哺乳动物滋养层细胞在胚胎植入中的作用

胚胎植入是哺乳动物生殖的关键环节,是一个非常复杂的过程.在胚胎植入过程中,多种着床相关因子、激素在母体-胚胎之间进行多重作用,引发复杂的生理作用,从而完成胚胎着床.在母体-胚胎界面上,胎源性滋养层细胞与母体子宫内膜细胞在信号联系（妊娠识别）和组织紧密连接（胚胎植入）过程中起着决定性作用,尤其是胚源性滋养层细胞,在胚胎植入过程中起主导作用.本文通过对滋养层细胞在胚胎植入中的作用的阐述,为进一步阐明胚胎植入的分子机制提供思路.     

降钙素对胚胎着床的影响机理

降钙素(calcitonin,CT)是甲状腺滤泡旁细胞分泌的一种含有32个氨基酸残基的肽类激素,是动物体内重要的调节钙磷代谢的内分泌因子。近年来的研究发现CT在胚胎着床过程中起着重要的作用。胚胎着床涉及到母体子宫和胚胎之间的复杂而精确的调控。在孕激素作用下,围着床期子宫内膜表达CT,CT与其膜受体结合后可激活腺苷酸环化酶(adenylate cyclase,AC)和磷脂酶(Cphospholipase C,PLC)等激酶的活性,促进细胞外Ca2 内流,从而促使子宫内膜和胚胎发生一系列的变化,有利于胚胎的植入。     

Decreased NDRG1 expression is associated with pregnancy loss in mice and attenuates the in vitro decidualization of endometrial stromal cells

Embryo implantation is an essential step for a successful pregnancy, and any defect in this process can lead to a range of pregnancy pathologies. The objective of this study was to explore the role of N‐myc downregulated gene 1 (NDRG1) in embryo implantation. It was found that uterine NDRG1 expression has a dynamic pattern during the estrous cycle in nonpregnant mice and that uterine NDRG1 expression was elevated during the implantation process in pregnant mice. The distinct accumulation of NDRG1 protein signals was observed in the primary decidual zone adjacent to the implanting embryo during early pregnancy. Furthermore, uterine NDRG1 expression could be induced by activated implantation or artificial decidualization in mice. Decreased uterine NDRG1 expression was associated with pregnancy loss in mice and was associated with recurrent miscarriages in humans. The in vitro decidualization of both mouse and human endometrial stromal cells (ESCs) was accompanied by increased NDRG1 expression and downregulated NDRG1 expression in ESCs effectively inhibited decidualization. Collectively, these data suggest that NDRG1 plays an important role in decidualization during the implantation process, and the abnormal expression of NDRG1 may be involved in pregnancy loss.     

Heparanase expression and function during early pregnancy in mice

Embryo implantation is a complex process that involves interactions between cell-surface and extracellular components of the blastocyst and the uterus, including blastocyst adhesion to the uterine luminal epithelium, epithelial basement membrane penetration and stromal extracellular matrix remodeling, angiogenesis, and decidualization. These processes all involve interactions with heparan sulfate (HS) proteoglycans, which harbor various growth factors and cytokines and support cell adhesion. Heparanase (HPSE) is an endo-beta-glucuronidase that cleaves HS at specific sites. HPSE also can act as an adhesion molecule independent of its catalytic activity. Thus, HPSE is a multifunctional molecule contributing to and modulating HS-dependent processes. Exogenously added HPSE improves embryo implantation in mice; however, no information is available regarding the normal pattern of HPSE expression and activity during the implantation process in any system. Using several approaches, including real-time RT-PCR, in situ hybridization, and immunohistochemistry, we determined that uterine HPSE expression increases dramatically during early pregnancy in mice. Heparanase mRNA and protein were primarily expressed in decidua and were rapidly induced at the implantation site. Uterine HPSE activity was characterized and demonstrated to increase >40-fold during early pregnancy. Finally, we demonstrate that the HPSE inhibitor PI-88 severely inhibits embryo implantation in vivo. Collectively, these results indicate that HPSE plays a role in blastocyst implantation and complements previous studies showing a role for HS-dependent interactions in this process.     

Expression of plasminogen activators in preimplantation rat embryos developed <Emphasis Type="Italic">in vivo</Emphasis> and <Emphasis Type="Italic">in vitro</Emphasis>

Background  

Embryo implantation plays a major role in embryogenesis and the outcome of pregnancy. Plasminogen activators (PAs) have been implicated in mammalian fertilization, early stages of development and embryo implantation. The invasion of trophoblast cells into the endometrium during the implantation process can be blocked by inhibitors of serine proteases, illustrating the role of these enzymes in the invasion process. As in vitro developing embryos resulted in lower implantation rate than those developed in vivo we assume that a reduced PAs activity may lead to it. There is hardly any information regarding qualitative or quantitative differences in expression of PAs in preimplantation embryos, or comparisons between in vivo and in vitro developed embryos. The purpose of this study was to assess the expression of urokinase type (uPA) and tissue type (tPA) plasminogen activators in in vivo and in vitro preimplantation development in rat embryos using immunofluorescence confocal microscopy and computerized image analysis.     

Evaluation of the role of leukotrienes on ovum implantation in mice

Prostaglandins are considered to be one of the important mediators of ovum implantation. Various lipoxygenase products also have been implicated along with PGs for this process. A specific rather than preferential inhibitor of 5-lipoxygenase is used to investigate the role of leukotrienes in the event of implantation and decidualization process in mice. AA861, a selective inhibitor of 5-lipoxygenase is used in different dose levels like 50,100 and 500 μg in (A) intact pregnant mice (on D1-D4 and D2-D4 and D4); (B) delayed mice on (D3-D8); (C) pseudopregnant traumatized mice (on D1-D4). All the experimental animals of group A were killed on D6. Estrogen injected delayed animals of group  were killed 48 h after the induction of implantation. Implantation sites were counted as blue spot and compared with those of control animals. Traumatized animals of group C were killed 24 h after the mechanical traumatization and uterine weights were compared with those of vehicle treated controls. Results show that AA861 could not inhibit ovum implantation in either intact or ovariectomized delayed animals. It also did not show any adverse effect on tubal transport or development of embryos. AA861 did not have any inhibitory role on decidualization of pseudopregnant uteri also. This experiment shows that a selective inhibitor of 5-lipoxygenase enzyme may not impair the implantation in mice indicating a doubt about the involvement of 5-lipoxygenase products in implantation.     

转录因子在哺乳动物围着床期的作用

胚胎着床是非常复杂的生理过程,既需要胚胎具有着床能力,又需要子宫处于接受态。在围着床期,很多转录因子的表达发生变化。一个转录因子可以调控多个靶基因,一个基因也可同时受到多个转录因子的调控,从而形成复杂的基因表达网络调控机制,这对胚胎着床是非常重要的。文章对在围着床期起重要作用的转录因子进行了综述。     

Differential expression of insulin-like growth factors in the uterine epithelium and extracellular matrix during early pregnancy

We have studied the simultaneous expression of insulin-like growth factor I (IGF-I) and insulin-like growth factor II (IGF-II) in the uterine epithelium and extracellular matrix during the time of trophoblast attachment and implantation. These studies reveal that IGF-I and IGF-II display different spatial and temporal patterns of expression during early pregnancy, and suggest a role for them in the process of attachment and implantation. Specifically, IGF-I is strongly expressed in the basal lamina which is the site of trophoblast invasion into the maternal stroma, and also in the apical epithelium, the site of initial trophoblast attachment. IGF-II is expressed to a lesser extent in the basal lamina, lateral plasma membranes and apical epithelium on day 3 but is only prominent apically at the time of implantation, suggesting a role in attachment.     

人类胚胎植入过程中的细胞黏附分子(英文)

人类胚胎植入过程不仅受到在进化上保守的机制调节,而且也受到人类一种独有的机制调节。有证据显示,细胞黏附分子L-选择蛋白和trophinin在人类胚胎植入过程扮演独特的角色。在本文中,我们描述了L-选择素和trophinin的黏蛋白糖配体的双重作用,也描述了trophinin相关蛋白bystin和tastin的双重作用。我们随后描述了滋养外胚层细胞和子宫内膜上皮细胞中由trophinin调节的信号转导。本综述也涵盖了钙依粘连蛋白和整合素在人类胚胎植入过程中的作用。     

Leptin-directed embryo implantation: leptin regulates adhesion and outgrowth of mouse blastocysts and receptivity of endometrial epithelial cells

Leptin is a 16-kDa multifunctional protein. Recent reports indicate that leptin is an important molecule during implantation and placentation, implicated in embryonic-maternal cross-talk and cytotrophoblast invasiveness, however, the role of leptin playing in the process of normal blastocyst implantation has not been well characterized. In the present study, the possible mechanisms of leptin playing in mouse blastocyst implantation were investigated. Leptin and receptor isoforms mRNAs were detected in whole mouse uteri during estrous cycle and peri-implantation periods. Immunofluorescent analysis further confirmed Ob-R protein was present in mouse uterus. The differential amounts of leptin and Ob-R isoforms suggested a role for leptin in such endometrial issues as blastocyst implantation. In vitro culture model for studying embryo implantation, leptin promoted mouse blastocyst adhesion and blastocyst outgrowth on fibronectin. Blastocysts treated with 300 ng/ml leptin had the greatest adhesion rate of 76.58+/-6.41% (P=0.046), and blastocysts treated with 30 ng/ml leptin had the greatest outgrowth rate of 78.64+/-8.48% (P=0.005). In isolated endometrial epithelial cells, leptin upregulated amounts of alpha v and beta 3 integrin, and promoted cell adhesion to such extracellular matrix proteins as fibronectin, laminin and type IV collagen, showing a dose- and time-dependent cell-adhesive capacity. Collectively, the information from the present study may partly account for leptin-induced mouse blatocyst implantation.     

Maternal pentraxin 3 deficiency compromises implantation in mice

Reduced litter sizes in mice missing pentraxin 3 (Ptx3) have been attributed to fertilization failure. However, our global gene expression studies showed high uterine Ptx3 expression at the implantation site in mice, suggesting its role in blastocyst implantation. We initiated molecular and genetic studies in mice to explore the importance of uterine Ptx3 in this process. We found that Ptx3 is expressed in a unique and transient fashion at implantation sites. With the initiation of implantation on midnight of Day 4 of pregnancy, Ptx3 is expressed exclusively in stromal cells at the site of blastocysts. On Day 5, its expression is more intense in decidualizing stromal cells, but it disappears on Day 6. The expression again becomes evident in the deciduum on Day 7, followed by a more robust expression on Day 8, particularly at the antimesometrial pole. From Day 9, with the initiation of placentation, Ptx3 expression becomes undetectable. These results suggest a role for PTX3 in implantation and decidualization. Indeed, deletion of Ptx3 results in both compromised implantation and decidualization. Interleukin 1B (IL1B), a known inducer of Ptx3, is also transiently expressed in stromal cells at the implantation site, suggesting that IL1B is an inducer of uterine Ptx3 expression. In fact, uterine Ptx3 expression follows that of Il1b induced by lipopolysaccharide treatment on Day 7 of pregnancy. Collectively, these findings provide evidence for an important role for PTX3 in implantation and decidualization. This study has clinical implications, since PTX3 is expressed in the receptive endometrium, and trophoblast cells influence decidual Ptx3 expression in humans.     

胎盘发生过程中的细胞凋亡

细胞凋亡是一种正常的生理现象,在胚泡着床过程中,伴随有大量细胞凋亡。研究表明,胎盘发生过程中的细胞凋亡,对调控子宫内膜基质细胞的蜕膜化和滋养层细胞的浸润以形成胎盘具有重要意义;另外,由Fas/FasL系统介导的细胞凋亡可能与母体对胎儿的免疫耐受性有关。本文主要评述细胞凋亡的一般通路以及胎盘发生过程中细胞凋亡的调控。     

Steroids modulate the expression of alpha4 integrin in mouse blastocysts and uterus during implantation

Blastocyst implantation and successful establishment of pregnancy require delicate interactions between the embryo and the maternal uterine milieu, which are controlled at the embryo-maternal interface by the coordinated interplay of a variety of growth factors, cytokines, hormones, and cell adhesion molecules expressed by both the decidualized endometrium and the trophoblast cells. Proper implantation of the embryo is solely dependent on the initial endometrial receptivity and the preparation of the blastocyst to glue itself to the uterine wall. Both these events are considered to be mediated by cell adhesion molecules and integrins expressed by the blastocyst as well by as the maternal endometrium. Integrin expression by the blastocyst and the uterus is a dynamic process. However, reports on the expression and the hormonal modulation of integrins and their role in blastocyst activation and uterine receptivity during implantation are meager. The present study investigates the expression and hormonal regulation of alpha4beta1 integrin by steroid hormones in the blastocyst and the receptive uterus using an in vivo, delayed-implantation mouse model system. The dormant and activated blastocysts as well as the uteri were recovered from ovariectomized mice after progesterone-alone and progesterone-plus-estrogen therapy, respectively. Immunolocalization of protein expression of alpha4 and beta1 integrin subunits indicate that steroids modulate the expression of alpha4beta1 integrin receptor in the mouse blastocyst as well as the uterus and that a differential expression is observed with exposure to progesterone and estrogen. Intrauterine blocking of alpha4 integrin by specific antibody resulted in implantation failure in normal as well as in delayed-implantation mice. Based on our data, we propose here, to our knowledge for the first time, that alpha4beta1 integrin, which is responsible for binding to fibronectin and vascular cell adhesion molecule-1, is induced by estradiol and is down-regulated by progesterone in mice during implantation. Furthermore, the results also indicate the direct role of alpha4 integrin in the process of implantation.     

Inhibition of the beta-catenin signaling pathway in blastocyst and uterus during the window of implantation in mice

Beta-catenin, the mammalian homolog of Drosophila armadillo protein, was first identified as a cadherin-associated protein at cell-cell junctions. Another function of beta-catenin is the transduction of cytosolic signals to the nucleus in a variety of cellular contexts, which usually are elicited by the active form of beta-catenin. The aim of the present study was to examine the potential role of active beta-catenin in the mouse embryo and uterus during embryo implantation. Active beta-catenin was detected differentially in mouse embryos and uteri during the peri-implantation period. Aberrant activation of beta-catenin by LiCl, a well-known glycogen synthase kinase-3 inhibitor, significantly inhibited blastocyst hatching and subsequent adhesion and outgrowth on fibronectin. Results obtained from pseudopregnant and implantation-delayed mice imply an important role for implanting blastocysts in the temporal and spatial changes of active beta-catenin in the uterus during the window of implantation. Collectively, these results suggest that the beta-catenin signaling pathway is inhibited in both blastocyst and uterus during the window of implantation, which may represent a new mechanism to synchronize the development of preimplantation embryos and differentiation of the uterus during this process.     

Expression of obesity gene and obesity gene long form receptor in endometrium of Yorkshire sows during embryo implantation

There is accumulating evidence that leptin may be directly involved in mammalian reproduction, however, the potential role of obesity gene/obesity gene long form receptor (ob/ob-Rb) system in porcine implantation is poorly understood. To further confirm this role, mRNA and protein expression of ob/ob-Rb in implantation site and inter-implantation sites of porcine uterus on pregnancy day 13, 18 and 24 were compared in this study. Ob mRNA level went up with the advance of pregnancy and was higher in implantation site than inter-implantation site (P < 0.05). But ob-Rb mRNA, which was negative-regulated by leptin, went down with the advance of pregnancy and lessened in implantation site compared with inter-implantation site (P < 0.05). During the three implantation phase, leptin protein peaked at day 18 pregnancy (P < 0.05) and leptin protein at implantation site were always higher than inter-implantation site (P < 0.05). The higher ob-Rb protein in implantation site compared with inter-implantation site (P < 0.05) only appeared at day 18 pregnancy. Localization of ob/ob-Rb protein in porcine uterus was assayed using immunohistochemistry and found that ob/ob-Rb protein mainly located in luminal epithelium and glandular epithelium in pregnant pigs, but distinct immune-staining of leptin also detected in stroma in non-pregnancy porcine uterus except for luminal epithelium and glandular epithelium. In conclusion, the peak of leptin and the peak of ob-Rb protein in implantation site specifically appeared on day 18 pregnancy of pig. Another funning discovery is ob-Rb mRNA in porcine endometrium was mainly negative-regulated by leptin. The space–time difference of gene and protein expression for ob/ob-Rb confirmed ob/ob-Rb system role as delicate regulator of porcine implantation process.     

腺病毒E4启动子结合蛋白-4(E4BP4)基因在小鼠胚胎着床期间子宫组织中的表达

腺病毒E4启动子结合蛋白-4(E4BP4)是哺乳动物细胞核内的一种碱性亮氨酸拉链(bZIP)型转录因子,参与调控细胞的存活和增殖。前期研究表明,它在孕第5天的小鼠着床位点有明显的高表达。本文分别应用Northem blot、in situ杂交、Western blot和免疫组织化学技术,对E4BP4基因在小鼠妊娠初始期子宫、着床期胚胎着床位点和非着床位点的表达情况进行了研究。观察发现：在小鼠妊娠初始期,E4BP4基因在子宫组织中的表达逐步上调;至胚胎着床期间,其在胚胎着床位点的表达水平进一步提高,并明显高于非着床位点;该基因的表达不依赖于胚胎,人工蜕膜化可诱导其表达：E4BP4 mRNA和E4BP4蛋白分子都主要分布于子宫腔周围的基质细胞和蜕膜细胞。上述结果提示E4BP4基因可能通过促进着床位点基质细胞的增殖和抑制蜕膜细胞的凋亡而参与胚胎着床过程的调控。     

Effect of cyclooxygenase on "window of implantation" in mouse

The major determinants of uterine receptivity are the ovarian progesterone and estrogen hormones, respectively. Different prostaglandins (PGs) have been elucidated in reproduction and also in this process of implantation in various ways. The blastocyst undergoes implantation on the uterine epithelium in defined hormone prepared period known as "implantation window". However, any definitive role of PGs in the window of receptivity remains elusive. It is demonstrated herein that selective COX1 inhibitor (SC560) and selective COX2 inhibitor (nimesulide) separately had no significant effect on blastocyst implantation while combination of both inhibitors in lower dose showed partial delay in implantation by more than 24h and became implanted beyond the window of implantation, i.e. on D6 but these implantation sites were significantly reduced on D10 and the pregnancy is lost in significant number. However, the higher doses of inhibitors in combination completely prevented implantation. Embryos retrieved from these treated mice showed significantly lower number of embryonic cells (77+/-3.3 and 65.2+/-3.9) than the optimum number of embryonic cells (93.4+/-2.6). The lower doses of both the inhibitors reduced uterine PGE2 and PGI2 content on D5 but did not inhibit as efficiently as higher doses. In addition, our immunohistochemistry result shows that there was no COX1 and COX2 localization on D5 of treated mice but COX2 begins expressing on D6 like normal D5 of pregnancy. Therefore, we can conclude that embryos implanted after the delay showed defective post-implantation development because of lower number of embryonic cells of implanting blastocyst and implantation beyond the proper time in window of receptivity.     

前列腺素F（PGF）抗血清对小鼠胚泡着床的影响

本文试图利用自制的PGP抗血清,对小鼠子宫局部进行注射,以观察其对胚泡着床的影响。结果表明,于妊娠第3天(孕卵在输卵管阶段)单侧子宫角注射PGF抗血清,对胚泡着床无影响。而妊娠第4天(胚泡在子宫阶段〕单侧或双侧子宫角注射PGF抗血清,对胚泡着床均有明显的抑制作用。这一结果提示小鼠胚泡着床中PGF起着重要的作用。