Matrix metalloproteinases in the cervical mucus plug in relation to gestational age,plug compartment,and preterm labor

Background  

High concentrations of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) have been identified in the cervical mucus plug (CMP) at term of pregnancy. Their physiological and pathophysiological implications, however, remain to be elucidated, and CMPs from preterm labor have never been examined. This study was therefore conducted to describe the concentrations of MMP-2, TIMP-1, MMP-8 and MMP-9 in the CMP in relation to gestational age, IL-8 as an indicator of inflammation, compartment of the CMP, and preterm labor.     

Cyclic changes of sialidase in human cervical mucus

• 1.1. Sialidase activity is detectable in whole cervical mucus of normal women throughout the menstrual cycle and presents cyclic variations towards endogenous and exogenous substrates.
• 2.2. The level of sialic acid bound to the mucus increases progressively till mid-cycle and declines in the post-ovulatory phase.
• 3.3. The sialidase of the mucus probably derives from different sources and its role remains speculative.

     

Composition and function of human cervical mucus

Human cervical mucus was collected from seven donors during the follicular, ovulatory and luteal phases of the ovulatory menstrual cycle. Individual mucus samples were solubilized and fractionated on Sepharose columns into excluded mucins and low-molecular-weight proteins. Mucin fractions were highly purified, as evidenced by the presence of a single N-terminal amino acid residue, threonine, and by the absence of contaminating plasma proteins. Amino acid compositions of mucins isolated during different menstrual phases of a single donor or from different donors were similar. Mucin carbohydrate compositions were also similar, except for the sialic acid-to-fucose ratio, which varied significantly between donors but not within the menstrual cycle of a single donor. An analysis of variance was applied to evaluate the contribution of mucin composition to viscoelasticity, as quantitated by microrheometry. Viscoelasticity was dependent on the donor, on the percent nondialyzable solids and on the mucin content, but not on the phase of the menstrual cycle during which the sample was collected. These findings suggest that mucus function (viscoelasticity) is reflected in carbohydrate composition and/or structure and that this menstrual relationship is unique for each donor. Furthermore, the absence of menstrual phase-dependent differences in mucins suggests that mucin concentration and not composition changes in response to alterations in the hormonal milieu.     

Bioconversion of arachidonic acid by human uterine cervical tissue and endocervix in late pregnancy

Prostaglandins (PGs) may play an important role on cervical ripening in late pregnancy, namely cervical dilatation and softening. To investigate this, arachidonic acid metabolites of cervical tissue and endocervix were studied. To separate and identify the metabolites, silicic acid chromatography, thin layer chromatography, reversed phase chromatography, gas-liquid chromatography and GC-MS were used. In cervical tissue, arachidonic acid was converted to 6-ketoPGF1 alpha, PGF2 alpha, PGE2, thromboxane B2, and 12-HETE. In endocervix, arachidonic acid was converted to PGF2 alpha, PGE2, thromboxane B2, 12-hydroxy-5, 8, 10-heptadecatrienoic acid, and 12-HETE. There was no relation between the arachidonic acid conversion rate and the Bishop score (points of cervical ripening).     

Scanning electron microscope study of human cervical mucus

The ultrastructure of human cervical mucus was studied by scanning electron microscopy. In fertile women, naturally occurring midcycle cervical mucus showed an arrangement of parallel fibers oriented along the main axis of the mucus sample. Sperm migration through a column of cervical mucus in vitro was also studied. It was found that sperm present among the longitudinal fibers were oriented parallel to the them and to the main axis of the mucus sample.     

Diffusion of macromolecules and virus-like particles in human cervical mucus

To determine whether or not large macromolecules and viruses can diffuse through mucus, we observed the motion of proteins, microspheres, and viruses in fresh samples of human cervical mucus using fluorescent recovery after photobleaching and multiple image photography. Two capsid virus-like particles, human papilloma virus (55 nm, approximately 20,000 kDa) and Norwalk virus (38 nm, approximately 10,000 kDa), as well as most of the globular proteins tested (15-650 kDa) diffused as rapidly in mucus as in saline. Electron microscopy of cervical mucus confirmed that the mesh spacing between mucin fibers is large enough (20-200 nm) for small viruses to diffuse essentially unhindered through mucus. In contrast, herpes simplex virus (180 nm) colocalized with strands of thick mucus, suggesting that herpes simplex virus, unlike the capsid virus particles, makes low-affinity bonds with mucins. Polystyrene microspheres (59-1000 nm) bound more tightly to mucins, bundling them into thick cables. Although immunoglobulins are too small to be slowed by the mesh spacing between mucins, diffusion by IgM was slowed by mucus. Diffusion by IgM-Fc(5 mu), the Fc pentamer core of an IgM with all 10 Fab moieties removed, was comparably slowed by mucus. This suggests that the Fc moieties of antibodies make low-affinity bonds with mucins.     

Effect of dehydroepiandrosterone sulfate on uterine cervical ripening in late pregnancy

In order to elucidate the effects of dehydroepiandrosterone sulfate (DHAS) on softening and dilatation of the uterine cervix, changes of oestriol, 17 beta-oestradiol and progesterone levels in serum and cervix, Bishop score and collagenase activity in the cervical tissue were assessed in pregnant women before and after treatment with DHAS. 17 beta-oestradiol level in the serum and cervical tissue markedly increased after the administration of DHAS, while oestriol level remained unchanged. Serum progesterone level did not change in the majority of cases, while it decreased within several hours in patients in whom delivery was accomplished within 24 hours after the administration of DHAS. Among the factors connected with the Bishop score, effacement and consistency of the cervix were remarkably improved by DHAS administration. Total collagenase activity in the cervical tissue of patients treated with DHAS was elevated by an average of 152%. These results suggest that DHAS is potent in ripening the uterine cervix through an activation of collagenase activity induced by the enhanced conversion to 17 beta-oestradiol. Thus, DHAS administration in the late stage of pregnancy is valuable in prepartal treatment for induction of labour.     

Cyclic AMP in cervical mucus

Cyclic adenosine monophosphate normally stimulates motility of spermatozoa. Its concentration in cervical mucus was studied by an isotopic competitive method in 15 normal women aged between 20 and 50 years. Values were very high, particularly in the periovulatory period, with a mean (+/-SD) value of 167.90 +/- 154.96 nmol/l. These are very high when compared with values in other biological fluids (blood serum and urine).     

DNA content in human uterine cervical dysplasias.

The DNA content of nuclei extracted from separate biopsies of normal cervical epithelium and from dysplastic sites in the same patient was determined biochemically. Mean percentage increase in the DNA content of dysplasias (mild: 143.3 +/- 14.9; moderate: 225.8 +/- 51.1; and severe: 359.8 +/- 45.8) was found to be statistically significant (F-Test: p less than 0.001) over the normal values in control cervical tissues.     

Relationship between human sperm motility characteristics and sperm penetration into human cervical mucus in vitro

A series of 100 modified Kremer tests of human sperm penetration into human cervical mucus was carried out as part of the routine investigation of couples presenting with infertility. The outcome of these tests was significantly correlated with the concentration and progressive motility of the spermatozoa in the semen sample used for the test. Other semen characteristics significantly correlated with the test result were the mean velocity of progression (VP) and the amplitude of lateral head displacement about the axis of progression (AH) of the progressive spermatozoa. Normal sperm morphology was also correlated with the outcome. Using these semen characteristics as the independent variables to predict the test outcome in a discriminant analysis (normal vs abnormal tests), 34.2% of the variance was accounted for. From the discriminant function equation 75.0% of the test results could be predicted correctly. In the 30 cases in which the semen samples used for the tests showed greater than or equal to 25 X 10(6) progressively motile spermatozoa per ml, mean VP of greater than or equal to 25 microns/sec and mean AH of greater than or equal to 7.5 microns, 83.3% had normal test results. Conversely, all 13 cases for which the semen characteristics were below these limits had abnormal test results. Therefore, both the concentration of progressively motile spermatozoa and their movement characteristics are significant factors determining the outcome of homologous tests of human sperm-cervical mucus interaction.     

A study of peroxidase levels in human cervical mucus as an index of ovulation

Fourteen healthy women were screened for the following parameters throughout one complete menstrual cycle: levels of urinary oestrogens and pregnanediol; levels of plasma and urinary gonadotrophins; and pH, protein content and levels of peroxidase in the cervical mucus. It was found that concentrations of peroxidase in the cervical mucus were not a reliable index of ovulation.     

Microarray analysis of uterine gene expression in mouse and human pregnancy

Improved care of infants born prematurely has increased their survival. However, the incidence of preterm labor has not changed. To understand the processes involved in preterm labor, we used oligonucleotide microarrays to study gene expression in murine and human uterus during pregnancy. The induction of enzymes for prostaglandin synthesis was used as a marker for important changes during pregnancy because prostaglandins strongly contribute to both human and murine labor. We identified 504 genes that changed at least 2-fold between d 13.5 and 19.0 in the gravid mouse uterus. In the pregnant human myometrium, we found 478 genes that changed at least 2-fold in either term or preterm labor compared with preterm nonlabor specimens and 77 genes that significantly varied in both preterm and term labor. Patterns of gene regulation within functional groups comparing human preterm and term labor were similar, although the magnitude of change often varied. Surprisingly, few genes that changed significantly throughout pregnancy were the same in the mouse and human. These data suggest that functional progesterone withdrawal in human myometrium may not be the primary mechanism for labor induction, may implicate similar mechanisms for idiopathic preterm and term labor in humans, and may identify novel targets for further study.