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Apoptosis as the Mode of Uterine Epithelial Cell Deathduring Embryo Implantation in Mice and Rats
Abstract
An ultrastructural study of mouse and rat embryo implantation sites was undertaken to determine whether the uterine luminal epithelial cells surrounding the blastocyst exhibited the morphologic characteristics of apoptotic or necrotic cell death. In both species the epithelial cells exhibited all of the characteristics of apoptosis, including surface blebbing, shrinkage and fragmentation of the cells, condensation of chromatin, and indentation and fragmentation of nuclei. Cytoplasmic organelles remained morphologically intact, and the cytoplasm maintained normal or increased staining density. Also, the epithelial cells and cell fragments were phagocytosed by the adjacent trophoblast cells. The epithelial cells did not exhibit the characteristics of necrotic cell death, such as swollen cells and mitochondria, damaged surface membranes, and disintegrated cytoplasmic organelles. We conclude that uterine epithelial cells surrounding mouse and rat embryos during implantation undergo apoptotic cell death leading to their phagocytosis by trophoblast cells.
... Apoptosis, or the highly orchestrated form of programmed cell death in which cells neatly commit suicide without triggering an inflammatory response in the tissue, is becoming a relevant event in the study of reproductive physiology [1]. Programmed cell death has been implicated in gonadal function [2], human endometrial physiology [3], preimplantation embryo development [4], embryonic implantation [5], and placenta formation [6]. ...
... Several lines of evidence suggest that in addition to vital functions in maintaining homeostasis of the endometrium, locally regulated apoptosis is important during tissue remodeling in decidualization [13] and blastocyst implantation in animals [5,14,15,16]. Embryonic implantation consists of three related and consecutive phases: apposition, adhesion between trophoectoderm and endometrial epithelium, and invasion. During invasion, the embryonic trophoblast penetrates the endometrial epithelium, destroys the basal membrane, and introduces itself into the stroma (invading up to the uterine vessels). ...
... During invasion, the embryonic trophoblast penetrates the endometrial epithelium, destroys the basal membrane, and introduces itself into the stroma (invading up to the uterine vessels). In rodents, ultrastructural studies have demonstrated that uterine epithelial cells in the attachment site undergo apoptotic changes [5]. Recently, biochemical evidence of apoptosis and quantitative assessment of DNA fragmentation in the uterine epithelial cells of a mouse implantation model have been demonstrated. ...
The implanting blastocyst must appose and adhere to the endometrial epithelium and, subsequently, invade it. Locally regulated uterine epithelial apoptosis induced by the embryo is a crucial step of the epithelial invasion in rodents. To address the physiological relevance of this process in humans, we investigated the effect of single human blastocysts on the regulation of apoptosis in cultured human endometrial epithelial cells (hEEC) in both apposition and adhesion phases of implantation. Here, we report a co-ordinated embryonic regulation of hEEC apoptosis. In the apposition phase, the presence of a blastocyst rescues hEEC from the apoptotic pathway. However, when the human blastocyst adheres to the hEEC monolayer, it induces a paracrine apoptotic reaction. Fas ligand (Fas-L) was present at the embryonic trophoectoderm. Fas was localized at the apical cell surface of hEEC, and flow cytometry revealed that 60% of hEEC express Fas. Neutralizing adhesion assays revealed that the Fas/Fas-L death system may be an important mechanism to cross the epithelial barrier, which is crucial for embryonic adhesion, and the manipulation of this system could have potential clinical implications as an interceptive mechanism.
... The most likely source of cell free DNA is found in embryonic cells undergoing apoptosis. Programmed cell death occurs even at the preimplantation stage of development [10], as well as at the beginning of implantation [11] and during placenta creation [12]. However, it is yet not fully clear why and which cells undergo apoptosis. ...
... One of them may be of special interest for the cytogenetics of embryo development. The point is that the analysis of the first polar body showed an increased copy number for chromosomes 4,5,6,7,9,11,12,15,19,20, and X and a decreased copy num ber for chromosomes 1, 2, 3, 8, 10, 13, 14, 16, and 18, i.e., almost all chromosomes, except 17, 21, and 22, were involved in aneuploidy. Surprisingly, the analysis of the second polar body revealed reciprocal aneup loidies, namely an increased copy number for chro mosomes 1, 2, 3, 8, 10, 13, 14, 16, and 18 and a decreased copy number for chromosomes 4,5,6,7,9,11,12,15,19,20, and X. ...
... The point is that the analysis of the first polar body showed an increased copy number for chromosomes 4,5,6,7,9,11,12,15,19,20, and X and a decreased copy num ber for chromosomes 1, 2, 3, 8, 10, 13, 14, 16, and 18, i.e., almost all chromosomes, except 17, 21, and 22, were involved in aneuploidy. Surprisingly, the analysis of the second polar body revealed reciprocal aneup loidies, namely an increased copy number for chro mosomes 1, 2, 3, 8, 10, 13, 14, 16, and 18 and a decreased copy number for chromosomes 4,5,6,7,9,11,12,15,19,20, and X. It is probable that due to two consecutive chromosome segregation errors in the first and second meiotic divisions, normalization of the chromosomal set occurred in the oocyte, and the kary otype determined during DNA analysis on the blasto cyst fluid and trophectoderm cells appeared to be eup loid. ...
The discovery of cell-free DNA in blastocoele fluid opens new perspectives for the development of preimplantation genetic diagnosis of human chromosomal and genetic diseases. In this review we analyzed the results of the first studies, which made it possible to evaluate the effectiveness of the application of a new source of biological material and showed a high degree of agreement between the results of molecular karyotyping with cell-free DNA and blastocyst cells. The results suggest the possibility of developing a noninvasive method of preimplantation genetic diagnosis, which may open a new round of progress in the field of assisted reproductive technologies and the genetics of early stages of human ontogenesis.
... Loss of apical-basal polarity by epithelial cells is usually associated with epithelial-mesenchymal transition (EMT) to gain migratory capacity, such as during physiological development and pathological cancer metastasis. Although LE cells at the embryo entry site in mice and rats are eventually phagocytosed by trophoblasts [58], the LE cells remain as epithelial cells before embryo penetration through the LE layer, as indicated by the strong E-cadherin staining throughout early pregnancy ( Figure 1N). The LE cells also retain their structural polarity, as evidenced by deeper and more geometrically complex tight junctions on the apical side, but weakened interepithelial physical interactions on the rest of the lateral plasma membrane [34], as well as functional polarity, as evidenced by differential apical-to-basolateral and basolateral-to-apical intracellular vesicle trafficking in the LE during embryo implantation in mice and rats ( Figure 2) [49,89]. ...
... At around D4 20 h in mice ($D5 9 h in rats), LE cells surrounding the blastocyst are phagocytosed by protrusions of invading trophoblasts, with [8,33,58] or without [80] evidence of apoptosis. Disassembly of adhesive complexes, which might be an indication of LE apoptosis, in the LE cells at the trophoblast entry site is required for trophoblast invasion through LE [81]. ...
The uterine luminal epithelium (LE) is the first maternal contact for an implanting embryo. Intrauterine fluid resorption, cessation of LE proliferation and apoptosis, and LE structural changes are prerequisites for establishing transient uterine receptivity for embryo implantation. Vesicle trafficking in the LE and receptor-mediated paracrine and autocrine mechanisms are crucial both for LE preparation and LE communications with the embryo and stroma during the initiation of embryo implantation. This review mainly covers recent in vivo studies in LE of mouse models from 0.5 days post-coitus (D0.5) to ∼D4 20 h when the trophoblasts pass through the LE layer for embryo implantation. The review is organized into three interconnected sections: preimplantation LE preparation for embryo attachment, embryo-LE communications, and LE-stroma communications.
... In mice, the uterine LE cells are eliminated during implantation [14]. Based on EM studies, it is hypothesized that degeneration of LE cells is intrinsic to the uterus and embryos play a minor role [15,16], whereas another hypothesis proposed that trophoblast cells trigger apoptosis of LE cells [17]. Regardless of the mechanism involved, most studies found that uterine LE cells adjacent to the blastocyst exhibit characteristics of apoptosis, including cellular shrinkage and nuclear fragmentation, following attachment of blastocysts for implantation and that the apoptotic LE cells are phagocytized by trophoblast cells [17][18][19]. ...
... Based on EM studies, it is hypothesized that degeneration of LE cells is intrinsic to the uterus and embryos play a minor role [15,16], whereas another hypothesis proposed that trophoblast cells trigger apoptosis of LE cells [17]. Regardless of the mechanism involved, most studies found that uterine LE cells adjacent to the blastocyst exhibit characteristics of apoptosis, including cellular shrinkage and nuclear fragmentation, following attachment of blastocysts for implantation and that the apoptotic LE cells are phagocytized by trophoblast cells [17][18][19]. Our data show that LE cells express caspase 3, an executor in the apoptosis cascade, during syncytialization. ...
During the peri-implantation period, multinucleated syncytia are formed in the sheep placenta. For over 20 years the scientific consensus has been that during trophoblast syncytialization in sheep, binucleate trophoblast giant cells (BNCs) differentiate from mononuclear trophoblast cells, and individual BNCs fuse with individual luminal epithelial (LE) cells to form trinucleate cells. These trophoblast–LE syncytial plaques then grow through continued BNC migration and fusion. Therefore, LE cells are thought to be incorporated into syncytial plaques. However, these ideas were based on electron microscopy studies, without benefit of molecular markers for BNC and LE cells to support conclusions. The aim of this study was to observe interactions between BNCs and uterine LE cells using immunohistochemical localization for molecular markers for BNCs and uterine LE cells. We performed immunofluorescence staining, laser capture microdissection, and TUNEL staining on the uterine–placental tissues of sheep during early placentation. We observed: (1) syncytial cells containing more than two nuclei within the trophoblast cell layer; (2) depolarized LE cells that express caspase 3 and stain positively for TUNEL; (3) engulfment of caspase 3-positive LE cells by trophoblast giant cells (TGCs) and empty spaces within the LE layer at sites of implantation; (4) rapid enlargement of syncytial plaques; and (5) E-cadherin and TUNEL-positive cells within the uterine stroma underlying degenerating LE was coincident with accumulation of CD45-positive cells at these sites. These data suggest that during early placentation: (1) fusion between trophoblasts is not limited to the formation of BNCs, and the term ‘trophoblast giant cell (TGC)’ may be appropriate; (2) LE cells undergo apoptosis; (3) apoptotic LE cells are eliminated by TGCs; (4) fusion is not limited to the incorporation of new BNCs but involves the lateral fusion between growing syncytial plaques; and (5) TGCs carry apoptotic LE cells away from the uterine–placental interface for elimination by immune cells within the stroma. These data indicate that uterine LE cells are not incorporated into syncytial plaques, but are engulfed and eliminated, and that early placentation in sheep is more similar to early placentation in humans than is currently understood in that both develop mononucleated cytotrophoblast and multinucleated syncytiotrophoblast layers of entirely placental origin. The elimination of LE cells by sheep TGCs might provide insights into elimination and penetration of LE cells during human embryo implantation.
... The six-membered amino acid ring structure (amino acid [16][17][18][19][20][21] connected by one disulfide bond (between Cys16 and Cys21) was initiated to be responsible for the vasodilator activity in human (h) AM [11,12]. Champion et al. [12] demonstrated that hAM (15)(16)(17)(18)(19)(20)(21)(22) possessed vasodepressor activity analogous to that of hAM in the systemic arterial pressure of the rat. However, hAM lacked vasodepressor activity when injected intravenously in doses up to 300 nmol/kg [12,13]. ...
... Early pregnancy in rodents is characterized by a progressive interaction between the embryo and the maternal compartment. Rodent uterine epithelium around the embryo undergoes apoptosis in response to the presence of the blastocyst [15][16][17]. The blastocyst signals that induce the apoptotic cascade, as well as the genes that regulate this local event, are still unknown. ...
Objective: Adrenomedullin (ADM) is a currently exposed hypotensive peptide that is articulated in a variety of cell and tissue types. The existence of ADM has been immunohistochemically demonstrated in pathologic uterioimplantation regions, but no systematic study of ADM expression in early pregnancy in uterioimplantation region has been reported.Methods: Rats on the gestational day 2 were implanted subcutaneously with osmotic (Alzet) minipumps delivering 125 and 250 μg rat/day/of AM22–52 and were killed on the gestational day 9. We have ascertained the hypothesis that ADM, a multiregulatory ubiquitous peptide hormone, works as a trophoblast pro-invasion factor.Results: We confirmed ADM significance in in vitro assay using ACH-3P cell line, which is first-trimester trophoblast cell line.Conclusion: Our data support the conception that ADM is involved in the human implantation process through regulating trophoblast proliferation and differentiation.
... Death of uterine epithelial cells during implantation. At the site of implantation, uterine epithelial cells die and are internalized by embryonic trophoblast cells 101 (Figure 4b). These dying epithelial cells in normal development exhibit compacted chromatin, but also swollen organelles and irregular nuclear envelopes 101,102 (Figure 1p). ...
... At the site of implantation, uterine epithelial cells die and are internalized by embryonic trophoblast cells 101 (Figure 4b). These dying epithelial cells in normal development exhibit compacted chromatin, but also swollen organelles and irregular nuclear envelopes 101,102 (Figure 1p). One study reported activated Caspase-3 in TUNEL-positive dying cells in wild-type hamster and mouse uterine epithelial cells at the site of implantation. ...
Programmed cell death (PCD) is an important process in the development of multicellular organisms. Apoptosis, a form of PCD characterized morphologically by chromatin condensation, membrane blebbing, and cytoplasm compaction, and molecularly by the activation of caspase proteases, has been extensively investigated. Studies in Caenorhabditis elegans, Drosophila, mice, and the developing chick have revealed, however, that developmental PCD also occurs through other mechanisms, morphologically and molecularly distinct from apoptosis. Some non-apoptotic PCD pathways, including those regulating germ cell death in Drosophila, still appear to employ caspases. However, another prominent cell death program, linker cell-type death (LCD), is morphologically conserved, and independent of the key genes that drive apoptosis, functioning, at least in part, through the ubiquitin proteasome system. These non-apoptotic processes may serve as backup programs when caspases are inactivated or unavailable, or, more likely, as freestanding cell culling programs. Non-apoptotic PCD has been documented extensively in the developing nervous system, and during the formation of germline and somatic gonadal structures, suggesting that preservation of these mechanisms is likely under strong selective pressure. Here, we discuss our current understanding of non-apoptotic PCD in animal development, and explore possible roles for LCD and other non-apoptotic developmental pathways in vertebrates. We raise the possibility that during vertebrate development, apoptosis may not be the major PCD mechanism.
... Apoptosis plays a crucial role in the process of embryo implantation. At the site of embryo implantation, endometrial epithelial cells exhibit distinct morphological characteristics of apoptosis [20][21][22]. Evidence suggests that TGF-β may trigger apoptosis by interacting with the PI3K/Akt survival pathway and decreasing the expression of XIAP (X-linked inhibitor of the apoptosis protein) [23]. ...
Transforming growth factor beta (TGF-β), a multifunctional cytokine, is one of the most important inflammatory cytokines closely related to pregnancy. It plays significant roles in hormone secretion, placental development, and embryonic growth during pregnancy. TGF-β is implicated in embryo implantation and inhibits the invasion of extraepithelial trophoblast cells. It also moderates the mother-fetus interaction by adjusting the secretion pattern of immunomodulatory factors in the placenta, consequently influencing the mother’s immune cells. The TGF-β family regulates the development of the nervous, respiratory, and cardiovascular systems by regulating gene expression. Furthermore, TGF-β has been associated with various pregnancy complications. An increase in TGF-β levels can induce the occurrences of pre-eclampsia and gestational diabetes mellitus, while a decrease can lead to recurrent miscarriage due to the interference of the immune tolerance environment. This review focuses on the role of TGF-β in embryo implantation and development, providing new insights for the clinical prevention and treatment of pregnancy complications.
... morphogenetic protein-7 (BMP7), a transforming growth factor-β (TGF-β) also known as osteogenic protein-1, near to the implantation site, in the decidua [36]. Another possible hypothesis is the presence of dystrophic calcification, a physiological mechanism by which extracellular calcium combines with phosphate resulting in the formation of hydroxyapatite crystals during apoptosis and tissue perforation caused by trophoblast invasion into phagocyte epithelial and decidual cells [37,38]. Gross external morphology, visceral morphology, and skeletal evaluations are the key fetal developmental endpoints that were investigated to determine the effect of E. schimperi [16,19]. ...
Introduction:
Embelia schimperi Vatke (family Myrsinaceae) is a commonly consumed anthelminthic plant in Ethiopia. The plant has significant efficacy in treating intestinal worms. However, there are limited data about the safety/toxicity of the plant. Moreover, the teratogenic effect of the plant is not yet well studied despite significant number of Ethiopian mothers consuming herbal medication during their pregnancy.
Purpose:
This study aimed to evaluate the teratogenic effect of the hydroalcoholic extract of E. schimperi fruit on rat embryos and fetuses.
Methods:
Pregnant albino Wistar rats were treated with 80% hydroalcoholic fruit extract of E. schimperi at 250 mg/kg, 500 mg/kg, and 1000 mg/kg dosage, whilst the controls were pair-fed and ad libitum groups. Maternal food intake, maternal weight gain, number of implantations, number of prior resorptions, fetal viability, fetal weight, fetal and embryonic crown-ramp length, placental weight, placental gross morphology and histopathology of placental tissue, number of somites, embryonic system, gross/visceral morphological malformations, and ossification centers were evaluated as teratogenicity indices.
Results:
The crude extract of E. schimperi did not exhibit a significant difference in most developmental indices including the development of a circulatory system, nervous system, and musculoskeletal systems among treated animals and the controls. However, histopathological evaluation of placentas from the treatment groups showed that inflammatory reactions and calcifications compared to the pair-fed and ad libitum controls.
Conclusion:
Administration of the 80% hydroalcoholic extract of E. schimperi fruit during the period of organogenesis in rats did not show a significant toxic effect on embryonic and fetal developmental indices. However, it might affect the structural integrity of the placenta as it is evidenced by inflammatory reactions and calcifications of decidua basalis of rat placenta.
... It remains unclear whether similar luminal epithelium-syncytium fusions occur in primates [164] or if the maternal nuclei are broken down [165]. In mouse, the entire luminal epithelium undergoes apoptosis after implantation, including regions away from the implantation site [166,167]. By contrast to mouse, primates sustain a distinct layer of cells lining the uterine cavity [38,50,57]. ...
Implantation of the conceptus into the uterus is absolutely essential for successful embryo development. In humans, our understanding of this process has remained rudimentary owing to the inaccessibility of early implantation stages. Non-human primates recapitulate many aspects of human embryo development and provide crucial insights into trophoblast development, uterine receptivity and embryo invasion. Moreover, primate species exhibit a variety of implantation strategies and differ in embryo invasion depths. This review examines conservation and divergence of the key processes required for embryo implantation in different primates and in comparison with the canonical rodent model. We discuss trophectoderm compartmentalization, endometrial remodelling and embryo adhesion and invasion. Finally, we propose that studying the mechanism controlling invasion depth between different primate species may provide new insights and treatment strategies for placentation disorders in humans.
This article is part of the theme issue ‘Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom’.
... Since these processes are initiated from the mTE, the acquisition of adhesion and migration ability in the mTE is critical for the implantation progression (Sutherland, 2003). Some characteristic changes of the mTE which allow it to adhere to and invade the endometrium have already been identified, such as the activation of integrin signaling, the phagocytosis-like mechanism and the vascular-like gene expression patterns (El-Shershaby and Hinchliffe, 1975;Parr et al., 1987;Armant, 2005;Chaen et al., 2012;Li et al., 2015;Govindasamy et al., 2021). However, the overall picture and time-course of the characteristic changes of the mTE, and their regulatory mechanisms remain largely unclear. ...
Implantation of the blastocyst into the uterus is a specific and essential process for mammalian embryonic development. In mice, implantation is initiated from the mural trophectoderm of the blastocyst and the mTE controls implantation progression by acquiring the ability to attach and invade into the endometrium while differentiating into primary trophoblast giant cells. Nevertheless, it remains largely unclear when and how the mTE differentiates and acquires this ability during implantation. Here, by RNA sequencing analysis with the pre- and peri-implantation mTE, we show that the mTE undergoes stage-specific and dynamic changes of gene expression during implantation. We also reveal that the mTE begins down-regulating Cdx2 and up-regulating differentiation marker genes during the peri-implantation stage. In addition, using trophectoderm (TE) -specific lentiviral vector-mediated gene transduction, we demonstrate that TE-specific Cdx2 overexpression represses differentiation of the mTE into the primary trophoblast giant cells. Moreover, we reveal that TE-specific Cdx2 overexpression also represses the up-regulation of cell adhesion- and migration-related genes, including Slc6a14, Slc16a3, Itga7, Itgav and Itgb3, which are known to regulate migration of trophectoderm cells. In particular, the expression of Itgb3, an integrin subunit gene, exhibits high inverse correlation with that of Cdx2 in the TE. Reflecting the down-regulation of the genes for TE migration, TE-specific Cdx2 overexpression causes suppression of the blastocyst outgrowth in vitro and abnormal progression of implantation in vivo. Thus, our results specify the time-course changes of global gene expression in the mTE during implantation and uncover the significance of Cdx2 down-regulation for implantation progression.
... Results of our present study showed localization of KLF5 in the luminal epithelium and glandular epithelium suggests its role in embryo attachment and glandular secretion. With the progression of gestation, the lateral luminal epithelium surrounding the blastocyst undergoes apoptosis or entosis by the trophectodermal cell to accommodate the embryo in the stromal compartment [6,31]. In conditionally ablated Klf5 mice uterus, the luminal epithelium remains intact at this particular time leading to implantation failure [15]. ...
Background
Embryo implantation is a tightly regulated sequence of events regulated by ovarian steroids, estrogen and progesterone, and their downstream targets. Ovarian steroids regulate most of the genes involved in embryo implantation and pregnancy. However, some factors are not regulated by ovarian steroids, estrogen, progesterone, or both. Kruppel-like factor 5 (Klf5) is an example of an ovarian steroid–independent factor having a role in cellular proliferation, differentiation. The detailed expression profile of Klf5 during uterine receptivity and periimplantation has not been studied till now. In the present research work, an attempt was made to investigate the expression pattern of Klf5 in mice fetal-maternal tissue during periimplantation (day 4–day 8). The expressional and functional independence of Klf5 on the ovarian steroids was studied using estrogen and progesterone antagonist. The study was carried out in female Swiss albino mice of LACA strain during the periimplantation period. KLF5 was localized in the fetal-maternal tissues using the immunofluorescence technique in paraffin-embedded tissues. Ovarian steroid antagonists were administered subcutaneously from day 1 to day 3 of gestation, and the uterus was collected on the morning of day 4. Klf5 protein and mRNA levels were studied by western blot and quantitative real-time PCR (qPCR), respectively.
Results
KLF5 was localized in the embryo, uterine luminal epithelium, glandular epithelium, and proliferating stromal cells during periimplantation. In ovarian steroid antagonist–treated groups, KLF5 was localized in the luminal and glandular epithelium and stroma. Western blot and qPCR confirmed translation and transcription of KLF5 during the experimental period. The KLF5 protein level significantly increased on day 6, day 7, and day 8 when compared with day 4 ( P < 0.05). The mRNA level of Klf5 increased significantly on day 7 and day 8 when compared with day 4 ( P < 0.05). In ovarian steroid antagonist–treated groups, protein and mRNA corresponding to Klf5 were observed. From this finding, it can be assumed that Klf5 may be a steroid-independent factor expressed during uterine receptivity.
Conclusion
Spatiotemporal KLF5 expression in fetal-maternal tissue was observed during the experimental period. The results suggest that Klf5 is an ovarian steroid–independent factor that may play a pivotal role in implantation, decidualization, and embryogenesis.
... In mice those endometrial LE cells are eliminated, allowing trophoblast cells to make direct physical contact with the underlying stroma to provide an unencumbered path to invasion of the uterine stroma for successful implantation. Until recently, the consensus has been that trophoblast cells invade through the endometrial LE by initiating apoptosis of the LE followed by phagocytosis of the LE by the trophoblast cells [48]. However, entosis is similar to phagocytosis, wherein one cell will engulf another, the difference being that phagocytosis engulfs dying or dead cells, whereas entosis internalizes live cells. ...
Secreted phosphoprotein 1 [SPP1, also known as osteopontin (OPN)] binds integrins to mediate cell–cell and cell-extracellular matrix communication to promote cell adhesion, migration, and differentiation. Considerable evidence links SPP1 to pregnancy in several species. Current evidence suggests that SPP1 is involved in implantation and placentation in mice, but in vivo localization of SPP1 and in vivo mechanistic studies to substantiate these roles are incomplete and contradictory. We localized Spp1 mRNA and protein in the endometrium and placenta of mice throughout gestation, and utilized delayed implantation of mouse blastocysts to link SPP1 expression to the implantation chamber. Spp1 mRNA and protein localized to the endometrial luminal (LE), but not glandular epithelia (GE) in interimplantation regions of the uterus throughout gestation. Spp1 mRNA and protein also localized to uterine naturel killer (uNK) cells of the decidua. Within the implantation chamber, Spp1 mRNA localized only to intermittent LE cells, and to the inner cell mass. SPP1 protein localized to intermittent trophoblast cells, and to the parietal endoderm. These results suggest that SPP1: 1) is secreted by the LE at interimplantation sites for closure of the uterine lumen to form the implantation chamber; 2) is secreted by LE adjacent to the attaching trophoblast cells for attachment and invasion of the blastocyst; and 3) is not a component of histotroph secreted from the GE, but is secreted from uNK cells in the decidua to increase angiogenesis within the decidua to augment hemotrophic support of embryonic/fetal development of the conceptus.
... After attachment, the embryo must penetrate through the luminal epithelium and the basement membrane. The luminal epithelial cells at the implantation site undergo specific changes such as controlled disassembly of adhesive complexes and apoptosis to assist the invasion of the embryo [10]. The embryo then needs to break through the basement membrane, which is a specialized extracellular scaffold composed of type IV collagen, laminin, perlecan, peroxidasin, and nidogen [11][12][13]. ...
Basigin (BSG) is a transmembrane glycoprotein involved in cell proliferation, angiogenesis and tissue remodeling. BSG has been shown to be essential for male and female reproduction although little is known about its role in normal uterine function. To study the potential function of BSG in the female reproductive tract, we generated mice with conditional knockout of Bsg in uterine cells using progesterone receptor-Cre and hypothesized that BSG is required for normal pregnancy in mice. Fertility study data showed that the conditional knockout mice had significantly reduced fertility compared to controls. Ovarian function of the conditional knockout mice appeared normal with no difference in the number of superovulated oocytes collected or in serum progesterone levels between the conditional knockout and the control mice. Uterine tissues collected at various times of gestation showed increased abnormalities in implantation, decidualization, placentation and parturition in the conditional knockout mice. Uterine cross sections on day 5 of pregnancy showed implantation failure and abnormal uterine epithelial differentiation in a large proportion of the conditional knockout mice. There was a compromised decidual response to artificial decidualization stimuli and decreased mRNA and protein levels for decidualization genes in the uteri of the conditional knockout mice. We also observed altered protein expression of monocarboxylate transporter 1 (MCT1), as well as impaired angiogenesis in the conditional knockout uteri compared to the controls. These results support that BSG is required for successful pregnancy through its functions in implantation and decidualization.
... Maternal body was weighed to certify that there was no characteristic anorexigenic effect of cocaine present in crack-cocaine samples. Both groups were exposed during the prenatal period (PN) from the 5th (embryonic implantation) to the 21st GD ( Parr et al., 1987 ). For the animals' exposure to the drug, a modified model of the system was used ( Ypsilantis et al., 2012 ). ...
Crack users suffer the effects of cocaine present in the drug and the action of other active compounds from its pyrolysis. An emergent fact is an increase in the number of pregnant crack cocaine users. Studies suggest that crack cocaine and its metabolites cross the placenta, promoting premature birth, fever, irritability, sweating, and seizures in the early months of life. In children, the effects of crack cocaine have been associated with cognitive deficits, difficulty in verbalization, aggressiveness, and depression, besides enhancing the susceptibility to epileptic seizures, including status epilepticus (SE) in adulthood. Therefore, we investigated the effect of maternal exposure to smoke crack cocaine on several behavioral parameters in the offspring during adulthood. A series of behavioral tests and intrahippocampal pilocarpine (H-PILO) microinjection at sub-convulsive and convulsive doses in a rat model demonstrated that exposure to crack cocaine during the embryonic period leads to anxiogenic-like behavior and long-term memory impairment in both genders and promotes depressive-like behavior in the female. Besides, crack cocaine offspring exposed to a sub-convulsive H-PILO dose showed higher susceptibility to SE, increased seizure frequency, and neurodegeneration, while animals that received a convulsive dose of H-PILO displayed no alteration in SE severity. Taken together, our data suggest that crack cocaine exposure during the gestational period leads to an increased predilection for anxiety and depression, long-term memory deficits, and reduction in the threshold for developing epileptic seizures associated with neuronal death, which predispose crack cocaine babies to develop neuropsychological disorders.
... The other aspect of structural changes in the preimplantation uterus is apoptosis. During the initial steps of implantation, the mouse uterine epithelium of the implantation chamber undergoes apoptosis in response to the interacting blastocyst (day4.5 of pregnancy in mouse) [15]. With progressing implantation, regression of the decidual cells allows a restricted and coordinated invasion of trophoblast cells into the maternal compartment. ...
Objective
Diabetic women have different reproductive problems. In pregnant diabetic women, high rates of perinatal mortality, spontaneous abortion and congenital anomalies are observed. We hypothesized that quercetin, as an antidiabetic and phytoestrogen, might have protective effects on the embryo implantation in pregnant diabetic mice. We investigated the ameliorative effects of quercetin on the levels of serum estrogen and progesterone, rate of blastocyst implantation, and uterine receptivity markers in diabetic mice.
Materials and methods
Diabetic and healthy female mice were treated with quercetin (30 mg/kg/day) four weeks before pregnancy. Plasma sex-steroid levels were determined on day 4 of pregnancy. Also, uteri were harvested for investigation of protein and mRNA expression changes. In another set of our study, implantation rate was determined on day 5 of pregnancy.
Results
Our results indicated that quercetin was significantly reduced blood glucose levels in diabetic mice. The number of implantation sites as well as serum estradiol level was reduced in diabetic mice, and then treatment with quercetin significantly increased both. On the other hand, insulin like growth factor1, integrin αvβ3, and cyclooxygenase2 mRNA expression in the uterus of diabetic mice were significantly reduced, and quercetin treatment augmented the expression level of these genes. Besides, the level of inactive β-catenin protein level in the uterus of diabetic mice was higher than normal group; treatment with quercetin reduced the level of inactive β-catenin protein as compared to diabetic mice.
Conclusion
We conclude that administration of quercetin before pregnancy can probably alleviate reproductive problems in diabetic women likely via its estrogenic and antihyperglycemic effects.
... There are species differences in the process of trophoblasts passing through the LE to reach the decidual cells during embryo implantation (https://www.trophoblast.cam.ac.uk/Resources/ enders). In rodents, the LE cells surrounding the blastocyst are phagocytosed by protrusions of invading trophoblasts at ~D4 20 h in mice and ~D5 9 h in rats, [73,74] implying the involvement of lysosomes in the trophoblasts for phagocytic LE removal. ...
The lysosome is the most acidic membrane-bound intracellular organelle. Lysosomal acidity is primarily maintained by vacuolar H+-ATPase (V-ATPase) and counter ion channels. There are >60 hydrolytic enzymes in the lysosome for its fundamental digestive role. Lysosomes also play important roles in endocytosis, exocytosis, autophagy, and cell death. Studies that have implicated roles of lysosomes in the female reproductive system are reviewed here. In the ovary, lysosomes are implicated in the preparation of free cholesterol for steroidogenesis and degradation of regulators of steroidogenesis, regulation of follicular atresia, follicle rupture during ovulation, luteal cell survival, and luteal regression. In the oviduct, lysosomes are involved in endocytosis of both serum and oviductal luminal components. In the uterus during the menstrual/estrous cycle, lysosomes are associated with endometrial secretion, apoptosis, and menstruation. In the uterus during early pregnancy, lysosomes are involved in the temporal and directional changes of endocytosis, uterine epithelial acidification upon embryo implantation initiation, and embryo-maternal mutual communications via extracellular vesicles. In the placenta, lysosomes are implicated in nutrient transport and placental separation from the uterus for parturition. In the mammary gland, lysosomes are important for mammary gland development and involution. These findings suggest/demonstrate functions of lysosomes in multiple processes of female reproduction, from ovulation to ovarian steroidogenesis for pregnancy maintenance, and from essential in utero nurturing of developing embryos/fetuses via embryo/fetal-maternal communications, to optional postpartum nurturing of newborns via lactation. Future studies using genetically or modified animal models and pharmacological approaches will provide novel insights into the functions and mechanisms of lysosomes in the mammalian female reproductive system.
Keywords: Autophagy; Endocytosis; Lysosome; Ovary; Steroidogenesis; Uterus
... There are species differences in the process of trophoblasts passing through the LE to reach the decidual cells during embryo implantation (https://www.trophoblast.cam.ac.uk/Resources/ enders). In rodents, the LE cells surrounding the blastocyst are phagocytosed by protrusions of invading trophoblasts at ~D4 20 h in mice and ~D5 9 h in rats, [73,74] implying the involvement of lysosomes in the trophoblasts for phagocytic LE removal. ...
The lysosome is the most acidic membrane-bound intracellular organelle. Lysosomal acidity is primarily maintained by vacuolar H+-ATPase (V-ATPase) and counter ion channels. There are >60 hydrolytic enzymes in the lysosome for its fundamental digestive role. Lysosomes also play important roles in endocytosis, exocytosis, autophagy, and cell death. Studies that have implicated roles of lysosomes in the female reproductive system are reviewed here. In the ovary, lysosomes are implicated in the preparation of free cholesterol for steroidogenesis and degradation of regulators of steroidogenesis, regulation of follicular atresia, follicle rupture during ovulation, luteal cell survival, and luteal regression. In the oviduct, lysosomes are involved in endocytosis of both serum and oviductal luminal components. In the uterus during the menstrual/estrous cycle, lysosomes are associated with endometrial secretion, apoptosis, and menstruation. In the uterus during early pregnancy, lysosomes are involved in the temporal and directional changes of endocytosis, uterine epithelial acidification upon embryo implantation initiation, and embryo-maternal mutual communications via extracellular vesicles. In the placenta, lysosomes are implicated in nutrient transport and placental separation from the uterus for parturition. In the mammary gland, lysosomes are important for mammary gland development and involution. These findings suggest/demonstrate functions of lysosomes in multiple processes of female reproduction, from ovulation to ovarian steroidogenesis for pregnancy maintenance, and from essential in utero nurturing of developing embryos/fetuses via embryo/fetal-maternal communications, to optional postpartum nurturing of newborns via lactation. Future studies using genetically or modified animal models and pharmacological approaches will provide novel insights into the functions and mechanisms of lysosomes in the mammalian female reproductive system.
... However, there might be other causes of altered placental echogenicity in the first trimester: during throphoblast invasion into the myometrium there is apoptosis and damage in the myometrial epithelium [20,21]. Kim et al. demonstrated that both mechanisms lead to dystrophic calcification [22]. ...
PurposeThe objective of this study was to evaluate the feasibility and value of measuring early placental echogenicity to predict fetal intrauterine growth restriction (IUGR).Methods
This is a single center, retrospective cohort study. Early ultrasound examination (6 + o to 8 + 6 weeks of gestation in singleton pregnancies) was used to measure placental dimensions and placental echogenicity. A ratio between placental echogenicity and myometrial echogenicity (PE/ME-ratio) was calculated for each patient. Study population was assigned to either the IUGR group or the control group based on clinical data.Results184 eligible pregnancies were analysed. 49 patients were included in our study. Of those, 9 (18.37%) cases were affected by IUGR and 40 (81.63%) were controls. Measuring the placental echogenicity was feasible in all cases. IUGR neonates had a significant lower placental echogenicity (1.20 (± 0.24) vs. 1.64 (± 0.60), p = 0.033), but no significant differences in the other placental outcomes were observed.Conclusion
Our results showed that measuring placental echogenicity is feasible in the early first trimester and demonstrated a significantly lower placental echogenicity in fetuses with subsequent IUGR. Further prospective studies are needed to validate those results.
... ِ ه ِ طائ َ ع ِ ل ال َ و ،ٌ ع ِ داف ِ ه ِ ضآئ َ ق ِ ل َ ْس ي َ ل ذى َّ ال ِ هلل ُ د ْ م َ ح ْ ل َ ا ُ واد َ ج ْ ال َ ُو ه َ و ع، ِ صان ُ ع ْ ُن ص ِ ه ِ ع ْ ُن َص ك ال َ و ،ٌ ع ِ مان ِ ه ِ ت َ م ْ ك ِ ح ِ ب نَ َ ق ْ ت َ وا ، ِ ع ِ دائ َ ب ْ ال َ ناس جْ َ ا َ ر َ ط َ ف ،ُ ع ِ واس ْ ال ابتدأتني ، َ ع ِ َّنائ الص ْئا َي ش ونَ ُ ك َ ا ْ ن َ ا َ ْل ب َ ق َ ك ِ ت َ ْم ع ِ ن ِ ب ، ذكورا َ م ِ آم ، َ الب صْ ْ اال ى ِ َن ت ْ َن ْك س َ ا َّ م ُ ث ، ِ راب ُّ الت ِنَ م َنى ت ْ ق َ ل َ خ َ و ِ ُور ُّه الد ِ الف ِ ت ْ اخ َ و ، ِ ون ُ ن َ م ْ ال ِ ْب ي َ ر ِ ل، سمحاق الغضروف (PC) والخاليا الغضروفية Ch) ، ) الفجوات حول الخاليا الغضروفية ( L) ، تنخر الى يشير السهم الغضروفية، الخلية Hp) ) الخاليا تكون فرط ، (Cy) كيس، (Bv) دموي، وعاء (Inf) االلتهابية. الخاليا ارتشاح 57 صورة 4 - 14 ( a,b :) مقطع مستعرض جنين فخذ في للعظم الجرذ االبيض في اليوم 20 من الحمل ،يالحظ ( وجود Cart )الغضروف،( T العظم حويجزات ) ، Mc) ) العظم (Parr et al.,1987;Paria et al.,2001). (Critchley et al.,1999;Salamonsen and Lathbury, 2000 (Craven et al,. ...
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... Moreover, the investigations revealed the incidence of apoptosis in endometrial epithelial cells at the embryo implantation site and its crucial role in the embryo implantation [109,111]. It has been reported that apoptosis of the endometrial cells takes place in especial temporal and spatial patterns and it is important for successful implantation and the fetal-placental development [112,113]. ...
TGF-β signaling in the endometrium is active during the implantation period and has a pivotal role in regulating endometrial receptivity and embryo implantation. During embryo implantation, both apoptosis and proliferation of endometrial cells happen at the same time and it seems TGF-β is the factor that controls both of these processes. As shown in cancer cells, in special conditions this cytokine can have a dual effect and switch the action from apoptosis to proliferation. Owing to the similarity between embryo implantation and cancer development and also unusual pattern of proliferation and remodeling in the uterus, in this review we suggest the existence of such a switching in endometrium during the early pregnancy. Moreover, we address some potential mechanisms that could regulate the switching. A better understanding of the molecular mechanisms regulating TGF-β action and signaling during the implantation period could pave the way for introducing novel therapeutic strategies in order to solve implantation-associated issues such as repeated implantation failure.
... It is suggested that the apoptotic process in the ICM removes cells that failed to translocate correctly to their correct position [38]. Moreover, the direct connection between the trophectoderm cells and the uterine epithelium encourages apoptosis at the attachment site, allowing penetration of the blastocyst into the underlying stroma [39]. ...
Bisphenol A (BPA) is an endocrine-disrupting chemical used in the manufacture of many products used daily. In the present study, the effects of BPA (1 × 10-4 to 1 × 10-9 M) on migration and on the expression of some apoptotic genes were examined in vitro using ovine trophectoderm (oTr1) primary cell line. The results revealed that BPA at 1 × 10-9, 1 × 10-8 and 1 × 10-7M increased migration of oTr1 cells, while 1 × 10-6, 1 × 10-5 and 1 × 10-4 M BPA decreased cell migration. Regarding apoptosis, expression of the anti-apoptotic gene Bcl-2 mRNA was greater at 1 × 10-8 and 1 × 10-9 M BPA and was down-regulated at 1 × 10-4 to 1 × 10-7 M BPA; however, expression of pro-apoptotic genes (Bax, cathepsin B, caspase-3 and c-myc) was reduced at the higher concentrations of BPA. Results of this study suggest that BPA may impair implantation by decreasing migration of oTr1 cells and inhibiting apoptosis.
... The mechanisms of LE clearance at the site of attachment are species-specific and are poorly characterized in the human due to ethical constraints. Interestingly, the apoptotic LE in the murine uterus is phagocytosed by the adjacent trophoblast [40]. Recently, it was demonstrated that during implantation, the LE cells in direct contact with the blastocyst are endocytosed by trophoblast cells in a process known as entosis [5]. ...
Successful embryo implantation requires a receptive endometrium. Poor uterine receptivity can account for implantation failure in women who experience recurrent pregnancy loss or multiple rounds of unsuccessful in vitro fertilization cycles. Here, we demonstrate that the transcription factor Forkhead Box O1 (FOXO1) is a critical regulator of endometrial receptivity in vivo. Uterine ablation of Foxo1 using the progesterone receptor Cre (PgrCre) mouse model resulted in infertility due to altered epithelial cell polarity and apoptosis, preventing the embryo from penetrating the luminal epithelium. Analysis of the uterine transcriptome after Foxo1 ablation identified alterations in gene expression for transcripts involved in the activation of cell invasion, molecular transport, apoptosis, β-catenin (CTNNB1) signaling pathway, and an increase in PGR signaling. The increase of PGR signaling was due to PGR expression being retained in the uterine epithelium during the window of receptivity. Constitutive expression of epithelial PGR during this receptive period inhibited expression of FOXO1 in the nucleus of the uterine epithelium. The reciprocal expression of PGR and FOXO1 was conserved in human endometrial samples during the proliferative and secretory phase. This demonstrates that expression of FOXO1 and the loss of PGR during the window of receptivity are interrelated and critical for embryo implantation.
... ِ ه ِ طائ َ ع ِ ل ال َ و ،ٌ ع ِ داف ِ ه ِ ضآئ َ ق ِ ل َ ْس ي َ ل ذى َّ ال ِ هلل ُ د ْ م َ ح ْ ل َ ا ُ واد َ ج ْ ال َ ُو ه َ و ع، ِ صان ُ ع ْ ُن ص ِ ه ِ ع ْ ُن َص ك ال َ و ،ٌ ع ِ مان ِ ه ِ ت َ م ْ ك ِ ح ِ ب نَ َ ق ْ ت َ وا ، ِ ع ِ دائ َ ب ْ ال َ ناس جْ َ ا َ ر َ ط َ ف ،ُ ع ِ واس ْ ال ابتدأتني ، َ ع ِ َّنائ الص ْئا َي ش ونَ ُ ك َ ا ْ ن َ ا َ ْل ب َ ق َ ك ِ ت َ ْم ع ِ ن ِ ب ، ذكورا َ م ِ آم ، َ الب صْ ْ اال ى ِ َن ت ْ َن ْك س َ ا َّ م ُ ث ، ِ راب ُّ الت ِنَ م َنى ت ْ ق َ ل َ خ َ و ِ ُور ُّه الد ِ الف ِ ت ْ اخ َ و ، ِ ون ُ ن َ م ْ ال ِ ْب ي َ ر ِ ل، سمحاق الغضروف (PC) والخاليا الغضروفية Ch) ، ) الفجوات حول الخاليا الغضروفية ( L) ، تنخر الى يشير السهم الغضروفية، الخلية Hp) ) الخاليا تكون فرط ، (Cy) كيس، (Bv) دموي، وعاء (Inf) االلتهابية. الخاليا ارتشاح 57 صورة 4 - 14 ( a,b :) مقطع مستعرض جنين فخذ في للعظم الجرذ االبيض في اليوم 20 من الحمل ،يالحظ ( وجود Cart )الغضروف،( T العظم حويجزات ) ، Mc) ) العظم (Parr et al.,1987;Paria et al.,2001). (Critchley et al.,1999;Salamonsen and Lathbury, 2000 (Craven et al,. ...
الديكساميثازون من الادوية السترويدية ولها استعمال واسع في الطب لعلاج الكثير من الحالات المختلفة. هدفت هذه الدراسة الى معرفة تأثير الديكساميثازون على غرس الكيس الارومي في اليومين السابع والعاشر من الحمل وعلى تكوين الغضروف والعظم في اجنة الجرذان البيض في اليوم 15 و20 من الحمل ومعرفة بعض المعايير الوظيفية لدى الإناث الحوامل.
أجريت الدراسة في قسم علوم الحياة /كلية التربية للعلوم الصرفة /جامعة كربلاء في المدة من نيسان 2016 لغاية ايار 2017 استخدمت حيوانات الجرذان البيض وعددها 94 جرذاً، منها عشرة ذكور للتلقيح فقط أما الإناث وعددها 84 جرذاً، قسمت عشوائيا على ثلاث مجموعات (تضم كل مجموعة 28 انثى ) حقنت المجموعة الأولى (السيطرة) بالمحلول الملحي الفسيولوجي0.9% داخل البريتون طيلة مدة الحمل ، حقنت المجموعتين الثانية والثالثة(المعاملتين الأولى والثانية ) داخل البريتون بعقار الديكساميثازون Dexamethasone يوميا بتركيز 0.2 و 0.4ملغم/0.25 كغم من وزن الجسم على التوالي .
قسمت كل مجموعة الى أربعة مجموعات فرعية ضمت كل منها سبعة اناث حوامل تم التضحية بها في الأيام 7و10و15و20 من مدة الحمل على التوالي، وخصصت المجموعة الثالثة والرابعة لدراسة التكوين الجنيني للغضروف والعظم، في يوم 20 من الحمل وزعت الاجنة بمعدل عشرة اجنة نصفها للتقطيع النسجي والنصف الاخر لاستعمال ملون الاليزارين الاحمر.
وضعت عينات الكيس الارومي المغروس والاجنة بنوعين من المثبتات: في محلول الفورمالين 10% ومحلول بوين. مررت العينات حسب طريقة التقانة النسجية لأجل الطمر في شمع البارافين. لونت المقاطع النسجية المقطعة بسمك 5 مايكرون بملوني الهيموتوكسلين -الايوسين وملون الكومورى الثلاثية الألوان وكاشف شيف الدوري مع وبدون Diastase وملون الالسين الازرق ذات الاس الهايدروجيني 1و2.5. كما استعملت طريقة تحضير الهيكل العظمي للجنين باستعمال الملون المزدوج الذي تم تحضيره بطريقة كل منDix Whitaker and.
... This contrast in the stromal cell morphology may be due to the deciduogenic effect of peanut oil administered to the experimental rats (Buxton & Murdoch, 1982). Interestingly, the uterine stromal cells in the control peanut oil-treated rats were apoptotic, which characterised the process of decidualisation during blastocyst implantation in mice and rats (Parr et al., 1987). These events implicate peanut oil directly in the successful implantation of blastocysts seen in the experimental and control peanut oil-treated rats. ...
Oil extracts from Arachis Hypogea is often used clinically for the administration of
exogenous hormone during the assisted reproduction. But its capacity to induce follicular
growth after fertilisation to maintain the formation of progesterone has not yet been clarified.
We assessed the effects of peanut oil on stem cell factors (SCF) for follicular maturation and
meiotic activities in the superovulated rat. Female rats were superovulated and treated with
peanut oil (S+Pn), while the controls were either superovulated and treated with saline
solution (S+N), or non-superovulated and treated with saline solution (N) or peanut oil (Pn).
After mating, uterine horns and ovaries were obtained and a morphometry of granulosa cells
and theca interna (TI) was carried out. The mitotic index (MI) of the granulosa cells and the
protein expression of SCF on ovarian stromal cells were evaluated, as well as the
ultramorphology of the endometrium. Results showed a successful implantation in S+Pn, N
and Pn groups. The MI was high in Pn group, moderate in S+Pn and N groups, and poor in
the S+N group. However, both follicular size and TI levels varied significantly (P<0.05)
across intervention groups. In multiple comparisons, both follicular size and TI values in the
experimental group were the highest (P<0.0001). Protein expressions of SFC were high on
ovarian stromal cells in both S+Pn and N groups, while decidualisation was observed in the
experimental groups. We conclude that peanut oil may be implicated in mitotic activities of
granolusa cells, induce the release of SCF and sustain implantation.
... They can physically remove them, coalesce with them, or trespass through them and invade. In rodents, electron microscopic studies have demonstrated apoptosis of luminal epithelial cells at the site of implantation (51), which could be viewed as death of the guards by the Figure 2. Expression of E-cadherin in the luminal epithelium of pregnant mice. Paraffin-embedded mouse uterine sections on Day 4 (2100 hours) were stained using rabbit polyclonal E-cadherin primary antibody (catalog no. ...
Contrary to widespread belief, the implantation of an embryo for the initiation of pregnancy is like a battle, in that the embryo uses a variety of coercive tactics to force its acceptance by the endometrium. We propose that embryo implantation involves a three step process: 1) identification of a receptive endometrium; 2) superimposition of a blastocyst-derived signature onto the receptive endometrium prior to implantation; and finally 3) breaching by the embryo and trophoblast invasion, culminating in decidualization and placentation. We review here the story that is beginning to emerge, focusing mostly on the cells that are in “combat” during this process.
... Several studies performed in humans and different animal species, such as horses, dogs, rats and rabbits, have shown that the cyclic pattern of ovarian secretion of E2 and P4 affects cell proliferation and apoptosis in the uterine endometrium. It is well documented that the rodent uterine epithelium around the embryo undergoes apoptosis in response to the presence of the blastocyst (Parr et al. 1987). ...
Endometrium receptivity, an absolutely necessary part of successful embryo implantation, and several morphological and biochemical endometrial receptivity biomarkers have already been studied and proposed in some animals. However, to our knowledge, no such a study has as yet been undertaken in dairy goat. In the present study, the serum and uterus of dairy goat were studied at gestational days 5 and 15, the estrogen (E2) and progesterone (P4) concentrations in serum were determined by electrochemiluminescence immunoassay, the surface topography of endometrium was observed by scanning electron microscopy. Furthermore, the estrogen receptors (ER), prolactin (PRL), some marker genes of receptive endometrium, and cell proliferation and apoptosis in the uterus were also detected. Well-formed pinopodes were found on the surface of endometrium at day 15 with higher E2 and P4 concentrations in the serum and higher estrogen receptors ERα and ERβ expression levels and a lower PRL level in the endometrium. Moreover, some expression levels of marker genes of receptive endometrium (OPN, VEGF, LIF, PRLR) were increased at day 15 compared to day 5, but no significant differences were observed in the cell proliferation and apoptosis in the uterus. The results showed that the endometrium reached the receptive state at gestational day 15 in dairy goats.
... During this time, vascular bed in endometrium expands markedly. Sequential events of increased vascular permeability, decidualization in endometrial stroma and subsequent apoptosis in epithelial cells at the site of blastocyst implantation facilitate the invasion of trophoblast cells through the base membrane and stroma [17]. At the fetal-maternal interface, angiogenesis is characterized by uterine vascular permeability and subsequent development of maternal wall separating a fluid filled cavity where growth and development of the embryo take place. ...
Objective: Vascular Endothelial Growth Factor (VEGF) is a glycoprotein acting as a potent angiogenic factor. This growth factor initiates vasculogenesis and promotes angiogenesis during early embryogenesis which is crucial for successful pregnancy. The present study determines the cell types expressing VEGF-C and its intensity in mice fetal-maternal tissue during periimplantation (D4–D7).
Settings: Molecular Endocrinology & Reproductive Biology Research Laboratory, Department of Zoology, Rajiv Gandhi University, Arunachal Pradesh, India.
Materials and methods: VEGF-C was localized in the fetal-maternal tissues using anti VEGF-C monoclonal antibody in paraffin embedded sections. Western blot and immunohistochemical studies were performed using DAB for chromogenic reactions to study the expression of VEGF-C. The growth factor transcript was detected by Reverse Transcriptase-PCR (RT-PCR).
Main outcome measures: VEGF-C was localized in the uterine epithelium and glandular epithelium on D4 and D5 of gestation. The decidual cells of primary decidual zone (PDZ) on D5 which expands to secondary decidual zone (SDZ) on D6 showed the expression of VEGF-C. The trophectodermal cells and cells of ectoplacental cone on the embryo showed expression of the growth factor. Intensity of the growth factor was different in different cell types. Western blot and RT-PCR analysis confirmed translation and transcription of the growth factor during this period.
Major conclusion: Programmed spatio - temporal VEGF-C expression in fetal-maternal tissue during periimplantation (D4–D7) in mice could be the key process for growth and development of the embryo. Expression of the growth factor changes quantitatively in different cell types according to the requirements during early embryogenesis.
... In species that have displacement penetration such as rodents and humans (Schlafke & Enders 1975), the UECs must be removed for the implanting blastocyst to invade the underlying stroma. This removal was thought to be mediated via apoptotic mechanisms (Parr et al. 1987); however, recent evidence suggests that luminal UECs surrounding the implanting blastocyst undergo entosis (Li et al. 2015). Regardless of the mode of removal of UECs, it is necessary for the UECs to become less adherent to the underlying basal lamina, and then the UECs in the region immediately surrounding the implantation chamber are removed. ...
Controlled ovarian hyperstimulation is an essential component of IVF techniques to ensure proliferation and development of multiple ovarian follicules but the effects of these hormones on the endometrium are largely unknown. During normal pregnancy in rats, there are significant changes in the basal plasma membrane of uterine epithelial cells (UECs) at the time of receptivity, including loss of focal adhesions. This enables the UECs to be removed from the implantation chamber surrounding the blastocyst, thus allowing invasion into the underlying stroma. This study investigated the influence of ovarian hyperstimation (OH) on the basal plasma membrane of UECs during early pregnancy in the rat. Immunofluorescence results demonstrate the presence of paxillin, talin, integrin ?1 and phosphorylated FAK (Y397FAK) in the basal portion of UECs at the time of implantation in OH pregnancy. TEM analysis demonstrated a flattened basal lamina and the presence of focal adhesions on the basal surface at this time in OH pregnancy. Significantly less full length paxillin, more paxillin ? and integrin ?1 were seen at the time of implantation in OH compared to normal pregnancy. The increase in paxillin ? suggests that these cells are less mobile, while the increase in integrin ?1 and Y397FAK suggests retention of a stable FA complex. Taken together with the increase in morphological focal adhesions, this represents a cell type which is stable and less easily removed for blastocyst implantation. This may be one mechanism explaining lower implantation rates after fresh embryo transfers compared to frozen cycles.
... Therefore, we suggest the phagocytic ability of blastocysts may be associated with embryo development and an increased trend of phagocytic activity may exist toward the time of human blastocyst implantation. In rodents, one ultrastructural study indicated that uterine epithelial cells in the attachment site undergo apoptotic changes leading to their phagocytosis by adjacent trophoblast cells during implantation [Parr et al. 1987]. In humans, the process of adhesion and penetration has not been elucidated. ...
Unlabelled:
Trophoblast phagocytosis has been considered important in pregnancy. However, whether human preimplantation blastocysts possess phagocytic activity is still unclear. In this study, we determined the phagocytosis potential in human trophectoderm cells of blastocysts prior to implantation. Fluorescent microspheres were used as markers for phagocytic analysis under transmission electron microscope (TEM) and fluorescence microscopy. Phagocytosis of 1 μm fluorescent microspheres was observed in most (9/11) day-6 and even some (2/9) day-5 blastocysts. More effective phagocytosis occurred in blastocysts at the morula-blastocyst stage of day-6. Furthermore, we observed an increased trend of phagocytic acitivities in polar trophectoderm. Our findings indicated phagocytic ability exists in human blastocysts prior to implantation and the differentiation between polar and mural trophectoderm may be associated with blastocyst implantation.
Abbreviations:
TEM: transmission electron microscope; ZP: zona pellucida; PGD: preimplantation genetic diagnosis; ICM: inner cell mass; FGF4: fibroblast growth factor 4.
... The attachment of the embryo to the epithelial lining promotes the disappearance of epithelium. This depends on a mechanism of entosis (cell-eat-cell) by the trophoblast cells followed by apoptosis at the site of implantation (Parr et al. 1987, Li et al. 2015 and subsequent stimulation of stromal cell proliferation and differentiation into secretory decidual cells. This series of events form the decidualization bed at the blastocyst site (Huet-Hudson et al. 1989). ...
Adherence of an embryo to the uterus represents the most critical step of the reproductive process. Implantation is a synchronized event between the blastocyst and the uterine luminal epithelium, leading to structural and functional changes for further embryonic growth and development. The milieu comprising the complex process of implantation is mediated by estrogen through diverse but interdependent signaling pathways. Mouse models have demonstrated the relevance of the expression of estrogen-modulated paracrine factors to uterine receptivity and implantation window. More importantly, some factors seem to serve as molecular links between different estrogen pathways, promoting cell growth, acting as molecular chaperones, or amplifying estrogenic effects. Abnormal expression of these factors can lead to implantation failure and infertility. This review provides an overview of several well-characterized signaling pathways that elucidates the molecular cross talk involved in the uterus during early pregnancy.
... After the attachment reaction between the mouse blastocyst and uterine epithelium, differentiated trophoblast cells migrate through apposing epithelial cells that undergo localized cell death (Welsh and Enders 1991;Parr et al. 1987) and adhere to the basement membrane in preparation for invasion of the underlying stroma on embryonic day 5 (Blankenship and Given 1992). At this point, the adherent trophoblast cells dissociate from the trophectoderm and commence invasion. ...
The key, versatile role of intracellular Ca2+ signaling during egg activation after fertilization has been appreciated for several decades. More recently, evidence has accumulated supporting the concept that cytoplasmic Ca2+ is also a major signaling nexus during subsequent development of the fertilized ovum. This chapter will review the molecular reactions that regulate intracellular Ca2+ levels and cell function, the role of Ca2+ signaling during egg activation and specific examples of repetitive Ca2+ signaling found throughout pre- and peri-implantation development. Many of the upstream and downstream pathways utilized during egg activation are also critical for specific processes that take place during embryonic development. Much remains to be done to elucidate the full complexity of Ca2+ signalling mechanisms in preimplantation embryos to the level of detail accomplished for egg activation. However, an emerging concept is that because this second messenger can be modulated downstream of numerous receptors and is able to bind and activate multiple cytoplasmic signaling proteins, it can help the coordination of development through up- and downstream pathways that change with each embryonic stage.
... As delineated by Straszewski-Chavez et al. [22], apoptosis is present in varying capacities throughout the beginning of normal pregnancies. The implantation stage, for example, involves blastocysts eliciting apoptosis in the uterine epithelium [23] and in the decidua. Additionally, as Allaire et al. [24] suggested, the invading trophoblast and maternal immune system require a careful and mutual balance of apoptosis in order to prevent fetal allograft rejection. ...
During the first trimester of pregnancy, appropriate regulation of estradiol is essential for normal placental development. Previous studies demonstrate that premature elevation in estradiol concentrations can lead to abnormal placentation, but have not fully elaborated the mechanism of this effect in the first trimester trophoblast. Our aim was to determine whether estradiol elicits trophoblast cell death or inhibits proliferation. The first trimester human cytotrophoblast cell line HTR-8/SV-neo was cultured in phenol red-free medium containing charcoal-stripped serum and treated with 17beta-estradiol (E2) at concentrations between 0 and 100 nM. TUNEL and invasion assays indicated that E2 significantly increased cell death and reduced cell invasion at 10 nM, and nuclear Ki67 expression revealed that it decreased cell proliferation at 1 nM. A similar effect on cell death was observed in first trimester placental explants. The E2 antagonist Fulvestrant blocked all effects of E2. Immunohistochemistry showed that expression of the pro-apoptotic proteins caspases 3, 8, and 9 increased at E2 concentrations of 25 nM and greater, whereas expression of the anti-apoptotic protein BCL2-alpha decreased at E2 concentrations of 10 nM and greater. Additionally, treatments with ERalpha-specific and ERbeta-specific agonists at concentrations between 0 and 1000 nM indicated that only ERalpha mediates E2's effects, although immunohistochemistry and Western immunoblotting showed that HTR-8/SV-neo cells and placental explants express both ERalpha and ERbeta. Taken together, these findings reveal the interplay between elevated serum E2 and apoptosis in the first trimester of pregnancy. These factors could be associated with pregnancy complications including infertility and uteroplacental insufficiency.
Copyright 2015 by The Society for the Study of Reproduction.
Embryo implantation is composed of three steps: blastocyst apposition, adhesion/attachment and invasion. Blastocyst invasion has been studied less extensively than the other two events. Historically, studies conducted using electron microscopy have shown the removal of epithelial cells in the vicinity of the attached blastocysts in rodents, although the underlying mechanisms have remained unclear. Here, we describe recent studies using mice with uterine‐specific gene deletion that demonstrated important roles for nuclear proteins such as progesterone receptor, hypoxia inducible factor and retinoblastoma in the regulation of embryo invasion. In these mouse models, the detachment of the endometrial luminal epithelium, decidualization in the stroma, and the activation of trophoblasts have been found to be important in ensuring embryo invasion. This review summarizes the molecular signaling associated with these cellular events, mainly evidenced by mouse models.
The human endometrium shows a remarkable regenerative capacity that enables cyclical regeneration and remodeling throughout a woman's reproductive life. Although early postnatal uterine developmental cues direct this regeneration, the vital factors that govern early endometrial programming are largely unknown. We report that Beclin-1, an essential autophagy-associated protein, plays an integral role in uterine morphogenesis during the early postnatal period. We show that conditional depletion of Beclin-1 in the uterus triggers apoptosis and causes progressive loss of Lgr5+/Aldh1a1+ endometrial progenitor stem cells, with concomitant loss of Wnt signaling, which is crucial for stem cell renewal and epithelial gland development. Beclin-1 knockin (Becn1 KI) mice with disabled apoptosis exhibit normal uterine development. Importantly, the restoration of Beclin-1-driven autophagy, but not apoptosis, promotes normal uterine adenogenesis and morphogenesis. Together, the data suggest that Beclin-1-mediated autophagy acts as a molecular switch that governs the early uterine morphogenetic program by maintaining the endometrial progenitor stem cells.
Although the importance of apoptosis in the field of cancer therapy is known, the signalling mechanisms underlying this process were largely uncharacterized at the commencement of this study. Therefore, in these studies, inhibitors of protein kinases and protein phosphatases were employed to investigate the role of these enzymes in the induction of apoptosis in leukaemic cells. Low concentrations of the serine/threonine phosphoprotein phosphatase (PP) inhibitor okadaic acid (OKA) induced apoptosis in proliferating cell lines and in quiescent cells from chronic lymphocytic leukaemia (CLL) patients. However, later features of apoptosis such as nuclear condensation were abrogated by treatment with N-benzyloxycarbonyl- Val-Ala-Asp-(0-methyl)fluoromethane (ZVADfmk), an inhibitor of interleukin-1- -converting enzyme (ICE)-like proteases suggesting that the down-regulation of phosphoprotein phosphatases results in ICE protease activation. Bcl-2 protein and messenger RNA (mRNA) were decreased following treatment of HL60 cells with OKA. Therefore, I determined whether bcl-2 promoter activity was altered by OKA treatment. A decrease in the read-out from a bcl-2 promoter construct was not observed, suggesting that alterations in bcl-2 mRNA stability and/or protein half-life could mediate the decrease in bcl-2 protein expression seen in HL60 cells treated with OKA. Conversely, treatment of the HL60 cell line and cells from CLL patients with y irradiation and etoposide resulted in an initial rise in PP2A-like activity which declined within several hours. Therefore, the activation of some phosphatases and the inhibition of others may have roles in the induction of apoptosis in leukaemic cells. The deregulated protein tyrosine kinase activity of the bcr/abl fusion oncoprotein, found on the Philadelphia (Ph) chromosome, abrogates apoptosis following treatment of Ph+ve leukaemic cells with DNA damaging agents. I observed that the bcr/abl-selective protein kinase inhibitor herbimycin A (HMA) synergized with etoposide or with y irradiation in several Ph+ve cell lines by dramatically increasing the induction of nuclear apoptosis and DNA fragmentation caused by these agents alone. Conversely, in Ph-ve cell lines, HMA treatment either protected cells from apoptosis or failed to affect killing induced by cytotoxic agents. Selective protein tyrosine kinase inhibitors may be of value in securing the death of Ph+ve leukaemia cells.
Embryo implantation is essential for normal pregnancy, and the process of decidualization is critical for embryo implantation. However, the mechanism of decidualization during early pregnancy is still unknown. Forkhead box O3a (FOXO3a) is the most important functional transcription factor of the forkhead box family and is a highly conserved transcription factor of apoptosis‐related genes. In the mouse uterus, FOXO3a was found to be expressed regularly from Days 1–7 of early pregnancy. Upon further exploration, it was found that FOXO3a was expressed at significantly higher levels at the implantation site than at the interimplantation site on Days 5–7 of pregnancy. Under artificial decidualization, FOXO3a was highly expressed in the first and second decidual zones. After decidualization, the expression of FOXO3a was significantly increased both in vivo and vitro. In primary stromal cells, apoptosis was reduced by decreased expression of FOXO3a after inducing decidualization. Moreover, when FOXO3a‐small interfering RNA was transfected into the uteri of mice, the expression of decidualization‐ and apoptosis‐related factors was impaired. Thus, FOXO3a might play an important role in decidualization during early pregnancy, and cell apoptosis might be one of pathways for FOXO3a‐regulated decidualization. Embryo implantation is essential for normal pregnancy, and the process of decidualization is critical for embryo implantation. The expression of forkhead box O3a (FOXO3a) was significantly increased when decidualization both in vivo and vitro. FOXO3a might play an important role in decidualization during early pregnancy.
This study describes ciliated, nonciliated and mitochondrial luminal epithelial cells of the isthmus in laying and moulting domestic fowls using histological and ultrastructural techniques. The ciliated cells were nonsecretory, while numerous electron‐dense secretory granules were present in the nonciliated cells of laying birds. Mitochondrial cells, occurring in two morphologically distinct forms, constituted the third type of epithelial cell present in the isthmus. The SEM study showed that the luminal epithelium was dominated by ciliated cells, the cilia of which partially obscured adjacent nonciliated cells. The involution of the luminal epithelium in moulting birds occurred via autophagy, apoptosis and necrosis. Autophagic inclusions, which included autophagosomes and autolysosomes, were present in the early degenerative phases of ciliated, nonciliated and mitochondrial cells. Nonciliated cells underwent degeneration via apoptosis, which was characterized by nuclear and cytoplasmic condensation. Apoptotic and necrotic ciliated cells were evident during the intermediate and advanced stages of regression. The presence of apoptotic cell death was confirmed using the TUNEL assay. Loss of cilia via the formation of cilia packets was observed using TEM and SEM. Necrotic cell death occurred in mitochondrial cells during the intermediate and late stages of degeneration. In conclusion, the findings of the study on isthmus involution in moulting birds suggest that autophagy is a process confined to the early stages of degeneration, while apoptosis and/or necrosis occur in the terminal stages of regression.
Study question:
How do interactions between blastocyst-stage embryos and endometrial epithelial cells regulate the early stages of implantation in an in vitro model?
Summary answer:
Mouse blastocyst apposition with human endometrial epithelial cells initiates trophectoderm differentiation to trophoblast, which goes on to breach the endometrial epithelium.
What is known already:
In vitro models using mouse blastocysts and human endometrial cell lines have proven invaluable in the molecular characterisation of embryo attachment to endometrial epithelium at the onset of implantation. Genes involved in embryonic breaching of the endometrial epithelium have not been investigated in such in vitro models.
Study design, size, duration:
This study used an established in vitro model of implantation to examine cellular and molecular interactions during blastocyst attachment to endometrial epithelial cells.
Participants/materials, setting, methods:
Mouse blastocysts developed from embryonic day (E) 1.5 in vitro were hatched and co-cultured with confluent human endometrial adenocarcinoma-derived Ishikawa cells in serum-free medium. A scale of attachment stability based on blastocyst oscillation upon agitation was devised. Blastocysts were monitored for 48 h to establish the kinetics of implantation, and optical sectioning using fluorescence microscopy revealed attachment and invasion interfaces. Quantitative PCR was used to determine blastocyst gene expression. Data from a total of 680 mouse blastocysts are reported, with 3-6 experimental replicates. T-test and ANOVA analyses established statistical significance at P < 0.05, P < 0.01 and P < 0.001.
Main results and the role of chance:
Hatched E4.5 mouse blastocysts exhibited weak attachment to confluent Ishikawa cells over the first 24 h of co-culture, with intermediate and stable attachment occurring from 28 h (E5.5 + 4 h) in a hormone-independent manner. Attached embryos fixed after 48 h (E6.5) frequently exhibited outgrowths, characterised morphologically and with antibody markers as trophoblast giant cells (TGCs), which had breached the Ishikawa cell layer. Beginning co-culture at E5.5 also resulted in intermediate and stable attachment from E5.5 + 4 h; however, these embryos did not go on to breach the Ishikawa cell layer, even when co-culture was extended to E7.5 (P < 0.01). Blastocysts cultured from E4.5 in permeable transwell inserts above Ishikawa cells before transfer to direct co-culture at E5.5 went on to attach but failed to breach the Ishikawa cell layer by E6.5 (P < 0.01). Gene expression analysis at E5.5 demonstrated that direct co-culture with Ishikawa cells from E4.5 resulted in downregulation of trophectoderm transcription factors Cdx2 (P < 0.05) and Gata3 (P < 0.05) and upregulation of the TGC transcription factor Hand1 (P < 0.05). Co-culture with non-endometrial human fibroblasts did not alter the expression of these genes.
Large scale data:
None.
Limitations, reasons for caution:
The in vitro model used here combines human carcinoma-derived endometrial cells with mouse embryos, in which the cellular interactions observed may not fully recapitulate those in vivo. The data gleaned from such models can be regarded as hypothesis-generating, and research is now needed to develop more sophisticated models of human implantation combining multiple primary endometrial cell types with surrogate and real human embryos.
Wider implications of the findings:
This study implicates blastocyst apposition to endometrial epithelial cells as a critical step in trophoblast differentiation required for implantation. Understanding this maternal regulation of the embryonic developmental programme may lead to novel treatments for infertility.
Study funding and competing interest(s):
This work was supported by funds from the charities Wellbeing of Women (RG1442) and Diabetes UK (15/0005207), and studentship support for SCB from the Anatomical Society. No conflict of interest is declared.
Embryonic implantation, which is the process by which the human embryo orientates, attaches, and finally invades the underlying maternal endometrial tissue is a highly regulated mechanism. Embryonic implantation requires a receptive endometrium, a competent blastocyst, and a coordinated development and communication between them. Considerable advances have been made in understanding the cell biology of the embryo and the maternal endometrium separately. Nevertheless, communication between them, and the reciprocal effect on each other, constitute an exciting and as yet unsolved paradigm in reproductive medicine. This embryo—maternal dialogue is differentially regulated in an autocrine/paracrine manner during the apposition and adhesion phases. We will show in this chapter the capacity of the human embryo to regulate the endometrial antiadhesion molecule MUC1 to prevent unwanted attachment in the apposition phase and to allow selective attachment in the adhesion phase. In addition, similar coordinated mechanism will be shown for the embryonic regulation of endometrial epithelial cell (EEC) apoptosis in the apposition and adhesion phase of human implantation.
In the adult organism angiogenesis is generally rare and is usually confined to pathological conditions. However, one marked exception to this is the female reproductive tract. In both the ovary and the uterus, there is cyclic growth and regression of specialized tissues that necessitates the growth and regression of vascular structures. These events are coordinated by steroid hormones, but it is now increasingly recognized that local effectors mediate their actions. Thus the female reproductive tract permits the study of the cyclic growth and regression of blood vessels in a normal physiological setting. This is obviously of importance to reproductive biology, but is also relevant to the study of blood vessels generally.
Synchronized development of the embryo to the blastocyst stage and differentiation of the uterus to the receptive state are critical to the process of implantation (1). The attainment of a differentiated uterus to support embryo development and implantation is primarily the result of the coordinated effects of estrogen and progesterone (P4) (1, 2). In rodents the first conspicuous sign that the implantation process has been initiated is an increased endometrial vascular permeability at the site of the blastocyst apposition. This can be visualized as discrete blue bands along the uterus after an intravenous (IV) injection of a macromolecular blue dye solution (1). This increased vascular permeability coincides with the initial attachment reaction between the trophectoderm and uterine luminal epithelium (ULE) (3). The permeability reaction is considered one of the earliest prerequisite events in the implantation process (1). In the mouse the attachment reaction occurs at 2200–2300 h on day 4 of pregnancy and is preceded by luminal closure that results in an intimate apposition of the blastocyst to the ULE (1, 3, 4). The attachment reaction is followed by stromal decidualization and ULE apoptosis at the site of blastocyst (3, 5). This results in the subsequent adherence and penetration by trophoblasts through the underlying basement membrane (6). Trophoblast invasion continues through the stroma in a regulated manner by the remodeling of the extracellular matrix (ECM).
Initially, the mammalian embryo moves freely through the reproductive tract as it undergoes cell division and the first morphogenetic and differentiative steps of its development. After several days a cavity forms in the embryo and it develops into the blastocyst containing an inner clump of cells, the inner cell mass, from which all the tissues of the fetus and some of the extraembryonic membranes are derived. The outer layer surrounding the cavity and inner cell mass, the trophectoderm epithelium, will form the trophoblast of the placenta. It is responsible for attachment of the embryo to the wall of the uterine lumen and the process of implantation.
Blastocyst implantation involves interaction between two independently controlled yet highly interdependent systems, the embryo and its maternal environment. In rodents the preimplantation blastocyst becomes closely surrounded by uterine epithelium in an “implantation chamber” (Enders, 1975), which precedes the first irreversible interaction between the embryo and uterus — adhesion between the apical surfaces of the first embryonic epithelium (trophectoderm) and the uterine epithelium (“1” in Figure 1). In mice, adhesion occurs about 100 hours after the morning in which the coital vaginal plug is discovered (Potts, 1968). In rats this is brought about by a nidatory surge of estradiol, accompanying increasing levels of progesterone (Psychoyos, 1973). There is no clear separation in time between the appearance of apical adhesion and the initiation of basolateral changes, which occur between about 3.5 and 4.5 days after mating (“2” in Figure 1). These changes are characterized by a loosening of lateral cell associations, involving ultimately the junctional complexes (“3” in Figure 1) and a separation of the epithelium from its basal lamina (Schlafke et al., 1985), preparatory to its subsequent sloughing and cell death (Parr et al., 1987).
Attachment of the mammalian embryo to the maternal uterus is a signal event in the highly regulated program of synchronized, apparently independent but interdependent events which define unique interactions between two organisms of different genetic derivation. The focus of this essay will be the role of the individual endometrial cell types, vis-a-vis the blastocyst, in these implantation related events. This paper will suggest that at the present time, only a very generalized understanding of the regulatory mechanisms underlying blastocyst attachment has been established. Present models are, therefore, of limited predictive use in resolving problems in human infertility. In an effort to recognize elements with which to formulate a more functional model particular emphasis will be placed on the responses to endocrine, paracrine, and autocrine mechanisms which come into play following the attachment of trophoblast to the uterine epithelium, i.e., the adhesive and post-implantation phases of implantation.
The evolution of the reproductive process has resulted in the development of elaborate adaptive mechanisms to ensure the survival of the offspring. In viviparous animals such adaptations include the development of complex and diverse forms of implantation and placentation in order to support the attachment and development of embryos in utero. The implantation process exhibits remarkable diversity among species, most prominently in the extent of trophoblastic invasion into the uterus. Yet the general aim of implantation is accomplished in all species: to attach the embryo to the uterine wall and to establish an intimate union between maternal and fetal tissues so that an exchange of nutrients and waste products can occur. The details of the earliest interactions between the blastocyst and endometrium have been the focus of extensive study. It is our purpose to summarize some of the more important developments in this field since the publication of Finn’s fine review of the subject in the second edition of this book (Finn, 1977). In this chapter we have chosen to discuss four aspects of the implantation process: (1) adhesion of the trophoblast to the uterine epithelium; (2) increased vascular permeability at implantation sites; (3) the decidual cell reaction; and (4) loss of epithelial cells surrounding the implanting blastocyst. Our discussion is based primarily on the results of investigations using common laboratory animals, namely, the rat, mouse, and rabbit. In addition, other recent reviews and symposia may be of interest to the reader (Weitlauf, 1979; Glasser and McCormack, 1981; Finn, 1980; Leroy et al., 1980; Glasser and Bullock, 1981; Dey and Johnson, 1980; Kearns and Lala, 1983; Bell, 1983; Kennedy, 1983a; Chévez, 1984; Enders et al., 1983, 1985; Enders and Schlafke, 1986; Yoshinaga et al., 1986).
Trabajo de actualizacion y recopilacion de investigacion utilizando el modelo BALB/c. Trabajo en prensa en los Anales de la Academia Nacional de Agronomia y Veterinaria
Numerous drugs, hormones and environmental pollutants induce liver growth by hypertrophy and/or hyperplasia, and promote preferential growth of putative preneoplastic foci in the liver. In the present study the regression of hyperplasia after cessation of inducer/promoter treatment was studied in normal liver and in liver foci. High doses of cyproterone acetate (CPA), a synthetic sex steroid, were administered to rats and produced a doubling of liver size; after cessation of treatment liver size declined, and 27% of the total liver DNA disappeared within 6 days. In histological sections from the involuting liver no necroses, but numerous apoptotic bodies (ABs) were found; retreatment with CPA interrupted the formation of ABs. These findings suggest that elimination of excess liver DNA after cessation of CPA treatment is due to controlled cell death by apoptosis. In a further series of experiments putative preneoplastic foci were produced by a single dose of N-nitrosomorpholine and subsequently stimulated to grow by 10 or 28 weeks of phenobarbital (PB) treatment. After withdrawal of PB numerous ABs were present in normal liver and in the foci; in both, retreatment with PB decreased the appearance of ABs. It appears that inhibition of cell death by PB may contribute to tumour promotion. Under all conditions tested more ABs were found in the foci than in non-focal parts of the liver, suggesting an enhanced cell turnover in foci. The apparent sensitivity of foci to mechanisms controlling cell death might eventually provide a means for elimination of preneoplastic lesions.
In glucocorticoid-treated rat thymocytes and the murine lymphoid cell lines L5178 and S49 the morphology of apoptosis is associated with chromatin cleavage. The cleavage is at internucleosomal sites, apparently through activation of an endogenous endonuclease. In variants of the cell lines selected for resistance to glucocorticoid, neither apoptosis nor chromatin cleavage were observed after steroid treatment, and steroid receptors were undetectable. In thymocytes, both the morphological changes of apoptosis and chromatin cleavage were inhibited by cycloheximide and actinomycin D. The calcium-magnesium ionophore A23187 induced apoptosis and chromatin cleavage in thymocytes, and these effects were also inhibited by cycloheximide. The data confirm that the condensed chromatin which characterizes apoptosis morphologically consists of endogenously digested chromatin fragments. They also provide support for the view that at least some cells enter apoptosis by a process dependent upon macromolecular synthesis.
The ultrastructure of human NK cells, NK/target cell conjugates, and the effect of monensin, a secretion inhibitor, were studied. Human peripheral blood lymphocytes, highly enriched (75 to 85%) in large granular lymphocytes (LGL), which are known to be the mediators of human NK activity, were used as effectors, and K562 cells as targets. LGL-type of cells were characterized in electron microscopy by a low nucleocytoplasmic ratio, indented nucleus, several large mitochondria, prominent Golgi apparatus, and cytoplasmic osmiophilic granules bound by a unit membrane. Their surface was of intermediate villous type. Two types of effector/target contacts were seen: either effector cell protrusions were pushed deep into pouches and lacunae of the target cell surface, or a wide area of intimate cell-to-cell contact was formed. The contact formation was followed by polarization of the effector cell Golgi apparatus towards the contact area. Monensin, a carboxylic ionophore, which interrupts the vesicular traffic of Golgi-derived vacuoles to the cell surface, caused an accumulation of cytoplasmic vesicles in the LGL but had no effect on the effector/target contact formation. Monensin inhibited the NK lysis apparently via cessation of secretion by the LGL. It did not affect the viability of the effector cells. The lytic steps of human NK cells thus involve binding to the target cell, polarization of cytoplasmic organelles towards the target, and apparently a precisely directed exocytosis of secretory material.
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