胚胎着床的分子调控网络

胚胎着床是活性胚胎与接受态子宫相互对话,并建立紧密联系的过程。在雌激素和孕酮的协同调控下,一些粘附分子、细胞因子和生长因子等呈时空特异性表达,许多信号通路间相互协作对于胚胎着床至关重要。近年来发现,miRNA等非编码RNA也参与胚胎着床的分子调控网络。本文旨在综述近年来胚胎着床分子调控网络方面的研究进展。     

胚胎着床的过程与机制研究进展

哺乳动物的胚胎着床是胚胎与子宫内膜建立紧密联系的过程,是妊娠的起始和关键步骤,胚胎着床的失败直接导致妊娠失败和不孕。近年来,随着技术的进步,胚胎着床的研究工作取得了长足的进展。本文旨在对近10年取得的和胚胎着床有关的研究成果进行综述,重点关注包括腔上皮和腺上皮的子宫内膜上皮在着床过程中的变化、作用及分子机制,以及上皮细胞与胚胎滋养层细胞和子宫基质细胞之间的相互作用。     

Wnt3a在小鼠孤雌胚胎及正常胚胎早期着床部位的表达变化

目的研究小鼠孤雌激活胚胎和体内正常发育胚胎在子宫中发生着床过程时,在早期着床部位上Wnt3a信号分子的表达变化。方法运用免疫组织化学染色法比较受体子宫中的孤雌胚胎着床位点和体内正常发育胚胎着床位点上Wnt3a的表达状况。结果免疫组织化学染色结果发现:(1)在着床期怀孕第5.5天和6.5天,受体子宫中孤雌胚胎的着床位点处和体内正常发育胚胎的着床位点处,Wnt3a在两种子宫上的表达情况相似,而在两种胚胎上的表达情况不同;(2)Wnt3a信号在空怀假孕母鼠子宫上表达情况与相同怀孕期有正常胚胎着床的子宫上的表达情况相似。结论胚胎着床与否及胚胎正常与否均不影响Wnt3a在小鼠早期着床期子宫上的表达,但在怀孕第5.5天和6.5天时孤雌激活胚胎和体内正常发育胚胎上Wnt3a的表达有差异。     

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。     

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.     

生命过程的相似性--从着床部位母体细胞的凋亡谈起

胚胎着床受许多因素的精确调控,其中着床部位母体细胞的凋亡在围植入期执行着重要的生理任务。但它自身的发生机制尚不完全清楚,在胚胎着床中的调节机制就更远远落后于凋亡在其他系统领域中的相知程度。因此,对细胞凋亡在着床部位母体细胞中出现的深入研究,将进一步完善我们对着床机制的理解,同时,因为肿瘤和胚胎对机体作用相似性也使这个领域的研究具有特殊的意义。     

哺乳动物的延迟着床及其分子调控

延迟着床是指胚胎在发育到胚泡阶段时暂时进入休眠状态,并不立即着床。在这个时期,胚泡或者停止细胞分化与增长,以使其大小及内部细胞数量保持稳定,或者经历一个少量细胞发生分化的缓慢增长阶段。共有7个目中的近100种哺乳动物有延迟着床现象。延迟着床受光周期、哺乳刺激和营养等各方面因素的影响,同时还受激素和多种生长因子等调节。虽然各种动物中延迟着床的机制各不相同,但延迟着床均可有效地延长妊娠期,使该物种在一年中最适宜的时期进行交配和产仔。利用在小鼠或大鼠中建立的延迟着床模型,可模拟正常的胚胎着床过程,有利于研究胚胎着床过程中的分子调控机制。     

子宫内膜糖原代谢在胚胎着床中的作用研究进展

糖原的合成与分解可动态调节体内葡萄糖含量以维持细胞内变化的能量需求。胰岛素作为体内唯一降血糖的激素,通过作用于磷脂酰肌醇3-激酶(phosphatidylinositol 3-kinase, PI3K)/蛋白激酶B (Akt)信号通路,促进葡萄糖转运体转位以促进糖原合成,也可抑制糖异生以降低血糖。而子宫内膜糖代谢有其特殊性,不发生糖异生,尚未被利用的葡萄糖均以糖原形式储存。子宫内膜的糖原代谢除受经典糖代谢激素调控外,还受卵巢激素调控。子宫内膜在着床窗口期发生的与着床有关的功能活动都需要葡萄糖供给能量。着床前子宫内膜上皮细胞内大量葡萄糖合成糖原,在着床窗口期分解为葡萄糖,以满足增加的能量需求,保证胚胎着床的顺利进行。糖尿病时子宫内膜糖原代谢受损,糖原合成或分解异常可导致胚胎着床失败、早期流产。本文就子宫内膜的糖原代谢及其在胚胎着床中的作用等方面进行综述,以期为胚胎着床的研究及不孕诊断和治疗提供新思路。     

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。     

Utero‐tubal transfer of mouse embryos

Summary: A successful embryo transfer depends on the quality of the transferred embryos, recipients, and the transfer techniques. Among these, transfer techniques are often the limiting factor because transfer methodologies and personal skills vary. Suboptimal embryo transfer procedures can compromise transgenic experiments (pronuclear microinjection and gene targeting) and critical steps of mouse colony maintenance (embryo cryopreservation and mouse line rederivation). Here we present an efficient and simple procedure utilizing specific designs to improve the transfer quality. A 100% implantation rate is observed after the utero‐tubal embryo transfer, which indicates that the modified method successfully prevents the embryos from flowing out of the punctured hole during embryo transfer. We believe this alternative methodology is able to fulfill the need of high efficiency of animal production. genesis 30:77–81, 2001. © 2001 Wiley‐Liss, Inc.     

Early embryo‐maternal communication in the oviduct: A review

An intact embryo‐maternal communication is critical for the establishment of a successful pregnancy. To date, a huge number of studies have been performed describing the complex process of embryo‐maternal signaling within the uterus. However, recent studies indicate that the early embryo communicates with the oviductal cells shortly after fertilizationand that this is important for the successful establishment of pregnancy. Only if the early embryo is capable to signal the mother within a precise timeframe and to garner a response, will the embryo be able to survive and reach the uterus. This review will give an overview of all the experimental designs which have investigated embryo‐maternal interaction in the oviduct. In addition to that, it will provide a comprehensive analysis of the findings to date elucidating the morphological and molecular changes in the oviduct which are induced by the presence of the early embryo highlighting how the tubal responses affect embryo development and survival.     

多胚水稻胚位与苗位的观察研究

多胚水稻是进行水稻无融合生殖研究的重要材料,通过对4个多胚水稻品系种子胚位及萌发后的苗位观察发现这些品系中存在着多种胚位及苗位类型,其中以双-13的类型最为丰富。认为不定胚在与合子胚共存的情况下难以萌发表达,而只有当合子胚败育时才有可能得以萌发,并且认为反向单苗,侧向单苗及倒序单苗可能起源于不定胚,因而可能成为进行水稻无融合生殖筛选的重要标志。     

被子植物胚柄研究进展

胚柄在胚胎发育过程中是一个暂时性的结构, 但却起着为胚体提供营养和生长调节因子的作用。相对胚体而言, 胚柄具有细胞类型单一、结构相对独立及发育时间短等特点, 其在胚胎发育的基因调控和细胞命运决定研究中具有独特的优势。该文从胚柄的形成及特点、胚柄在胚胎发育中的作用、信号传递系统对胚柄的影响以及与胚柄相关基因的功能等方面进行综述, 以期为研究胚柄在胚胎发育过程中所起的作用以及胚柄的命运决定提供参考信息。     

Acorns containing deeper plumule survive better: how white oaks counter embryo excision by rodents

Several squirrel species excise the embryo of acorns of most white oak species to arrest germination for long‐term storage. However, it is not clear how these acorns counter embryo excision and survive in the arms race of coevolution. In this study, we simulated the embryo excision behavior of squirrels by removing 4 mm of cotyledon from the apical end of white oak acorns differing in embryo depths to investigate the effects of embryo excision on acorn germination and seedling performance of white oak species. The embryo depth in the cotyledons was significantly different among white oak acorns, with Quercus mongolica containing the embryo most deeply in the acorns. We found that artificial embryo excision significantly decreased acorn germination rates of Quercus variabilis, Quercus acutissima, Quercus aliena, Quercus aliena var. acutiserrata, Quercus serrata. var. brevipetiolata but not Q. mongolica. Artificial embryo excision exerted significant negative impacts on seedling performance of all oak species except Quercus aliena. Our study demonstrates the role of embryo depth of acorns in countering embryo excision by squirrels and may explain the fact that squirrels do not perform embryo excision in acorns of Q. mongolica with deeper embryos. This apparent adaptation of acorns sheds light on the coevolutionary dynamics between oaks and their seed predators.     

Parthenogenetic and nuclear transfer rabbit embryo development and apoptosis after activation treatments

Previous studies mainly evaluated the effect of culture conditions on preimplantation embryo apoptosis. In order to inhibit apoptosis of nuclear transfer (NT) embryos, putative apoptosis inhibitors were used to treat donor cells. However, little is known about the effect of activation treatments on embryo apoptosis. We firstly investigated the effect of various parthenogenetic activation (PA) treatments on embryo development, blastocyst cell number, and apoptosis, and then one of these activation treatments proved to be most efficient was selected for activation rabbit NT embryos. The activation by electrical pulses and 30 min later, electroporation with 25 muM D-myoinositol 1,4,5-trisphosphate (IP3) in Ca(2+)- and Mg(2+)-free PBS, then exposure to 2.0 mM 6-dimethylaminopurine (6-DMAP) for 3 hr effectively activated rabbit oocytes, and resulted in significantly a higher blastocyst development rate (72.7%) and total cell number (175 +/- 14.1), and markedly lower apoptosis level of blastocyst (4.3 +/- 0.5) than all the other groups. When the same activation protocol was applied in NT embryo activation, we found that exposure of the embryos to 6-DMAP for 3 hr could decrease the apoptosis level of blastocyst and increase blastocyst rate and cell number. The results demonstrate that oocyte activation affects not only embryo development and quality but also embryo apoptosis.     

Deep and intermediate complex morphophysiological dormancy in seeds of Ferula gummosa (Apiaceae)

We tested the hypothesis that seeds of the monocarpic perennial Ferula gummosa from the Mediterranean area and central Asia have deep complex morphophysiological dormancy. We determined the water permeability of seeds, embryo morphology, temperature requirements for embryo growth and seed germination and responses of seeds to warm and cold stratification and to different concentrations of GA₃. The embryo has differentiated organs, but it is small (underdeveloped) and must grow inside the seed, reaching a critical embryo length, seed length ratio of 0.65–0.7, before the seed can germinate. Seeds required 9 weeks of cold stratification at <10°C for embryo growth, dormancy break and germination to occur. Thus, seeds have morphophysiological dormancy (MPD). Furthermore, GA₃ improved the germination percentage and rate at 5°C and promoted 20 and 5% germination of seeds incubated at 15 and 20°C, respectively. Thus, about 20% of the seeds had intermediate complex MPD. For the other seeds in the seed lot, cold stratification (5°C) was the only requirement for dormancy break and germination and GA₃ could not substitute for cold stratification. Thus, about 80% of the seeds had deep complex MPD.     

A moral argument for frozen human embryo adoption

Some people (e.g., Drs. Paul and Susan Lim) and, with them, organizations (e.g., the National Embryo Donation Center) believe that, morally speaking, the death of a frozen human embryo is a very bad thing. With such people and organizations in mind, the question to be addressed here is as follows: if one believes that the death of a frozen embryo is a very bad thing, ought, morally speaking, one prevent the death of at least one frozen embryo via embryo adoption? By way of a three-premise argument, one of which is a moral principle first introduced by Peter Singer, my answer to this question is: at least some of those who believe this ought to. (Just who the “some” are is identified in the paper.) If this is correct, then, for said people, preventing the death of a frozen embryo via embryo adoption is not a morally neutral matter; it is, instead, a morally laden one. Specifically, their intentional refusal to prevent the death of a frozen embryo via embryo adoption is, at a minimum, morally criticizable and, arguably, morally forbidden. Either way, it is, to one extent or another, a moral failing.     

Embryo donation and receipt in Australia: views on the meanings of embryos and kinship relations

Research on embryo donation and receipt continues to grow, highlighting how specific national contexts shape views and experiences. The present article reports on a qualitative study on embryo donation and receipt in Australia. Interviews were conducted with 15 participants: embryo donors and those seeking to donate (6), embryo recipients and those seeking donors (3), people with embryos in storage or previously in storage (5), and egg donors where resulting embryos were donated to a third party (1). A deductive thematic analysis identified four key themes: understandings of embryos as cells, potential children, and/or children; a focus on relationships between “siblings”; importance of language and “family words” in discussing relationships; and extended family members having difficulty understanding the concept of embryo donation. The article concludes with a consideration of the implications of the findings in terms of the practice of embryo donation and the policies that surround it.