Inflammation of the amnion and chorion

Inflammation of the amnion and chorion was found forty-eight times in one thousand consecutive placentas. Taken as an evidence of infection, its presence indicates that in nearly all cases of intrapartum fever (not due to intercurrent conditions) there has been entrance of bacteria into the uterus. On the other hand, the absence of temperature elevation does not mean that bacterial invasion has not occurred. Intrapartum infection is an indication for acceleration of delivery in the interests of both mother and child; but its presence, as indicated by inflammation of the amnion and chorion, may often be unsuspected in the absence of fever. The increased incidence of inflammation with prolonged labor, vaginal examinations, and especially premature rupture of the membranes confirms previous impressions as to the increased danger of cesarean section under such circumstances, regardless of the presence or not of fever.     

Study of lipids in human amnion and chorion

Most previous fetal membrane studies have focused primarily on their phospholipids as the precursors of arachidonic acid and the obligate precursors of prostaglandins E2 and F2 alpha, with little attention being afforded nonpolar lipids as another possible source. In this presentation, a special emphasis is placed on nonpolar lipids and their acyl group makeup. A substantial amount of acyl group (20:4) lipids was found. The implication of this finding could be that a nonpolar lipid source is necessary for the production of prostaglandins E2 and F2 alpha.     

Antibacterial properties of human amnion and chorion in vitro

OBJECTIVE: The purpose of the present study was to explore the direct effects of amnion and chorion on bacterial growth in vitro including the antibacterial spectrum. Chorioamniotic membranes were obtained under sterile conditions from 13 healthy women undergoing elective cesarean section at term. Likewise, chorioamniotic membranes were obtained from 10 healthy women with spontaneous vaginal delivery at term. Five strains of Hemolytic streptococci group B (GBS) were tested and one clinical isolate of the following species or bacterial groups: Hemolytic streptococcus group A, Staphylococcus aureus, Staphylococcus saprophyticus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter calcoaceticus and Lactobacillus species. Bacteriological media included (1) blood-agar medium; (2) a transparent agar medium for submerged cultures; and (3) a nutrient broth medium. RESULTS: An inhibitory effect of fetal membranes against a range of bacteria was found. Consistent results were obtained in experiments with cultures on agar and cultures suspended in agar (membranes from eight women in both studies). In experiments with liquid cultures (seven women) only chorion showed a marginal inhibitory effect. All strains were inhibited, but the most pronounced inhibition was obtained for streptococcus group A, S. aureus and S. saprophyticus by both chorion and amnion. CONCLUSION: This study demonstrated an inhibitory effect of the fetal membranes on a diverse panel of bacteria     

Ripening of the human uterine cervix related to changes in collagen, glycosaminoglycans, and collagenolytic activity

Connective tissue in biopsy specimens taken from the lower part of the uterine cervix in 40 pregnant women at various gestational ages was compared to that in similar biopsy specimens from 15 nonpregnant women. The concentrations of collagen, sulfated glycosaminoglycans, and hyaluronic acid decreased during pregnancy. At the gestational age of 10 weeks, the collagen concentration was 70%, and at term 30%, of that in the nonpregnant cervix. After delivery, no further decrease was observed. The extractability of collagen increased during pregnancy, as well as during labor. Also, the water concentration increased. An increase in the collagenolytic activity was observed with advancing gestational age. The 2,4-dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gin-D-Arg hydrolytic activity (collagenase) and the concentration of leukocyte elastase increased gradually by a factor of 10. The physiologic importance of the collagen was also demonstrated, since the cervical dilatation time during spontaneous labor was long in women with high concentrations of collagen and short in women with low concentrations of collagen.     

Comparative study of the human amnion, chorion and chorioamnion permeability to monovalent cations

Amnion, chorion and chorioamnion from human term placenta were mounted between two Ussing chambers. The monovalent cation transfer was estimated by potentials (dilution, bi-ionic) and conductance measurements. This study revealed that amnion and chorioamnion discriminate the monovalent cations (the sequence is: Rb = Cs = K greater than Na greater than Li), while the chorion does not discriminate these cations. This discrimination relies on the size of the sites on the cell membrane and in intercellular spaces. The monovalent cation conductance for the three layers is gA greater than gC = gCA, and reveals that the chorioamnion properties derive in part from the properties of the isolated amnion (cationic discrimination) and those of the isolated amnion + chorion (size of sites and hydration pathways). The transfer is dependent on the three membranes' orientation and corresponds to fetal needs; the conductance ratio (g mother-fetus/g fetus-mother) is always superior to 1 when the two sides are bathed by the same medium.     

Progesterone synthesis by human amnion, chorion, and decidua at term

We investigated the ability of human fetal membranes to produce progesterone from a variety of substrates. Chorion is more active than decidua, and amnion produces little progesterone. Cholesterol or low-density lipoprotein cholesterol was not used as a substrate. Chorion used pregnenolone, pregnenolone sulfate, and 20 alpha-dihydroprogesterone for progesterone synthesis. Decidua also used these three substrates but produced significantly less progesterone than chorion. Amnion used only 20 alpha-dihydroprogesterone as a substrate. Exogenous human chorionic gonadotropin or gonadotropin-releasing hormone or its analogues did not influence progesterone production by any of the tissues. There were several significant changes in substrate usage for progesterone synthesis by the tissues around the time of the onset of labor. Tissue concentrations of progesterone are approximately 4 ng/mg protein, and it appears that local production rates could completely account for this. These data are compatible with the hypothesis that local regulatory mechanisms may determine progesterone concentrations in fetal membrane tissues and that important changes may occur around the time of the onset of parturition.     

A study of angiotensin II binding sites in human placenta, chorion, and amnion

The binding of tritiated angiotensin II to 20,000 x g particulate tractions of human placenta, chorion, and amnion was investigated. Binding to particles from the three tissues reached equilibrium within 10 minutes at 29 degrees C and was displaced by the addition of 1,000-fold excess of unlabeled angiotensin II. Scatchard analysis of the data showed that two classes of binding sites were present in the placental preparation. For the high-affinity site, values of 9 x 10(-9) M and 300 fmoles/mg of protein were obtained for the dissociation constant and the binding capacity, respectively. There was little specific binding in chorion and amnion.     

Vascularization of the ovine amnion and chorion: a morphometric characterization of the surface area of the intramembranous pathway.

OBJECTIVE: The purpose of this study was to characterize the vascularization of the ovine amnion, allantois, and chorion. STUDY DESIGN: A white silicone vascular casting material was infused into both umbilical arteries of nine fetal sheep ranging in age from 58 to 142 days' gestation. A morphometric analysis of photomicrographs of the membranes was then performed with computerized image analysis techniques. RESULTS: After removal of the uterus, the fetus was surrounded by a layer of white silicone-filled microvessels in the chorion. The amniotic membrane after separation from the chorion was covered by a fine mesh of microvessels, whereas the allantois was avascular. The amniotic membrane readily separated into an outer vascularized layer and an inner, avascular layer containing the amnion. Approximately 50% of the surface of the chorionic membrane was covered by microvessels; this appeared independent of gestational age. At midgestation 30% of the surface of the amnion was covered by microvessels, and this decreased to 17% at 142 days. Relative to fetal weight, the amniotic and chorionic vascular surface areas decreased from 6 to 0.3 and from 15 to 1.5 cm2/gm fetal weight, respectively, over the last half of gestation. CONCLUSIONS: There is an extensive network of microscopic fetal blood vessels within the ovine chorion and covering the outer surface of the amnion. These vessels appear to be ideally situated to facilitate a direct exchange of water and solutes between amniotic or allantoic fluids and fetal blood through the intramembranous pathway.     

Myofibroblast differentiation in the connective tissues of the amnion and chorion of term human fetal membranes-implications for fetal membrane rupture and labour

An area of the fetal membranes, within the rupture tear after spontaneous delivery at term, exhibits altered morphology compared to more distal sites. It is characterized by marked swelling of the amniotic and chorionic connective tissue layers, consistent with structural weakness, and a marked reduction of the thickness of both the cytotrophoblast and decidual layers. These features, albeit less extreme, have been identified in fetal membranes in the lower uterine pole in patients prior to labour. In this study of pre-labour, labour-affected and post-labour term fetal membranes, we report that these regions are associated with an alteration in the phenotype of the vimentin positive mesenchymal cell population of the chorionic connective tissue reticular layer, and are consistent with myofibroblastic differentiation, i.e. alpha-smooth muscle actin (alpha-sma) expression. In the reticular layer of the lower uterine pole biopsies in the labour-affected group the numbers and densities of alpha-sma immunoreactive positive cells were 17-fold (P=0.04) and 8.5-fold (P=0.02) higher than in mid-zone biopsies. After delivery, in rupture line biopsies the numbers and densities were 50-fold (P=0. 002) and 36-fold (P=0.003) higher compared to mid zone biopsies. The percentage of the vimentin positive population positive for alpha-sma was 2-5 per cent in mid-zone biopsies compared to 49 per cent (P=0.03) in the labour-affected 'cervical' biopsies and 69 per cent (P=0.05) in the rupture line biopsies. Within the tear sites, alpha-sma positive cells were also detected within the fibroblastic layer of the amniotic connective tissue. Although there was no significant difference between the numbers and density of alpha-sma cells in the reticular layers between mid and lower uterine pole biopsies in the pre-labour group, in a proportion of patients the biopsies were similar to labour-affected biopsies indicating that this alteration occurs prior to clinically apparent labour in these patients. The incidence of alpha-sma positive cells in the reticular layer correlated with morphological changes within the fetal membranes, for example thickness of reticular (r(2)=0.349, P=0.0006) and amniotic connective tissue layers (r(2)=0.389, P=0.0002). This suggests that cellular activities associated with myofibroblastic differentiation in the reticular layer of the chorion may be associated with the observed connective tissue changes, fetal membrane rupture and labour.     

Release and lubricating properties of amniotic surfactants and the very hydrophobic surfaces of the amnion, chorion, and their interface

Surface hydrophobicity of 17 fresh human chorioamniotic membranes was measured as the contact angle (theta) subtended when a drop of saline is placed upon any non-wettable surface. The contact angle averaged 75.5 +/- 4.2 degrees and 76.8 +/- 5.6 degrees on the epithelial surfaces of the amnion and chorion, respectively. The interface proved to be particularly hydrophobic, averaging 108.2 +/- 8.7 degrees on the amnionic side and 121.7 +/- 4.2 degrees on the chorionic side, especially when compared with 108 degrees for Teflon. High surface hydrophobicity implies good boundary (solid-to-solid) lubrication, good release from neighboring tissues, and water repellency, which is a possible factor enabling the chorioamniotic membrane to retain amniotic fluid. Good release (68 to 71%) and boundary lubrication (coefficient of kinetic friction = 0.24 +/- 0.072) were obtained from oriented monolayers of the phospholipid extracted from samples of human amniotic fluid obtained from term patients by amniocentesis. These results support the concept that the amnionic and chorionic membrane surfaces exhibit good release and boundary lubrication probably imparted by adsorbed surfactant.     

Messenger RNA encoding thiol protein disulphide isomerase in amnion, chorion and placenta in human term and preterm labour

Objective To investigate levels of messenger RNA (mRNA) encoding thiol protein disulphide isomerase, in human amnion, chorion and placenta during pregnancy and in relation to term and preterm labour.
Design Amnion, chorion and placenta from 33 women delivered between 24 and 41 weeks of gestation were used in the study.
Setting Reproductive Molecular Research Group, Department of Obstetrics and Gynaecology, University of Cambridge Clinical School, Rosie Maternity Hospital, Cambridge.
Results Women who were delivered spontaneously before 30 weeks of gestation had higher levels of mRNA encoding thiol protein disulphide isomerase in placenta and chorion than those who were delivered spontaneously after this time (placenta   P < 0.01, chorion P < 0.01  ) and compared with those who were delivered by elective caesarean section before 30 weeks of gestation (placenta   P < 0.001, chorion P < 0.05  ). In the group in whom spontaneous labour occurred, at all gestations studied, there were increased levels of mRNA encoding thiol protein disulphide isomerase in the placenta (   P < 0.001  ) and chorion (   P < 0.001  ) compared with the amnion.
Conclusion Changes in the steady state level of mRNA encoding thiol protein disulphide isomerase may play a role in the onset of preterm labour before 30 weeks of gestation.     

Type IV collagenolytic activity in human preovulatory follicular fluid

During normal ovulation, the two basement membrane layers of the ovarian follicle are degraded locally. The main component of basement membranes is type IV collagen, which is specifically cleaved by type IV collagenase. According to our results, type IV collagenolytic activity is present within follicular fluid and increases toward ovulation, decreasing rapidly as the follicles rupture. These results suggest that importance of type IV collagenolytic activity in the ovulatory process.     

Source of prostaglandin precursor in human fetal membranes: arachidonic acid content of amnion and chorion laeve in diamnionic-dichorionic twin placentas

The lipids of the avascular human amnion and chorion laeve are known to be enriched in the essential fatty acid arachidonic acid, the obligate precursor of prostaglandins of the 2-series. The present investigation was conducted to evaluate the source of arachidonic acid that is present in human fetal membranes. To do so we determined the arachidonic acid content of the lipid fractions of amnion and chorion laeve tissues from diamnionic-dichorionic twin placentas. We found that the arachidonic acid content of amnion from twin placentas was similar to that of amnion from singleton placentas irrespective of the site of amnion sampling. However, the same was not true of chorion laeve of diamnionic-dichorionic twin placentas. The arachidonic acid content of chorion laeve that was contiguous to the chorion laeve of its twin was strikingly reduced compared to that of chorion laeve contiguous to decidua vera obtained from either singleton or twin placentas. We conclude that the arachidonic acid in amnion is derived primarily from essential fatty acids in the amniotic fluid. However, the arachidonic acid in chorion laeve may be derived from essential fatty acid in the amniotic fluid as well as in maternal plasma by way of the decidua vera.     

Immunocytochemical localization and messenger ribonucleic acid concentrations for human placental lactogen in amnion, chorion, decidua, and placenta

Human placental lactogen is one of the major hormones secreted by the placental syncytiotrophoblast and detected in the maternal circulation. Other sources of this hormone in intrauterine tissues at term have been sought by means of immunohistochemistry and northern analysis. Avidin-biotin immunoperoxidase staining with a specific polyclonal antibody to human placental lactogen showed this hormone to be present in groups of cells at the interface between chorionic cytotrophoblast and decidua parietalis and in some cells of the basal plate in addition to the classic source, the syncytiotrophoblast. Hybridization of polyadenylic-(+)ribonucleic acid extracted from amnion, chorion, decidua parietalis, basal plate, and placental trophoblast with a radiolabeled 48 mer oligonucleotide and a 540 base pair complementary deoxyribonucleic acid probe to human placental lactogen showed the placental trophoblast to be the major source of human placental lactogen and the extravillous chorion and basal plate to be additional minor sources.