Gemeprost-induced cervical ripening: histological and biophysical effects

Cervical relaxation for non-surgical uterus access in Santa Inês ewes

ABSTRACT The present study was composed by two experiments aiming to develop a cervical dilation technique for non-surgical access to Santa Inês ewe’s uterus. In Experiment 1, thirty ewes underwent four epidural treatments. The three experimental treatments used 2.0mg/kg ketamine. The group receiving this drug alone was denominated KG, whereas other group had ketamine associated with 0.1mg/kg morphine (KM) and KX a third group had ketamine associated with 0.05mg/kg xylazine (KX). Control treatment was 1mL/7.5kg saline solution epidurally (CON). Cervical dilation was evaluated in both experiments by attempting to pass a metal rod through the cervix. In Experiment 2, three different hormonal protocols for cervical dilation were tested in thirty ewes. Epidural anesthesia with 2.0mg/kg ketamine was the control treatment (KG) and was combined with hormonal treatments: Misoprostol (MI); Oxytocin + Estradiol (OE); Misoprostol + Oxytocin + Estradiol (MOE). In Experiment 1 transposition rate was not different among groups. In Experiment 2, OE presented the highest rate (90%) while MOE presented 86.2%, MI 68.9% and CON 62.1%. The study developed a pharmacological protocol that increased cervical transposition making the non-surgical access to the uterus feasible in Santa Inês ewes.

Effects of selective and nonselective PGE2 receptor agonists on cervical tensile strength and collagen organization and microstructure in the pregnant rat at term

OBJECTIVE

The purpose of this study was to determine which of the 4 PGE2 receptors (EP1-EP4) is involved in cervical ripening in the rat, and to correlate its activity with changes in tensile strength and collagen microstructure.

STUDY DESIGN

We assessed tensile strength after administration of selective and nonselective PGE2 receptor agonists. Quantification of collagen organization and microstructure was accomplished with polarized light microscopy and transmission electron microscopy.

RESULTS

Selective agonists for EP1-3 did not produce significant differences when compared with each other or control animals. Significant differences in tensile strength, proportion of organized collagen, and microstructure were found between treatment and control animals with the nonselective receptor agonist (PGE2). This was taken as an indirect measure of EP4 activity.

CONCLUSION

Changes in cervical collagen organization and microstructure are quantifiable and correlate with changes in tensile strength. These data implicate EP4 as the PGE2 receptor involved in producing these changes in the rat cervix.

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.

A retrospective comparison between lamicel and gemeprost for cervical ripening before surgical interruption of first-trimester pregnancy

To study the effect and complication rate of lamicel versus gemeprost as pretreatment to vacuum aspiration for the interruption of early pregnancy, the files of 622 medical records of women having a first-trimester abortion at Söder Hospital were studied retrospectively. Group A consisted of 317 women treated with lamicel in 1995 and Group B of 305 women treated with gemeprost in 1996. Complications were more common in Group A than in Group B (55 vs. 22; p < 0.05). Re-admission took place more often in Group A (25) than in Group B (6) (p < 0.05). The complications were more severe in Group A than in Group B. Using multivariate logistic regression analysis, the only impact factor for having a complication was the use of product for cervical priming. Gemeprost for preoperative treatment was found to render a fairly low rate of complications in this study, while complication rate was higher after treatment with lamicel.

Determinants of response to intracervical prostaglandin E2 for cervical ripening. Gruppo di Studio sull'Induzione del Travaglio di Parto

OBJECTIVE

To analyze the determinants of response to intracervical prostaglandin E2 (PGE2) in cervical ripening.

STUDY DESIGN

A total of 250 women with normal pregnancy, parae three or less, with intact membranes between 40 and 42 weeks of gestation and Bishop's score < or = 4 were treated with 0.5 mg PGE2 intracervical repeated after 12 hours if cervical Bishop's score was still < or = 4.

RESULTS

After the first administration of PGE2, labor was induced in 106 (42.4%) women. Nulliparae had a significant longer interval from the first PGE2 dose to delivery and more failures of treatment and caesarean sections than parae. There was a tendency towards a shorter interval between the first administration and delivery and a decrease in the frequency of treatment failures with increasing Bishop's score, but the finding was not statistically significant. No fetal or neonatal death occurred. There were eight neonates at one min and three neonates at five min with an Apgar score less than seven. There were 22 neonates admitted to Neonatal Intensive Care Unit. There were 20 cases of jaundice.

CONCLUSIONS

The study confirms that the main determinant of treatment failure with PGE2 gel in cervical ripening is nulliparity.

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.

Randomised trial of nitric oxide donor versus prostaglandin for cervical ripening before first-trimester termination of pregnancy

BACKGROUND

Vaginal administration of the nitric oxide donor isosorbide mononitrate can induce effective ripening of the human cervix. We investigated whether this drug is associated with fewer side-effects than prostaglandins when used to ripen the cervix before first-trimester surgical termination of pregnancy, and assessed whether the extent of cervical ripening it induces is clinically sufficient.

METHODS

66 primigravid women scheduled for surgical termination were assigned to receive before surgery, per vaginam, isosorbide mononitrate 40 mg or 80 mg, or the prostaglandin analogue gemeprost 1 mg. The primary measured outcome was onset of new symptoms before termination of pregnancy.

FINDINGS

More women remained symptom-free after isosorbide mononitrate than after gemeprost (28/44 [64%] vs 3/22 [14%], p<0.005). Pretreatment with gemeprost resulted in abdominal pain in 73% of women and vaginal bleeding in 32% compared with 3% and 0%, respectively, after isosorbide mononitrate, whereas, more women developed headache after isosorbide mononitrate (27%) than after gemeprost (0%). Cervical resistance and measured intraoperative blood loss were lowest after pretreatment with gemeprost. The measured cervical resistance and intraoperative blood loss with either dose of isosorbide mononitrate did not differ from those in a comparison group of 22 parous women not in the randomised trial.

INTERPRETATION

Pretreatment with isosorbide mononitrate to ripen the cervix before first-trimester termination of pregnancy is associated with fewer side-effects than gemeprost treatment and adequately decreases cervical resistance. Isosorbide mononitrate could be used as an alternative to gemeprost for this indication.

The effects of gemeprost on the second trimester fetus

OBJECTIVE

To determine whether the use of gemeprost is associated with histological changes in the second trimester fetus.

SETTING

Histopathology department of a university hospital.

DESIGN

Retrospective comparison of histological features in fetuses aborted following maternal administration of gemeprost, with those in fetuses after spontaneous miscarriage.

OUTCOME MEASURES

Degree of tissue fragmentation; other histological abnormalities.

RESULTS

Significantly greater fragmentation of the liver was found in fetuses exposed to gemeprost (P = 0.046). Nonsignificant effects were found for brain (P = 0.082) and heart (P = 0.183), and no effect was seen on the kidney, adrenal and lung. No other significant histological differences were found between the two groups.

CONCLUSIONS

This study is the first to document an effect of gemeprost on the fetus, but confirmation is required in further studies. Other implications are discussed.

Interleukin-8 induces cervical ripening in rabbits

OBJECTIVE

The purpose of this study was to determine whether cervical ripening can be induced in rabbits by interleukin-8.

STUDY DESIGN

Nonpregnant and pregnant rabbits were treated for 5 days with vaginal suppositories containing 100 ng of interleukin-8. Collagen and glycosaminoglycan concentration in the cervices were assessed histologically by picrosirius red and alcian blue, and the mean optical density was calculated. The mean neutrophil count in five random fields was calculated from each biopsy specimen.

RESULTS

Interleukin-8 induced softening and dilatation of the rabbit cervices. Water content was significantly increased (p < 0.0001 and p < 0.001, respectively). Cervical collagen concentration was found to be significantly decreased (p < 0.0004 and p < 0.0001, respectively). Glycosaminoglycan concentration was significantly increased in nonpregnant and pregnant cervices (p < 0.0009 and p < 0.1, respectively). The mean number of neutrophils was significantly increased (p < 0.0005 and p < 0.006, respectively).

CONCLUSION

Interleukin-8 can induce cervical ripening in nonpregnant and pregnant rabbits.

Cervical priming with prostaglandin E1 analogues, misoprostol and gemeprost

Although it is well established that cervical priming before surgically induced abortion reduces the incidence of complications, its use is infrequent and confined to groups perceived to be at high risk. We compared the effect of prostaglandin E1 analogues, gemeprost and misoprostol, on the cervix. Both induced clinical and histochemical changes that were significantly different from controls and were likely to have therapeutic value. Misoprostol, however, is cheap, easily stored, and associated with few side-effects. Cervical pre-dilation with misoprostol may be considered in all women having surgically induced abortions.