Effects of ovarian hormones on cell membranes in the rat uterus. III. The surface carbohydrates at the apex of the luminal epithelium

Direct Cell⁻Cell Interactions in the Endometrium and in Endometrial Pathophysiology

Cell contacts exhibit a considerable influence on tissue physiology and homeostasis by controlling paracellular and intercellular transport processes, as well as by affecting signaling pathways. Since they maintain cell polarity, they play an important role in cell plasticity. The knowledge about the junctional protein families and their interactions has increased considerably during recent years. In contrast to most other tissues, the endometrium undergoes extensive physiological changes and reveals an extraordinary plasticity due to its crucial role in the establishment and maintenance of pregnancy. These complex changes are accompanied by changes in direct cell–cell contacts to meet the various requirements in the respective developmental stage. Impairment of this sophisticated differentiation process may lead to failure of implantation and embryo development and may be involved in the pathogenesis of endometrial diseases. In this article, we focus on the knowledge about the distribution and regulation of the different junctional proteins in the endometrium during cycling and pregnancy, as well as in pathologic conditions such as endometriosis and cancer. Decoding these sophisticated interactions should improve our understanding of endometrial physiology as well as of the mechanisms involved in pathological conditions.

Prominin-1 glycosylation changes throughout early pregnancy in uterine epithelial cells under the influence of maternal ovarian hormones

In preparation for uterine receptivity, the uterine epithelial cells (UECs) exhibit a loss of microvilli and glycocalyx and a restructuring of the actin cytoskeleton. The prominin-1 protein contains large, heavily glycosylated extracellular loops and is usually restricted to apical plasma membrane (APM) protrusions. The present study examined rat UECs during early pregnancy using immunofluorescence, western blotting and deglycosylation analyses. Ovariectomised rats were injected with oestrogen and progesterone to examine how these hormones affect prominin-1. At the time of fertilisation, prominin-1 was located diffusely in the apical domain of UECs and 147- and 120-kDa glycoforms of prominin-1 were identified, along with the 97-kDa core protein. At the time of implantation, prominin-1 concentrates towards the APM and densitometry revealed that the 120-kDa glycoform decreased (P<0.05), but there was an increase in the 97-kDa core protein (P<0.05). Progesterone treatment of ovariectomised rats resulted in prominin-1 becoming concentrated towards the APM. The 120-kDa glycoform was increased after oestrogen treatment (P<0.0001), whereas the 97-kDa core protein was increased after progesterone treatment (P<0.05). Endoglycosidase H analysis demonstrated that the 120-kDa glycoform is in the endoplasmic reticulum, undergoing protein synthesis. These results indicate that oestrogen stimulates prominin-1 production, whereas progesterone stimulates the deglycosylation and concentration of prominin-1 to the apical region of the UECs. This likely presents the deglycosylated extracellular loops of prominin-1 to the extracellular space, where they may interact with the implanting blastocyst.

Ovarian Hyperstimulation Reduces Vascular Endothelial Growth Factor-A During Uterine Receptivity

The angiogenic factor vascular endothelial growth factor-A (VEGFA) plays a critical role during early pregnancy in many species including the rat, and any alterations in VEGFA levels can severely impact blastocyst implantation rates. The rat ovarian hyperstimulation (OH) model is useful in studying how the induction of superovulation affects VEGFA levels and endometrial receptivity to blastocyst implantation. The present study shows that the major isoform in the rat uterus, Vegf₁₈₈, is reduced at the time of receptivity in OH compared to normal pregnancy, whereas there is no change in Vegf₁₆₄ and Vegf₁₂₀ messenger RNA (mRNA). The VEGFA receptor 2 (VEGFR2) protein levels are also reduced at the time of receptivity in OH. Our ovariectomy studies show that Vegf₁₆₄, Vegf₁₈₈, and Vegf₁₂₀ are significantly decreased by estrogen, and, to a lesser extent progesterone, when compared to control animals. Although no change in the percentage of endometrial blood vessels was seen across all stages of pregnancy, at the time of receptivity in OH pregnancies, blood vessels were typically larger compared to other stages. The altered progesterone-estrogen ratio seen in OH, taken together with our ovariectomy studies, explains the changes to Vegfa mRNA in OH at the time of receptivity. Since VEGFA is important during implantation, the changes to Vegfa and VEGFR2 levels in the endometrium may help explain the observed lower endometrial receptivity following OH. This study aimed to analyse how ovarian hyperstimulation alters the levels of vascular endothleial growth factor and its major receptor, VEGFR2 in the uterus in a rat model.

Actin crosslinking protein filamin A during early pregnancy in the rat uterus

During early pregnancy the endometrium undergoes a major transformation in order for it to become receptive to blastocyst implantation. The actin cytoskeleton and plasma membrane of luminal uterine epithelial cells (UECs) and the underlying stromal cells undergo dramatic remodelling to facilitate these changes. Filamin A (FLNA), a protein that crosslinks actin filaments and also mediates the anchorage of membrane proteins to the actin cytoskeleton, was investigated in the rat uterus at fertilisation (Day 1) and implantation (Day 6) to determine the role of FLNA in actin cytoskeletal remodelling of UECs and decidua during early pregnancy. Localisation of FLNA in UECs at the time of fertilisation was cytoplasmic, whilst at implantation it was distributed apically; its localisation is under the influence of progesterone. FLNA was also concentrated to the first two to three stromal cell layers at the time of fertilisation and shifted to the primary decidualisation zone at the time of implantation. This shift in localisation was found to be dependent on the decidualisation reaction. Protein abundance of the FLNA 280-kDa monomer and calpain-cleaved fragment (240 kDa) did not change during early pregnancy in UECs. Since major actin cytoskeletal remodelling occurs during early pregnancy in UECs and in decidual cells, the changing localisation of FLNA suggests that it may be an important regulator of cytoskeletal remodelling of these cells to allow uterine receptivity and decidualisation necessary for implantation in the rat.

PTRF is associated with caveolin 1 at the time of receptivity: but SDPR is absent at the same time

The plasma membrane of uterine epithelial cells undergoes a number of changes during early pregnancy. The changes in the basolateral membrane at the time of implantation in particular change from being smooth to highly tortuous in morphology, along with a dramatic increase in the number of morphological caveolae at this time. The major protein of caveolar membranes is caveolin, and previous studies have shown that RNA pol I transcription factor (PTRF) and serum deprivation protein response (SDPR) are the two members of the cavin protein family. These proteins are known to be involved in caveolae biogenesis, where they directly bind to cholesterol and lipids and have been reported to promote membrane curvature. As there is an increase in membrane tortuosity and caveolae at the time of implantation, this study investigated PTRF and SDPR to explore the possible roles that they play in the morphology of the uterine epithelium during early pregnancy. PTRF protein abundance did not change in uterine epithelial cells during early pregnancy or in response to ovarian hormones. At the time of implantation in uterine epithelial cells, PTRF co-immunoprecipitated with caveolin 1, thereby demonstrating an association with caveolin-1 at the basal plasma membrane in caveolae. SDPR protein was observed to be present only at the time of fertilisation, and also under the influence of oestrogen alone, where a cytoplasmic localisation in uterine epithelial cells was observed. The localisation and expression PTRF and SDPR in uterine epithelial cells during early pregnancy suggest that they have roles in the maintenance of lipids and cholesterol in the plasma membrane. PTRF and lack of SDPR may contribute not only to the morphology of the basal plasma membrane as observed at the time of implantation, but also to the maintenance of epithelial polarity during early pregnancy.

Biological studies on the effect of estrogen on experimentally induced asthma in mice

This study evaluates the influence of estrogen hormone on the experimentally induced asthma in male mice. The animals were divided into four groups, with 20 mice in each group; group I (control mice) included mice that received no treatment, group II included mice that received intraperitoneal estrogen injection (0.25 mg/kg body weight (bw), twice on day 28 of the experiment), group III (asthmatic mice) included asthmatic mice that received intraperitoneal injection of two doses of ovalbumin (OVA; 2 µg of OVA mixed with 100 µg of aluminum potassium sulfate) on days 1 and 14 of the experiment and then challenged intranasally with a single dose of OVA (50 µg dissolved in 0.05 ml phosphate-buffered saline; PBS) on day 28 of the experiment, and group IV (asthmatic mice treated with estrogen) included asthma model male mice that received the estrogen (0.5 mg/kg bw in 40 ml PBS, twice on the day 28 of the experiment). The immunohistochemical studies observed a marked intensity of CD15 immunoreactivity in the lung tissues of asthma model mice. Physiological results recorded that the total and differential count of leukocytes in bronchoalveolar lavage fluid (BALF) of asthma model mice recorded a significant increase in the number of leukocytes especially in the number of eosinophil cells. The BALF of asthma model mice showed high levels of interleukins 4 and 5 (IL-4 and IL-5), and there was a significant decrease in both the levels of IL-4 and IL-5 in BALF of asthma model mice treated with estrogen. In conclusion, the obtained results indicated that the asthma is responsible for certain immunohistochemical and physiological alterations induced in lung tissues of mice. The administration of estrogen to asthmatic male mice could improve these changes. For this reason, the present findings support the possible role of estrogen in modulating the inflammatory effects caused by asthma in male mice and may be helpful to cure many asthmatic progressions.

Ovarian hormones regulate expression of the focal adhesion proteins, talin and paxillin, in rat uterine luminal but not glandular epithelial cells

During early pregnancy in the rat, focal adhesions disassemble in uterine luminal epithelial cells at the time of implantation to facilitate their removal so that the implanting blastocyst can invade into the underlying endometrial decidual cells. This study investigated the effect of ovarian hormones on the distribution and protein expression of two focal adhesion proteins, talin and paxillin, in rat uterine luminal and glandular epithelial cells under various hormone regimes. Talin and paxillin showed a major distributional change between different hormone regimes. Talin and paxillin were highly concentrated along the basal cell surface of uterine luminal epithelial cells in response to oestrogen treatment. However, this prominent staining of talin and paxillin was absent and also a corresponding reduction of paxillin expression was demonstrated in response to progesterone alone or progesterone in combination with oestrogen, which is also observed at the time of implantation. In contrast, the distribution of talin and paxillin in uterine glandular epithelial cells was localised on the basal cell surface and remained unchanged in all hormone regimes. Thus, not all focal adhesions are hormonally dependent in the rat uterus; however, the dynamics of focal adhesion in uterine luminal epithelial cells is tightly regulated by ovarian hormones. In particular, focal adhesion disassembly in uterine luminal epithelial cells, a key component to establish successful implantation, is predominantly under the influence of progesterone.

Uterine receptivity and the plasma membrane transformation

This review begins with a brief commentary on the diversity of placentation mechanisms, and then goes on to examine the extensive alterations which occur in the plasma membrane of uterine epithelial cells during early pregnancy across species. Ultrastructural, biochemical and more general morphological data reveal that strikingly common phenomena occur in this plasma membrane during early pregnancy despite the diversity of placental types--from epitheliochorial to hemochorial, which ultimately form in different species. To encapsulate the concept that common morphological and molecular alterations occur across species, that they are found basolaterally as well as apically, and that moreover they are an ongoing process during much of early pregnancy, not just an event at the time attachment, the term 'plasma membrane transformation' is suggested which also emphasises that alterations in this plasma membrane during early pregnancy are key to uterine receptivity.

In vivo regulation of syndecan-3 expression in the rat uterus by 17 beta-estradiol

The immature rat uterus has been extensively used as an in vivo model system to study the molecular mechanisms of steroid hormone actions. In this study, we demonstrated the regulated expression of syndecan-3 in the rat uterus by the steroid hormone 17 beta-estradiol. Administration of a single physiological dose of 17 beta-estradiol (40 microg/kg) to ovariectomized immature animals induced a rapid and transient increase in uterine syndecan-3 mRNA. Transcript levels reached a peak elevation of 3-fold above saline control tissues 4 h after hormone administration. Inhibition of message up-regulation by actinomycin D but not cycloheximide indicated a hormone response dependent on RNA transcription but not new protein synthesis. The estrogenic ligands estriol and tamoxifen were also effective at raising syndecan-3 mRNA levels; however, nonestrogenic ligands, including progesterone, 5 alpha-dihydrotestosterone, and dexamethasone, failed to stimulate a change in mRNA levels. Hormone-induced changes in mRNA led to transient changes in syndecan-3 protein content and significant alteration in the temporal and spatial expression in endometrial epithelial cells. Collectively, these data show that the steroid hormone 17 beta-estradiol, regulates transcription of the syndecan-3 gene in the uterus via an estrogen receptor-dependent mechanism. This estrogen-regulated expression of syndecan-3 may play an important role in changes in tissue ultrastructure crucial for proper uterine growth.

Understanding the apical surface markers of uterine receptivity: pinopods-or uterodomes?

The plasma membrane of uterine epithelial cells is very sensitive to ovarian hormones and protrusions of the apical portion of this membrane have been used as indicators of endocrine status and preparation for implantation in the human uterus in particular. Protrusions of the apical plasma membrane were first identified in rats and mice where their established pinocytotic function gave rise to the name 'pinopod'. In humans and many other animals however, little evidence of the functional nature of such protrusions is available but what is available suggests that human 'pinopods' (useful though they are as indicators of endocrine status) might be more similar morphologically to other, larger, membrane protrusions, or apical domes, which have been shown not to be pinocytotic. Hence, I propose that these latter protrusions, including those in the human uterus, should be referred to by a term which does not imply a particular function and have settled on the name 'uterodome'.

The plasma membrane transformation facilitates pregnancy in both reptiles and mammals

Mechanisms of placentation are very diverse in mammals and range from types in which the uterine epithelium is breached by the implanting blastocyst to those where the epithelium remains intact. Despite these differences in mechanisms, the initial response of the plasma membrane of uterine epithelial cells is remarkably similar across mammalian species which has led to the term 'plasma membrane transformation' to encapsulate the concept of a common beginning to implantation. Membrane phenomena similar to those of mammals have now been observed in some viviparous lizards at the ultrastructural level during early pregnancy, and we propose extending the concept of 'plasma membrane transformation' to lizards with live birth.

Expression of glucosamine trisaccharides on the rat uterine surface is altered by clomiphene citrate

We have studied histochemically the effects of clomiphene citrate on the expression of oligosacchrides on the apical plasma membrane of uterine epithelial cells using the lectin Phytolacca americana. Ovariectomized sexually mature rats were given a single injection of either clomiphene in two concentrations or estradiol 17 beta or progesterone and were killed 24 hr later. Uterine tissue was labeled with Phytolacca americana conjugated with avidin and subsequently labeled with biotinalyted ferritin and prepared for transmission electron microscopy. Our results indicate that clomiphene and to a lesser degree progesterone significantly increased lectin binding. However, the increase was not as large as that observed with a single dose of estrodiol 17 beta. When the proportion of lectin positivity in relation to total membrane length was analyzed, treatment with clomiphene and progesterone did not have significantly different effects. Low dose clomiphene did not have a significant effect as compared with controls. Our data show that clomiphene has a dose-dependent adverse effect on lectin binding as compared with ovarian hormones. We suggest that these effects contribute to low pregnancy rates with clomiphene use.

Ultrastructural studies of glycan changes in the apical surface of the uterine epithelium during pre-ovulatory and and pre-implantation stages in the marmoset monkey

It has been postulated that carbohydrates are involved in a variety of cell-cell interactions including blastocyst implantation. In primates, there are only limited investigations on the ultrastructural localisation of the cyclic changes in uterine epithelial surface carbohydrates. Our aim was to investigate such changes during the pre-ovulatory and pre-implantation stages of the reproductive cycle in the marmoset monkey. After fixation of endometrial tissues, avidin-ferritin lectin cytochemistry was employed for apical surface glycan detection at the ultrastructural level. Five lectins were used including Canavalia ensiformis (Con A), Lotus tetragonolobus (LTA), Glycine max (SBA), Phytolacca americana (PWM) and Triticum vulgaris (WGA). Morphometry was used to quantitate changes in the intensity of lectin staining by determining the total number of ferritin particles per unit length of membrane. Surface and intra-cytoplasmic vesicles, stained by the lectins, were also examined. Quantitative ferritin assessment showed that 1 day before presumed implantation (days 11 to 12 after ovulation in the marmoset monkey) there was a significant increase in Con A, LTA and SBA staining on the apical uterine epithelial plasma membrane compared to the pre-ovulatory phase and earlier stages of pregnancy (days 4-8 after ovulation). A significant increase in PWM was also detected from early pregnancy to pre-implantation stages. All lectins except WGA produced reproducible staining within reproductive cycle groups. The greatest variation and intensity of epithelial surface staining was observed with WGA and the weakest with LTA. The patchy staining with LTA compared with thick coverage by WGA indicated the complexity of the carbohydrate arrangement in the glycocalyx of the uterine surface plasma membrane. Reduction of WGA reactivity after neuraminidase treatment suggested that the lectin binding might be related to the presence of heavily sialylated apical uterine membrane glycoconjugates. This is the first high-resolution study in primates to report quantitative cyclic changes in fucosyl, galactosyl, glucosyl, and mannosyl sugar residues of the apical uterine epithelial glycocalyx. The findings support the concept that uterine epithelial glycocalyx surface carbohydrates play a role in preparing a receptive uterine surface.

Estrogen protects lenses against cataract induced by transforming growth factor-beta (TGFbeta)

Cataract, already a major cause of visual impairment and blindness, is likely to become an increasing problem as the world population ages. In a previous study, we showed that transforming growth factor-beta (TGFP) induces rat lenses in culture to develop opacities and other changes that have many features of human subcapsular cataracts. Here we show that estrogen protects against cataract. Lenses from female rats are more resistant to TGFbeta-induced cataract than those from males. Furthermore, lenses from ovariectomized females show increased sensitivity to the damaging effects of TGFbeta and estrogen replacement in vivo, or exposure to estrogen in vitro, restores resistance. Sex-dependent and estrogen-related differences in susceptibility to cataract formation, consistent with a protective role for estrogen, have been noted in some epidemiological studies. The present study in the rat indicates that estrogen provides protection against cataract by countering the damaging effects of TGFbeP. It also adds to an increasing body of evidence that hormone replacement therapy protects postmenopausal women against various diseases.

Sterility in neonatally androgenized female rats and the decidual cell reaction

In female rats, administration of androgen during early postnatal life results in anovulatory sterility characterized by polyfollicular ovaries and persistent vaginal cornification in adulthood. In these androgen-sterilized rats, the acyclic male pattern of gonadotropin secretion results from permanent damage to hypothalamic centers normally responsive to steroid feedback. The capacity of the endometrium to differentiate into deciduoma in response to endometrial stimulation is markedly reduced in the uterus of the androgenized rats receiving an appropriate regimen of progesterone and estrogen injections. The hypothesis is presented that the lowered uterine responsiveness in the androgenized rats is largely ascribable to the effect of androgen given neonatally rather than to the influence of continued exposure to ovarian estrogen. This review deals with the nature of the uterine response to ovarian hormones and the deciduogenic stimulus in androgenized rats in order to verify the mechanism involved in androgen action on the neonatal uterus.

Production of an endothelial cell migratory signal in rat endometrium during early pregnancy

Rat endometrial explants were cultured in a three-dimensional collagen/endothelial cell matrix to measure angiogenic activity, as represented by migration of vascular endothelial cells towards the explants. Minimal endothelial cell migratory activity was observed with endometrial explants taken during the four-day oestrous cycle and days 3 and 4 of pregnancy. In contrast, a surge of endothelial cell migration occurred in response to endometrial explants taken from day-5-pregnant rats. Activity was found in explants taken approximately 5 h prior to implantation, but returned to minimal levels by day 6 of pregnancy. Endothelial cell migration remained minimal in response to both implantation and intersite tissue explants taken from days 6 and 7 of pregnancy. Endometrium from ovariectomised rats produced no endothelial cell migratory activity as measured by this technique. However, near preimplantation levels of endothelial cell migratory activity could be induced in ovariectomised rat endometrium by administering progesterone for 72 hours. Oestrogen given in conjunction with progesterone had no additional effect. These results demonstrate the presence of an endometrial signal that controls endothelial cell migration, and demonstrate this activity can be induced by progesterone without the addition of oestrogen.

Cell surface glycoconjugates as modulators of embryo attachment to uterine epithelial cells

Attachment of mammalian embryos to the uterine wall involves the coordinated development of both the embryo and the uterine epithelium to an attachment-competent state. This coordination is achieved directly or indirectly through the actions of ovarian steroids. Acquisition of attachment competence is proposed to reflect two processes. The first is the loss of non-adhesive glycoproteins at the cell surface of embryos, e.g. zona pellucida subunits, as well as uterine epithelial cells, e.g. mucin glycoproteins. The second process is the functional expression of complementary adhesion-promoting molecules at these cell surfaces. A series of studies indicates that heparan sulfate proteoglycans and their corresponding binding sites can play an important role in the initial stage of embryo attachment to the uterine surface.

Thiamine pyrophosphatase cytochemistry in rat endometrium during the oestrous cycle

The functional morphology of the Golgi apparatus was studied in various types of cells in the rat endometrium during the oestrous cycle. A cerium-based enzyme-cytochemical method was used for the ultrastructural visualization of the activity of thiamine pyrophosphatase (TPPase). The cerium-based method was evidently superior to the classical lead technique, which was used for comparison. TPPase activity in luminal and glandular epithelial cells displayed cyclical modulation and redistribution. It was restricted to only one or two narrow trans lamellae during dioestrus but extended during proestrus and oestrus into nearly all trans-to-cis lamellae of the well-compartmentated Golgi apparatus. A homogeneous staining reaction, which was particularly intense during the latter two phases and only partly due to unspecific alkaline phosphatase, was confined to the apical and basolateral plasma membranes of luminal epithelial cells. In the stromal fibroblasts, only one short Golgi saccule was positive at dioestrus, whereas three or more trans Golgi lamellae were filled with reaction product during oestradiol-dominated oestrus. TPPase activity was furthermore observed in the lysosomes in epithelial cells, stromal fibroblasts, capillary endothelial cells and pericytes. The present findings of cyclic changes in TPPase activity in epithelial cells and stromal fibroblasts provide the first evidence of cyclic modulation and redistribution of this enzyme in the endometrium.

Effect of progesterone on hydrophobic cell-associated proteoglycans bound to cholesterol sulfate in glandular epithelial cells of guinea-pig endometrium

Sulfate incorporation was studied in subcultured glandular epithelial cells of guinea-pig endometrium untreated or treated with 10(-8) M 17 beta-estradiol alone or associated with various concentrations of progesterone. In the cells treated with progesterone in association with 17 beta-estradiol, the maximum of the 35S-labelled cell-associated macromolecules failed to bind with an anion-exchange resin (53% of total radioactivity) and had a hydrophobic character. This fraction was separated as an aggregate when the cells were extracted with 4 M guanidine-HCl, and separated as a single component in the presence of Triton X-100, suggesting that it aggregates with cellular lipid. The guanidine-extracted material contained 23.5% proteoglycans. However, the bulk of the radioactivity was in the sulfated lipids (68-75%), essentially represented by cholesterol sulfate. In the progesterone-treated cells, the amount of cholesterol sulfate was significantly higher than in 17 beta-estradiol-treated or untreated cells (1.35-1.5-fold). Thus, the effect of progesterone is located on a lipophilic proteoglycan associated with cholesterol sulfate. These results are discussed in relation to the preparation of the endometrium for embryo implantation.

Changes in histochemical distribution of cell surface heparan sulfate proteoglycan in mouse uterus during the estrous cycle and early pregnancy

We have investigated the changes in immunolocalization of a cell surface heparan sulfate proteoglycan (HSPG) in the mouse uterus during the estrous cycle and at the time of implantation in early pregnancy. A monoclonal antibody prepared against syndecan, a cell surface HSPG from mouse mammary epithelium (gift of Dr. M. Bernfield), was reacted with unfixed and fixed frozen sections of uteri from normally cycling, 3.5 and 4.5 days pregnant, and estradiol-treated immature and ovariectomized mature mice. A polyclonal antibody prepared against basal lamina HSPG from Engelbreth-Holm-Swarm (EHS) tumor cells (gift of Dr. John Hassell) was used as a positive control. The latter showed no variation during the estrous cycle or early pregnancy. Localization of syndecan in uterine epithelium changed from basolateral to predominantly basal as the cycle progressed from metestrus toward estrus. A similar pattern was seen in immature and ovariectomized mature females that had received estradiol injections. With the onset of pregnancy, the basolateral localization became progressively less intense from 3.5 days through 4.5 days of pregnancy. Thus, cell surface HSPG distribution is modulated by hormonally dependent changes in cycling and pregnant mice, supporting previous suggestions that early pregnancy in mice is accompanied by a turnover and rearrangement of uterine epithelial cell surface.

Changes in the apical microfilaments of rat uterine epithelial cells in response to estradiol and progesterone

This study investigates the interaction of hormones and the cytoskeleton within the apical cytoplasm of uterine epithelial cells of the rat. The effects of the hormones estradiol-17 beta and progesterone on the microfilament configuration were studied using myosin subfragment 1 (S1) decoration of actin microfilaments (MF) and transmission electron microscopy. In control ovariectomized animals, a sparse MF distribution was found in the apical cytoplasm underlying short microvilli with S1-decorated core MF. Hormone treatment experiments consisted of injecting ovariectomized rats with either progesterone or estradiol-17 beta. For the study of the MF configuration accompanying an apical surface primed for blastocyst receptivity, progesterone treatment was immediately followed by a single dose of estradiol-17 beta. The long, regular microvilli associated with estradiol only treatment contained bundled, decorated MF with tightly bundled rootlets. Progesterone alone produced numerous short microvilli with decorated core bundle MF and pronounced rootlets that frequently appeared splayed. The irregular microvilli and luminal surface of the uterine epithelial cells associated with the receptivity hormone sequence contained variable MF configurations, including MF bundles, networks, and areas with a "felted" appearance. The results show that the various hormone regimes produce characteristically different MF configurations and that this component of the cytoskeleton appears to be under the control of a delicate hormone balance within these uterine cells. The responses of uterine MF to specific regimes of steroid hormones used in this study are not only important for the understanding of the mechanisms at work during early pregnancy, but also contribute to the body of knowledge concerning the ways in which hormones in general effect the cytoskeleton of target cells.

Structure of premenstrual endometrium in HMG + HCG induced anovulatory women

In this study structural alterations were tested on anovulatory infertile women who had undergone treatment of HMG + HCG to induce ovulation and subsequently to achieve pregnancy. For this purpose, a single premenstrual endometrial fundal biopsy was performed and evaluated using light and electron microscopy. The aim of the study was to evaluate the biopsies with respect to 'in-phase' or 'out-of-phase' at light microscopic level, in which a series of strict criteria were chosen, and then to detect the additional structural abnormalities at electron microscopic level, if present. Only one of the women in our study who had an in-phase endometrium became pregnant after proper treatment protocol individually adjusted and consequently terminated by an early abortion. Histologic features of the biopsies revealed that about half were normal while the rest had various types of structural abnormalities in the transformation of the secretory endometrium detected by light and/or electron microscopy. At the electron microscopic level, multiple alterations were seen in cellular and intercellular components even in those diagnosed as normal by light microscopy. As a result of the above data it was concluded that the cause of inconceivability might arise from some fine structural alterations which may affect the endometrial receptivity of an implanting embryo.

Culture of human endometrial cells under polarizing conditions

Glandular epithelial and stromal cells were isolated from human endometrial biopsies and cultured in a dual-chambered system (Millicell; Millipore, Bedford, Ma., USA) that provides access of the medium to both sides of a membrane coated with reconstituted basement membrane material (Matrigel; Collaborative Research Inc., Bedford, Ma., USA). Examination by electron microscopy revealed that the epithelial cells formed a polarized cuboidal-columnar monolayer on the Matrigel surface. The cells exhibited apical microvilli, basal nuclei, and numerous cytoplasmic structures consistent with a well-differentiated cytoplasm; they were joined basally by interdigitating processes and apically by tight junctions and desmosomes. In contrast, epithelial cells cultured in parallel on plastic dishes were flattened, had fewer microvilli and cytoplasmic structures, and no junctional complexes.

Changes in intralysosomal environment in the uterine epithelium during early pregnancy in the rat

Non-specific acid phosphatase activity was studied in the rat uterine luminal and glandular epithelium at oestrous, late dioestrous, and 6th d of pregnancy using the substrates beta-glycerophosphate and p-nitrophenyl phosphate, at both pH = 5.0 and pH = 6.0. At late dioestrous and 6th d of pregnancy, a significantly larger lysosomal population in the luminal and glandular epithelium was operating at pH = 5.0 rather than pH = 6.0. At oestrous, the epithelial lysosomes showed no preference for an operational pH = 5.0 or 6.0. Uniquely, the luminal epithelial lysosomes showed a significant preference for the hydrolysis of p-nitrophenyl phosphate over beta-glycerophosphate at 6th d of pregnancy, compared to no substrate preference at oestrous and late dioestrous. The activity of 5-Nucleotidase was also estimated semi-quantitatively at oestrous, late dioestrous, and 6th d of pregnancy in the luminal and glandular epithelium. 5-Nucleotidase activity was greatest in the luminal and glandular epithelium at 6th d of pregnancy. These findings are considered with respect to the possible mechanisms involved in implementing the changes and the relevance to blastocyst implantation.

Cytoskeletal alterations in the microvilli of uterine epithelial cells during early pregnancy

We have studied the arrangement of microfilaments in uterine microvilli during early pregnancy, using transmission electron microscopy and immunofluorescence microscopy. Observations indicate that changes in actin microfilament organization occur in association with the alterations to the uterine cell surface which precede blastocyst implantation. We consider these findings with reference to the possible mechanisms involved.

Endometrial morphology in stimulated in vitro fertilization cycles and after steroid replacement therapy in cases of primary ovarian failure

Endometrial morphology and ultrastructure are studied in 17 spontaneous, 23 stimulated, and 18 artificial cycles in cases of primary ovarian failure. Normal light-microscopic aspect was found, but impaired development of nucleolar channel system and stronger intercellular junction have been observed by electron-microscopic studies in stimulated cycles with relative excess of luteal estrogen. Normal glandular maturation can be obtained in patients with premature menopause, given adequate steroid replacement, but an abnormally dense fibrocytic aspect of the stroma is characteristic of the first treatment cycles.

Digitonin cytochemistry reveals cholesterol-rich vesicles in uterine epithelial cells

Freeze-fracture cytochemistry with digitonin has been used to examine the cholesterol content of the large apical vesicles of uterine epithelial cells. The vesicles are found to have cholesterol-rich membranes which supports the view that they are involved in cell secretion. We comment on the possible role of the vesicles in implantation.

Glucose transport by uterine plasma membranes

Uterine plasma membrane preparations were obtained by centrifugation on discontinuous sucrose gradients. The specific activity of the plasma membrane marker 5'-nucleotidase was increased 10-fold while the specific activity of glucose-6-phosphatase was increased 3-fold. Electron microscopy showed mainly closed vesicles having diameters mainly in the range of 0.1 to 0.4 micron and an absence of other recognizable organelles such as mitochondria. D-Glucose transport was inhibited by sulfhydryl reagents, phloretin, and cytochalasin B. Uptake was prevented at high osmotic pressures. The Km of glucose transport was 12.2 +/- 1.1 mM. Studies of the inhibition of [3H]cytochalasin B binding by D-glucose indicated that the value of the Kd of the cytochalasin B-transporter complex was larger than 1 microM. These data demonstrate the potential usefulness of these preparations in the study of glucose transport in rat uterus and its control by steroid hormones.

Effects of ovarian hormones on manifestation of purulent endometritis in rat uteruses infected with Escherichia coli

To assess the influence of hormones on uterine infections, Escherichia coli was infused into uterine lumens of ovariectomized or adrenoovariectomized rats receiving exogenous administration of various doses of ovarian hormones. Large numbers of E. coli were recovered from the rat uterine lumens, irrespective of hormonal influences. The number of leukocytes in the uterine flushings, representing the magnitude of purulent inflammation, differed significantly depending upon the hormonal regimen given to each host. Purulent endometritis was induced by E. coli in ovariectomized rats receiving progesterone or corn oil (hormone vehicle). Infections were asymptomatic in rats receiving estradiol, but promethazine-treated uterine horns were susceptible to infection. When progesterone was administered along with estradiol, purulent inflammation was caused by E. coli, but the number of leukocytes in the uterine lumens was significantly less than that obtained from the rats treated with progesterone or corn oil. These effects of ovarian hormones on uterine infections were observed in adrenoovariectomized rats as well as in ovariectomized rats. It is suggested that estradiol alters the nature of endometrial epithelium and prevent manifestation of purulent endometritis; progesterone antagonizes estradiol. Adrenal hormones appear not to participate in the pathogenesis of endometritis induced by E. coli.

Alterations in epithelial glycocalyx of rabbit uteri during early pseudopregnancy and pregnancy, and following ovariectomy

Pseudopregnant, pregnant, and ovariectomized rabbits were utilized to study hormonal mediation of uterine epithelial surface negativity and glycocalyx morphology, and to seek local effects of blastocysts at sites of implantatioN. A loss of surface negativity [polycationic ferritin (PCF) binding] by day 6 of pregnancy or pseudopregnancy was noted, accompanied by alterations in epithelial glycocalyx. Uteri from estrous animals, or ovariectomized animals receiving oil or estradiol injections, bound PCF and exhibited a "globular" glycocalyx. Uteri from day 6 pseudopregnant or pregnant animals, or ovariectomized animals receiving progesterone injections, did not bind PCF or exhibit a globular glycocalyx. Both PCF binding and the globular character of the epithelial glycocalyx were sensitive to neuraminidase and trypsin treatment, suggesting sialoglycoprotein contribution to surface negativity. Implanting blastocysts had no detectable local effect on surface negativity, but did induce local reduction of epithelial glycocalyx at sites of implantation. Results of this study suggest that uterine epithelial glycocalyx alterations during the preimplantation period reflect a general response to progesterone stimulation, primarily qualitative in nature, related to the acquisition of receptivity to ovo-implantation.

Colloidal iron hydroxide staining of surface carbohydrates after glycerol treatment of uterine epithelial cells

The structural relationships between intramembraneous particles (IMPs) and surface carbohydrates has been studied in uterine epithelial cells with a colloidal iron hydroxide (CIH) technique. To aggregate IMPs, glycerol treatment of unfixed cells was used and this treatment also caused some patching of CIH deposits on the cell surface. We conclude that some of the CIH receptors may be the surface expression of the IMPs.