Maintenance Of Human Pregnancy Research Articles

Absence of the genetic variant Val79Met in human chorionic gonadotropin-beta gene 5 in five European populations.

Chorionic gonadotropin (CG) is an essential signal in establishment and maintenance of pregnancy in humans and higher primates. A G-to-A transition in exon 3 of human CGbeta gene 5, changing the naturally occurring valine residue to methionine in codon 79 (Val(79)Met) has been reported at carrier frequency 4.2% in a random population from the Midwest of the United States. The biological activity of the variant hCG was similar to that of wild-type (WT) hCG. However, the Val(79)Met beta-subunit displayed impaired ability to assemble with alpha-subunit, and the amount of hCG alpha/beta heterodimers formed and secreted by transfected cells was seriously impaired in the previous study. Because of these functional implications we found it important to study the occurrence of the Val(79)Met hCGbeta variant in other populations. By using a PCR-RFLP method, a search for the Val(79)Met hCGbeta variant was carried out on a total of 580 DNA samples from five European populations (Finland, Denmark, Greece, Germany and the UK). The results demonstrated an absence of the polymorphism in these populations. Hence, the naturally occurring variant (Val(79)Met) of the hCGbeta gene 5, found previously at high frequency in the US, is clearly less common, or absent, in the European populations studied.

Immunological aspects of implantation and implantation failure.

The human endometrium contains a significant proportion of leukocytes (8-35% of all cells), the absolute numbers and proportions varying during both the menstrual cycle and early in pregnancy. T cells, macrophages and a population of phenotypically unusual large granular lymphocytes (LGL) are commonly present, although B cells are absent. Relative T cell numbers decrease significantly in first trimester decidua, and hence are unlikely to play an important role in maintenance of human pregnancy, but T cells could be important in implantation where their relative numbers are greater. In addition to producing cytokines, local tissue macrophages may provide an immediate antigen non-specific host defence to infection. Most attention has, nevertheless, focused on a role for LGL in implantation and maintenance of pregnancy since, at the time of implantation, LGL comprise 70-80% of the total endometrial leukocyte population. Although endometrial LGL have been shown to express natural killer (NK) cell-type cytotoxicity against classical NK cell targets, such cytotoxicity against trophoblast is induced only after activation by interleukin (IL)-2. Selective expression of the unusual class I human leukocyte antigen (HLA) molecule, HLA-G, by extravillous cytotrophoblast may assist in protecting invasive cytotrophoblast from potential maternal NK cell attack, probably via interactions with killer inhibitory receptor molecules on LGL. Many cytokines have been demonstrated to be expressed at the maternal-fetal interface although, currently, in mice only two (IL-11 and leukaemia inhibitory factor) appear to be absolutely essential for successful pregnancy outcome. Immune effector cells and cytokines may also play a role in human pregnancy pathologies, such as recurrent early pregnancy loss.

Myometrial constitutive nitric oxide synthase expression is increased during human pregnancy.

Nitric oxide (NO), derived from L-arginine by the action of nitric oxide synthase (NOS), is a mediator of many diverse biological activities, including vasodilation, neurotransmission and inhibition of platelet adhesion. A role for NO in the maintenance of rat and rabbit pregnancy is supported by a variety of studies. A recent study in women demonstrated that myometrial inducible NOS (iNOS) expression was greater in the early third trimester than either the late third trimester or in the non-pregnant condition, suggesting that increased iNOS expression is involved in the maintenance of human pregnancy. Constitutive NOS (cNOS) expression was not determined. The aim of this study was to compare constitutive NOS (both eNOS and bNOS) expression in the human non-pregnant uterus, preterm pregnant uterus (25-34 weeks gestation) and term pregnant uterus (>37 weeks gestation) using immunohistochemistry and Western blotting. Preterm pregnant samples were taken from women with a variety of pathologies necessitating early delivery. We found that eNOS and bNOS protein concentrations were greater in the preterm pregnant myometrium than non-pregnant myometrium. eNOS, but not bNOS, protein concentration was lower in myometrial samples obtained at term compared with those obtained preterm. We conclude that the constitutive isoforms of NOS are also up-regulated in human pregnancy and may play a role in the maintenance of myometrial quiescence.

The role of nitric oxide in the maintenance of human pregnancy

The role of nitric oxide in the maintenance of human pregnancy

Cytotoxic activity of endometrial granulated lymphocytes during the menstrual cycle in humans.

CD56+ CD16- granulated lymphocytes, termed endometrial granulated lymphocytes (eGLs), have been suggested to play a role in the maintenance of human pregnancy, although their in vivo function in both pregnant and nonpregnant endometrium remains unknown. The present study compared the cytotoxic activity of CD56+ CD16- eGLs (> 98% purity) positively selected from early and late proliferative-phase, early and late secretory-phase, and menstrual-phase endometrium with that of CD56+ CD16- eGLs purified from first-trimester decidua and CD56+ predominantly CD16+ cells from peripheral blood. From the late proliferative phase onwards, the major histocompatibility complex (MHC)-nonrestricted cytotoxic activity of eGLs was comparable between phases of the menstrual cycle. In contrast, eGLs from early proliferative-phase endometrium displayed significantly lower cytotoxic activity. With the exception of eGLs purified from early proliferative-phase endometrium, the cytotoxic activity of CD56+ CD16- eGLs purified from nonpregnant endometrium was comparable to that of CD56+ CD16- eGLs in decidua and CD56+ predominantly CD16+ cells from peripheral blood. No endogenous lymphokine-activated killer cell activity was detected in eGLs from endometrium or decidua. The present study using highly purified eGLs demonstrates that, with the exception of early proliferative-phase samples, CD56+ CD16- eGLs from nonpregnant endometrium and early pregnancy decidua have cytotoxic activity comparable to that of "classical" natural killer cells from peripheral blood.

Quantitative analysis of T lymphocyte subsets in pregnant and nonpregnant human endometrium.

The purpose of this study was to characterize and quantify T lymphocyte populations and to investigate T cell antigen receptor (TcR) expression in human endometrium throughout the menstrual cycle and in early pregnancy. Frozen sections of endometrium were labeled using the highly sensitive avidinbiotin method and a panel of monoclonal antibodies. CD3-positive, CD8-positive, CD4-positive, TcR alpha beta-positive, and TcR gamma delta-positive cells were demonstrated in all phases of the menstrual cycle and in early pregnancy. There were no differences between pregnant and nonpregnant human endometrium in the proportion that each T cell subpopulation formed relative to the total CD3-positive T cell population. However, significantly fewer T cells were detected in early pregnant compared with nonpregnant endometrium. Our results clarify the TcR expression by T cells in pregnant and nonpregnant human endometrium and indicate that endometrial T cells are unlikely to play a significant role in implantation and the maintenance of human pregnancy since they decrease in number considerably in the first trimester of gestation.

Transforming growth factor-beta stimulates, and glucocorticoids and epidermal growth factor inhibit brain natriuretic peptide secretion from cultured human amnion cells.

We previously reported the massive secretion of brain natriuretic peptide (BNP) from human amnion cells and suggested the possible role of BNP in the maintenance of human pregnancy. In this study, to elucidate the regulatory mechanism of BNP secretion from amnion cells, we measured the BNP level in the culture medium of amnion cells by RIA after incubation in the presence of various substances. Among the agents examined, cortisol (1 x 10(-7) to 1 x 10(-6) mol/L), dexamethasone (1 x 10(-8) to 1 x 10(-6) mol/L), and epidermal growth factor (EGF; 2 x 10(-11) to 2 x 10(-8) mol/L) inhibited BNP secretion from the cultured amnion cells in a dose-dependent manner. By contrast, transforming growth factor-beta (TGF beta; 4 x 10(-11) to 4 x 10(-9) mol/L) caused a 3- to 5-fold increase in BNP secretion. TGF beta-augmented BNP secretion was abolished by the addition of cortisol or EGF to the culture medium. Moreover, in this study, we revealed the presence of bioactive TGF beta in human amniotic fluid (approximately 4 x 10(-10) mol/L). The present finding of tight regulation of BNP secretion from amnion cells by cortisol, EGF and TGF beta, all at the concentrations physiologically present in human amniotic fluid, implies a physiological role of BNP secretion from amnion cells in the pregnant uterus.

Is the luteo-placental shift a myth? Analysis of low progesterone levels in successful art pregnancies.

Progesterone (P4) is considered vital to the maintenance of human pregnancy, but the minimal concentration of P4 necessary to sustain human pregnancy remains unclear. The aim of this study was to examine endocrine profiles for serum P4, 17 beta-estradiol (E2), and human (h) beta-CG in early pregnancy from a group of assisted reproductive technologies (ART) patients. These subjects delivered normally but had P4 concentrations below the fifth percentile of the normal singleton pregnancy range from 2 weeks after ART. Normal ranges of these hormones were determined from 118 consecutive ART pregnancies which resulted in singleton births. Values below the fifth percentile (P4 < 35.9 nmol/L at 4 weeks gestation) were considered abnormal. Eight patients who subsequently delivered normally, with serum P4 values below this criterion at 4 weeks gestation, were found. They had serum P4 values at 4 weeks gestation ranging from 1.9-29.9 nmol/L, and their mean P4 values at 5 weeks (30.2 +/- 9.2 nmol/L; mean +/- SE) and 6 weeks gestation (48.0 +/- 10.2 nmol/L) remained below the fifth percentile. No statistically significant increase in serum P4 concentrations occurred between 7 and 11 weeks gestation in these women. Their mean E2 value in serum at 4 weeks gestation (382 +/- 73 pmol/L) was also below the fifth percentile but their mean beta-hCG concentration was within the normal range. We conclude that successful human pregnancy is possible with serum P4 values within the anovulatory range in early gestation and that, in individual patients, serum P4 concentration of 2 nmol/L can be sufficient to maintain human pregnancy.

PRODUCTION RATE OF PROGESTERONE IN THE LAST MONTH OF HUMAN PREGNANCY

The significance of progesterone in the maintenance of human pregnancy has been under discussion for several decades. Until recently most research in progesterone problems in the human was performed by means of urinary pregnanediol determinations in normal and abnormal pregnancies and by therapeutic trials of gestagens in threatened abortion and premature labour. It is now evident that these complicated problems must be attacked on a much broader basis, including the chemistry, production, circulation, storage, metabolism, excretion and physiology of progesterone. One of the first links in this chain of problems is the rate of progesterone production in different stages of pregnancy. This is of both theoretical and clinical significance. From a theoretical point of view, it should be known whether the reactivity of the myometrium during human pregnancy is related to the amount of progesterone produced, as it seems to be in the rabbit (Mikhail et al., I 961). From a clinical point of view, only reliable data on the rate of progesterone production in normal pregnancy can guide our attempts to compensate for a suspected progesterone insufficiency.

PRODUCTION RATE OF PROGESTERONE IN THE LAST MONTH OF HUMAN PREGNANCY.

The significance of progesterone in the maintenance of human pregnancy has been under discussion for several decades. Until recently most research in progesterone problems in the human was performed by means of urinary pregnanediol determinations in normal and abnormal pregnancies and by therapeutic trials of gestagens in threatened abortion and premature labour. It is now evident that these complicated problems must be attacked on a much broader basis, including the chemistry, production, circulation, storage, metabolism, excretion and physiology of progesterone. One of the first links in this chain of problems is the rate of progesterone production in different stages of pregnancy. This is of both theoretical and clinical significance. From a theoretical point of view, it should be known whether the reactivity of the myometrium during human pregnancy is related to the amount of progesterone produced, as it seems to be in the rabbit (Mikhail et al., I 961). From a clinical point of view, only reliable data on the rate of progesterone production in normal pregnancy can guide our attempts to compensate for a suspected progesterone insufficiency.