Claire A. Higgins

The Effect of Progesterone on Myometrial Contractility, Potassium Channels, and Tocolytic Efficacy

Objectives: Recent clinical trials have demonstrated a beneficial effect of supplementation with progesterone to prevent preterm labor. We aimed to determine the effects of progesterone treatment in vitro and in vivo and 17α-hydroxyprogesterone caproate (17OHPC) in vitro on myometrial contractions. Methods: Myometrial strips were taken from women undergoing cesarean delivery at term. We also obtained myometrial biopsies from women participating in a clinical trial of progesterone to prevent preterm labor in twins (STOPPIT). After establishment of spontaneous contractions, strips were exposed to progesterone or 17OHPC. Separate strips were exposed to oxytocin and tocolytics alone and in combination with progesterone. Potassium channel blockers were added in conjunction with progesterone. STOPPIT samples were used to compare the effects of in vivo progesterone and placebo. We measured amplitude, frequency and activity integral of contractions. Results: Maximum inhibition of contraction amplitude was 93 ± 2% and 67 ± 14% for progesterone at 30 μM and vehicle (70% ethanol), respectively, P < 0.05. 17OHPC did not exert an inhibitory effect. Water soluble progesterone exerted a maximal inhibitory effect on amplitude of contractions of 82 ± 10% at 100 μM, P < 0.05. The inhibitory effect of progesterone was unaffected by potassium channel blockers. There was no difference between in vivo placebo and progesterone-treated groups in either amplitude or frequency of contractions, nor was there any difference in the response to oxytocin or the tocolytic drugs. Conclusions: Progesterone exerts rapid inhibition of the amplitude of myometrial contractions in vitro but 17OHPC does not. The action of progesterone does not appear to operate via potassium channels nor does it enhance the activity of certain tocolytic drugs.

Maternal Obesity and its Relationship With Spontaneous and Oxytocin-Induced Contractility of Human Myometrium In Vitro

Maternal obesity is associated with increased rates of labor induction, dysfunctional labor requiring intrapartum cesarean delivery, and postpartum hemorrhage, implying that maternal obesity has an inhibitory effect on myometrial function and its ability to respond to oxytocin. This study aimed to use an in vitro model to investigate the relationship between maternal body mass index (BMI) and the ability of myometrium to contract spontaneously and in response to oxytocin. Linear mixed effects regression modeling was applied to contractile data from 609 strips from 85 women. No correlation was found between maternal BMI and any indices of spontaneous myometrial activity. A single addition of oxytocin increased contractility, however, this was not related to maternal BMI. Similarly, oxytocin concentration-response curves were unrelated to BMI. Overall, the results from this in vitro study suggest that the observed implications of obesity on parturition in vivo cannot be explained by a direct effect on myometrial contractile mechanisms per se.

Mast cells reside in myometrium and cervix, but are dispensable in mice for successful pregnancy and labor

Parturition is associated with myometrial and cervical inflammation. The causes and consequences of this inflammatory response are not clear. Mast cells (MCs) are important inducers of allergic and non‐allergic inflammation, and their secreted products can induce myometrial contractions. Thus, mast cell activation has been hypothesized to have a role in initiating labor and/or driving labor‐associated inflammation. We report that small numbers of MCs expressing chymase and tryptase are present in the myometrium and cervix of pregnant women. Labor did not lead to any change in mast cell abundance in these tissues, but was associated with reduced expression of the mast‐cell regulator FcεR1A, indicative of a change in mast cell properties. This coincided with contraction‐dependent myocyte production of interleukin‐10 (IL‐10), a known suppressor of FcεR1A expression. MCs were also found in the uterine horn and cervical region of pregnant C57BL/6 mice, increasing in number in the cervix, but not the myometrium, with labor. As expected, these cells were absent from mast‐cell‐deficient KitW−sh mice. Nonetheless, pregnant KitW−sh mice showed no defects in the timing of labor induction or in the upregulation of leukocyte markers during labor. Thus, MCs are present in the uterus and cervix of humans and mice, and our mouse studies suggest that they do not have a vital role in the induction of labor, or in the promotion of labor‐associated inflammation.

A population-based case–control study of aetiological factors associated with vulval lichen sclerosus

We aimed to investigate the association between possible aetiological factors and the risk of developing vulval lichen sclerosus (VLS). A population-based case–control questionnaire study was performed comparing women with a diagnosis of VLS (n= 92), with those attending a general gynaecology clinic with no known anogenital dermatosis (n= 66). After adjustment for confounders, factors associated with VLS included a family history of diabetes mellitus (OR= 7.0, p= 0.012) and previous pelvic surgery (OR= 4.75, p= 0.007). The use of barrier and progesterone only methods of contraception (OR= 0.19, p= 0.045), hormone replacement therapy (OR= 0.209, p= 0.025) or hayfever (OR= 0.18, p= 0.008) appeared to be associated with a reduced risk of VLS. In conclusion, we were unable to confirm many proposed aetiological theories associated with the development of VLS, in particular those associated with autoimmunity.

The Chemokine Receptor CCR2 Is Not Required for Successful Initiation of Labor in Mice

ABSTRACT Chemokine-driven neutrophil and monocyte recruitment into the uterus and cervix has been proposed to initiate labor. Chemokines that bind CXCR2 direct neutrophil migration and are induced during labor in humans. The chemokine CCL2, induced in the uterus by endocrine and mechanical signals, has been proposed to drive CCR2-dependent monocyte homing to the uterus to contribute to the initiation of labor. However, no direct evidence indicates that chemokines or their receptors play indispensable roles in labor-associated inflammation, and the impact of leukocyte infiltration on labor is unclear. Here, we have quantified expression of the principal monocyte- and neutrophil-attracting chemokines in the uteri of term pregnant (Day 18) and laboring wild-type mice. None of the neutrophil attractants we assayed were up-regulated with labor. Strikingly, however, Ccl2 was markedly increased, and this was concomitant with increased expression of Ccr2, the myeloid marker Itgam (also known as Cd11b), the monocyte/macrophage marker Emr1 (also known as F4/80). Moreover, in CCR2-deficient mice, this labor-associated increase in Itgam and Emr1 was not seen, consistent with the monocyte-trafficking defects that exist in these animals. Nonetheless, laboring CCR2-deficient and wild-type uteri showed similarly enhanced expression of the myometrial activation markers Gja1 and Oxtr (commonly known as connexin 43 and oxytocin receptor, respectively), and CCR2-deficient mice had gestation lengths, litter sizes, and fetal and placental weights no different from those of their wild-type counterparts. Thus, whereas labor is associated with an inflammatory response in gestational tissues, CCR2-dependent leukocyte recruitment into the mouse uterus is dispensable for the initiation of successful labor.

Investigation of myometrial gene expression in response to sustained spontaneous and oxytocin induced contraction in-vitro

Plenary Session: Trainee Plenary (Thursday, 3/19/2009, 9:00 AM 10:00 AM) Scientifi c Abstracts Reproductive Sciences Vol. 16, No. 3 (Supplement), March 2009 69ABackground: Small for Gestational Age (SGA) is defi ned as <10th centile on individualised birthweight centiles. SGA babies are at increased risk of complications in pregnancy and later life such as stillbirth, preterm delivery, cerebral palsy and heart disease and diabetes in adulthood. Metabolomics is the study of global metabolite profi les in a biological system. This technology has previously identifi ed differences in maternal plasma between normal and preeclamptic pregnancies. Aim: To examine the differences in the plasma metabolome in early pregnancy between women who develop a SGA baby and normal matched controls. Methods: 60 primigravid women who delivered a SGA baby were identifi ed within the SCOPE study (www.scopestudy.net) and matched to 60 controls. Venepuncture was performed at 15�1 weeks gestation. Samples were analysed using Ultra Performance Liquid Chromatography(UPLC)/LTQ-Orbitrap Mass Spectrometry (MS). Univariate statistical analysis was performed. Subsequently all the peaks in each class were grouped and analysed in combination by employing Multivariate Discriminant Analysis. Results: Univariate analysis of the UPLC/LTQ-Orbitrap MS data at 15 weeks gestation identifi ed 111 ?information rich? peaks (p < 0.05). The multivariate discriminant model (all 111 peaks), provided an area under the ROC curve of 0.96. Downloaded from rsx.sagepub.com at The John Rylands University Library, The University of Manchester on January 28, 2011Plenary Session: Trainee Plenary (Thursday, 3/19/2009, 9:00 AM 10:00 AM) Scienti c Abstracts Reproductive Sciences Vol. 16, No. 3 (Supplement), March 2009 69A