The role of leukemia inhibitory factor in tubal ectopic pregnancy

Introduction

Ectopic pregnancy is unique to humans and a leading cause of maternal morbidity and mortality. The etiology remains unknown however factors regulating embryo implantation likely contribute. Leukemia inhibitory factor (LIF) has roles in extravillous trophoblast adhesion and invasion and is present in ectopic implantation sites. We hypothesised that LIF facilitates blastocyst adhesion/invasion in the Fallopian tube, contributing to ectopic pregnancy.

Methods

We immunolocalised LIF receptor (R) in tubal ectopic pregnancy (N = 5). We used an oviduct cell line (OE-E6/E7) to model Fallopian tube epithelial cells and a trophoblast spheroid co-culture model (HTR-8/SVneo cell line formed spheroids) to model blastocyst attachment to the Fallopian tube. We examined LIF signaling pathways in OE-E6/E7 cells by Western blot. The effect of LIF and LIF inhibition (using a novel LIF inhibitor, PEGLA) on first-trimester placental outgrowth was determined.

Results

LIFR localised to villous and extravillous trophoblast and Fallopian tube epithelium in ectopic pregnancy. LIF activated STAT3 but not the ERK pathway in OE-E6/E7 cells. LIF stimulated HTR-8/SVneo spheroid adhesion to OE-E6/E7 cells which was significantly reduced after PEGLA treatment. LIF promoted placental explants outgrowth, while co-treatment with PEGLA blocked outgrowth.

Discussion

Our data suggests LIF facilitates the development of ectopic pregnancy by stimulating blastocyst adhesion and trophoblast outgrowth from placental explants. Ectopic pregnancy is usually diagnosed after 6 weeks of pregnancy, therefore PEGLA may be useful in targeting trophoblast growth/invasion.

Conclusion

LIF may contribute to the development of ectopic pregnancies and that pharmacologically targeting LIF-mediated trophoblast outgrowth may be useful as a treatment for ectopic pregnancy.     

Ghrelin影响小鼠胚泡着床的体外实验研究

目的:探讨Ghrelin在小鼠妊娠围植入期子宫表达的变化及其对胚胎着床的影响。方法:用免疫组化方法检测Ghrelin蛋白在小鼠妊娠围植入期子宫表达的变化;采用体外胚泡培养方法,观察重组Ghrelin蛋白对胚泡的孵化、黏附与扩展率的影响。结果:在小鼠妊娠的第1至2天,Ghrelin蛋白主要于腔上皮和腺上皮表达,随妊娠进展,其表达水平逐渐下降。体外胚泡培养48h时,与正常对照组相比[孵化率、黏附率和扩展率分别为(61.25±5.27)%、(71.45±6.56)%和(43.26±5.87)%],Ghrelin重组蛋白可明显抑制胚泡的孵化率[(20.36±4.78%),P<0.01]、黏附率[(53.23±4.98)%,P<0.01)]及扩展率[(18.34±7.12)%,P<0.05]。结论:Ghrelin可抑制胚泡孵化、黏附与扩展及抑制胚泡植入。     

Heparin binding-epidermal growth factor improves blastocyst hatching and trophoblast outgrowth in the golden hamster

The effect of heparin binding-epidermal growth factor (HB-EGF) on the in-vitro development of hamster 8-cell embryos was investigated. Supplementation of HB-EGF to culture medium accelerated zona escape of blastocysts (63 +/- 9% compared with 33 +/- 9% after 36 h; P < 0.05). Complete zona escape of blastocysts persisted even after 48 h (61 +/- 11% versus 30 +/- 4%) and 60 h (75 +/- 6% versus 42 +/- 8%). Addition of anti-HB-EGF antibody drastically reduced the percentage of zona escaped-blastocysts (30.0 +/- 5.0% versus 92.3 +/- 2.8%; P < 0.05). Interestingly, a significant increase in the area of trophoblast outgrowth occurred in the presence of HB-EGF (116 x 10(3) +/- 8 x 10(3) microm(2) versus 74 x 10(3) +/- 8 x 10(3) microm(2) at 48 h; P < 0.05). This, however, was not due to an increased number of trophectodermal cells in HB-EGF-treated blastocysts. Immunoreactive HB-EGF was localized in blastocysts and uterine sections, visible by intense immunostaining in the luminal epithelium, particularly on the apical surface. Moreover, the expression of HB-EGF in the uterus was maximum on day 4 of pregnancy, coinciding with the timing of zona escape and implantation. The receptor of HB-EGF, viz. EGF receptor was also detected in blastocysts and the luminal epithelium of day 4 pregnant uterus. These results show that HB-EGF improves blastocyst hatching and trophoblast outgrowth in hamsters.     

Heparin-binding epidermal growth factor (HB-EGF) may improve embryonic development and implantation by increasing vitronectin receptor (integrin ανβ3) 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.     

LIF及其抗体对小鼠胚胎着床影响的体外研究

目的 :研究外源性白血病抑制因子 (LIF)及其抗体对小鼠胚胎着床的影响。方法 :将妊娠 4d的小鼠胚胎种植于已建立的子宫内膜体外模型上 ,观察不同浓度的LIF及其抗体对小鼠胚胎的粘附、植入及扩展情况。并用RT PCR法测定子宫内膜上皮细胞整合素β3的变化。结果 :不同浓度的LIF促进了胚胎的粘附 (P <0 .0 5 ) ,胚胎的扩展率降低。加入LIF抗体 (5 ,1 0 μg/ml)降低了胚胎的粘附率 (P <0 .0 5 ) ,同时LIF对整合素β3的表达有明显的促进作用 (P <0 .0 1 ) ,加入抗体后整合素β3的表达降低。结论 :LIF可能通过上调整合素β3的表达促进胚胎的粘附和植入     

Sera from women with histories of repeated pregnancy losses cause abnormalities in mouse peri-implantation blastocysts

Incubation of peri-implantation mouse blastocysts in the presence of untreated human sera resulted in destruction of the blastocysts. Heating the serum resulted in deactivation of the non-specific toxic factor. Whereas heat-treated serum from women with normal obstetrical histories, and men, supported normal trophoblast attachment and outgrowth, sera from women with reproductive dysfunction resulted in inhibition of attachment or disruption of the trophoblast cells. The inner cell masses were not adversely affected by the sera which were toxic to trophoblast. Fractionation of a serum sample by affinity chromatography resulted in removal of the toxic factor with the IgG fraction. Absorption of the toxic serum with human trophoblast membranes resulted in serum that supported trophoblast outgrowth indicating that the toxic factor was an antibody directed against trophoblast antigens.     

Pregnancy-dependent expression of leukaemia inhibitory factor (LIF), LIF receptor-beta and interleukin-6 (IL-6) messenger ribonucleic acids in the porcine female reproductive tract

Leukaemia inhibitory factor (LIF) and interleukin-6 (IL-6) are candidate embryo-maternal signalling molecules which are present within the uterine luminal micro-environment. We examined the relative expression of the mRNAs encoding LIF and IL-6, as well as the LIF-binding subunit (LIFR-beta) of the LIF receptor and, as a potential downstream cytokine-responsive gene, beta(2)-microglobulin (beta(2)m), in porcine peri-implantation conceptuses, and in placenta and endometrium during early and mid-pregnancy. Peri-implantation spherical and filamentous conceptuses expressed LIFR-beta and beta(2)m mRNAs with no LIF mRNA present. Rapid development in days 11/12 spherical conceptuses to the filamentous stage was accompanied by transiently increased IL-6 gene expression. The corresponding endometrium, in contrast, expressed LIF in addition to these other mRNAs. LIFR-beta, IL-6 and beta(2)m, but not LIF mRNAs, were expressed in the Jag-1 cell line, an in vitro model for porcine day 14 trophoblast. The greatest steady-state amounts of LIF, LIFR-beta and IL-6 mRNAs in both the endometrium and placenta were evident at the post-implantation stages (days 30 and 60>day 18 of pregnancy). Treatment of porcine endometrial explants with human recombinant (hr)LIF or hrIL-6 resulted in no change in, or diminished, the presence of endometrial beta(2)m mRNA, respectively. Addition of LIF to peri-implantation conceptus explant cultures, in contrast, induced beta(2)m mRNA synthesis. These results highlight the potential importance of both the endometrium and placenta as sources, as well as targets, of these cytokines throughout pregnancy. Cytokine modulation of beta(2)m, a known in vitro mitogen, may constitute one mechanism for local control of trophoblast and endometrial proliferation.     

In vivo hatching phenomenon of mouse blastocysts during implantation

Purpose: To determine whether the blastocyst zona shedding process within the murine uterine cornus in vivo is due to a global lytic process caused by uterine proteolytic enzyme, or is triggered by the blastocyst hatching process as observed in vitro.Methods: Fifty-one female ICR mice aged 5–8 weeks were used for this study. From 8:00 p.m. of the 4th day postcoitus to 7:00 p.m. of the 5th day postcoitus, the uterine cornua of 51 mice were isolated at 30-min intervals. Blastocysts within the uterine cornua were flushed out with a balanced solution under the dissecting microscope. The stages of blastocyst development and the proportion of hatching or hatched blastocysts and the discarded zona pellucida (ZP) were inspected and counted.Results: A total of 672 blastocysts were recovered from the uterine horns of the 51 mice. They were divided into six groups according to the blastocyst developmental stages (before or after ZP escape; before or after the initiation of implantation). Group I represents the earliest embryonic stage and Group VI represents the most advanced blastocyst developmental stage during the peri-implantation period. The empty ZP recovery rates (number of discarded ZP/all hatched blastocysts) were 52.3%, 21.5%, 17.2%, 6.6%, 1.6%, and 0% in Groups I–VI, respectively. Five hatching blastocysts out of 199 embryos in Group I were found and a 100% of ZP recovery rate was obtained from 6 of 19 mice in Groups I and II.Conclusions: The present study shows that active blastocyst hatching occurs in vivo because both hatching blastocysts and empty ZP can be found within the uterine cornua of ICR mice before implantation. The empty ZP recovery rate declined significantly, along with a progression of embryo development and implantation, implying that intrauterine zona lytic activity occurs during the peri-implantation stage.     

Effect of Different Concentrations of Recombinant Leukemia Inhibitory Factor on Different Development Stage of Mouse Embryo In Vitro

Purpose: To assess the influence of different concentrationsof recombinant human leukemia inhibitory factor (LIF) onthe in vitro development of mouse embryos. Methods: The 2- to 4-cell embryos of CB6F1 mice werecultured in the human tubal fluid (HTF) media containingdifferent concentrations of LIF. Mouse embryos were dividedinto seven groups: (1) HTF; (2) 1500 IU/ml LIF; (3) 1000IU/ml LIF; (4) 750 IU/ml LIF; (5) 500 IU/ml LIF; (6) 250IU/ml LIF; (7) 125 IU/ml LIF. The embryonic numbers ofdifferent stages including 5–8 cell, 9–16 cell, morula, blastocyst,and hatching blastocyst were recorded. Results: The percentage of early embryo stage (2-cellembryos to 6- to 16-cell stages) in all groups were nonsignificantlydifferent. There were higher formation rates of preimplantationembryos (morula to hatching blastocyst) ingroups 2, 3, 4, and 5 than in groups 1, 6 and 7. Conclusions: LIF has positive effects on preimplantationembryo development and has nonsignificant influence onthe early embryo development. The lowest concentration ofLIF which could provide the optimal embryo developmentis 500 IU/ml.     

体外着床模型中人孵化后早胚细胞角蛋白和肌动蛋白的表达

目的:建立理想的体外胚胎着床模型,并检测模型中人孵化后早胚细胞角蛋白、肌动蛋白和hCG。方法:孵化后早胚与人子宫内膜蜕膜化的基质细胞共培养,观察胚泡在基质细胞层上的定位、黏附、铺展和侵入过程;用免疫荧光染色技术,测定共培养系统中的细胞角蛋白和肌动蛋白;用免疫荧光分析技术,测定培养液中的hCG水平。结果:胚泡和基质细胞共培养5h起,胚泡开黏附在基质细胞层上,最终侵入蜕膜化的基质细胞间。共培养48h后,细胞角蛋白仅仅在滋养层细胞中表达;肌动蛋白在人蜕膜化的基质细胞和滋养层细胞中均有表达。囊胚与子宫内膜基质细胞共培养的培养液中的hCG水平明显高于囊胚单独培养的(P<0.01)。结论:成功建立了一个能反映人胚泡黏附、铺展及侵入到人子宫基质细胞的体外着床模型,细胞角蛋白、肌动蛋白和hCG在着床早胚细胞中起相应变化。     

Screening test for mouse blastocysts as an index of the vitality of embryos

Summary We attempted to investigate the viability of mouse blastocysts in vitro, comparing with embryo transfer to recipient mice. Despite normal appearances of the blastocysts, the rate of trophoblastic outgrowth of blastocysts fertilized in vitro was lower than that of blastocysts fertilized in vivo. However, the rate of transferred blastocysts developing into fetuses did not differ significantly between in vivo and in vitro fertilized blastocysts. It is considered that blastocyst hatching, attachment, and trophoblastic outgrowth in vitro can serve as indices for the vitality of individual embryos.     

The in vitro development of mouse embryos beyond the blastocyst stage into the hatching and outgrowth stage using different energy sources

Purpose: The purpose of this study was to investigate the effect of male and female serum supplementation on the in vitro development of mouse embryos beyond the blastocyst stage until the outgrowth stage since the latter may be related to the nidation of the embryo. We also studied the effect of EGF addition on embryo culture and blastocyst outgrowth. Methods and Results: The blastocyst and hatching rates of two-cell mouse embryos cultured in Ham's F-10+BSA, Ham's F-10+male serum, or Ham's F-10+female serum were found to be comparable (P>0.05). The outgrowth rate of hatched blastocysts was significantly increased, though, when they were transferred to 50% male serum compared to either 50% BSA or 50% female serum (P<0.01 and P<0.05, respectively). In the last experiment, either 100 or 150 ng/ml EGF was added to the culture medium from the two-cell stage till blastocyst development and the latter were cultured till outgrowth in 50% BSA, male serum, or female serum. For both concentrations of EGF, the outgrowth rate was significantly higher in male serum compared to the other conditions (P<0.01 and P<0.05, respectively). The outgrowth rate was also higher when EGF was used compared to plain medium before transferring the blastocysts to either male or female serum (P<0.01 for both). Conclusions: We conclude that the development of embryos to the outgrowth stage is significantly enhanced by male serum. The addition of EGF from the two-cell stage also significantly improves the outgrowth success rate for both male and female serum conditions.Presented at the IXth World Congress on In Vitro Fertilization and Alternate Assisted Reproduction, April 3–7, 1995, Vienna, Austria.     

A trophoblast specific antigen, recognized by monoclonal antibody MA21, locates a unique trophoblast cell population in the murine placenta

Monoclonal antibody MA21 recognized a 44kDa plasma membrane protein on F9 teratocarcinoma cells, trophectoderm of mouse peri-implantation-stage blastocyst and ectoplacental cone cells of 5 day postcoitum implanted blastocyst (Vernon, Linnemeyer and Hamilton, 1989). We show here that this antigen is expressed by trophoblast cells of the maturing placenta. Immunohistochemical assays of early and mature placental tissue sections, indirect immunofluorescence labelling of placental cultures and blastocyst outgrowths in vitro, and immunoprecipitation of 35S-labelled NP-40 extracts of placental cultures indicate the presence of a plasma membrane-associated antigen with the same characteristics as MA21 antigen of peri-implantation embryos and F9 teratocarcinoma cells. In sections of placentae, antigen-positive cells are always situated in a thin layer between trophoblastic giant cells and maternal tissue. In cultures of postimplantation stage embryos, attached trophoblast cells express MA21 antigen initially, but following transformation to the giant cell state, antigen is no longer expressed. These results indicate the presence of a plasma membrane protein antigen associated with a distinct population of cells believed to be trophoblast. We believe that these cells are the foremost trophoblast cells opposing maternal decidua and that they may give rise to secondary trophoblastic giant cells.     

The chrondroitin sulfate proteoglycan (CSPG4) regulates human trophoblast function

Introduction

Trophoblast growth and invasion of the uterine endometrium are critical events during placentation and are tightly regulated by locally produced factors. Abnormal placentation can result in early miscarriage or preeclampsia and intrauterine growth restriction, leading to impaired fetal and/or maternal health. Chondroitin sulfate proteoglycan 4 (CSPG4) is involved in cancer cell migration and invasion, processes which are critical during placentation but unlike in cancer, trophoblast invasion is highly regulated. CSPG4 expression and function in trophoblast is unknown. We determined CSPG4 expression in human first trimester placenta and implantation sites, and investigated whether CSPG4 influenced proliferation, migration and invasion of a human extravillous trophoblast (EVT) cell line (HTR8/SVneo cells) as a model for extravillous trophoblast (EVT).

Methods and results

Immunoreactive CSPG4 localized to EVT cells in the trophoblast shell, subpopulations of interstitial EVT cells within the decidua and cytotrophoblast cells in placental villi. In HTR8/SVneo cells, siRNA knockdown of CSPG4 stimulated proliferation and decreased migration/invasion. In primary first trimester placental villi explants two cytokines, interleukin 11 (IL11) and leukemia inhibitory factor (LIF) with known roles in trophoblast function, stimulated CSPG4 mRNA expression and immunoreactive protein in the cyotrophoblast.

Discussion and conclusion

This is the first demonstration of the production and function of CSPG4 in human placentation. These data suggest that locally produced CSPG4 stimulates human EVT migration and invasion and suggests that IL11 and LIF regulate villous cytotrophoblast differentiation towards the invasive phenotype at least in part via CSPG4.     

Angiogenesis and intrauterine growth restriction

Human placental development involves co-ordinated angiogenesis and trophoblast outgrowth that are compromised in intrauterine growth restriction. Adaptive angiogenesis in IUGR placental villi is a result of an imbalance in the orderly progression of the expression profile of vascular endothelial growth factor, placenta growth factor and angiopoietin during placental development. VEGF receptors and the angiopoietin receptor Tie-2 are expressed on trophoblast, and their activation leads to trophoblast proliferation, migration and production of nitric oxide. Thus, these vascular factors act as autocrine regulators of trophoblast behaviour in the development of the utero-/feto-placental circulation, an action independent of their well-established roles in vascular endothelium.     

sLe~X抗体对小鼠胚泡在E-选择素上黏附和扩展的影响

目的:探讨E-选择素及其配体在着床中的作用。方法:建立小鼠胚泡的体外培养模型,在倒置相差显微镜下观察不同条件下小鼠胚泡在细胞外基质E-选择素上黏附、扩展的改变。结果:小鼠胚泡能在一定浓度E-选择素上黏附、扩展,E-选择素对胚泡的脱透明带有促进作用。结论:确定了E-选择素体外实验的最佳作用浓度。小鼠胚泡在特定浓度的E-选择素上能黏附、扩展,但这种作用能被sLe~X 抗体所阻断,并呈浓度依赖性。     

Endocrinology of the peri-implantation period.

Current research suggests that the appearance of endometrial integrins and pinopode appearance signal the opening of the receptive phase of the endometrium. These integrins may be activated by the interleukin-1 system (IL-1). IL-1beta, expressed by the blastocyst, induces vascular endothelial growth factor (VEGF) which, in turn, promotes angiogenesis and integrin expression in endometrial cells. The IL-1 system also triggers the expression of gamma interferon (IFN-gamma) from T lymphocytes. Decidual natural killer (NK) lymphocytes interact with invading trophoblast to generate leukaemia inhibitory factor (LIF). LIF induces uPA and gelatinase, enzymes which play a crucial role in trophoblastic invasion.Progesterone is a potent inhibitor of LIF, while oestrogen is a potent inducer. Oestrogen in serum reflects follicular IL-1beta level and correlates with the outcome of embryo transfer after in vitro fertilization (IVF). Progesterone induces nitric oxide (NO) synthesis in the decidua, and NO promotes local vasodilatation and uterine quiescenceMeasurement of placental protein 14 (PP14, glycodelin-A) in serum may be of value as a screening test for implantation potential. However, human chorionic gonadotrophin (hCG) remains the most reliable predictor of successful implantation and pregnancy viability. An ovulation + 14 hCG level < 50 IU/l is often predictive of a non-viable outcome, while an ovulation + 21 hCG of < 200 IU/l always indicates a non-viable pregnancy. hCG secretion by invading trophoblast appears to be negatively modulated by endothelin-1 (ET-1) and prostaglandin F(2alpha)(PGF2alpha), while tissue growth factors and collagenases are positive modulators of hCG expression.ProalphaC, an inhibin pro-monomer, may have some value in monitoring corpus luteum function. Inhibin A, activin A and follistatin all rises throughout pregnancy and peak at 36 weeks of gestation. Relaxin is another ovarian hormone that may have a role in predicting implantation. Relaxin induces placental protein 14 (PP14, glycodelin-A) expression in a receptive endometrium, and measurement of serum PP14 may be of value as a screening test for implantation potential.     

Evidence of embryo- and trophoblast-toxic cellular immune response(s) in women with recurrent spontaneous abortion.

OBJECTIVE: The purpose of this study was to determine whether reproductive antigens stimulate lymphocytes and macrophages from women with recurrent abortion to secrete factors that are toxic to preimplantation embryos or trophoblast cells in vitro. STUDY DESIGN: Mononuclear cells were isolated from 30 fertile controls and 300 nonpregnant women being evaluated for recurrent abortion. Supernatants generated from these cells after separate culture with sperm and trophoblast antigen extracts were added to two-cell mouse embryo cultures and trophoblast proliferation assays. Toxicity was assumed when the median percentage of embryos developing to blastocysts or trophoblast proliferation was less than or equal to 50% of control values. Both parametric and nonparametric statistical methods were used where appropriate. RESULTS: Mouse embryo development and/or trophoblast proliferation were significantly inhibited by supernatants from trophoblast and/or sperm antigen-activated peripheral blood leukocyte cultures from a majority of 300 women with recurrent abortion but not from 30 women with normal reproductive histories. The mouse blastocyst development assay was more sensitive than the trophoblast proliferation assay in determining toxic factor production. Embryo-toxic factors were produced by activated leukocyte cultures from 90% of 180 women with a history of recurrent abortion of unexplained etiology, whereas trophoblast-inhibitory factors were detected in 50% of women from the same group. The embryo-toxic factor(s) was heat labile, had a molecular weight(s) between 10 and 30 kd, and was absorbed out by passage through affinity columns containing anti-interferon gamma beads. CONCLUSION: We conclude that recurrent abortion in some women is associated with embryo- and/or trophoblast-toxic factor production in response to stimulation by sperm or trophoblast antigens and that the principal factor may involve the 18 kd, heat-labile, T-lymphocyte cytokine interferon gamma. This study suggests a new cause of recurrent abortion.