Trophoblast: Difference between revisions
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==Introduction== | ==Introduction== | ||
[[File:Human_embryo_day_5.jpg|thumb| | [[File:Human_embryo_day_5.jpg|thumb|200px|Human Blastocyst (day 5), trophoblast cells form the peripheral flattened epithelial layer of cells directly under the zona pellucida.<ref name="PMID19924284"><pubmed>19924284</pubmed>| [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2773928 PMC2773928] | [http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0007844 PLoS One]</ref>]] | ||
[[File:Mouse blastocyst trophoblast 01.jpg|thumb|Mouse blastocyst labelled with trophoblast marker.<ref name=PMID16681851><pubmed>16681851</pubmed>| [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1479373 PMC1479373] | [http://www.translational-medicine.com/content/4/1/20 J Transl Med.]</ref>]] | [[File:Mouse blastocyst trophoblast 01.jpg|thumb|200px|Mouse blastocyst labelled with trophoblast marker.<ref name=PMID16681851><pubmed>16681851</pubmed>| [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1479373 PMC1479373] | [http://www.translational-medicine.com/content/4/1/20 J Transl Med.]</ref>]] | ||
(Greek, ''trophe'' = "nutrition" and -blast, a [[P#primordial|primordial]] cell) During early development the trophoblast cells have an important contribution to extraembryonic tissues (fetal [[P#placenta|placenta]] and membranes) and processes of early development (adplantation, implantation and endocrine support of pregnancy). | (Greek, ''trophe'' = "nutrition" and -blast, a [[P#primordial|primordial]] cell) During early development the trophoblast cells have an important contribution to extraembryonic tissues (fetal [[P#placenta|placenta]] and membranes) and processes of early development (adplantation, implantation and endocrine support of pregnancy). | ||
Revision as of 10:10, 26 August 2016
Embryology - 2 May 2024 Expand to Translate |
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Introduction
(Greek, trophe = "nutrition" and -blast, a primordial cell) During early development the trophoblast cells have an important contribution to extraembryonic tissues (fetal placenta and membranes) and processes of early development (adplantation, implantation and endocrine support of pregnancy).
In humans, week 1 blastocyst formation the outer layer of cells (adjacent to the zona pellucida) form a flat squamous epithelial layer of cells, the trophoblast layer. Week 2 following blastocyst hatching the trophoblast layer is involved with initial adhesion to the uterine wall and subsequent implantation within the wall. During this period the trophoblast layer differentiates into two distinct layers (syncitiotrophoblast and cytotrophoblast).
- Links: Blastocyst | Implantation | Week 2 | Week 3 | Placenta Development | Trophoblast - Protein Expression | Ectopic Implantation Research
Some Recent Findings
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More recent papers |
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Trophoblast and Placental Villi
Early placental development cartoon showing trophoblast contribution to placental villi.[11]
Legend
- SYN - syncytiotrophoblasts
- sCTB - subsyncytial cytotrophoblasts (this layer grows increasingly discontinuous in later trimesters)
- EVT - extravillous cytotrophoblasts (anchor the villous tree in the decidua)
Cytotrophoblasts
Hyperglycosylated human Chorionic Gonadotropin (hCG) promotes the growth of cytotrophoblast cells and the endometrial invasion by these cells during implantation.[12]
Extravillous Cytotrophoblasts
Maintain open maternal spiral arteries emptying into the maternal lacunae[13]
Syncytiotrophoblasts
- form by fusion of rapidly dividing cytotrophoblast cells
- secrete proteolytic enzymes, enzymes break down extracellular matrix around cells
- Allow passage of blastocyst into endometrial wall, totally surround the blastocyst
- generate spaces, lacunae, that fill with maternal blood
- secrete Human Chorionic Gonadotropin (hCG), hormone, maintains decidua and Corpus Luteum, basis of pregnancy diagnostic test, present in urine is diagnostic of pregnancy
- Later in development placenta will secrete hCG
Cell–cell Fusion Activity
Two pairs of envelope genes of retroviral origin, syncytins, have fusogenic properties. Human endogenous retroviruses (HERVs) make up about 8% of the human genome. Recent study has shown that placentae from intrauterine growth restriction have impaired cell fusion and differentiation that correlates with reduced levels of HERV envelope genes.[14]
Human - syncytin 1 and syncytin 2
- Syncytin 2 is an envelope gene from the human endogenous retrovirus FRD (HERV-FRD)[15]
- Syncytin 2 receptor is Major Facilitator Superfamily Domain Containing 2 (MFSD2) (at chromosomal position 1p34.2)
- belongs to family of presumptive carbohydrate transporters with 10-12 membrane-spanning domains
- Syncytin 1 (-FRD) receptor is ASCT-1/-2
Mouse - syncytin A and syncytin B
- syncytin A is essential for trophoblast cell differentiation and syncytiotrophoblast morphogenesis[16]
- Links: OMIM Syncytin-2
Human Chorionic Gonadotropin
hCG sources - produced by villous syncytiotrophoblast cells, hyperglycosylated hCG produced by cytotrophoblast cells, free beta-subunit made by multiple primary non-trophoblastic malignancies, and pituitary hCG made by the gonadotrope cells of the anterior pituitary.
- levels peak at 8 to 10 weeks of pregnancy, then decline and are lower for rest of pregnancy
- 0-1 week: 0-50 mIU/ml
- 1-2 weeks: 40-300 mIU/ml
- 3-4 weeks: 500-6,000 mIU/ml
- 1-2 months: 5,000-200,000 mIU/ml
- 2-3 months: 10,000-100,000 mIU/ml
- 2nd trimester: 3,000-50,000 mIU/ml
- 3rd trimester: 1,000-50,000 mIU/ml
Non-pregnant females: <5.0 mIU/ml Postmenopausal females: <9.5 mIU/ml
HLA-G
An acronym for histocompatibility antigen, class I, G (also called: Human Leukocyte Antigen G, (HLA-6.0; HLA60, T-CELL A LOCUS, TCA) and is expressed on placental cytotrophoblast cells and other adult tissues. This distinct tissue distribution differs from the other HLA antigens (HLA-A, HLA-B, HLA-C) leading to the description as a non-classical class I antigen. May have a role in protecting the fetus from the maternal immune response.
Human gene is located at 6p22.1 and there exist several protein isoforms from alternative splicing of messenger RNAs, membrane-bound isoforms (HLA-G 1-4) and soluble soluble (HLA-G 5-6)[17]. The molecule is a heterodimer consisting of both a heavy chain and a light chain (beta-2 microglobulin). The membrane-bound isoform heavy chain is anchored in the membrane and increased expression of the soluble form is related to higher implantation rates. Changes in HLA-G expression have been associated with increased miscarriage rates.[18] Killer cell immunoglobulin-like receptor (KIR) 2DL4 (KIR2DL4) has been shown to act as a receptor for the soluble HLA-G, leading to a stimulation of resting natural killer (NK) cells.[19]
- Links: HLA-G | OMIM142871
Trophoblast Infiltration
Trophoblast plugs within Spiral Arteries Week 9, GA week 11.[3]
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Trophoblast Cell Lines
A useful component of current placentation and trophoblast research are a number of trophoblast cell lines that have been derived from a number of different sources including term placenta, choriocarcinomas and transformation of primary isolated cells. BeWo cell line is the earliest human choriocarcinoma, established in 1968[20]. Most appear to be examples of extravillous trophoblast cells, some examples of various human "trophoblast" cell lines are listed below.
- BeWo - human choriocarcinoma[20], hypotetraploid (modal number = 86; range = 71 to 178) (ATCC CCL-98)
- JEG-3 - choriocarcinoma HTR8/SVneo a transformed extravillous trophoblast line
- SGHPL-4 - [21][22]
- TEV-1 - (HPV16) E6/E7 infection first-trimester extravillous trophoblast cell line[23]
- ACH-3P - fusion of primary human first trimester trophoblasts (GA week 12) with a human choriocarcinoma cell line (AC1-1).[24]
- HChEpC1b - retroviral infection by E6/E7/hTERT[25]
History
The name "Trophoblast" was used for the first time by Ambrosius Arnold Willem Hubrecht (1853 – 1915) at the meeting of the Anatomical Congress at Wiirzburg in 1888, and its earliest definition is found in the report of that meeting in Nos. 17 and 18 of the Anatomischer Anzeiger, Bd. III. "We there read, concerning a very early stage of the hedgehog (p. 510) : Die aussere Wand der Keimblase ist verdickt (drei bis vierschichtig) und besitzt wabige Lacunen. Fur diese aussere (epiblastische) Schicht sei der. Name Trophoblast gewahlt."
- Links: The Trophoblast - A Rejoinder (1904) | Ambrosius Arnold Willem Hubrecht | Hubrecht Collection | Embryologists | Embryology History
Abnormalities
Hydatidiform Mole
A type of placental abnormality when only the conceptus trophoblast layers proliferates and not the embryoblast, no embryo develops, this is called a "hydatidiform mole", which is due to the continuing presence of the trophoblastic layer, this abnormal conceptus can also implant in the uterus. The trophoblast cells will secrete human chorionic gonadotropin (hCG), as in a normal pregnancy, and may appear maternally and by pregnancy test to be "normal". Prenatal diagnosis by ultrasound analysis demonstrates the absence of a embryo.
There are several forms of hydatidiform mole: partial mole, complete mole and persistent gestational trophoblastic tumor. Many of these tumours arise from a haploid sperm fertilizing an egg without a female pronucleus (the alternative form, an embryo without sperm contribution, is called parthenogenesis). The tumour has a "grape-like" placental appearance without enclosed embryo formation. Following a first molar pregnancy, there is approximately a 1% risk of a second molar pregnancy.
This topic is also covered in Placenta - Abnormalities
Trophoblast Infections
- Malaria (More? Abnormal Development - Malaria)
- Chlamydia trachomatis[26]
- Herpesvirus 8 (HHV-8)[27]
- Group B streptococcus (GBS)[28]
References
- ↑ <pubmed>19924284</pubmed>| PMC2773928 | PLoS One
- ↑ <pubmed>16681851</pubmed>| PMC1479373 | J Transl Med.
- ↑ 3.0 3.1 <pubmed>27510415</pubmed>
- ↑ <pubmed>27088357</pubmed>
- ↑ Renaud, SJ. entail., OVO-like 1 regulates progenitor cell fate in human trophoblast development PNAS
- ↑ <pubmed>25203285</pubmed>
- ↑ <pubmed>24186980</pubmed>| Genes Dev.
- ↑ <pubmed>22423048</pubmed>
- ↑ <pubmed>20195529</pubmed>| PLoS One
- ↑ <pubmed>20338637</pubmed>
- ↑ <pubmed>20107601</pubmed>| PLoS
- ↑ <pubmed>20735820</pubmed>
- ↑ <pubmed>20359743</pubmed>
- ↑ <pubmed>20664994</pubmed>
- ↑ <pubmed>18988732</pubmed>| PNAS
- ↑ <pubmed>19564597</pubmed>
- ↑ <pubmed>16339579</pubmed>
- ↑ <pubmed>24557735</pubmed>
- ↑ <pubmed>16366734</pubmed>
- ↑ 20.0 20.1 <pubmed>5753554</pubmed>
- ↑ <pubmed>9804259</pubmed>
- ↑ <pubmed>16226120</pubmed>
- ↑ <pubmed>15866109</pubmed>
- ↑ <pubmed>18093301</pubmed>
- ↑ <pubmed>19148547</pubmed>
- ↑ <pubmed>19265152</pubmed>
- ↑ <pubmed>19115001</pubmed>
- ↑ <pubmed>18599257</pubmed>
Reviews
<pubmed>19876840</pubmed>
Articles
<pubmed>20081188</pubmed> <pubmed>20033790</pubmed> <pubmed>19617545</pubmed> <pubmed>19564597</pubmed> <pubmed>19582159</pubmed>
Search PubMed
Search October 2010
- Syncytiotrophoblast - All (10230) Review (1104) Free Full Text (2508)
- Cytotrophoblast - All (9828) Review (1062) Free Full Text (2401)
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Cite this page: Hill, M.A. (2024, May 2) Embryology Trophoblast. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Trophoblast
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G