurements and provides further insight. Ultimately, a comprehensive understanding of specific microstructural cervical change in pregnancy should lead to novel approaches to the prevention of preterm birth.

Beyond cervical length: emerging technologies for assessing the pregnant cervix

Spontaneous preterm birth is a heterogeneous phenotype. A multitude of pathophysiologic pathways culminate in the final common denominator of cervical softening, shortening, and dilation that leads to preterm birth. A precise description of specific microstructural changes to the cervix is imperative if we are to identify the causative upstream molecular processes and resultant biomechanical events that are associated with each unique pathway. Currently, however, we have no reliable clinical tools for quantitative and objective evaluation, which likely contributes to the reason the singleton spontaneous preterm birth rate has not changed appreciably in >100 years. Fortunately, promising techniques to evaluate tissue hydration, collagen structure, and/or tissue elasticity are emerging. These will add to the body of knowledge about the cervix and facilitate the coordination of molecular studies and ultimately lead to novel approaches to preterm birth prediction and, finally, prevention.

Quantitative ultrasound assessment of cervical microstructure

The objective of this preliminary study was to determine whether quantitative ultrasound (QUS) can provide insight into, and characterization of, uterine cervical microstructure. Throughout pregnancy, cervical collagen reorganizes (from aligned and anisotropic to disorganized and isotropic) as the cervix changes in preparation for delivery. Premature changes in collagen are associated with premature birth in mammals. Because QUS is able to detect structural anisotropy/isotropy, we hypothesized that it may provide a means of noninvasively assessing cervical microstructure. Thorough study of cervical microstructure has been limited by lack of technology to detect small changes in collagen organization, which has in turn limited our ability to detect abnormal and/or premature changes in collagen that may lead to preterm birth. In order to determine whether QUS may be useful for detection of cervical microstructure, radiofrequency (rf) echo data were acquired from the cervices of human hysterectomy specimens (n = 10). The angle between the acoustic beam and tissue was used to assess anisotropic acoustic propagation by control of transmit/receive angles from -20 degrees to +20 degrees. The power spectrum of the echo signals from within a region of interest was computed in order to investigate the microstructure of the tissue. An identical analysis was performed on a homogeneous phantom with spherical scatterers for system calibration. Power spectra of backscattered rf from the cervix were 6 dB higher for normal (0 degree) than steered (+/- 20 degrees) beams. The spectral power for steered beams decreased monotonically (0.4 dB at +5 degrees to 3.6 dB at +20 degrees). The excess difference (compared to similar analysis for the phantom) in normally-incident (0 degree) versus steered beams is consistent with scattering from an aligned component of the cervical microstructure. Therefore, QUS appears to reliably identify an aligned component of cervical microstructure; because collagen is ubiquitously and abundantly present in the cervix, this is the most likely candidate. Detection of changes in cervical collagen and microstructure may provide information about normal versus abnormal cervical change and thus guide development of earlier, more specific interventions for preterm birth.

The transcriptome of cervical ripening in human pregnancy before the onset of labor at term: identification of novel molecular functions involved in this process

OBJECTIVE

The aim of this study was to identify changes in the cervical transcriptome in the human uterine cervix as a function of ripening before the onset of labor.

STUDY DESIGN

Human cervical tissue was obtained from women at term not in labor with ripe (n = 11) and unripe (n = 11) cervices and profiled using Affymetrix GeneChip HGU133Plus2.0 arrays. Gene expression was analyzed using a moderated t-test (False Discovery Rate 5%). Gene ontology and pathway analysis were performed. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used for confirmation of selected differentially expressed genes.

RESULTS

(1) Ninety-one genes were differentially expressed between ripe and unripe groups. (2) Cervical ripening was associated with enrichment of specific biological processes (e.g. cell adhesion, regulation of anatomical structure), pathways and 11 molecular functions (e.g. extracelluar matrix (ECM)-structural constituent, protein binding, glycosaminoglycan binding). (3) qRT-PCR confirmed that 9 of 11 tested differentially expressed genes (determined by microarray) were upregulated in a ripe cervix (e.g. MYOCD, VCAN, THBS1, COL5A1). (4) Twenty-three additional genes related to ECM metabolism and adhesion molecules were differentially regulated (by qRT-PCR) in ripe cervices.

CONCLUSION

(1) This is the first description of the changes in the human cervical transcriptome with ripening before the onset of labor. (2) Biological processes, pathways and molecular functions were identified with the use of this unbiased approach. (3) In contrast to cervical dilation after term labor, inflammation-related genes did not emerge as differentially regulated with cervical ripening. (4) Myocardin was identified as a novel gene upregulated in human cervical ripening.

Gestagen treatment enhances the tocolytic effect of salmeterol in hormone-induced preterm labor in the rat in vivo

OBJECTIVE

The purpose of this study was to determine whether gestagen treatment enhances the effects of beta2-mimetics in hormone-induced preterm delivery in pregnant rats in vivo.

STUDY DESIGN

Preterm birth was induced with a combination of mifepristone and prostaglandin E2 on day 19 of pregnancy. The animals were treated with salmeterol or gestagens (progesterone or 17alpha-hydroxyprogesterone) or their combination. The treatments were launched on different days (15-18) of pregnancy. The efficacy of treatment was determined in terms of the delivery time counted from the mifepristone injection.

RESULTS

Salmeterol treatment delayed premature labor by 2.4 hours, whereas the delay because of the gestagen-salmeterol combinations was more than 5 hours. Progesterone had no effect on the delivery time.

CONCLUSION

Parallel treatment with salmeterol and gestagens can be more than twice as effective as salmeterol therapy alone. These results open up a possibility for human trials of combined beta2-agonist-gestagen therapy in threatening preterm delivery.

Rupture of the uterine scar during term labour: contractility or biochemistry?

OBJECTIVE

Vaginal birth after a prior low transverse caesarean section (VBAC) is advocated as a safe and effective method to reduce the total caesarean section rate. However, the risk of uterine rupture has dampened the enthusiasm of practising clinicians for VBAC. Uterine rupture occurs more frequently in women receiving prostaglandins in preparation for the induction of labour. We hypothesised that similar to the cervix, prostaglandins induces biochemical changes in the uterine scar favouring dissolution, predisposing the uterus to rupture at the scar of the lower segment as opposed to elsewhere.

DESIGN

We tested aspects of this hypothesis by investigating the location of uterine rupture associated with prostaglandins and compared it with the sites of rupture in the absence of prostaglandins.

SETTINGS

Two North American University Hospitals.

POPULATION

Twenty-six women with a prior caesarean section, experiencing uterine rupture in active labour.

METHODS

Retrospective review of all pregnancies complicated by uterine rupture at two North American teaching hospitals from 1991 to 2000.

MAIN OUTCOME MEASURE

Site of the uterine rupture.

RESULTS

Thirty-four women experienced rupture after a previous caesarean section with low transverse uterine incision. Ten of the women who ruptured (29%) received prostaglandins for cervical ripening (dinoprostone: n= 8 or misoprostol: n= 2) followed by either spontaneous contractions (n= 3) or oxytocin augmentation during labour (n= 7). In 16 women (47%), oxytocin alone was sufficient for the induction/augmentation of labour. Eight (23%) women ruptured at term before reaching the active phase of labour in the absence of pro-contractile agents or attempted VBAC. There were no differences among the groups in terms of age, body mass index, parity, gestational age, fetal weight or umbilical cord pH measurements. Women treated with prostaglandins experienced rupture at the site of their old scar more frequently than women in the oxytocin-alone group whose rupture tended to occur remote from their old scar (prostaglandins 90%vs oxytocin 44%; OR: 11.6, 95% CI: 1.2-114.3).

CONCLUSION

Women in active labour treated with prostaglandins for cervical ripening appear more likely to rupture at the site of their old scar than women augmented without prostaglandins. We propose that prostaglandins induce local, biochemical modifications that weaken the scar, predisposing it to rupture.

Physical and biomechanical characteristics of rat cervical ripening are not consistent with increased collagenase activity

OBJECTIVE

The cervix progressively softens during pregnancy to allow stretch without rupture in labor. Cervical softening is the product of complex modifications that include increased proteoglycan-to-collagen ratio, increased hyaluronic acid and water content, and breakdown of collagen by matrix metalloproteases. The relative contribution of collagen breakdown to cervical ripening is unclear. We sought to identify, discriminate, and quantify the physical characteristics of rat cervix during pregnancy, labor, and both before and after exposure to either prostaglandin (PGE(2)) or the collagenolytic enzyme matrix metalloprotease-1 (MMP-1).

STUDY DESIGN

Cervices were collected from nonpregnant rats in diestrus (n=4) and pregnant rats on d10 (n=4), d16 (n=11), d20 (n=5), and d22 (term) nonlabor (NL: n=4) and d22 in term labor (TL: n=7). Cervices were also collected from a separate group in preterm labor induced by RU486 (PTL: n=10). The effect of PGE(2) on cervical characteristics was determined after intravaginal placement of PGE(2) gel (0.5 mg PGE(2): n=3) or placebo metylcellulose gel (CRL(PG) n=6) for 20 hours before euthanasia on d16. The effect of collagen was determined by incubating in vitro cervices from untreated d16 rats with (MMP-1: n=3) and without (CRL(MMP): n=7) activated collagenase before tensile testing. Tensile properties were quantitated by using Shimadzu EZ-test instrumentation (Shimadzu North America, Columbia, Md) with a stretching regimen that mimicked labor contractions while recording the force opposed by the tissue. Parameters such as the slope (a measure of stiffness), yield point (YP; moment the tissue changes its proprieties from elastic to plastic), and break point (BP; a measure of tissue strength) were recorded and analyzed. The plateau was defined as the phase after YP but before BP.

RESULTS

Compared with d16, cervical extensibility increased significantly by d20 (slope d16: 0.41 +/- 0.03 N/mm vs d20: 0.19 +/- 0.05 N/mm, P < .01), and during both PTL (slope: 0.17 +/- 0.03 N/mm) and TL (slope: 0.11 +/- 0.02 N/mm). This increase was mimicked by PGE(2) (slope PGE(2): 0.24 +/- 0.03 vs CRL(PG): 0.40 +/- 0.05 N/mm, P=.04), but not by collagenase (slope MMP-1: 0.35 +/- 0.02 vs CRL(MMP): 0.38 +/- 0.05 N/mm, P>.05). YP was significantly reduced as pregnancy advanced, whereas BP increased, suggesting both increased plasticity (compliance) and strength. However, the plateau length increased 3-fold both by d20 and after PGE(2). In contrast, the addition of MMP-1 reduced the plateau. BP occurred significantly earlier in collagenase-treated tissues, but later in PTL-, TL-, and PGE(2)-treated cervices.

CONCLUSION

The changes in physical properties of the rat cervix during physiologic ripening are similar to those induced by PGE(2) and RU486, and consist of increased extensibility, compliance, and strength. These changes cannot be attributed to increased collagenase activity, which would decrease tissue compliance and strength.

Maternal serum levels of dehydroepiandrosterone sulfate and labor induction in postterm pregnancies

OBJECTIVES

To study the relationship between maternal endogenous dehydroepiandrosterone sulfate (DHEAS) levels, success of labor induction, and Bishop scores in postterm pregnancies.

METHODS

There were 65 postterm pregnancies. Group 1 consisted of women spontaneously in the active phase of labor, and group 2 of women with hypotonic uterine contractions whose labor was inducted by oxytocin. Levels of DHEAS were studied from venous blood samples. Demographic data and Bishop scores were recorded.

RESULTS

The demographic characteristics of patients were similar, but DHEAS levels were higher in group 1 than in group 2 (P<0.001). Linear regression analysis showed a significant relationship between DHEAS and Bishop scores. DHEAS levels in women delivered vaginally were significantly higher than in women delivered by cesarean section. From the receiver operating characteristics (ROC) curve, DHEAS levels might determine the mode of delivery and success of labor induction; however, Bishop scores do not.

CONCLUSIONS

DHEAS levels may be an important factor influencing the efficiency of labor and the success of labor induction in postterm pregnancies.

Expression and regulation of the rat prostaglandin E2 receptor type 4 (EP4) in pregnant cervical tissue

OBJECTIVE

Prostaglandins play an important role in the regulation of parturition and cervical ripening. Prostaglandin E(2) (PGE(2))-induced tissue remodeling is mediated through activation of prostaglandin E(2) receptor type 4 (EP4). EP4 is known to regulate matrix metalloproteinase secretion and expression and therefore may play a role in cervical ripening. We hypothesized that EP4 expression is regulated in the rat cervix to coincide with cervical ripening. In addition, we analyzed transcriptional regulation of the rat EP4 gene.

STUDY DESIGN

EP4 expression was evaluated in the cervix in timed pregnancy Sprague-Dawley rats by real-time reverse transcriptase polymerase chain reaction and Western blot. The genomic structure of the rat EP4 gene was determined by sequencing rat genomic clones obtained by plaque hybridization. Northern blots were performed to identify the number of different transcripts. The transcriptional start site was identified on the basis of sequence comparison to the human and mouse EP4 gene. The minimal promoter was identified by using reporter constructs containing portions of the 5' flanking region. Reporter activity was evaluated in vitro. Identified regulatory regions were mutated to determine their role in transcription.

RESULTS

Cervical EP4 expression (messenger RNA and protein) peaks on the day of parturition. The rat EP4 gene is structurally similar to other prostaglandin receptors as well as the human EP4 gene and contains three exons separated by two introns. The coding regions are located in the second and third exons separated in the sixth transmembrane spanning region. Northern blot identified a single EP4 transcript with an estimated size of 4 kb, indicating a single transcription initiation site. The first 80 bases of the 5' flanking region were required for constitutive expression of EP4. Expression was lost after mutation of the GC/Sp1 binding site located at position -78 to -66 downstream from the transcription initiation site. Three Sp1 binding sites were identified and appear to cooperate to enhance EP4 transcription.

CONCLUSION

EP4 expression is regulated in the cervix and peaks on the day of parturition. The genomic structure of the human and rat EP4 gene is conserved between these two species. A GC rich/Sp1 binding site located within the first 80 bases of the transcription start site is important in transcription initiation of the EP4 gene.

Regulation of matrix metalloproteinases (type IV collagenases) and their inhibitors in the virgin, timed pregnant, and postpartum rat uterus and cervix by prostaglandin E(2)-cyclic adenosine monophosphate

OBJECTIVE

Our purpose was to examine whether the type IV collagenases (metalloproteinase [MMP]-2 and MMP-9) and their inhibitors (TIMP-1 and TIMP-2) are regulated by a prostaglandin E(2) (PGE(2))-cyclic adenosine monophosphate (cAMP) mechanism in nonpregnant virgin, preterm and term pregnant and postpartum rats.

STUDY DESIGN

Sprague-Dawley rats were infused with either saline solution or PGE(2) over 24 hours or were noninfused. Plasma and tissue were analyzed for cAMP, MMP-2 and MMP-9, and TIMP-1 and TIMP-2.

RESULTS

PGE(2) evoked elevations in plasma and tissue levels of cAMP and MMP-2 in the preterm and term pregnant rats. MMP-9 levels were elevated in the preterm plasma and uterus, whereas in the term pregnant and postpartum rats, MMP-9 levels were increased in the cervix.

CONCLUSIONS

MMP levels in the pregnant and postpartum rat uterus and cervix are regulated in part by a PGE(2)-cAMP mechanism. Specifically, MMP-9 may be involved in preterm labor, cervical maturity, and involution of the postpartum uterus.

Anatomy and physiology of the uterine cervix

The human uterine cervix undergoes extensive changes during pregnancy. Collagen is reorganized and consolidated early in gestation with proliferation and hyperplasia of the cellular component. As term approaches, multiple factors work together in complex interactions that cause collagen dispersion and the cervix to ripen (clinically become softer). Increases in decorin levels, hyaluronic acid, and physiologic cell death are in part responsible for this remodeling process. As the collagen bundles disperse and lose strength, cytokines, hyaluronic acid, collagenases, and elastase possibly work together to allow effacement. Then, the mechanical forces of uterine contractions extend the elastin and allow dilatation. During dilation, levels of cytokines and hyaluronic acid begin to decrease, which may serve to decrease collagenolytic activity and allow the cervix to begin the process of repairing itself. Despite this advance knowledge of cervical ripening, the signals responsible for the initiation of these changes remain to be elucidated. If we can understand the exact mechanisms that affect these changes, then we may be better able to address such complex issues as cervical incompetence, preterm delivery, postterm delivery, and proper "ripening" of the cervix to avoid surgical delivery for arrest disorders of the active phase.

Further evidence of a decorin-collagen interaction in the disruption of cervical collagen fibers during rat gestation

OBJECTIVE

Our purpose was to determine the histologic distribution and expression of decorin in rat cervix throughout the course of rat gestation and to correlate the findings with the known progression of collagen fiber disruption and cellular turnover in this tissue.

STUDY DESIGN

Cervices from pregnant animals at 5, 11, 18, and 21 days were studied. A proteoglycan of low molecular weight, decorin, was detected by sensitive and specific immunohistochemical analysis with a biotin-avidin horseradish peroxidase method.

RESULTS

Decorin was not detected on day 5. By day 11 moderate decorin staining was detected in the subepithelial layer and in the deep stroma. Decorin staining progressed to a strong expression in the subepithelial layer and to a moderate expression in the deep stroma on day 18. On day 21 (term in rat) the staining was fairly homogeneous throughout the connective tissue stroma.

CONCLUSION

These findings clearly demonstrate that decorin expression increased progressively throughout pregnancy and are consistent with the hypothesis that an excess of decorin near term is capable of initiating a decorin-collagen interaction that leads to collagen fibril disruption and decreased cervical tensile strength.

Characterization of decorin mRNA in pregnant intrauterine tissues of the ewe and regulation by steroids

In this study, we characterized the changes in the extracellular matrix proteoglycan decorin in pregnant intrauterine tissues in late gestation and in association with labor and delivery in sheep. In addition, we examined the effects of estradiol and progesterone on regulation of decorin mRNA expression in myometrium from the nonpregnant ovariectomized sheep. Using suppression subtractive hybridization in combination with Northern blot analysis, we identified a significant increase in decorin mRNA in the pregnant sheep myometrium during labor. The abundance of decorin mRNA paralleled myometrial contractility. The increase in decorin mRNA during labor was only demonstrated in the myometrium; no increase was observed in the endometrium or fetal membranes. Estradiol upregulated decorin mRNA and may act as a potential stimulator responsible for the increased decorin in the myometrium during parturition. The ovine decorin cDNA spans 1288 nt, includes 1083 nt of coding sequence predicted to encode a protein of 360 amino acids, 119 nt of 5'-untranslated region (UTR) and 86 nt of 3'-UTR. Over the coding region, the protein shares 79-96% nt sequence identity and 73-94% identity in the deduced amino acid sequence with homologous mammalian sequences. Using cloned decorin cDNA, we observed that the fibroblasts are the predominant cell type in the pregnant sheep myometrium containing decorin mRNA. These data suggest that increased decorin synthesis participates in the matrix changes that may play a role in myometrial activation.

Matrix metalloproteinases-2 and -9 and their inhibitors are produced by the human uterine cervix but their secretion is not regulated by nitric oxide donors

We have investigated the presence of matrix metalloproteinases (MMP)-2 and -9 and their tissue inhibitors (TIMP) in the human uterine cervix. We postulate that during the process of cervical ripening, there is an increase in the activity of MMP in order to facilitate cervical connective tissue change. We have previously demonstrated that nitric oxide (NO) donors induce cervical ripening in vivo. A secondary hypothesis is that NO donors regulate MMP activity within the human uterine cervix. Cervical tissue biopsies were obtained from both pregnant and non-pregnant subjects. Cervical fibroblasts were cultured from the non-pregnant tissue. MMP-2 was present in conditioned media from pregnant and non-pregnant cervical explants and non-pregnant cervical fibroblasts. MMP-9 secretion was only detected in explants from non-pregnant women. TIMP-1, -2 and -4 were released by all cervical explants and fibroblast preparations. Pregnant women, in the first trimester, were treated with an NO donor (isosorbide mononitrate) in vivo. Cervical explants and fibroblasts from non-pregnant women were treated with the NO donor spermine nonoate in vitro. Treatment with an NO donor either in vivo or in vitro had no effect on the secretion of the MMP or TIMP studied. Further studies evaluating the mechanisms involved in cervical ripening are required.

Proliferation and apoptosis of fibroblasts and smooth muscle cells in rat uterine cervix throughout gestation and the effect of the antiprogesterone onapristone

OBJECTIVE

The purpose of this study was to determine the relative percentages of apoptosis and proliferation in fibroblasts and cervical smooth muscles throughout gestation and the effect of an antiprogesterone on these processes.

STUDY DESIGN

Rats were studied at days 5, 15, 18, and 21 and immediately postpartum (day 22). Apoptosis and proliferation as detected by specific immunohistochemistry quantitative morphometric analysis was performed. Onapristone, an antiprogesterone, was used to study effects of hormonal change on these processes in 16- and 19-day timed-pregnant rats.

RESULTS

Proliferation of fibroblasts and smooth muscle cells was highest in early pregnancy and decreased progressively, whereas apoptosis increased progressively in later pregnancy. Onapristone inhibited apoptosis.

CONCLUSION

Changes in cervical cellular turnover are initiated early in gestation and are under hormonal influence. Antiprogesterone inhibits cell death at days 16 and 19 of gestation.