Zonula occludens-1 and E-cadherin are coordinately expressed in the mouse uterus with the initiation of implantation and decidualization

Two-way interactions between the blastocyst trophectoderm and the uterine luminal epithelium are essential for implantation. The key events of this process are cell-cell contact of trophectoderm cells with uterine luminal epithelial cells, controlled invasion of trophoblast cells through the luminal epithelium and the basement membrane, transformation of uterine stromal cells surrounding the blastocyst into decidual cells, and protection of the "semiallogenic" embryo from the mother's immunological responses. Because cell-cell contact between the trophectoderm epithelium and the luminal epithelium is essential for implantation, we investigated the expression of zonula occludens-1 (ZO-1) and E-cadherin, two molecules associated with epithelial cell junctions, in the mouse uterus during the periimplantation period. Preimplantation uterine epithelial cells express both ZO-1 and E-cadherin. With the initiation and progression of implantation, ZO-1 and E-cadherin are expressed in stromal cells of the primary decidual zone (PDZ). As trophoblast invasion progresses, these two molecules are expressed in stroma in advance of the invading trophoblast cells. These results suggest that expression of these adherence and tight junctions molecules in the PDZ serves to function as a permeability barrier to regulate access of immunologically competent maternal cells and/or molecules to the embryo and provide homotypic guidance of trophoblast cells in the endometrium.     

Antibody against single-stranded DNA detects both programmed cell death and drug-induced apoptosis

Cyclophosphamide induced fragmented nuclei in mouse thymic epithelial cells. Agarose gel electrophoresis showed the fragmentation of the DNA extracted from mouse thymus exposed to cyclophosphamide. The cell death induced by cyclophosphamide was considered to be apoptotic. Polyclonal antibody against single-stranded DNA was used immunohistochemically to detect apoptotic cell death in thymic epithelial cells. This antibody also detected programmed cell death in the interdigital necrotic zone of the mouse limb plate on day 14 of gestation, and in the ganglion of the trigeminal nerve on day 13 of gestation. These results show that the antibody specific for single-stranded DNA detected both drug-induced apoptosis and programmed cell death during embryogenesis.     

Trophectoderm surface expression of the cell adhesion molecule cell-CAM 105 on rat blastocysts

A variety of cellular interactions is involved in the process of implantation of the mammalian embryo into the uterine tissue. Recent discoveries have demonstrated that intercellular recognition and adhesive events are governed by a class of cell surface molecules known as cell adhesion molecules (CAMs). In the present report, we have investigated the occurrence of the well-characterized cell adhesion molecule cell-CAM 105 on the surface of rat pre- and peri-implantation embryos of various stages. This was carried out by indirect immunofluorescence microscopy employing affinity-purified rabbit antibodies against cell-CAM 105. The embryonal stages investigated comprised morulae, normal day-4 blastocysts, and delayed and adhesive blastocysts obtained by using the method of experimentally delayed implantation. Cell-CAM 105 was absent in the early-morula stage, but in normal day-4 blastocysts and delayed blastocysts a specific staining for cell-CAM 105 was seen on the entire surface. However, adhesive-stage blastocysts exhibited a marked polarity with staining of the polar trophoblast cells. Scanning electron microscopy of adhesive-stage blastocysts revealed that the stronger staining of the polar region was not due to a greater number of microvilli on the polar trophoblast cells. Thus, it seems as if cell-CAM 105 is lost or masked from the surface of the mural trophoblast cells of adhesive-stage rat blastocysts. Since the mural trophoblast cells are the first to adhere to the uterine luminal epithelium during the onset of implantation and subsequently invade the uterine stroma, we suggest that the apparent downregulation of cell-CAM 105 in the mural trophoblast cells might be linked to the acquisition of trophoblast invasiveness.     

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.     

Chorioallantoic placenta formation in the rat: I. Luminal epithelial cell death and extracellular matrix modifications in the mesometrial region of implantation chambers.

On days 7 and 8 of pregnancy, mesometrial regions of rat gestation sites were examined by light microscopy and transmission electron microscopy to determine what changes occur before the chorioallantoic placenta forms in that region. By day 7, gestation sites contained a uterine lumen mesometrially and an antimesometrial extension of the uterine lumen, the implantation chamber. The implantation chamber consisted of a mesometrial chamber between the uterine lumen and the conceptus, an antimesometrial chamber that contained the conceptus, and a decidual crypt antimesometrial to the conceptus. Stromal cells that formed the walls of the implantation chamber were closely packed decidual cells, while those that surrounded the uterine lumen were loosely arranged. Late on day 7, a portion of the epithelium lining the mesometrial chamber was degenerating, but this area of initial degeneration was never adjacent to the antimesometrial chamber. By early day 8, most of the epithelial cells lining the mesometrial chamber were degenerating and were being sloughed into the chamber lumen. Although degeneration of these epithelial cells morphologically resembled necrosis, it was precisely controlled, since adjacent epithelial cells lining the uterine lumen remained healthy. The space that separated the denuded luminal surface of the mesometrial chamber from underlying decidual cells became wider and was occupied by an extracellular matrix rich in cross-banded collagen fibrils. Decidual cell processes, that earlier had penetrated the basal lamina beneath healthy epithelial cells, protruded into this matrix and penetrated the basal lamina at the luminal surface. By late day 8, large areas of denuded chamber wall were covered with decidual cell processes, little remained of the basal lamina, and cross-banded collagen fibrils were scarce in the area occupied by decidual cell processes. During the times studied, uterine tissues that formed the walls of the mesometrial chamber were not in direct contact with the conceptus. This study indicates that trophoblast does not play a direct role in epithelial degeneration, basal lamina penetration, or extracellular matrix modifications in the mesometrial region of implantation chambers where part of the chorioallantoic placenta forms, although trophoblast may be required to trigger or modulate some of the changes.     

Quantification of apoptotic DNA fragmentation in a transformed uterine epithelial cell line, HRE-H9, using capillary electrophoresis with laser-induced fluorescence detector (CE-LIF)

Apoptotic cell death of uterine epithelial cells is thought to play an important role in the onset of menstruation and the successful implantation of an embryo during early pregnancy. Abnormal apoptosis in these cells can result in dysmenorrhoea and infertility. In addition, decreased rate of epithelial apoptosis likely contributes to endometriosis. A key step in the onset of apoptosis in these cells is cleavage of the genomic DNA between nucleosomes, resulting in polynucleosomal-sized fragments of DNA. The conventional technique for assessing apoptotic DNA fragmentation uses agarose (slab) gel electrophoresis (i.e. DNA laddering). However, recent technological advances in the use of capillary electrophoresis (CE), particularly the introduction of the laser-induced fluorescence detector (LIF), has made it possible to perform DNA laddering with improved automation and much greater sensitivity. In the present study, we have further developed the CE-LIF technique by using a DNA standard curve to quantify accurately the amount of DNA in the apoptotic DNA fragments and have applied this new quantitative technique to study apoptosis in a transformed uterine epithelial cell line, the HRE-H9 cells. Apoptosis was induced in the HRE-H9 cells by serum deprivation for 5, 7 and 24 h, resulting in increased DNA fragmentation of 2.2-, 3.1- and 6.2-fold, respectively, above the 0 h or plus-serum controls. This ultrasensitive CE-LIF technique provides a novel method for accurately measuring the actions of pro- or anti-apoptotic agents or conditions on uterine epithelial cell lines.     

Morphology of development in the primate: Blastocyst to villous placental stage

Examination of plastic-embedded rhesus monkey and baboon blastocysts through the implantation period has provided information on normal differentiation and development. The blastocysts show many features in common with non-primate laboratory animals, including differentiation of endoderm and its extension beyond the inner cell mass prior to implantation. However, there appears to be more cell death, and more aberrations in development. Implantation involves the adherence of trophoblast to healthy uterine luminal epithelial cells, and intrusion of syncytial trophoblast between these cells, followed by lateral expansion of the site of invasion prior to penetration of the uterine epithelial basal lamina. An amnionic cavity is formed within the inner cell mass, and is preceded by establishment of cell polarity. The definitive yolk sac is formed by an aggregation of endodermal cells adjacent to the inner cell mass. The trophoblast does not give rise to mesodermal cells, but some of these cells may be formed from endoderm prior to primitive streak formation. In both rhesus monkey and baboon, syncytial trophoblast taps the maternal vascular system relatively rapidly. In the baboon in particular large blood-filled spaces elevate the implantation site from the level of the endometrium at the stage of primary and secondary villus formation.     

Apoptosis in uterine epithelium and decidua in response to implantation: evidence for two different pathways

During the initial steps of implantation, the mouse uterine epithelium of the implantation chamber undergoes apoptosis in response to the interacting blastocyst. With progressing implantation, regression of the decidual cells allows a restricted and coordinated invasion of trophoblast cells into the maternal compartment. In order to investigate pathways of apoptosis in mouse uterine epithelium and decidua during early pregnancy (day 4.5–7.0 post coitum), we have investigated different proteins such as TNFalpha, TNF receptor1, Fas ligand, Fas receptor1, Bax and Bcl2 as well as caspase-9 and caspase-3 using immunohistochemistry. To detect cells undergoing apoptosis the Tunel assay was performed. Immunoreactivity for TNFalpha as well as for TNF receptor1 was observed exclusively in the epithelium of the implantation chamber and the adjacent luminal epithelium from day 4.5 post coitum onwards. In the developing decidua the Fas ligand, but not the Fas receptor, was expressed. Bax and Bcl2 revealed a complementary expression pattern with Bax in the primary and Bcl2 in the adjacent decidual zone. Strong immunolabelling for the initiator caspase-9 was restricted to the decidual compartment, whereas caspase-3 expression characterized the apoptotic uterine epithelium. Only some caspase-3 positive decidual cells were found around the embryo which correlated to the pattern of Tunel staining. Taken together, the apoptotic degeneration of the uterine epithelium seems to be mediated by TNF receptor1 followed by caspase-3, whereas the very moderate regression of the decidua did not show the investigated death receptor, but Bax and Blc2 instead and in addition caspase-9, which indicates a different regulation for epithelial versus decidual apoptosis.     

Blastocyst implantation in the Chinese hamster (Cricetulus griseus)

Embryonic development of the Chinese hamster (Cricetulus griseus) was studied from the onset of implantation to the formation of the parietal yolk sac placenta. Implantation began on day 6 of pregnancy, when the embryo became fixed to the uterine luminal epithelium. At this time there was no zona pellucida, and microvilli of the trophoblast and uterine epithelium were closely apposed. Stromal cells immediately adjacent to the implantation chamber began to enlarge and accumulate glycogen. By day 7 the mural trophoblast penetrated the luminal epithelium in discrete area. The trophoblast appeared to phagocytize uterine epithelial cells, although epithelium adjoining the points of penetration was normal. In other areas nascent apical protrusions from the uterine epithelium indented the surface of the trophoblast. The epiblast had enlarged and both visceral and parietal endoderm cells were present. The well-developed decidual cells were epithelioid and completely surrounded the implantation chamber. On day 8 the uterine epithelium had disappeared along the mural surface of the embryo. The embryonic cell mass was elongated and filled the yolk sac cavity. Reichert's membrane was well developed. The uterine epithelial basal lamina was largely disrupted, and the trophoblast was in direct contact with decidual cells. Primary and secondary giant trophoblast cells were present and in contact with extravasated maternal blood. The mural trophoblast formed channels in which blood cells were found in close proximity to Reichert's membrane. Decidual cells were in contact with capillary epithelium and in some cases formed part of the vessel wall. Structural changes occurring in the embryo and endometrium during implantation in the Chinese hamster are described for the first time in this report and are compared to those described for some other myomorph rodents.     

Gestation stage-dependent intrauterine trophoblast cell invasion in the rat and mouse: novel endocrine phenotype and regulation

Trophoblast cell invasion into the uterine wall is characteristic of hemochorial placentation. In this report, we examine trophoblast cell invasion in the rat and mouse, the endocrine phenotype of invasive trophoblast cells, and aspects of the regulation of trophoblast cell invasion. In the rat, trophoblast cells exhibit extensive interstitial and endovascular invasion. Trophoblast cells penetrate through the decidua and well into the metrial gland, where they form intimate associations with the vasculature. Trophoblast cell invasion in the mouse is primarily interstitial and is restricted to the mesometrial decidua. Both interstitial and endovascular rat trophoblast cells synthesize a unique set of prolactin (PRL)-like hormones/cytokines, PRL-like protein-A (PLP-A), PLP-L, and PLP-M. Invading mouse trophoblast cells also possess endocrine activities, including the expression of PLP-M and PLP-N. The trafficking of natural killer (NK) cells and trophoblast cells within the mesometrial uterus is reciprocal in both the rat and mouse. As NK cells disappear from the mesometrial compartment, a subpopulation of trophoblast cells exit the chorioallantoic placenta and enter the decidua. Furthermore, the onset of interstitial trophoblast cell invasion is accelerated in mice with a genetic deficiency of NK cells, Tg epsilon 26 mice, implicating a possible regulatory role of NK cells in trophoblast cell invasion. Additionally, the NK cell product, interferon-gamma (IFNgamma), inhibits trophoblast cell outgrowth, and trophoblast cell invasion is accelerated in mice with a genetic deficiency in the IFNgamma or the IFNgamma receptor. In summary, trophoblast cells invade the uterine wall during the last week of gestation in the rat and mouse and possess a unique endocrine phenotype, and factors present in the uterine mesometrial compartment modulate their invasive behavior.     

Apoptotic and non-apoptotic cell death in hormone-dependent glands

The proliferation of cells and cell death are involved in the maintenance of appropriate tissue homeostasis. In the present study, two different mechanisms of cell death were identified in the prostate and pituitary glands when morphological data, fragmentation of DNA, and TUNEL labelling of apoptotic nuclei were compared. Typical cell death by apoptosis was identified by morphological and molecular approaches in the prostate after orchidectomy. By contrast, neither DNA fragmentation nor TUNEL labelling were found in dead cells occurring in the pituitary gland after interruption of lactation. Regressing lactotrophs were characterised by condensation and disruption of the cytoplasmic matrix, but preserved intact nuclei until advanced stages of regression. Degenerating “dark” cells comparable to those described in the pituitary were also seen coexisting with typical apoptosis in the prostate epithelial lining of orchidectomised rats. Both forms of cell death could be clearly differentiated, because dark cells suffer severe alterations of cytoplasmic organelles while maintaining the integrity of the nucleus. In contrast, apoptotic cells present well-preserved cytoplasmic organelles, but grossly disrupted nuclei with fragmentation and condensation of chromatin.     

Progesterone-modulated induction of apoptosis by interferon-tau in cultured epithelial cells of bovine endometrium

Interferon-tau (IFN-tau) is produced by the trophoblast prior to implantation in ruminants. It is involved in maternal recognition of pregnancy, and is a pleiotropic molecule that can alter the synthesis of endometrial proteins and inhibit proliferation of some cells. We have observed that IFN-tau reduces the DNA content in cultures of bovine endometrial epithelial cells; therefore, the objective of this study was to determine whether IFN-tau would induce apoptosis in bovine endometrial cells. Epithelial cells were prepared, cultured to confluence, and then incubated for 24 or 48 h in the presence or absence of 10 ng/ml progesterone, 100 ng/ml IFN-tau, or 10 microg/ml cycloheximide (CHX; an apoptosis inducer used as a positive control). Cells undergoing apoptosis exhibit such characteristics as the appearance of apoptotic bodies and DNA fragmentation. The incidence of apoptosis was assessed by using TUNEL, DNA fragmentation analysis, and Western blot analysis of Bax-alpha protein expression. The results showed that IFN-tau and CHX significantly increased the percentage of cells with apoptotic nuclei (33.6% and 44.8%, respectively) compared with controls (11.7%; P < 0.05). Progesterone treatment of the cells significantly inhibited the ability of IFN-tau to induce apoptosis (14.6%) compared with IFN-tau alone (33.6%; P < 0.05). DNA fragmentation analysis showed that INF-tau and CHX treatment resulted in an increase in the appearance of DNA laddering compared with that in untreated control cultures. Western blot analysis showed that IFN-tau and CHX treatment resulted in a greater expression of the proapoptotic protein Bax-alpha compared with that in control cultures. These data demonstrate that IFN-tau can induce apoptosis in bovine uterine epithelial cells and that this effect is modulated by progesterone. We speculate that IFN-tau might play a critical role in the remodeling of the endometrium around the time of implantation.     

Trophoblast giant-cell differentiation involves changes in cytoskeleton and cell motility

Trophoblast giant-cell differentiation is well-characterized at the molecular level, yet very little is known about how molecular changes affect the cellular functions of trophoblast in embryo implantation. We have found, using both explanted E7.5 mouse embryo ectoplacental cone and the rat choriocarcinoma (Rcho-1) cell line, that trophoblast differentiation is distinguished by dramatic changes in cytoarchitecture and cell behavior. Undifferentiated trophoblast cells contain little organized actin and few small, peripheral focal complexes and exhibit high membrane protrusive activity, while differentiated trophoblast giant cells contain prominent stress fibers, large internal as well as peripheral focal adhesions, and become immotile. The dramatic changes in cell behavior and cytoskeletal organization of giant cells correlate with changes in the activities of the Rho family of small GTPases and a decrease in tyrosine phosphorylation of focal adhesion kinase. Together, these data provide detailed insight into the cellular properties of trophoblast giant cells and suggest that giant-cell differentiation is characterized by a transition from a motile to a specialized epithelial phenotype. Furthermore, our data support a phagocytic erosion, rather than a migratory infiltration, mechanism for trophoblast giant-cell invasion of the uterine stroma.     

Caspase inhibition in apoptotic T cells triggers necrotic cell death depending on the cell type and the proapoptotic stimulus

CD95 (Fas/Apo-1) triggers apoptotic cell death via a caspase-dependent pathway. Inhibition of caspase activation blocks proapoptotic signaling and thus, prevents execution of apoptosis. Besides induction of apoptotic cell death, CD95 has been reported to trigger necrotic cell death in susceptible cells. In this study, we investigated the interplay between apoptotic and necrotic cell death signaling in T cells. Using the agonistic CD95 antibody, 7C11, we found that caspase inhibition mediated by the pancaspase inhibitor, zVAD-fmk, prevented CD95-triggered cell death in Jurkat T cells but not in A3.01 T cells, although typical hallmarks of apoptosis, such as DNA fragmentation or caspase activation were blocked. Moreover, the caspase-independent cell death in A3.01 cells exhibited typical signs of necrosis as detected by a rapid loss of cell membrane integrity and could be prevented by treatment with the radical scavenger butylated hydroxyanisole (BHA). Similar to CD95-induced cell death, apoptosis triggered by the DNA topoisomerase inhibitors, camptothecin or etoposide was shifted to necrosis when capsase activation was inhibited. In contrast to this, ZVAD was fully protective when apoptosis was triggered by the serpase inhibitor, Nalpha-tosyl-phenyl-chloromethyl ketone (TPCK). TPCK was not protective when administered to anti-CD95/ZVAD-treated A3.01 cells, indicating that TPCK does not possess anti-necrotic activity but fails to activate the necrotic death pathway. Our findings show (a) that caspase inhibition does not always protect apoptotic T cells from dying but merely activates a caspase-independent mode of cell death that results in necrosis and (b) that the caspase-inhibitor-induced shift from apoptotic to necrotic cell death is dependent on the cell type and the proapoptotic stimulus.     

Recognition-dependent signaling events in response to apoptotic targets inhibit epithelial cell viability by multiple mechanisms: implications for non-immune tissue homeostasis

Apoptosis allows for the removal of damaged, aged, and/or excess cells without harm to surrounding tissue. To accomplish this, cells undergoing apoptosis acquire new activities that enable them to modulate the fate and function of nearby cells. We have shown that receptor-mediated recognition of apoptotic versus necrotic target cells by viable kidney proximal tubular epithelial cells (PTEC) modulates the activity of several signaling pathways critically involved in regulation of proliferation and survival. Generally, apoptotic and necrotic targets have opposite effects with apoptotic targets inhibiting and necrotic targets stimulating the activity of these pathways. Here we explore the consequences of these signaling differences. We show that recognition of apoptotic targets induces a profound decrease in PTEC viability through increased responder cell death and decreased proliferation. In contrast, necrotic targets promote viability through decreased death and increased proliferation. Both target types mediate their effects through a network of Akt-dependent and -independent events. Apoptotic targets modulate Akt-dependent viability in part through a reduction in cellular β-catenin and decreased inactivation of Bad. In contrast, Akt-independent modulation of viability occurs through activation of caspase-8, suggesting that death receptor-dependent pathways are involved. Apoptotic targets also activate p38, which partially protects responders from target-induced death. The response of epithelial cells varies depending on their tissue origin. Some cell lines, like PTEC, demonstrate decreased viability, whereas others (e.g. breast-derived) show increased viability. By acting as sentinels of environmental change, apoptotic targets allow neighboring cells, especially non-migratory epithelial cells, to monitor and potentially adapt to local stresses.     

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.     

RELT induces cellular death in HEK 293 epithelial cells

RELT is a recently identified Tumor Necrosis Factor Receptor that possess two homologues in humans named RELL1 and RELL2. We investigated whether RELT and its homologues could induce cellular death when transiently transfected into HEK 293 epithelial cells. Transfection of RELT family members into HEK 293 epithelial cells induced cell death characterized by rounding and lifting of cells accompanied by DNA fragmentation, characteristics that are consistent with the activation of an apoptotic pathway. Overexpression of RELT in COS-7 cells resulted in cell rounding and lifting without DNA fragmentation, suggesting that the effects of RELT signaling may vary among different cell types. In summary, we report that overexpression of RELT or its homologues RELL1 and RELL2 in HEK 293 epithelial cells results in cell death with morphological characteristics consistent with the activation of an apoptotic pathway.     

纤粘连蛋白对小鼠胚胎体外发育和体外着床的作用

应用小鼠胚泡和外胎盘锥体外培养的方法,研究了纤粘连蛋白对小鼠胚泡发育及胚泡或外胎盘锥粘附和扩展的影响。结果显示,纤粘连蛋白对小鼠胚泡发育有一定的促进作用;对胚泡及外胎盘锥的粘附和胚泡初生滋养层细胞及外胎盘锥次生滋养层细胞扩展均有显著促进作用。纤粘连蛋白分子活性位点的合成肽段精－苷－天冬－丝氨酸可有效抑制纤粘连蛋白对胚泡或外胎盘锥发育、粘附和扩展的促进作用。结果表明,纤粘连蛋白在小鼠胚胎发育和着床过     

Adhesion of trophoblast to uterine epithelium as related to the state of trophoblast differentiation: in vitro studies using cell lines

At the initial phase of embryo implantation, the trophoblast must have acquired competence for adhesion to the uterine epithelium, a condition whose cell biological basis is far from understood. In the present study, trophoblast-type cells (BeWo, JAr, and Jeg-3 choriocarcinoma cell lines) were treated with retinoic acid, methotrexate, dibutyryl-cAMP, or phorbol-12-myristate-13-acetate in order to modulate their ability to adhere to uterine epithelial cells (RL95-2). In an established model, multicellular spheroids of choriocarcinoma cells were transferred onto the surface of monolayer cultures of RL95-2 cells followed by a centrifugal force-based adhesion assay. In controls, about 45% of BeWo and JAr cell spheroids and 75% of Jeg-3 spheroids adhered to uterine monolayers within 30 min. Pretreatment of spheroids with either of the agents stimulated differentiation as indicated by the rate of chorionic gonadotropin secretion, but consistently reduced the adhesion to the endometrial monolayer in all three choriocarcinoma cell lines. While previous investigations had shown that invasiveness of trophoblast cells (into extracellular matrix) does not seem to be linked to the differentiation program in a simple manner, the present data suggest that such an (inverse) link may indeed exist with respect to the ability to initiate an adhesive interaction with the uterine epithelium. These observations support the view that epithelial cell interactions as typical for the initial phase of embryo implantation are regulated in a way that is clearly different from cell-matrix interactions governing later phases of trophoblast invasion into the endometrial stroma.     

IL-1 system in apoptosis of murine hippocampal neurons of dentate gyrus induced by trimethyltin administration

Growing evidence suggests that two modes of cell death, known as apoptosis and necrosis, are involved in postanoxic injury. The current opinion on these two types of cell death is that apoptosis and necrosis are not always the uniform and distinct events. The aim of this study was to determine ultrastructural criteria of postanoxic neuronal changes in model of anoxia in vitro . The organotypic cultures of rat hippocampus exposed to 10- and 20-min of anoxic insult revealed the morphological features classic for both necrotic and apoptotic neuronal cell injury. Some neurones exhibited the typical necrotic lysis whereas others clearly reflected an active apoptotic form of cell death consisting of nuclear condensation with early preservation of cell membranes. However, numerous damaged cells shared both apoptotic and necrotic ultrastructural characteristics. These results evidenced the morphological continuum between apoptosis and necrosis under anoxia in vitro .