Blockade of the alpha(v)beta(3) integrin adversely affects implantation in the mouse

Maternal plasma TIMP-4 levels combined with clinical risk factors for the early prediction of pregnancy-induced hypertension

OBJECTIVE

The objective of this study was to create a model for early predicting pregnancy-induced hypertension (PIH) using plasma markers and clinical risk factors.

METHODS

A nested case-control study was performed at the Laboratory Department of Guangzhou Women and Children's Medical Center. From a prospective cohort of tens of thousands of unselected women with singleton pregnancies at 8-20 weeks gestation, maternal plasma samples were obtained from 73 women who subsequently developed PIH (PIH group) and 146 gestational age- and maternal age-matched women with normotensive pregnancies (control group). Proteins extracted from the plasma samples were screened by microchip and verified by ELISA. Clinical risk factor data were analyzed retrospectively.

RESULTS

Compared to the control group, high concentrations of tissue inhibitor of metalloproteinase-4 (TIMP-4) were found in women with PIH (P = 0.000). Univariate risk factor analysis identified three variables with significant differences between the groups: family history of PIH (P = 0.031), body mass index (BMI; P < 0.001), and non-glucose-6-phosphate dehydrogenase deficiency-induced anemia (P < 0.027). Multiple regression analyses revealed a significant relationship of PIH with TIMP-4 levels, BMI, and family history (combined area under the receiver operating characteristic curve = 0.820).

CONCLUSION

Upregulation of plasma TIMP-4 might contribute to PIH processes. Potential risk factors of this disease may include a family history of PIH and BMI. The combination of TIMP-4 levels and these risk factors may have some predictive values for PIH. Future multicenter studies including greater numbers of samples, analyzed proteins, and risk factors are needed to obtain a higher predictive value of the model for the clinical diagnosis of PIH.

Mmu-miR-126a-3p plays a role in murine embryo implantation by regulating Itga11

miR-126a-3p has been found to be specifically up-regulated in the process of murine embryo implantation. This study aimed to further clarify the role of miR-126a-3p in embryo implantation. The expression of miR-126a-3p in implantation sites was significantly higher than that in interimplantation sites (P = 0.009). Its expression dynamics in a series of models, including pseudopregnancy, delayed implantation and artificial decidualization, suggested that the induction of miR-126a-3p is dependent on hormonal signalling and decidualization of the endometrium. Bioinformatic analysis predicted and luciferase activity assay confirmed that Itga11, a member of the integrin family, was a target gene of miR-126a-3p. miR-126a-3p bound to the 3' untranslated region of Itga11 and regulated Itga11 by inhibiting mRNA translation and affecting mRNA stability. Transwell assay showed that miR-126a-3p promoted cell migratory and invasive capacity in vitro. Loss of function of miR-126a-3p significantly reduced the number of implantation sites in vivo (P = 0.013). Collectively, miR-126a-3p may play a major role in embryo implantation by regulating Itga11, possibly through impairing cell migratory and invasive capacity. These findings should contribute to a better understanding of the miRNA-based mechanism of embryo implantation.

Relocalisation and activation of integrins induced rapidly by oestrogen via G-protein-coupled receptor 30 in mouse blastocysts

Integrins are the dominant and final adhesion molecules in the attachment process between the blastocysts and endometrium. It is necessary for oestrogen to rapidly activate mouse blastocysts so that they attach to the endometrial epithelium. Our previous study suggested that oestrogen can rapidly induce an increase in intracellular calcium in mouse blastocysts via G-protein-coupled receptor 30 (GPR30). Thus, we deduced that integrins may be involved in GPR30 mediation of the fast effect of oestrogen on mouse blastocysts in implantation. To prove our hypothesis, we used immunofluorescence staining and in vitro coculture of mouse blastocysts and endometrial epithelial cell line (EECs), Ishikawa cells, in the present study. We found that αv and β1 integrin clustered in mouse blastocysts, and that β3 integrin was relocalised to the apical membrane of blastocyst cells when embryos were treated with 1 μM 17β-estradiol (E2), 1 μM E2 conjugated to bovine serum albumin (E2-BSA) and 1 μM G-1, a specific GPR30 agonist, for 30 min respectively, whereas pretreatment with 1 μM G15, a specific GPR30 antagonist, and 5 μM 1,2-Bis(2-aminophenoxy)ethane-N,N,N'',N''-tetraacetic acid tetrakis (acetoxymethyl ester)(BAPTA/AM), a cellular Ca2+ chelator, blocked the localisation of integrins induced by oestrogen via GPR30 in mouse blastocyst cells. E2, E2-BSA and G-1 increased the fibronectin (FN)-binding activity of integrins in blastocysts, whereas G15 and BAPTA/AM blocked the activation of integrins induced by oestrogen via GPR30 in mouse blastocysts. Inhibition of integrins by Arg-Gly-Asp peptide in blastocysts resulted in their failure to adhere to EECs in vitro, even if oestrogen or G-1 was provided. Together, the results indicate the fast effect of oestrogen via the GPR30 membrane receptor further induces relocalisation and activation of integrins in mouse blastocysts, which play important roles in the adhesion of blastocysts to EECs.

Activation of Toll-like receptor 3 reduces actin polymerization and adhesion molecule expression in endometrial cells, a potential mechanism for viral-induced implantation failure

STUDY QUESTION

Does activation of endometrial Toll-like receptor 3 (TLR 3) affect cell receptivity to trophoblast adhesion?

SUMMARY ANSWER

TLR 3 activation in vitro reduces the attachment of trophoblast cells to endometrial cells by altering the cell cytoskeleton and reducing the expression of adhesion molecules in human endometrial cells.

WHAT IS KNOWN ALREADY

It is well documented that the presence of an infection at the time of implantation can lead to implantation failure. The female reproductive tract recognizes invading micro-organisms through the innate pathogen recognition receptors such as the TLRs.

STUDY DESIGN, SIZE, DURATION

Poly I:C was used as a TLR 3-specific ligand and endometrial cells were either treated or not with Poly I:C (treated versus control) in vitro. The experiments were performed in three replicates on three separate days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An in vitro assay was developed using RL95-2 (a human endometrial cell line) and JAr (a human trophoblast cell line) cells. Initially, the percentage of attached JAr spheroids to RL95-2 was measured in response to TLR 3 activation. Next, actin polymerization in RL95-2 cells was assessed in response to TLR 2/6, 3 and 5 activation. Phalloidin was used to assess the mean fluorescence intensity of F-actin by flow cytometry or confocal microscopy. Secondly, the influence of TLR 2/6, 3 and 5 activation on the expression of cluster of differentiation 98 (CD98) and β3 integrin was determined. To further understand through which pathways the TLR 3-induced alterations occur, inhibitors were applied for Toll/interleukin-1 receptor domain-containing adaptor inducing interferon-beta (TRIF), myeloid differentiation primary response 88 (MYD88), mitogen-activated protein kinases (MAPK) and nuclear factor pathways.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed that stimulation of TLR 3 in endometrial cells with different concentrations of Poly I:C led to a reduction in the percentage of trophoblasts attached to the endometrial cells in a dose-dependent manner (P < 0.05). This decrease was consistent in the Poly I:C treated group regardless of the co-incubation time (P < 0.05). In addition, our results demonstrated that actin polymerization and CD98 expression significantly decreased only in response to TLR 3 activation (P < 0.05). Activation of endometrial cells with TLR 2/6, 3 and 5 significantly reduced β3 integrin expression (P < 0.05). These alterations were shown to work via MYD88-MAPK pathways (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study has been performed in vitro. Future in vivo studies will be required in order to confirm our data.

WIDER IMPLICATIONS OF THE FINDINGS

This is a novel discovery which extends our current knowledge concerning diagnosis and treatment of viral-induced infertility cases.

STUDY FUNDING/COMPETING INTERESTS

This research was supported by the COST Action FA1201 (GEMINI) by granting a Short Term Scientific Mission and the Instituto de Salud Carlos III by granting Grant PI11/01645. The authors have no conflict of interest to declare.

Systematic review of cell adhesion molecules and estrogen receptor expression in the endometrium of patients with polycystic ovary syndrome

BACKGROUND

Infertility associated with polycystic ovary syndrome (PCOS) could be related to many mechanisms including endometrial factors.

OBJECTIVES

To review cell adhesion molecule and estrogen receptor expression in the endometrium.

SEARCH STRATEGY

A systematic review was performed of the Medline and Cochrane databases for papers published in any language between 2004 and 2014. The search term was "'polycystic ovary syndrome' OR 'Stein Leventhal syndrome' OR 'anovulation' AND 'endometrium' OR 'endometria.'"

SELECTION CRITERIA

Research studies on endometrial cell adhesion molecules and estrogen receptor expression among women with PCOS diagnosed according to the Rotterdam criteria were included.

DATA COLLECTION AND ANALYSIS

Data were extracted from identified studies and the quality of assessment was analyzed.

MAIN RESULTS

Six studies were included. Data were controversial with respect to MUC1 and αVβ3 integrin expression with significantly higher and lower levels, respectively, in women with PCOS. Estrogen receptor expression was enhanced among patients with PCOS as compared with healthy women.

CONCLUSIONS

Endometrial factors influence embryo receptivity as indicated by the molecular mediators identified in the studies, including cell adhesion molecules and the estrogen receptor.

Osteopontin: a leading candidate adhesion molecule for implantation in pigs and sheep

Osteopontin (OPN; also known as Secreted Phosphoprotein 1, SPP1) is a secreted extra-cellular matrix (ECM) protein that binds to a variety of cell surface integrins to stimulate cell-cell and cell-ECM adhesion and communication. It is generally accepted that OPN interacts with apically expressed integrin receptors on the uterine luminal epithelium (LE) and conceptus trophectoderm to attach the conceptus to the uterus for implantation. Research conducted with pigs and sheep has significantly advanced understanding of the role(s) of OPN during implantation through exploitation of the prolonged peri-implantation period of pregnancy when elongating conceptuses are free within the uterine lumen requiring extensive paracrine signaling between conceptus and endometrium. This is followed by a protracted and incremental attachment cascade of trophectoderm to uterine LE during implantation, and development of a true epitheliochorial or synepitheliochorial placenta exhibited by pigs and sheep, respectively. In pigs, implanting conceptuses secrete estrogens which induce the synthesis and secretion of OPN in adjacent uterine LE. OPN then binds to αvβ6 integrin receptors on trophectoderm, and the αvβ3 integrin receptors on uterine LE to bridge conceptus attachment to uterine LE for implantation. In sheep, implanting conceptuses secrete interferon tau that prolongs the lifespan of CL. Progesterone released by CL then induces OPN synthesis and secretion from the endometrial GE into the uterine lumen where OPN binds integrins expressed on trophectoderm (αvβ3) and uterine LE (identity of specific integrins unknown) to adhere the conceptus to the uterus for implantation. OPN binding to the αvβ3 integrin receptor on ovine trophectoderm cells induces in vitro focal adhesion assembly, a prerequisite for adhesion and migration of trophectoderm, through activation of: 1) P70S6K via crosstalk between FRAP1/MTOR and MAPK pathways; 2) MTOR, PI3K, MAPK3/MAPK1 (Erk1/2) and MAPK14 (p38) signaling to stimulate trohectoderm cell migration; and 3) focal adhesion assembly and myosin II motor activity to induce migration of trophectoderm cells. Further large in vivo focal adhesions assemble at the uterine-placental interface of both pigs and sheep and identify the involvement of sizable mechanical forces at this interface during discrete periods of trophoblast migration, attachment and placentation in both species.

Biopsy-induced inflammatory conditions improve endometrial receptivity: the mechanism of action

A decade ago, we first reported that endometrial biopsy significantly improves the success of pregnancy in IVF patients with recurrent implantation failure, an observation that was later confirmed by others. Recently, we have demonstrated that this treatment elevated the levels of endometrial pro-inflammatory cytokines and increased the abundance of macrophages (Mac) and dendritic cells (DCs). We therefore hypothesised that the biopsy-related successful pregnancy is secondary to an inflammatory response, and aimed at deciphering its mechanism of action. Supporting our hypothesis, we found that the pro-inflammatory TNFα stimulated primary endometrial stromal cells to express cytokines that attracted monocytes and induced their differentiation into DCs. These monocyte-derived DCs stimulated endometrial epithelial cells to express the adhesive molecule SPP1 (osteopontin (OPN)) and its receptors ITGB3 and CD44, whereas MUC16, which interferes with adhesion, was downregulated. Other implantation-associated genes, such as CHST2, CCL4 (MIP1B) and GROA, were upregulated by monocyte-derived Mac. These findings suggest that uterine receptivity is mediated by the expression of molecules associated with inflammation. Such an inflammatory milieu is not generated in some IVF patients with recurrent implantation failure in the absence of local injury provoked by the biopsy treatment.

Prospective assessment of midsecretory endometrial leukemia inhibitor factor expression versus ανβ3 testing in women with unexplained infertility

OBJECTIVE

To evaluate endometrial leukemia inhibitor factor (LIF) expression as a marker of endometrial receptivity in women with unexplained infertility (UI).

DESIGN

Prospective case-control study.

SETTING

University-associated infertility clinics.

PATIENT(S)

Women with UI for more than 1 year and healthy control women.

INTERVENTION(S)

Endometrial biopsy.

MAIN OUTCOME MEASURE(S)

Time to pregnancy was compared between patients with UI who were evaluated for endometrial LIF protein as well as ανβ3 integrin expression. Endometrium was evaluated using immunohistochemistry (IHC) and messenger RNA by real time reverse transcriptase-polymerase chain reaction (PCR) (quantitative real-time reverse transcriptase-PCR) in samples from women with UI as well as healthy control women.

RESULT(S)

Leukemia inhibitor factor was expressed in epithelial cells in a cyclic fashion in controls, and overall expression in the secretory phase was similar between controls and women with UI, whereas ανβ3 integrin expression was reduced. However, using quantitative real-time PCR, LIF messenger RNA abundance was 4.4-fold lower in women with low levels of ανβ3 integrin expression compared with samples with normal integrins. By immunohistochemistry, ανβ3 integrin expression was always lacking when the histology was out of phase, whereas LIF expression was only negative in a subset of those samples. Reduced endometrial LIF expression was strongly associated with poor reproductive outcomes.

CONCLUSION(S)

Endometrial LIF expression peaks in the midsecretory phase and is reduced in some women with UI. The use of LIF in combination with ανβ3 integrin as biomarkers appears to be superior to integrin testing alone when evaluating endometrial receptivity, primarily because of its earlier pattern of expression during the secretory phase.

The role of inflammation for a successful implantation

Approximately half of all human embryo implantations result in failed pregnancy. Multiple factors may contribute to this failure, including genetic or metabolic abnormalities of the embryo. However, many of these spontaneous early abortion cases are attributed to poor uterine receptivity. Furthermore, although many fertility disorders have been overcome by a variety of assisted reproductive techniques, implantation remains the rate-limiting step for the success of the in vitro fertilization (IVF) treatments. We, as well as others, have demonstrated that endometrial biopsies performed either during the spontaneous, preceding cycle, or during the IVF cycle itself, significantly improve the rate of implantation, clinical pregnancies, and live births. These observations suggest that mechanical injury of the endometrium may enhance uterine receptivity by provoking the immune system to generate an inflammatory reaction. In strong support of this idea, we recently found that dendritic cells (DCs), an important cellular component of the innate immune system, play a critical role in successful implantation in a mouse model. In this review, we discuss the hypothesis that the injury-derived inflammation in the biopsy-treated patients generates a focus for uterine DCs and Mac accumulation that, in turn, enhance the endometrial expression of essential molecules that facilitate the interaction between the embryo and the uterine epithelium.

Mmu-miR-193 is involved in embryo implantation in mouse uterus by regulating GRB7 gene expression

Embryo implantation is a complicated process involving a series of endometrial changes that depend on differential gene expression. MicroRNAs (miRNAs) are important for regulation of gene expression. Previous studies have shown that miRNAs may participate in the regulation of gene expression during embryo implantation. To explore the role of endometrial miRNAs in early murine pregnancy, we used microarrays to investigate whether miRNAs were differentially expressed in the mouse endometrium on pregnancy day 4 (D4) and day 6 (D6). The results demonstrated that 17 miRNAs were upregulated and 18 were downregulated (>2-fold) in D6 endometria compared to D4. We identified that mmu-miR-193 exhibited the highest upregulation on D6, and the upregulation of mmu-miR-193 before embryo implantation could reduce the embryo implantation rate. Further, we demonstrated that mmu-miR-193 influenced embryo implantation by regulating growth factor receptor-bound protein 7 expression. In summary, our study suggests that mmu-miR-193 plays an important role in embryo implantation.

Mmu-microRNA-200a overexpression leads to implantation defect by targeting phosphatase and tensin homolog in mouse uterus

Successful mouse embryo implantation requires a receptive uterus and an activated blastocyst. A large number of genes, cytokines, and other factors are involved in the process. MicroRNAs (miRNAs) regulate the expression of many genes, and previous studies have investigated the relationship between miRNA expression and embryo implantation. In this study, we show that mmu-microRNA-200a (mmu-miR-200a) is expressed in a spatiatemporal manner during implantation in mouse uterus and found that phosphatase and tensin homolog (PTEN), SON, and programmed cell death 4 (Pdcd4) are the target genes of mmu-miR-200a by bioinformatics analysis. In vitro gain and loss of function experiments confirm that PTEN, a critical gene for cell proliferation and apoptosis, is the target gene of mmu-miR-200a. Our experiments also show that injection of the uterine horn with mmu-miR-200a lentivirus leads to a decreased implantation rate. Collectively, our results suggest that mmu-miR-200a affects embryo implantation by regulating PTEN protein expression. Thus, clarifying the physiological functions of uterine miRNAs will help to elucidate the embryo implantation process and may even contribute to curing infertility and inventing new contraceptives.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Extracellular matrix proteins secreted from both the endometrium and the embryo are required for attachment: a study using a co-culture model of rat blastocysts and Ishikawa cells

Integrins are expressed in a highly regulated manner at the maternal-fetal interface during implantation. However, the significance of extracellular matrix (ECM) ligands during the integrin-mediated embryo attachment to the endometrium is not fully understood. Thus, the distribution of fibronectin in the rat uterus and blastocyst was studied at the time of implantation. Fibronectin was absent in the uterine luminal epithelial cells but was intensely expressed in the trophoblast cells and the inner cell mass suggesting that fibronectin secreted from the blastocyst may be a possible bridging ligand for the integrins expressed at the maternal-fetal interface. An Arg-Gly-Asp (RGD) peptide was used to block the RGD recognition sites on integrins, and the effect on rat blastocyst attachment to Ishikawa cells was examined. There was a significant reduction in blastocyst attachment when either the blastocysts or the Ishikawa cells were pre-incubated with the RGD-blocking peptide. Thus, successful attachment of the embryo to the endometrium requires the interaction of integrins on both the endometrium and the blastocyst with the RGD sequence of ECM ligands, such as fibronectin. Pre-treatment of both blastocysts and Ishikawa cells with the RGD peptide also inhibited blastocyst attachment, but not completely, suggesting that ECM bridging ligands that do not contain the RGD sequence are also involved in embryo attachment.

Involvement of microRNA lethal-7a in the regulation of embryo implantation in mice

MicroRNAs interact with multiple mRNAs resulting in their degradation and/or translational repression. This report used the delayed implantation model to determine the role of miRNAs in blastocysts. Dormant blastocysts in delayed implanting mice were activated by estradiol. Differential expression of 45 out of 238 miRNAs examined was found between the dormant and the activated blastocysts. Five of the nine members of the microRNA lethal-7 (let-7) family were down-regulated after activation. Human blastocysts also had a low expression of let-7 family. Forced-expression of a family member, let-7a in mouse blastocysts decreased the number of implantation sites (let-7a: 1.1±0.4; control: 3.8±0.4) in vivo, and reduced the percentages of blastocyst that attached (let-7a: 42.0±8.3%; control: 79.0±5.1%) and spreaded (let-7a: 33.5±2.9%; control: 67.3±3.8%) on fibronectin in vitro. Integrin-β3, a known implantation-related molecule, was demonstrated to be a target of let-7a by 3′-untranslated region reporter assay in cervical cancer cells HeLa, and Western blotting in mouse blastocysts. The inhibitory effect of forced-expression of let-7a on blastocyst attachment and outgrowth was partially nullified in vitro and in vivo by forced-expression of integrin-β3. This study provides the first direct evidence that let-7a is involved in regulating the implantation process partly via modulation of the expression of integrin-β3. (200 words).

Endometrial abnormality in women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy associated with infertility and metabolic disorder in women of reproductive age. Although the clinical and biochemical features are heterogeneous with individuals, the most widely accepted clinical characteristics of PCOS are oligo- or anovulation combined with hyperandrogenism. With the higher rate of implantation failure after induction of ovulation or higher risk of spontaneous miscarriage after pregnancy, the reduced fertility is apparently attributed not only to anovulation but also to endometrial dysfunction in patients with PCOS. Here we review the features of the endometrial abnormalities in women with PCOS. The ability to improve the endometrial functions is of potential therapeutic targets to increase reproductive outcome of women with PCOS.

Mechanisms of disease: the endocrinology of ectopic pregnancy

Ectopic pregnancy is defined as a pregnancy implanted outside the uterus, and >98% implant in the Fallopian tube. It has a major clinical and socioeconomic impact worldwide. The diagnosis of ectopic pregnancy is often difficult and resource intensive owing to a lack of accurate biomarkers, and there is a need for improved medical management of ectopic pregnancy using new or adjuvant treatments. The aetiology of ectopic pregnancy is uncertain, but tubal implantation is probably due to retention of the embryo in the Fallopian tube owing to impaired embryo-tubal transport and alterations in the tubal microenvironment. This comprehensive review of the literature supporting current understanding of the endocrinology of Fallopian tube biology and tubal implantation focuses on genes expressed in the Fallopian tube regulated by oestrogen and progesterone and discusses their potential functions. It concludes with a discussion of how advances in this field are enabling the development of novel biomarkers and could lead to the identification of potential new treatments for ectopic pregnancy.

Human fallopian tube epithelium constitutively expresses integrin endometrial receptivity markers: no evidence for a tubal implantation window

Understanding of ectopic implantation within the Fallopian tube (FT) is limited. In the human uterus, the putative 'window of implantation' in the mid-luteal phase of the menstrual cycle is accompanied by increased endometrial epithelial expression of the integrins α(1)β(1), α(4)β(1) and α(v)β(3) and its ligand osteopontin. Similar cyclical changes in FT integrin expression have been proposed to contribute to ectopic implantation, but supporting data are limited. In the current study, we present quantitative data on human FT transcription and translation of the integrin subunits α(1), α(4), α(V), β(1) and β(3) during the follicular and mid-luteal phases of the menstrual cycle, together with a supporting immuocytochemical analysis of their spatial distribution within the FT, and that of osteopontin. In contrast to previous studies, our data indicate that all five integrin receptivity markers are constitutively transcribed and translated in the FT, with no evidence for changes in their expression or distribution during the window of implantation in the mid-luteal phase of the cycle. Furthermore, we could find no evidence for cyclic redistribution of the integrin α(v)β(3) ligand osteopontin within the FT. Although we do not rule out the involvement of integrin endometrial receptivity markers in the establishment of ectopic pregnancy, our findings do not support their differential expression during a tubal implantation window.

Extracts from a traditional Chinese herbal remedy (Zhuyun recipe) improve endometrial receptivity in mice with embryonic implantation dysfunction and ovulation stimulation

OBJECTIVE

Although ovarian stimulation has an important role in assisted reproductive technologies (ART), it may also have detrimental effects on endometrial receptivity. Traditional Chinese herbal remedy, as a kind of traditional treatments, has been widely and increasingly applied in clinic. In this article, the impact of traditional Chinese medicines (TCM) on embryonic implantation, pregnant rate and underlying mechanisms will be investigated.

METHODS

One hundred and sixty-three female pregnant kunming mice were randomly divided into 6 groups, including A, control group; B, ovulation stimulation (OS) group; C, OS+TCM group; D, embryo implantation dysfunction (EID) group; E, EID+TCM group; F, TCM only group. Uterus samples were collected at gestation Day 4 and were detected with immunohistochemistry and Real Time-PCR analyses. Uterine horns were excised to determine the number of pregnant mice and implantation sites on the Day 8 postcoitum.

RESULTS

OS group and EID group showed a significant decrease in pregnant rate and the expression of both the endometrial leukaemia inhibitory factor (LIF) and integrin β3 subunit during the implantation window. OS+TCM group and EID+TCM group showed a higher pregnant rate and endometrial LIF and integrin β3 subunit expression compared to OS group and EID group. The number of implanted embryo in EID group was lower than in control group, but higher in EID+TCM group than in EID group. No significant difference was found in the measured indices between the TCM only group and control group.

CONCLUSIONS

OS model and EID model may have a negative influence on endometrial receptivity and embryonic implantation in mice. Conversely, TCM appears to reverse the expression of endometrial LIF and integrin β3 subunit, improves the uterine receptivity in mice and increases pregnant rate and embryonic implantation. It provides a new insight into the clinic infertility's treatment.

β(1) and β(3) integrins disassemble from basal focal adhesions and β(3) integrin is later localised to the apical plasma membrane of rat uterine luminal epithelial cells at the time of implantation

The present study investigated the expression of integrin subunits that are known to be associated with focal adhesions, namely β(1) and β(3) integrins in rat uterine luminal epithelial cells during early pregnancy. The β(1) and β(3) integrins were concentrated along the basal cell surface and were colocalised and structurally interacted with talin, a principal focal adhesion protein, on Day 1 of pregnancy. At the time of implantation, β(1) and β(3) integrins disassembled from the site of focal adhesions, facilitating the removal of uterine luminal epithelial cells for embryo invasion. Also at this time, β(3) integrin markedly increased along the apical membrane, suggesting a role in embryo attachment. This distributional change in β(1) and β(3) integrins seen at the time of implantation was predominantly under the influence of progesterone. Taken together, β(1) and β(3) integrin disassembly from focal adhesions and the increase in β(3) integrin apically are key components of hormonally regulated endometrial receptivity.

αv β3 Integrin may participate in conceptus attachment by regulating morphologic changes in the endometrium during peri-implantation in ovine

The objective of this study was to determine expression and potential functions of α(v) and β(3) integrin subunits in ovine endometrium during the peri-implantation period (days 8-17 after fertilization). The morphologic changes in the endometrium were observed histochemically following haematoxylin/eosin (HE) staining, whereas the expressions of α(v) and β(3) integrin subunits were analysed by RT-PCR, immunohistochemistry and Western blot. The filamentous conceptus attached to the luminal epithelium (LE) on day 17 of pregnancy, with no differences in endometrial morphology between days 8-12 of pregnancy. However, endometrial glands in the endometrial stroma (S) underwent extensive hyperplasia from day 14 to day 17, increased reductus of the LE with an obvious proliferation of caruncles, and an increased number and diameter of blood vessels (V) in the endometrium. The relative expression levels of α(v) and β(3) integrin subunits mRNA gradually increased until day 16, but sharply declined on day 17. Western blot analysis revealed that the expression pattern of α(v) and β(3) integrin subunit proteins paralleled that of the corresponding mRNA. In addition, immunohistochemical localization of α(v) and β(3) integrin subunits confirmed their presence in the glandular epithelium (GE), LE and endometrial stroma. Immunostaining on LE and stroma varied with the increasing days of pregnancy, with the strongest immunostaining on days 16 and 17. In conclusion, expression of α(V) and β(3) integrin subunits was closely related to the early progression of pregnancy and conceptus attachment; therefore, we inferred that α(v) β(3) integrin may participate in conceptus attachment by the regulation of endometrial morphology during peri-implantation in ovine.

Difucosylated oligosaccharide Lewis Y is contained within integrin αvβ3 on RL95-2 cells and required for endometrial receptivity

OBJECTIVE

To investigate whether Lewis Y (LeY) carried by integrin αvβ3 influences integrin αvβ3-mediated adhesion in an in vitro implantation model.

DESIGN

Laboratory research.

SETTING

Reproduction and glycobiology research laboratory.

INTERVENTION(S)

Specific antibody blockage of LeY or integrin αvβ3 and knockdown of FUT4 expression in RL95-2 cells by transient transfection of FUT4 siRNA.

MAIN OUTCOME MEASURE(S)

The expression of integrin αvβ3 and LeY in both endometrial tissues and RL95-2 cells was measured. LeY carried by integrin αvβ3 was identified by examining the immunoprecipitated integrin αvβ3. The effect of knocking down FUT4 on the expression of integrin αvβ3 and LeY and their impact on the adhesion of JAR cells to the RL95-2 cells were assessed.

RESULT(S)

Integrin αvβ3 and LeY are expressed in both secretory-stage human endometrial tissue and in RL95-2 cells. Although integrin αvβ3 carries LeY, knocking down FUT4 expression only reduces the expression of LeY but not of integrin αvβ3. Knocking down FUT4, antibody blockade of LeY or integrin αvβ3 consistently decreases the adhesion of JAR cells to the RL95-2 cells and prevents focal adhesion kinase (FAK) phosphorylation.

CONCLUSION(S)

LeY carried by integrin αvβ3 plays a critical role on the attachment of JAR cells to the RL95-2 cells and activates integrin αvβ3/FAK signaling.

Current knowledge of the aetiology of human tubal ectopic pregnancy

BACKGROUND An ectopic pregnancy is a pregnancy which occurs outside of the uterine cavity, and over 98% implant in the Fallopian tube. Tubal ectopic pregnancy remains the most common cause of maternal mortality in the first trimester of pregnancy. The epidemiological risk factors for tubal ectopic pregnancy are well established and include: tubal damage as a result of surgery or infection (particularly Chlamydia trachomatis), smoking and in vitro fertilization. This review appraises the data to date researching the aetiology of tubal ectopic pregnancy. METHODS Scientific literature was searched for studies investigating the underlying aetiology of tubal ectopic pregnancy. RESULTS Existing data addressing the underlying cause of tubal ectopic pregnancy are mostly descriptive. There are currently few good animal models of tubal ectopic pregnancy. There are limited data explaining the link between risk factors and tubal implantation. CONCLUSIONS Current evidence supports the hypothesis that tubal ectopic pregnancy is caused by a combination of retention of the embryo within the Fallopian tube due to impaired embryo-tubal transport and alterations in the tubal environment allowing early implantation to occur. Future studies are needed that address the functional consequences of infection and smoking on Fallopian tube physiology. A greater understanding of the aetiology of tubal ectopic pregnancy is critical for the development of improved preventative measures, the advancement of diagnostic screening methods and the development of novel treatments.

Tubulointerstitial nephritis antigen-like 1 is expressed in the uterus and binds with integrins in decidualized endometrium during postimplantation in mice

Extracellular matrix substrates contribute to both uterine and blastocyst functions during the peri-implantation period. Tubulointerstitial nephritis antigen-like 1 (TINAGL1, also known as adrenocortical zonation factor 1 [AZ-1] or lipocalin 7) is a novel matricellular protein that promotes cell adhesion and spreading. However, the physiological roles of TINAGL1 are still not clearly understood. We examined the expression and localization of TINAGL1 in peri-implantation mouse uteri. During the preimplantation period, TINAGL1 was expressed in the basement membranes of uterine luminal epithelial cells on Days 1 and 2 of pregnancy, while its expression levels declined after Day 3. In the whole uteri, the expression levels of Tinagl1 mRNA and TINAGL1 protein were similar on Days 1-4 of pregnancy. In contrast, the expression of Tinagl1 mRNA and TINAGL1 protein increased in postimplantation uteri. From Days 6 to 8, TINAGL1 was markedly expressed in the decidual endometrium. TINAGL1 is a ligand for integrins and promotes cell adhesion in cultured cells. Therefore, to address whether TINAGL1 interacts with integrins in the uterus, immunohistochemical analysis and immunoprecipitation were performed. Immunohistochemical analysis showed that ITGA2, ITGA5, and ITGB1 were expressed in stromal cells around the implanted embryos on Days 7 and 8. Biacore and immunoprecipitation analysis determined that TINAGL1 linked with ITGA5 and ITGB1 in the decidual endometrium. These results suggest that Tinagl1 functions during the postimplantation period; in particular, it associates with ITGA5B1 in the decidualized uterine endometrium.

Secreted phosphoprotein 1 (SPP1, osteopontin) binds to integrin alpha v beta 6 on porcine trophectoderm cells and integrin alpha v beta 3 on uterine luminal epithelial cells, and promotes trophectoderm cell adhesion and migration

Conceptus implantation involves pregnancy-specific alterations in extracellular matrix at the conceptus-maternal interface. Secreted phosphoprotein 1 (SPP1, osteopontin) is induced just before implantation and is present at the conceptus-maternal interface in mammals. In the present study, we investigated mechanisms by which SPP1 facilitates porcine conceptus and uterine luminal epithelial cell attachment. Native bovine milk and wild-type rat recombinant SPP1 stimulated trophectoderm cell migration. Bovine milk SPP1, ovine uterine SPP1, and recombinant wild-type, but not mutated, rat SPP1 promoted dose- and cation-dependent attachment of porcine trophectoderm and uterine luminal epithelial cells, which was markedly reduced in the presence of a linear Arg-Gly-Asp integrin-blocking peptide. Affinity chromatography and immunoprecipitation experiments revealed direct binding of alpha v beta 6 trophectoderm and alpha v beta 3 uterine epithelial cell integrins to SPP1. Immunofluorescence microscopy using SPP1-coated microspheres revealed colocalization of the alpha v integrin subunit and talin at focal adhesions as well as at the apical domain of trophectoderm cells. Similarly, immunofluorescence staining of implantation sites in frozen gravid uterine cross sections localized SPP1 and alpha v integrin to the apical surfaces of trophectoderm and luminal epithelium and beta 3 integrin to the apical surface of luminal epithelium. To our knowledge, the present study is the first to demonstrate functionally that SPP1 directly binds specific integrins to promote trophectoderm cell migration and attachment to luminal epithelium that may be critical to conceptus elongation and implantation.

Adhesion molecules in endometrial epithelium: tissue integrity and embryo implantation

Cell adhesion in endometrial epithelium is regulated to maintain the continuity and protectiveness of the luminal covering cell layer while permitting interstitial implantation of the embryo during a restricted period of about 4 days. Many apparently normal embryos fail to implant, and epithelial-embryo adhesion remains a poorly understood phenomenon. After menstruation, epithelial regeneration occurs by epiboly from the basal residues of glands, an activity that requires migration on extracellular matrix as well as cell-cell cohesion. Here we review current knowledge of adhesion molecules in the epithelium.

Comparative aspects of implantation

Uterine receptivity to implantation of blastocysts in mammals includes hatching from zona pellucida, precontact with uterine luminal (LE) and superficial glandular (sGE) epithelia and orientation of blastocyst, apposition between trophectoderm and uterine LE and sGE, adhesion of trophectoderm to uterine LE/sGE, and, in some species, limited or extensive invasion into the endometrial stroma and induction of decidualization of stromal cells. These peri-implantation events are prerequisites for pregnancy recognition signaling, implantation, and placentation required for fetal-placental growth and development through the remainder of pregnancy. Although there is a range of strategies for implantation in mammals, a common feature is the requirement for progesterone (P(4)) to downregulate expression of its receptors in uterine epithelia and P(4) prior to implantation events. P(4) then mediates its effects via growth factors expressed by stromal cells in most species; however, uterine luminal epithelium may express a growth factor in response to P(4) and/or estrogens in species with a true epitheliochorial placenta. There is also compelling evidence that uterine receptivity to implantation involves temporal and cell-specific expression of interferon (IFN)-stimulated genes that may be induced directly by an IFN or induced by P(4) and stimulated by an IFN. These genes have many roles including nutrient transport, cellular remodeling, angiogenesis and relaxation of vascular tissues, cell proliferation and migration, establishment of an antiviral state, and protection of conceptus tissues from challenges by the maternal immune cells.

Enhanced focal adhesion assembly reflects increased mechanosensation and mechanotransduction at maternal–conceptus interface and uterine wall during ovine pregnancy

The integrity of the fetal–maternal interface is critical for proper fetal nourishment during pregnancy. Integrins are important adhesion molecules present at the interface during implantation; however,in vivoevidence for integrin activation and focal adhesion formation at the maternal–conceptus interface is limited. We hypothesized that focal adhesion assembly in uterine luminal epithelium (LE) and conceptus trophectoderm (Tr) results from integrin binding of extracellular matrix (ECM) at this interface to provide increased tensile forces and signaling to coordinate utero-placental development. An ovine model of unilateral pregnancy was used to evaluate mechanotransduction events leading to focal adhesion assembly at the maternal–conceptus interface and within the uterine wall. Animals were hysterectomized on days 40, 80, or 120 of pregnancy, and uteri immunostained for integrins (ITGAV, ITGA4, ITGA5, ITGB1, ITGB3, and ITGB5), ECM proteins (SPP1, LGALS15, fibronectin (FN), and vitronectin (VTN)), cytoskeletal molecules (ACTN and TLN1), and a signal generator (PTK2). Focal adhesion assembly in myometrium and stroma was also studied to provide a frame of reference for mechanical stretch of the uterine wall. Large focal adhesions containing aggregates of ITGAV, ITGA4, ITGA5, ITGB1, ITGB5, ACTN, and PTK2 were detected in interplacentomal uterine LE and Tr of gravid but not non-gravid uterine horns and increased during pregnancy. SPP1 and LGALS15, but not FN or VTN, were present along LE and Tr interfaces in both uterine horns. These data support the idea that focal adhesion assembly at the maternal–conceptus interface reflects adaptation to increasing forces caused by the growing fetus. Cooperative binding of multiple integrins to SPP1 deposited at the maternal–conceptus interface forms an adhesive mosaic to maintain a tight connection between uterine and placental surfaces along regions of epitheliochorial placentation in sheep.

Expression of alphaVbeta3 integrin in rat endometrial epithelial cells and its functional role during implantation

The alpha(V)beta(3) integrin as a marker of endometrial receptivity has been well established in human and other mammalian species; however, its expression is still not known in rats. Our objective was to establish the expression of alpha(V)beta(3) integrin as a marker of endometrial receptivity in rat and to further prove its role in implantation by function-blocking studies in this species. Immunocytochemical, immunohistochemical and flow-cytometric studies were performed in rat endometrial epithelial cells (EEC) to demonstrate the expression of alpha(V)beta(3) integrin during non-receptive, pre-receptive and receptive phases of the uterus. Results revealed positive immunocytochemical staining for alpha(v) and beta(3) subunits on the surface of EEC of days 4 and 5p.c. (post-coitum), but the intensity was higher in cells of day 5p.c. Flow-cytometric study revealed higher level of alpha(V)beta(3) on day 5p.c. as compared to day 4p.c. and non-pregnant animals. Immunohistochemical analysis of uterine tissue also revealed that the alpha(V)beta(3) expression in LE was higher on day 5p.c. morning as compared to that observed on day 4p.c. In addition, the expression of beta(3) subunit was not evident in rats receiving ormeloxifene, an agent known to inhibit the uterine receptivity. Immunoblotting experiments also revealed higher expression of uterine beta(3) on day 5p.c. On day 6, expression of beta(3) was high in implantation sites than on inter-implantation sites. In immature ovariectomized rats, alpha(V)beta(3) was up-regulated by progesterone and by a combination of estrogen and progesterone. The expression of alpha(V)beta(3) was also up-regulated in EEC co-cultured with blastocysts. All the agents used for function-blocking studies showed significant reduction in the number of implantation sites in treated horn as compared to sham control horn. The present study has successfully demonstrated the expression of alpha(V)beta(3) in rat EEC as a marker of endometrial receptivity and showed that this molecule is indispensable for the process of implantation in this species.

Expression of alphaV and beta3 integrin subunits during implantation in pig

Integrin are adhesion molecules involved in uterine-conceptus interactions during the perimplantation period. In this study, the expression of alphaV and beta3 integrin subunits in endometrium during implantation in pigs was investigated. The immunohistochemical location was performed on paraformaldehyde-fixed, paraffin-embedded tissue sections, and the mRNA expression of alphaV was detected in endometrium. In addition, serum levels of estradiol, progesterone, follicle-stimulating hormone, and luteinizing hormone were measured on Days 0, 12, 18, and 25 of pregnancy. The results indicate that endometrium expressed integrin alphaV and beta3 in all stages examined. The most intensive staining for integrin alphaV and beta3 was observed in endometrial stroma in porcine pregnancy on Day 18. The mRNA of alphaV integrin strongly expressed on Day 18, and moderately expressed on Days 12 and 25. The correlation between serum hormone level and the mRNA expression of alphaV integrin was not significant. The expression patterns of integrin alphaV and beta3 during implantation provide insights into the important physiological function of alphaVbeta3 integrin in pig, and the strong expression of integrin alphaV and beta3 in mid-implantation may indicate its crucial role in successful implantation and embryo survival.

Roles of leptin in prenatal and perinatal brain development

Leptin is a hormone that reduces food intake and increases energy expenditure by acting on the arcuate nucleus in the hypothalamus. Recent studies indicated that the neuronal circuit related to food intake in the hypothalamus is formed in the neonatal period and that leptin is necessary for the formation of this circuit. Our studies have further suggested that leptin may act on the fetal cerebral cortex, including the cingulate cortex, which is involved in motor and cognitive processes, and that leptin may affect maintenance and differentiation of neural stem cells, glial-restricted progenitor cells and/or neuronal lineage cells. These recent studies showed that leptin not only has homeostatic functions in adults, but also regulates brain development in the prenatal and neonatal periods. These findings suggest that leptin is related to formation of the normal brain structure and regenerative potency of neural cells as well as the predisposition to homeostatic dysfunction, low locomotor activity or impairment of cognitive function.

Mouse models of implantation

The process of implantation, necessary for nearly all viviparous birth, consists of tightly regulated reactions including apposition of the blastocyst, attachment to the uterine epithelium and decidualization of the uterine stroma. In order for implantation to be successful, a reciprocal interaction between an implantation competent blastocyst and receptive uterus must be achieved. A more thorough understanding of the molecular mechanisms that regulate uterine receptivity and implantation is of clinical relevance to correct implantation failure and improve pregnancy rates. As molecular methodologies have evolved in recent times, the use of in vivo models to elucidate the molecular mechanisms involved in implantation has increased. The mouse has emerged as a powerful model to investigate implantation owing to the ability to control uterine physiology through exogenous stimuli, and more recently, the ability to manipulate gene expression. This review describes the evolution of the mouse as a model for understanding uterine implantation, including exciting new advances in this field, and describes a novel genetic pathway that can be elucidated from these models.

Secreted phosphoprotein 1 (osteopontin) is expressed by stromal macrophages in cyclic and pregnant endometrium of mice, but is induced by estrogen in luminal epithelium during conceptus attachment for implantation

Secreted phosphoprotein 1 (SPP1, osteopontin) is the most highly upregulated extracellular matrix/adhesion molecule/cytokine in the receptive phase human uterus, and Spp1 null mice manifest decreased pregnancy rates during mid-gestation as compared with wild-type counterparts. We hypothesize that Spp1 is required for proliferation, migration, survival, adhesion, and remodeling of cells at the conceptus-maternal interface. Our objective was to define the temporal/spatial distribution and steroid regulation of Spp1 in mouse uterus during estrous cycle and early gestation. In situ hybridization localized Spp1 to luminal epithelium (LE) and immune cells. LE expression was prominent at proestrus, decreased by estrus, and was nearly undetectable at diestrus. During pregnancy, Spp1 mRNA was not detected in LE until day 4.5 (day 1 = vaginal plug). Spp1-expressing immune cells were scattered within the endometrial stroma throughout the estrous cycle and early pregnancy. Immunoreactive Spp1 was prominent at the apical LE surface by day 4.5 of pregnancy and Spp1 protein was also co-localized with subsets of CD45-positive (leukocytes) and F4/80-positive (macrophages) cells. In ovariectomized mice, estrogen, but not progesterone, induced Spp1 mRNA, whereas estrogen plus progesterone did not induce Spp1 in LE. These results establish that estrogen regulates Spp1 in mouse LE and are the first to identify macrophages that produce Spp1 within the peri-implantation endometrium of any species. We suggest that Spp1 at the apical surface of LE provides a mechanism to bridge conceptus to LE during implantation, and that Spp1-positive macrophages within the stroma may be involved in uterine remodeling for conceptus invasion.

Changes in Fibrillin-1 in the Endometrium during the Early Stages of Pregnancy in Mice

Blastocyst reception and implantation require various adaptations of the uterine microenvironment. We have previously shown that in mice, remodeling of the extracellular matrix begins early in pregnancy, characterized by synthesis, degradation and alteration of collagen fibrillogenesis, accompanied by pregnancy stage-dependent expression of glycosaminoglycans and proteoglycans. Fibrillin-1 is a matrix glycoprotein that participates in the formation of elastic fibers and promotes cell adhesion through its integrin-binding domain. In the present study, we used light microscope immunohistochemistry to analyze the distribution of fibrillin-1 in the endometrial stroma of mice during estrous and diestrous, as well as in the pre- and postimplantation periods. Fibrillin-1 was found among endometrial fibroblasts and decidual cells, respectively, in the pre- and postimplantation periods. However, fibrillin-1 organization and distribution in the various regions of the endometrial stroma were found to be pregnancy stage dependent. Fibrillin-1 was also abundant in the basement membrane regions of blood vessels, as well as in the luminal and glandular epithelia. Fibrillin-1 at the maternal-fetal interface and in Reichert's membrane of embryos at up to 6 days of development might facilitate embryo expansion and fixation. Changes in the fibrillin-1 expression during the peri-implantation period suggest that fibrillin-1 plays a role in preparing the endometrium for embryo implantation.

Expression pattern of integrins and their ligands in mouse feto-maternal tissues during pregnancy

The role of integrins, the cell-surface glycoproteins involved in various cellular functions, is well documented. However, information about their role and expression profile during pregnancy is still scant. In the present study, the expression of the integrin subunits β3, α6 and α5, along with their ligands vitronectin, osteopontin, laminin and fibronectin, was investigated in mouse uterus during different stages of pregnancy, namely 6.5, 8.5 and 13.5 days post coitus (d.p.c.) by immunohistochemical localisation. Integrins β3, α6 and α5 and the extracellular matrix molecules vitronectin and osteopontin exhibited dynamic spatiotemporal changes in their expression pattern in gestational endometrium, whereas fibronectin and laminin demonstrated more-or-less ubiquitous expression. The inter-implantation sites showed localisation of most of these molecules predominantly in the luminal epithelium, whereas their expression was negligible in the stroma. The present study explores the possible role and relevance of the spatiotemporal expression of integrins and their ligands in endometrial/decidual function and the maintenance of pregnancy.

Ovarian stimulation with GnRH agonist, but not GnRH antagonist, partially restores the expression of endometrial integrin 3 and leukaemia-inhibitory factor and improves uterine receptivity in mice

BACKGROUND

The impact of different ovarian stimulation (OS) protocols on endometrial receptivity remains controversial. In this study, the effects of different OS on the expression of endometrial integrin beta3 subunit and leukaemia-inhibitory factor (LIF) during the implantation window and the implantation rate in mice were investigated.

METHODS

Three OS protocols were used, involving either pregnant mare's serum gonadotrophin (PMSG) alone, PMSG plus GnRH agonist or PMSG plus GnRH antagonist. Uterus samples were collected at 48 h after OS or ovulation and were detected with immunohistochemistry, Western blot and RT-PCR analyses. Normal embryos at gestation day 4 were transferred into the uteri of mice in the control and OS groups.

RESULTS

All OS groups showed a significant decrease in the expression of both the endometrial integrin beta3 subunit and LIF during the implantation window and the implantation rate. Among the three OS groups, GnRH agonist-treated mice showed a higher endometrial integrin beta3 subunit and LIF expression and a higher implantation rate. No significant difference was found in the measured indices between the GnRH antagonist and PMSG groups.

CONCLUSIONS

OS may inhibit the expression of endometrial integrin beta3 subunit and LIF and impair endometrial receptivity in mice. OS with GnRH agonist, but not GnRH antagonist, may partially restore the endometrial physiological secretion and improve uterine receptivity.

Endocrine regulation of HOX genes

Hox genes have a well-characterized role in embryonic development, where they determine identity along the anteroposterior body axis. Hox genes are expressed not only during embryogenesis but also in the adult, where they are necessary for functional differentiation. Despite the known function of these genes as transcription factors, few regulatory mechanisms that drive Hox expression are known. Recently, several hormones and their cognate receptors have been shown to regulate Hox gene expression and thereby mediate development in the embryo as well as functional differentiation in the adult organism. Estradiol, progesterone, testosterone, retinoic acid, and vitamin D have been shown to regulate Hox gene expression. In the embryo, the endocrine system directs axial Hox gene expression; aberrant Hox gene expression due to exposure to endocrine disruptors contributes to the teratogenicity of these compounds. In the adult, endocrine regulation of Hox genes is necessary to enable such diverse functions as hematopoiesis and reproduction; endocrinopathies can result in dysregulated HOX gene expression affecting physiology. By regulating HOX genes, hormonal signals utilize a conserved mechanism that allows generation of structural and functional diversity in both developing and adult tissues. This review discusses endocrine Hox regulation and its impact on physiology and human pathology.

Heparin-binding epidermal growth factor (HB-EGF) may improve embryonic development and implantation by increasing vitronectin receptor (integrin alphanubeta3) expression in peri-implantation mouse embryos

PURPOSE

This study investigated the effects of HB-EGF on expression of integrin alphanubeta3 and implantation of embryos.

METHODS

Two-cell embryos were recovered and cultured with or without 10 ng/mL HB-EGF for 96h. Expression of integrin alphanubeta3 in cultured embryos was examined by real time-RT-PCR and immunofluorescence analysis; embryos were cultured with or without HB-EGF, then transferred into the uteri of pseudo-pregnant female mice in order to analyze their implantation rate.

RESULTS

HB-EGF improved embryonic hatching and outgrowth during extended culture, and up-regulated expression of integrin alphanubeta3 in both the preimplantation embryo and outgrowing blastocyst. Also, integrin alphanubeta3 subunits were localized at the pericellular borders and cell-cell contact areas. The number of successful implantation sites of transferred HB-EGF-treated embryos in the uterus was increased when compared to number of implantation sites with non-treated controls.

CONCLUSIONS

HB-EGF may improve implantation by accelerating expression of integrin alphanubeta3 in peri-implantation mouse embryos.

Demonstration of uterine receptivity in vitro by co-culture of rat epithelial cells and blastocyst

Uterine receptivity is prerequisite for the attachment of the embryo to the uterine epithelium and involves a specialized polarity-dependent property of uterine epithelial (UE) cells. These UE cells, when polarized in culture, behave like cells in utero by exhibiting apico-basal polarity. In order to develop an implantation model in vitro, UE cells were polarized on extracellular matrix (ECM), and polarity was validated by response to estradiol-17beta administered exogenously. UE cells of pregnant rats at day-3 and day-4 post-coitum (p.c.) and of non-pregnant rats were cultured on bare and extracellular-matrix-coated petri dishes until confluency. Hatched blastocysts were transferred to the cultures, and adhesion was monitored every 24 h. Although blastocysts attached to UE cells that were taken from non-pregnant rats and from rats of day-3 p.c. and cultured on bare plastic, they failed to attach to these cells polarized on ECM. However, blastocysts attached firmly to UE cells that had been taken from rats of day-4 p.c. and polarized on ECM. Receptivity of UE cells taken from non-pregnant and pregnant (day-4 p.c.) rats was quantitated by flow cytometric estimation of cellular levels of beta3 integrin. The expression of beta3 integrin in UE cells from rats of day-4 p.c. was highly significant (P<0.01) when compared with its expression in UE cells from non-pregnant rats. The expression of beta3 integrin in UE cells of day-4 p.c. confirmed the receptivity of these cells to blastocyst implantation. Uterine receptivity was also validated in vivo by inducing the decidual cell reaction in rats ovariectomized on day-3 and day-4 p.c. Whereas remarkable deciduoma was noticed in the animals of day-4 p.c., it was absent in the animals of day-3 p.c., thereby indicating that the uterus was receptive on day-4 p.c. only. Thus, blastocysts do not attach to polarized UE cells that have been obtained from a non-receptive uterus. Attachment will occur only if the cells are obtained from a receptive uterus. UE cell receptivity is therefore essential for mimicking the process of implantation in vitro.

Human trophoblast function during the implantation process

The implantation process involves complex and synchronized molecular and cellular events between the uterus and the implanting embryo. These events are regulated by paracrine and autocrine factors. Trophoblast invasion and migration through the uterine wall is mediated by molecular and cellular interactions, controlled by the trophoblast and the maternal microenvironment. This review is focused on the molecular constituents of the human trophoblast, their actions and interactions, including interrelations with the uterine endometrium.

Epithelial membrane protein-2 regulates surface expression of alphavbeta3 integrin in the endometrium

The four-transmembrane protein epithelial membrane protein-2 (EMP2) was recently identified as an endometrial protein necessary for blastocyst implantation, but the mechanism of this role is uncertain. In other cell types, EMP2 controls delivery of certain classes of proteins to the cell surface, including various integrin isoforms (a class of receptors implicated in endometrial-blastocyst interaction). Since alphavbeta3 integrin is an important endometrial molecule involved in blastocyst interaction, we evaluated the role of EMP2 in modulating integrin expression in the HEC1A endometrial cell line and endometrial epithelium in vivo. Elevation of EMP2 expression in HEC1A cells selectively increased the expression of alphavbeta3 integrin on the plasma membrane and was functional as judged by increased cell binding to an alphavbeta3 ligand, fibronectin. Conversely, reduction in EMP2 expression using an EMP2 specific ribozyme decreased the cell alphavbeta3 surface expression. The influence of EMP2 on alphavbeta3 integrin was also observed in vivo as reduction of EMP2 using ribozymes or short hairpin RNA diminished alphavbeta3 integrin expression in glandular and luminal uterine epithelium. Colocalization and coimmunoprecipitation studies suggested that EMP2 and alphavbeta3 integrin predominantly exist in a physically associated state. This study demonstrates for the first time the influence of EMP2 on alphavbeta3 surface expression and suggests that surface trafficking of integrin alphavbeta3 by EMP2 during the window of implantation may be a mechanism for its requirement in endometrial-blastocyst interaction.