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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/15 15:08:47」(JST)

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Trophoblasts (from Greek trephein: to feed, and blastos: germinator) are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg. This layer of trophoblasts is also collectively referred to as "the trophoblast",^[1] or, after gastrulation,^[2] the trophectoderm, as it is then contiguous with the ectoderm of the embryo.

Structure

The trophoblast proliferates and differentiates into 2 cell layers at approximately 6 days after fertilization for humans:

Layer	Location	Description
cytotrophoblast	inner layer	Single celled, inner layer of the trophoblast.
syncytiotrophoblast	outer layer	Thick layer that lacks cell boundaries and grows into the endometrial stroma. It secretes hCG in order to maintain progesterone secretion and sustain a pregnancy.
intermediate trophoblast (IT)	implantation site, chorion, villi (dependent on subtype)	anchor placenta (implanation site IT), unknown (chorionic & villus IT)

Function

Trophoblasts are specialized cells of the placenta that play an important role in embryo implantation and interaction with the decidualised maternal uterus. The core of placental villi contain mesenchymal cells and placental blood vessels that are directly connected to the fetal circulation via the umbilical cord. This core is surrounded by two layers of trophoblast; a single layer of mononuclear cytotrophoblast that fuse together to form the overlying multinucleated syncytiotrophoblast layer that covers the entire surface of the placenta. It is this syncytiotrophoblast that is in direct contact with the maternal blood that reaches the placental surface, and thus facilitates the exchange of nutrients, wastes and gases between the maternal and fetal systems.^{[citation needed]}

In addition, cytotrophoblast in the tips of villi can differentiate into another type of trophoblast called the extravillous trophoblast. Extravillous trophoblast grow out from the placenta and penetrate into the decidualised uterus. This process is essential not only for physically attaching the placenta to the mother, but also for altering the vasculature in the uterus to allow it to provide an adequate blood supply to the growing fetus as pregnancy progresses. Some of these trophoblast even replace the endothelial cells in the uterine spiral arteries as they remodel these vessels into wide bore conduits that are independent of maternal vasoconstriction. This ensures the fetus receives a steady supply of blood, and the placenta is not subjected to fluctuations in oxygen that could cause it damage.^{[citation needed]}

Clinical significance

The invasion of a specific type of trophoblast (extravillous trophoblast) into the maternal uterus is a vital stage in the establishment of pregnancy. Failure of the trophoblast to invade sufficiently is important in the development of some cases of pre-eclampsia. Too firm an attachment may lead to placenta accreta.

Gestational trophoblastic disease represents a form of proliferation.

Additional images

Blastodermic vesicle of Vespertilio murinus.
Section through embryonic disk of Vespertilio murinus.
Transverse section of a chorionic villus.
Scheme of placental circulation.
The initial stages of human embryogenesis

References

^ http://www.britannica.com/EBchecked/topic/606502/trophoblast
^ Merriam-Webster's Medical Dictionary > trophectoderm Retrieved August 2010

External links

Swiss embryology (from UL, UB, and UF) iperiodembry/carnegie02

English Journal

Advances in culture and manipulation of human pluripotent stem cells.

Qian X1, Villa-Diaz LG, Krebsbach PH.Author information 1Department of Biologic and Materials Sciences, School of Dentistry.AbstractRecent advances in the understanding of pluripotent stem cell biology and emerging technologies to reprogram somatic cells to a stem cell-like state are helping bring stem cell therapies for a range of human disorders closer to clinical reality. Human pluripotent stem cells (hPSCs) have become a promising resource for regenerative medicine and research into early development because these cells are able to self-renew indefinitely and are capable of differentiation into specialized cell types of all 3 germ layers and trophoectoderm. Human PSCs include embryonic stem cells (hESCs) derived from the inner cell mass of blastocyst-stage embryos and induced pluripotent stem cells (hiPSCs) generated via the reprogramming of somatic cells by the overexpression of key transcription factors. The application of hiPSCs and the finding that somatic cells can be directly reprogrammed into different cell types will likely have a significant impact on regenerative medicine. However, a major limitation for successful therapeutic application of hPSCs and their derivatives is the potential xenogeneic contamination and instability of current culture conditions. This review summarizes recent advances in hPSC culture and methods to induce controlled lineage differentiation through regulation of cell-signaling pathways and manipulation of gene expression as well as new trends in direct reprogramming of somatic cells.
Journal of dental research.J Dent Res.2013 Nov;92(11):956-62. doi: 10.1177/0022034513501286. Epub 2013 Aug 9.
Recent advances in the understanding of pluripotent stem cell biology and emerging technologies to reprogram somatic cells to a stem cell-like state are helping bring stem cell therapies for a range of human disorders closer to clinical reality. Human pluripotent stem cells (hPSCs) have become a pro
PMID 23934156

PGE2 and PGF2α concentrations in human endometrial fluid as biomarkers for embryonic implantation.

Vilella F1, Ramirez L, Berlanga O, Martínez S, Alamá P, Meseguer M, Pellicer A, Simón C.Author information 1c/o Catedrático Agustín Escardino, 9. Paterna, Valencia 46980, Spain. felipe.vilella@ivi.es.AbstractBACKGROUND: Prostaglandin (PG) signaling has been implicated in embryonic implantation in several animal species including humans; however, this knowledge has not yet been clinically translated. The objective of this work is to investigate whether PGE2 and PGF2α in endometrial fluid (EF) can be used as biomarkers of human embryonic implantation.
The Journal of clinical endocrinology and metabolism.J Clin Endocrinol Metab.2013 Oct;98(10):4123-32. doi: 10.1210/jc.2013-2205. Epub 2013 Aug 26.
BACKGROUND: Prostaglandin (PG) signaling has been implicated in embryonic implantation in several animal species including humans; however, this knowledge has not yet been clinically translated. The objective of this work is to investigate whether PGE2 and PGF2α in endometrial fluid (EF) can be use
PMID 23979956

The H19 induction triggers trophoblast lineage commitment in mouse ES cells.

Fujimori H1, Mukai H, Murakami Y, Hemberger M, Hippo Y, Masutani M.Author information 1Division of Genome Stability Research, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.AbstractTrophoblast lineage differentiation is properly regulated to support embryogenesis. Besides normal developmental process, during germ cell tumor formation or development of other reproductive system diseases, unregulated trophoblast differentiation is also observed and affects the pathogenesis of the diseases. During normal embryogenesis, cell fate of late-stage blastcyst is regulated by a reciprocal repression of the key transcriptional factors; Oct3/4 dominancy inhibits Cdx2 expression in inner cell mass (ICM) and leads them to epiblast/primitive ectoderm but Cdx2 dominancy in trophectoderm (TE) leads them to trophoblast lineage. In contrast during early blastcyst stage, the Cdx2 expression is restricted in TE and not present in ICM, although Oct3/4 signaling does not inhibit the Cdx2 expression in ICM, implying that some factors could be inactivated leading to the suppressed Cdx2 expression in ICM of early blastcyst. ES cells (ESCs), which are derived from ICM, could be a unique model to study trophoblast differentiation in an ectopic context. We previously showed that poly(ADP-ribose) polymerase-1 (Parp-1) deficient ESCs highly expressed non-coding RNA H19 and could differentiate into trophoblast lineage. The expression of H19 is known to start at pre-blastcyst stage during mouse development, and the gene shows high expression only in trophoectoderm (TE) at blastcyst stage. However, its role in trophoblast differentiation has not been clarified yet. Thus, we hypothesized that the H19 activation may act as a trigger for induction of trophoblast differentiation cascade in mouse ESCs. To investigate this issue, we asked whether a forced H19 expression drives ESCs into trophoblast lineage or not. We demonstrated that the H19 induction leads to trophoblast lineage commitment through induction of the Cdx2 expression. We also showed that the expression of Cdx2 is induced in ESCs by forced H19 expression even under a high level of Oct3/4, which could act as a suppressor for Cdx2 expression. It is thus suggested that the H19 induction promotes trophoblast lineage commitment against the repression pressure by Oct3/4 in differentiating ESCs. Taken together, this study suggests that the H19 expression is able to function as a cascade activator of trophoblast lineage commitment possibly by overriding the Oct3/4 action in ESCs.
Biochemical and biophysical research communications.Biochem Biophys Res Commun.2013 Jun 28;436(2):313-8. doi: 10.1016/j.bbrc.2013.05.100. Epub 2013 Jun 4.
Trophoblast lineage differentiation is properly regulated to support embryogenesis. Besides normal developmental process, during germ cell tumor formation or development of other reproductive system diseases, unregulated trophoblast differentiation is also observed and affects the pathogenesis of th
PMID 23743205

Japanese Journal

Effect of Potassium Simplex Optimization Medium and NCSU23 Supplemented with Beta-mercaptoethanol and Amino Acids of In Vitro Fertilized Porcine Embryos

Hashem Md. Abul,Hossein Mohammad Shamim,Woo Jeong Yeon [他],KIM Sue,KIM Ji-Hye,LEE So-Hyun,KOO Ok-Jae,PARK Seon Mi,LEE Eu Gine,KANG Sung Keun,LEE Byeong Chun
The Journal of reproduction and development 52(5), 591-599, 2006-10-01
… 3 and 4 was evaluated by counting the number of total cells and determining the ratio of the inner cell mass (ICM) to trophoectoderm (TE) cells. …
NAID 130000054589

Heat shock induces differentiation of human embryonal carcinoma cells into trophoectoderm lineages

MARUYAMA T
Exp Cell Res 224, 123-127, 1996
NAID 30018226592

Related Pictures

★リンクテーブル★

リンク元	「栄養外胚葉」「trophectodermal」「trophectoderm」

「栄養外胚葉」

Trophoblast
	Blastocyst with an inner cell mass and trophoblast.
Details
Days	6
Gives rise to	caul
Identifiers
Latin	trophoblastus; massa cellularis externa
MeSH	A16.254.085.162
TE	E6.0.1.1.2.0.2
FMA	83029
	Anatomical terminology [edit on Wikidata]