Collagen distribution in the mouse endometrium during decidualization

The distribution of collagen and reticular fibers was studied in the endometrium of virgin and pregnant mice. The collagen and reticular fibers were examined in picrosirius-stained sections observed in a polarizing microscope and in silver-impregnated sections. Picrosirius-stained sections of animals in estrus, diestrus and on the 2nd day of pregnancy had fine greenish fibers distributed irregularly in the endometrium and thicker red fibers concentrated near the myometrium. Argyrophyl fibers in virgin mice were scarce and irregularly distributed. On the 4th day of pregnancy very few fibers were observed in the endometrium. On the 5th, 6th, and 7th days of pregnancy long greenish fibers were found surrounding decidual cells. A network of argyrophyl fibers was observed in the silver-impregnated decidua. It is suggested that new fibers are produced by decidual cells.     

Transforming growth factor beta isoforms regulation of Akt activity and XIAP levels in rat endometrium during estrous cycle, in a model of pseudopregnancy and in cultured decidual cells

Background  

During the estrous cycle, the rat uterine endometrium undergoes many changes such as cell proliferation and apoptosis. If implantation occurs, stromal cells differentiate into decidual cells and near the end of pregnancy, a second wave of apoptosis occurs. This process called decidual regression, is tightly regulated as is it crucial for successful pregnancy. We have previously shown that TGF-beta1, TGF-beta2 and TGF-beta3 are expressed in the endometrium during decidual basalis regression, but although we had demonstrated that TGF- beta1 was involved in the regulation of apoptosis in decidual cells, the ability of TGF- beta2 and TGF-beta3 isoforms to trigger apoptotic mechanisms in these cells remains unknown. Moreover, we hypothesized that the TGF-betas were also present and regulated in the non-pregnant endometrium during the estrous cycle. The aim of the present study was to determine and compare the specific effect of each TGF-β isoform in the regulation of apoptosis in sensitized endometrial stromal cells in vitro, and to investigate the regulation of TGF-beta isoforms in the endometrium during the estrous cycle in vivo.     

Epidermal growth factor stimulate cell proliferation and inhibits prolactin secretion of the human decidual cells in culture

Epidermal growth factor (EGF) has been found to be mitogenic in a variety of tissues. We investigated the biological effect of EGF on early pregnant human decidua and the non-pregnant decidualized human endometrium in the primary cell culture. EGF had a stimulatory action on cell proliferation in the early pregnant decidual cells and an inhibitory effect on prolactin (PRL) secretion from the decidual cells. The addition of progesterone into culture medium suppressed cell proliferation of decidual cells, whereas it enhanced PRL secretion from decidua. The analysis of the specific receptor for EGF in the early pregnant decidua and non-pregnant decidualized endometrium revealed that both tissues had a single component EGF receptor with a dissociation constant of nM order. These results suggest that EGF may play a role in the growth and function of endometrial stromal cells.     

Decidualisation: origin and role of associated cells

Proliferation of peri- and subluminal stroma following a stimulus from the blastocyst leads to the appearance of decidual cells in the mammalian endometrium. Decidualisation can also be elicited by artificial stimuli in pseudopregnant animals. A variety of histophysiological reactions accompany decidualisation and distinct morphological features characterize decidual cells localized in the antimesometrial and mesometrial area. Granulated metrial gland cells, arising in the endometrium of decidualising uterus, form a separate class of cells and become prominent in the mesometrial triangle as pregnancy advances. This review deals with factors related to induction of decidualisation; structural characteristics of decidual and metrial gland cells; the origin and postulated roles of decidualisation-associated cells. The functional role of decidual and metrial gland cells is discussed in relation to their structural complexity and recent observations on the haemopoietic origin of these cells.     

Endometrial NK cells are special immature cells that await pregnancy

NK cells populate the human endometrium before pregnancy. Unlike decidual NK cells that populate the decidua during pregnancy, the NK cells present in the human endometrium, before pregnancy, have not been fully characterized. In this study, we provide a detailed analysis of the origin, phenotype, and function of endometrial NK cells (eNK). We show that eNK cells have a unique receptor repertoire. In particular, they are negative for NKp30 and chemokine receptor expression, which distinguishes them from any other NK subset described so far. We further show that eNK cells lack NK-specific functional phenotype and activity such as cytokine secretion and cytotoxicity, before IL-15 stimulation. Following such stimulation, endometrial NK cells acquire phenotype and function that are similar to those of decidual NK cells. We therefore suggest that eNK cells are inactive cells (before IL-15 activation and in relation to the known NK activity) that are present in the endometrium before conception, waiting for pregnancy.     

In vitro decidualization of human endometrial stromal cells.

Stromal cells isolated from proliferative human endometrium undergo morphologic and biochemical changes when exposed to a mixture of ovarian hormones, acquiring characteristics of decidual cells. In addition to the previously reported progestin-induced secretion of prolactin (PRL) by explants of human proliferative endometrium, and of PRL and laminin by stromal cells in culture, "in vitro" induction of several other decidual cell products was demonstrated in the present study, using cultures of stromal cells isolated from proliferative endometrium. Incubation of stromal cells with a mixture of estradiol, medroxyprogesterone acetate and relaxin, at a concentration reported to yield maximal stimulation of PRL production, resulted in changes from elongated to rounder cells, approx. 90% of which showed immunostaining for PRL under these conditions. Immunocytochemical procedures were carried out on cytospins of decidual cells isolated from decidual tissue adherent to fetal membranes collected at delivery (positive controls), and on stromal cells cultured in Lab-Tek chamber-slides, in the absence (negative controls) or in the presence of added hormones. Antibodies to 24K (a heat-shock protein also named HRP27), desmin (present in intermediate filaments), p29 (a protein associated with the estrogen receptor), and PP12 (an insulin growth factor-1 binding protein), did not react with stromal cells isolated from proliferative endometrium but showed immunostaining of the rounder cells obtained after hormonal treatment when tested with the peroxidase-labeled second antibody complex. In another series of similar experiments, in which the same decidualization end-points were employed, changes in 24K, desmin and PP12 expression were obtained by adding to the insulin-containing medium PRL instead of the hormonal mixture, a finding suggesting sequential steps during the decidualization process.     

Human decidual natural killer cells express the receptor for and respond to the cytokine interleukin 15

The natural killer (NK) cells that are present in the uterine mucosa (decidua) during early pregnancy have a distinctive phenotype, CD56(bright) CD16(-). These cells have previously been shown to proliferate and be activated by interleukin (IL)-2. However, IL-2 is absent from the decidua and placenta, and we have therefore investigated whether IL-15 is present in the uterus and can act on decidual NK cells. Both IL-15 mRNA and protein were found in a variety of cells but particularly in decidual macrophages. IL-15 induced a proliferative response in decidual NK cells that was blocked by anti-IL-15 and was augmented by stem cell factor. The cytolytic activity of decidual NK cells against K562 was augmented. Interestingly, in contrast to IL-2, although activation with IL-15 resulted in some killing of JEG-3 choriocarcinoma cells, normal trophoblast cells remained resistant to lysis. These findings suggest that IL-15 is a candidate cytokine responsible for NK cell proliferation in vivo in the progesterone-dominated secretory endometrium and early decidua.     

Apoptosis of rat decidual cells: site specific initiation and related biochemical changes

The artificially induced rat deciduoma serves as a model to study cellular changes associated with implantation in the endometrium. The stromal cells differentiate to form two types of decidual cells and are restricted to specific anatomical sites of the uterus. Programmed cell death starts in the antimesometrial area and expression of glutathione-S-transferase, an antioxidant enzyme, enhances in these cells as the deciduoma enters the regressive phase. The enzyme activity is significantly high compared with that of mesometrial decidual cells. Similarly, lipid peroxide content of antimesometrial decidual cells is high during this phase. DNA fragmentation, a feature of cells undergoing programmed cell death, is initiated in the antimesometrial area during regression of deciduoma.     

Changes in the cellular composition of the deciduous membrane in physiologic pregnancy and late toxicosis

Cytochemical characteristics of the decidual membrane at a physiologically normal pregnancy and in cases of late toxicosis are presented. Three main cell types of the decidual membrane are defined: large decidual cells (LDC), small decidual cells (SDC) and granular cells of endometrium, or K-cells. Part of each cell type in the decidual membrane is determined. At physiologically normal pregnancy the part of the LDC makes 50-60% in the membranes and 80-85% in the basal plate of the placenta; SDC--10-18% in the fetal membranes and 1-2% in the basal plate of the placenta; K-cells--0.5-1%. At late toxicosis of pregnancy there is a change in relative and absolute amount of the decidual cells: the part of the LDC decreases up to 26-40% in the fetal membranes and up to 55% in the basal plate of the placenta; part of the K-cells at a slight form of preeclampsia rises up to 3-4%, at a severe form--up to 11-12%. The change in cell composition results in certain disturbances of physiological equilibrium of biologically active substances produced by the decidual cells. This correlates with the severity and clinical manifestations of the late toxicosis of pregnancy. Correlation of the decidual cells disfunction, directed to regulation of their reproduction and functioning, can become one of the elements of pathogenic treatment of the late toxicosis of pregnancy.     

Spatial and temporal patterns of deoxyribonucleic acid synthesis and mitosis in the endometrial stroma during decidualization in the pseudopregnant rat

A quantitative study was made of the spatial patterns of stromal cell mitosis and DNA synthesis in the endometrium of the pseudopregnant rat before and during decidualization. A colchicine block was used for mitotic counts, and DNA synthesis was studied by [3H] thymidine autoradiography. Observations were also made on the subsequent fates of [3H] thymidine-labeled stromal cells. Before the onset of decidualization, on Days 3 and 4 (vaginal cornification = Day 0), mitosis was largely confined to the subepithelial stroma along the sides and around the antimesometrial pole of the lumen. [3H] thymidine labeling and stromal mitosis following a decidualizing stimulus at noon on Day 4 of pseudopregnancy were first seen close to the uterine lumen, with subsequent spread to deeper layers of the endometrium. At noon on Day 5, mitotic figures were numerous on all sides of the lumen and at all depths in the endometrium. At later stages, mitosis and the development of polyploidy continued in the decidual tissue, but little DNA synthesis or mitosis occurred in the basal zone of the stroma adjacent to the myometrium. In this zone, many cells in animals given [3H] thymidine 18 to 24 h after induction of decidualization remained heavily labeled throughout the growth and regression of deciduomata. Labeled cells derived from the basal zone and outer edge of the decidual capsule were present in the stroma of the regenerated endometrium following the regression of deciduomata. It was concluded that although cells at all depths in the endometrial stroma undergo DNA synthesis and mitosis in the early stages of response to a decidualizing stimulus, their subsequent behavior and fate depend upon their position in the endometrium.     

Localization of ubiquitin and ubiquitin cross-reactive protein in human and baboon endometrium and decidua during the menstrual cycle and early pregnancy

We have examined the distribution of ubiquitin and the related ubiquitin cross-reactive protein (UCRP) in paraffin-embedded sections of human and baboon endometrium and decidua by immunoperoxidase or immunofluorescence cytochemistry with antibodies raised against ubiquitin, UCRP, CD45, and insulin-like growth factor-binding protein-1. Anti-ubiquitin immunoreactivity was present in the nonpregnant endometrium, particularly in the glandular epithelial cells, and up-regulated in endometrial stromal cells as they decidualized at the beginning of pregnancy. Anti-UCRP immunoreactivity was absent from nonpregnant tissue but accumulated to high levels in decidual cells during pregnancy. Western blotting indicated that immunoreactivity was primarily due to the presence of ubiquitin and UCRP conjugated to other proteins, and that although levels of ubiquitin-protein conjugates do not change substantially during pregnancy, decidualization is accompanied by the appearance of conjugates of UCRP. Baboon uterine tissues demonstrated a similar distribution of the two proteins, which indicates that the baboon may be a useful model for study of the role of the ubiquitin system and UCRP in the establishment of pregnancy in humans.     

Expression and function of PDCD1 at the human maternal-fetal interface

The failure to reject the semiallogenic fetus by maternal T lymphocytes suggests that potent mechanisms regulate these cells. PDCD1 is a CD28 family receptor expressed by T cells, and its ligand CD274 is strongly expressed by trophoblast cells of the human placenta. In this study, we examined whether human maternal T cells express PDCD1. Immunofluorescence examination of uterine tissues revealed PDCD1 expression on CD3+ cells was low in nonpregnant endometrium but increased in first-trimester decidua and remained elevated in term decidua (P < 0.05). In addition, higher relative proportions of term decidual CD8 bright, CD4+, and regulatory T cells expressed PDCD1 in comparison to autologous peripheral blood (P < 0.05). Term decidual T cells also expressed full-length and soluble PDCD1 mRNA isoforms more abundantly than their peripheral blood counterparts (P 相似文献   

Collagen remodeling during decidualization in the mouse

Summary An ultrastructural study of the features and distribution of collagen fibrils was performed in the endometrium of virgin and pregnant (2nd to 11th day) mice. Collagen-containing structures were observed in the cytoplasm of fibroblasts on the 2nd day of pregnancy. Treatment of tissues with lanthanum nitrate established that these structures were intracytoplasmic. Their association with lysosome-like bodies suggested the occurrence of intracellular digestion of collagen, probably connected with remodeling of the endometrial stroma prior to decidualization. On the 4th day of pregnancy, very few collagen fibrils were present in the intercellular space. From the 6th day of pregnancy onwards, thick collagen fibrils were observed between decidual cells. The diameter of these fibrils measured up to 300 nm whereas the fibrils present in the endometrium of virgin mice measured 40–68 nm.     

New insights into human endometrial aminopeptidases in both implantation and menstruation

The endometrium cycle involves proliferation of endometrial epithelial cells in preparation for implantation of fertilized ovum. With ovulation, the endometrium secretes nutrients such as peptides and amino acids into the endometrial cavity. The histological evidence of ovulation in normal menstrual cycle includes subnuclear glycogen vacuoles surrounded by placental leucine aminopeptidase (P-LAP) in endometrial epithelial cells. P-LAP is an essentially involved in intracellular trafficking of glucose transporter (GLUT) 4 which is primarily important for glucose uptake in skeletal muscles and fat tissues. On the other hand, glucose influx from blood into endometrial epithelial cells is not mainly mediated by GLUTs, but by coincident appearing progesterone just after ovulation. Progesterone increases permeability of not only plasma membranes, but also lysosomal membranes, and this may be primarily involved in glucose influx. Progesterone also expands the exocytosis in the endometrium after ovulation, and endometrial secretion after ovulation is possibly apocrine and holocrine, which is augmented and exaggerated exocytosis of the lysosomal contents. The endometrial spiral arteries/arterioles are surrounded by endometrial stromal cells which are differentiated into decidual/pre-decidual cells. Decidual cells are devoid of aminopeptidase A (APA), possibly leading to enhancement of Angiotensin-II action in decidual cell area due to loss of its degradation by APA. Angiotensin-II is thought to exert growth-factor-like effects in post-implantation embryos in decidual cells, thereby contributing to implantation. Without implantation, angiotensin-II constricts the endometrial spiral arteries/arterioles to promote menstruation. Thus, P-LAP and APA may be involved in homeostasis in uterus via regulating glucose transport and vasoconstrictive peptides.     

Organization of desmin-containing intermediate filaments during differentiation of mouse decidual cells

Decidualization of the mouse endometrium consists of a redifferentiation of the endometrial stromal fibroblasts. During decidualization these fibroblasts undergo growth, change of shape, multinucleation, and establishment of intercellular junctions. One feature of rodent decidual cells is the accumulation of intermediate filaments. In spite of the fact that fibroblasts normally have vimentin intermediate filaments, they acquire a large amount of desmin intermediate filaments while they undergo decidualization. The light and electron microscope immunocytochemical results of the present work show that during the initial stages of decidual transformation the desmin intermediate filaments accumulate around the nuclei, often forming caps around the nuclear envelope. As the decidual cells grow, the filaments form bundles and nets that radiate from the nuclei toward the cell surface. During the final stages of differentiation, on day 8 of pregnancy, staining of differentiated decidual cells decreases and most filaments accumulate under the cell surface. A role for intermediate filaments is suggested for decidualization of mouse endometrial cells.     

Development of the implantation chamber in the pregnant bitch.

Uteri taken from 25 bitches at various times during the early stages of pregnancy were studies cytologically to determine how the implantation chamber developed and how fetal-maternal relations were established. On day 13 after the end of estrus, knobs of trophoblastic syncytium formed and became wedged between cells of the uterine luminal epithelium. The syncytium quickly spread along the uterine lumen and into the mouths of the glands, dislodging and surrounding maternal cells. As invasion continued trophoblastic villi, consisting of cores of cytotrophoblast covered by a continuous layer of syncytium, penetrated deeper into the endometrium. The syncytium spread to surround maternal vessels and decidual cells. By day 26 the trophoblast had extended down to the large lacunae. Here syncytial trophoblast covering tips of the villi degenerated, leaving cytotrophoblast exposed to the necrotic zone. These cells possessed characteristics of absorbing cells. Hematomas were formed by focal necrosis of fetal and endometrial tissue at the poles of the implantation sites. Large pools of extravasated blood accumulated and red blood cells were phagocytized by surrounding trophoblastic cells. Therefore, the endotheliochorial relationship in the canine placenta appeared to be established by syncytial trophoblast invading a cellular endometrium. In the necrotic zone and hematomas, cellular trophoblast may have lost its syncytial covering, but elsewhere maternal vessels and decidual cells in the placenta were in direct contact only with syncytial trophoblast.     

Expression of nidogens in rat uterus and embryo during decidualization and implantation

The purpose of this study was to demonstrate the expression of nidogen-1 and nidogen-2 and their possible role in decidualization and implantation events during early pregnancy in rats. The tissue samples were examined from pregnant animals between gestational days 1-8 using immunocytochemistry. The uterine luminal epithelium, the glandular epithelium, and the myometrial smooth muscle cells stained strongly from gestational days 1-8 with both nidogen antibodies. At day 4 the decidual reaction areas began to appear in the stromal matrix and immunostaining of both nidogens revealed that the basement membrane of the surface epithelium was discontinuous. The differentiation of stromal cells into decidual cells was seen at gestational day 5 and both nidogens were weakly expressed in the decidualizing cells. At day 6, nidogen-2 immunoreactivity was higher in the primary decidual cells close to the embryo than nidogen-1, and during development of the decidual tissue both nidogens appeared in the endometrial stromal cells. At day 7, while expression of both nidogens declined in the primary decidual cells, their expression was markedly observed in the secondary decidual cells close to the myometrium. At day 8, expression of both nidogens was also observed to increase in the primary decidual cells. While nidogen-2 expression was seen in the parietal endoderm and primary ectoderm of the rat embryos at this developmental stage, nidogen-1 expression was only detected in the parietal endoderm. These results indicate that nidogen-1 and nidogen-2 could play important roles during embryogenesis, decidualization, and implantation in the endometrium of rat uterus.     

Natural Selection of Human Embryos: Decidualizing Endometrial Stromal Cells Serve as Sensors of Embryo Quality upon Implantation

Background

Pregnancy is widely viewed as dependent upon an intimate dialogue, mediated by locally secreted factors between a developmentally competent embryo and a receptive endometrium. Reproductive success in humans is however limited, largely because of the high prevalence of chromosomally abnormal preimplantation embryos. Moreover, the transient period of endometrial receptivity in humans uniquely coincides with differentiation of endometrial stromal cells (ESCs) into highly specialized decidual cells, which in the absence of pregnancy invariably triggers menstruation. The role of cyclic decidualization of the endometrium in the implantation process and the nature of the decidual cytokines and growth factors that mediate the crosstalk with the embryo are unknown.

Methodology/Principal Findings

We employed a human co-culture model, consisting of decidualizing ESCs and single hatched blastocysts, to identify the soluble factors involved in implantation. Over the 3-day co-culture period, approximately 75% of embryos arrested whereas the remainder showed normal development. The levels of 14 implantation factors secreted by the stromal cells were determined by multiplex immunoassay. Surprisingly, the presence of a developing embryo had no significant effect on decidual secretions, apart from a modest reduction in IL-5 levels. In contrast, arresting embryos triggered a strong response, characterized by selective inhibition of IL-1β, -6, -10, -17, -18, eotaxin, and HB-EGF secretion. Co-cultures were repeated with undifferentiated ESCs but none of the secreted cytokines were affected by the presence of a developing or arresting embryo.

Conclusions

Human ESCs become biosensors of embryo quality upon differentiation into decidual cells. In view of the high incidence of gross chromosomal errors in human preimplantation embryos, cyclic decidualization followed by menstrual shedding may represent a mechanism of natural embryo selection that limits maternal investment in developmentally impaired pregnancies.     

Distribution of laminin,vimentin and desmin in the rat uterus during initial stages of implantation

The aim of this study was to investigate the immunohistochemical distribution of laminin, vimentin and desmin during the implantation period in the rat since ECM remodelling and the expression of intermediate filaments (Ifs) is essential for successful decidualization and implantation. On day 4 of pregnancy, laminin was found in a few endometrial stromal cells (ESC), the basement membrane of the numerous endometrial blood vessels, in endometrial glands and as well as in the uterine epithelium. The localization of vimentin on day 4 of pregnancy was widespread in the ESC. However, desmin immunoreactivity was low in ESC on this day of pregnancy. On day 6 of pregnancy, laminin and vimentin were localized in the decidual area underlying luminal epithelium and around the implanting embryo. Additionally, desmin was found to be present densely in decidual cells of the anti-mesometrial region where implantation takes place. Finally, on day 8 of pregnancy, laminin was present in decidual and parietal endodermal cells, whereas vimentin was immunolocalized in primary and secondary decidual regions in the endometrium. In contrast, desmin was detected in some parts of the secondary decidual zone. In conclusion, these proteins could have crucial roles in decidualization and implantation.     

Decidualized and pre-decidualized normal endometrial stromal cells produce more O-linked N-acetylglucosamine containing epitope H than non-decidualized normal endometrial stromal cells

The epitope H contains an O-linked N-acetylglucosamine residue in a specific conformation and/or environment recognized by the monoclonal antibody H (mAbH). mAbH stains two bands with Mr x10(-3) of 209 and 62 in lysates of cultured rat astrocytes. In addition, in extracts of cultured MCF-7 breast carcinoma cell line cells it stains cytokeratin 8 and five polypeptides originating from Triton X-100-soluble (Mr x10(-3) of 232, 67 and 37) and from the Triton X-100-insoluble (Mr x10(-3) of 51 and 50) fractions, respectively. In our previous studies we used the mAbH to investigate by immunostaining the expression of the epitope H in normal human brains, human brains with a variety of lesions, astrocytic tumors, infiltrating ductal breast carcinomas, fibroadenomas, and mitochondria-rich normal, metaplastic and neoplastic cells. In order to gain further insight into the expression patterns of the epitope H in human tissues we used the mAbH to investigate the immunohistochemical expression of the epitope H in normal human endometrium, including 30 cases of proliferative endometrium, 30 cases of early secretory endometrium, 30 cases of mid secretory endometrium, 30 cases of late secretory endometrium and 30 cases of decidual tissues. The main results were the following: 1) The decidual stromal cells presented in all cases high cytoplasmic expression of the epitope H; 2) The pre-decidual stromal cells presented in all cases of late secretory endometrium significant cytoplasmic expression of the epitope H ranging from moderate to high expression; 3) The non pre-decidual stromal cells of the functional endometrial layer presented in all cases insignificant cytoplasmic expression of the epitope H ranging from null to low expression; 4) The stromal cells of the basal layer of the endometrium and decidua did not express the epitope H in any case; 5) The endometrial stromal granulocytes did not express the epitope H in any case and 6) The blood vessel wall cells (endothelial and smooth muscle) of the endometrium through the whole duration of the menstrual cycle and of the decidua presented high cytoplasmic expression of the epitope H. It is concluded that decidualized and pre-decidualized human normal endometrial stromal cells show increased expression of the O-linked N-acetylglucosamine containing epitope H compared to non-decidualized endometrial stromal cells. These findings suggest that the expression of the epitope H may be under positive progesteronic control in normal human endometrium. Further investigation of the antigens bearing the epitope H might help to gain further insight into the histophysiology and the pathology of human endometrium.