104 research outputs found
The Human placenta: an atypical endocrine organ
La placenta humana es caracteritza per la intensitat i especificitat de les seves funcions endocrines.
La hormones de la placenta són necessàries per a l'establiment i manteniment de
l'embaràs, per a l'adaptació a aquest de l'organisme femení, per al creixement del fetus així i
per al desenvolupament dels mecanismes implicats en el part. El teixit endocrí de la placenta
és el sinciciotrofoblast, que cobreix les vellositats coriòniques o estructura principal d'intercanvi.
La utilització de cultius primaris de citotrofoblasts ha proporcionat molta informació sobre
els mecanismes implicats en la formació del sinciciotrofoblast per fusió cèll. ula-cèll. ula. Immers
en la sang materna, el sinciciotrofoblast secreta la major part de les seves hormones polipeptídiques
a la circulació materna. Entre d'altres, la gonadotrofina coriònica (hCG) fa una funció
essencial en el manteniment del cos luti i està directament implicada en la diferenciació del
trofoblast. L'hormona de creixement (GH) placentària està també secretada contínuament pel
sinciciotrofoblast i substitueix la GH hipofisària durant l'embaràs. Mitjançant la captura del colesterol
a partir de les lipoproteïnes maternes, el sinciciotrofoblast sintetitza una gran quantitat
de progesterona necessària per a l'estabilitat de l'úter. El sinciciotrofoblast, en no tenir l'enzim
citocrom P450 17 α-hidroxilasa/17-20-liasa, utilitza els andrògens adrenals materns i fetals per
a sintetizar estrògens. Com a conclusió, és important esmentar que en l'observació de qualsevol
anomalia hormonal durant l'embaràs hauràn de tenir-se en compte aquestes dades i, en
particular, les característiques enzimàtiques de la placenta.The human placenta is characterized by the intensity and the specificity of its endocrine functions.
Placental hormones are required for the establishment and maintenance of pregnancy,
the adaptation of the maternal organism to pregnancy, fetal growth and well being, and the
development of the mechanisms involved in parturition. The endocrine tissue of the placenta is the syncytiotrophoblast, which covers the chorionic villi, the main structure of exchange.
Primary cultures of villous cytotrophoblasts have provided insight into the mechanisms involved
in syncytiotrophoblast formation by cell-cell fusion. Bathing in maternal blood, the syncytiotrophoblast
secretes the majority of its polypeptide hormones into maternal circulation.
Among those, hCG (human chorionic gonadotropin) plays an essential role in the maintenance
of the corpus luteum and is directly implicated in trophoblastic differentiation. The placental
GH (growth hormone) secreted continuously by the syncytiotrophoblast replaces the maternal
pituitary GH during pregnancy. Capturing the cholesterol from the maternal lipoproteins,
the syncytiotrophoblast synthesizes large amounts of progesterone essential for uterine quiescence.
Deprived of cytochrome P450 17αhydroxylase/17-20lyase, it uses the maternal and
fetal adrenal androgens to synthesize estrogens. The observation of any maternal hormonal
anomaly during pregnancy must take into account these data and, in particular, the enzymatic
characteristics of the placenta
Toward better understanding of the human placenta: development of “disease-in-a-dish” models
Cell fusions in mammals
Cell fusions are important to fertilization, placentation, development of skeletal muscle and bone, calcium homeostasis and the immune defense system. Additionally, cell fusions participate in tissue repair and may be important to cancer development and progression. A large number of factors appear to regulate cell fusions, including receptors and ligands, membrane domain organizing proteins, proteases, signaling molecules and fusogenic proteins forming alpha-helical bundles that bring membranes close together. The syncytin family of proteins represent true fusogens and the founding member, syncytin-1, has been documented to be involved in fusions between placental trophoblasts, between cancer cells and between cancer cells and host cells. We review the literature with emphasis on the syncytin family and propose that syncytins may represent universal fusogens in primates and rodents, which work together with a number of other proteins to regulate the cell fusion machinery
Screen for abnormal mitochondrial phenotypes in mouse ES cells identifies model for Succinyl-CoA Ligase deficiency and mtDNA depletion
The Human placenta: an atypical endocrine organ
La placenta humana es caracteritza per la intensitat i especificitat de les seves funcions endocrines.
La hormones de la placenta són necessàries per a l'establiment i manteniment de
l'embaràs, per a l'adaptació a aquest de l'organisme femení, per al creixement del fetus així i
per al desenvolupament dels mecanismes implicats en el part. El teixit endocrí de la placenta
és el sinciciotrofoblast, que cobreix les vellositats coriòniques o estructura principal d'intercanvi.
La utilització de cultius primaris de citotrofoblasts ha proporcionat molta informació sobre
els mecanismes implicats en la formació del sinciciotrofoblast per fusió cèll. ula-cèll. ula. Immers
en la sang materna, el sinciciotrofoblast secreta la major part de les seves hormones polipeptídiques
a la circulació materna. Entre d'altres, la gonadotrofina coriònica (hCG) fa una funció
essencial en el manteniment del cos luti i està directament implicada en la diferenciació del
trofoblast. L'hormona de creixement (GH) placentària està també secretada contínuament pel
sinciciotrofoblast i substitueix la GH hipofisària durant l'embaràs. Mitjançant la captura del colesterol
a partir de les lipoproteïnes maternes, el sinciciotrofoblast sintetitza una gran quantitat
de progesterona necessària per a l'estabilitat de l'úter. El sinciciotrofoblast, en no tenir l'enzim
citocrom P450 17 α-hidroxilasa/17-20-liasa, utilitza els andrògens adrenals materns i fetals per
a sintetizar estrògens. Com a conclusió, és important esmentar que en l'observació de qualsevol
anomalia hormonal durant l'embaràs hauràn de tenir-se en compte aquestes dades i, en
particular, les característiques enzimàtiques de la placenta.The human placenta is characterized by the intensity and the specificity of its endocrine functions.
Placental hormones are required for the establishment and maintenance of pregnancy,
the adaptation of the maternal organism to pregnancy, fetal growth and well being, and the
development of the mechanisms involved in parturition. The endocrine tissue of the placenta is the syncytiotrophoblast, which covers the chorionic villi, the main structure of exchange.
Primary cultures of villous cytotrophoblasts have provided insight into the mechanisms involved
in syncytiotrophoblast formation by cell-cell fusion. Bathing in maternal blood, the syncytiotrophoblast
secretes the majority of its polypeptide hormones into maternal circulation.
Among those, hCG (human chorionic gonadotropin) plays an essential role in the maintenance
of the corpus luteum and is directly implicated in trophoblastic differentiation. The placental
GH (growth hormone) secreted continuously by the syncytiotrophoblast replaces the maternal
pituitary GH during pregnancy. Capturing the cholesterol from the maternal lipoproteins,
the syncytiotrophoblast synthesizes large amounts of progesterone essential for uterine quiescence.
Deprived of cytochrome P450 17αhydroxylase/17-20lyase, it uses the maternal and
fetal adrenal androgens to synthesize estrogens. The observation of any maternal hormonal
anomaly during pregnancy must take into account these data and, in particular, the enzymatic
characteristics of the placenta
lnvolvement of gap junctional communication and connexin expression in trophoblast differentiation of the human placenta
Gap junctional intercellular communication (GJIC) permits coordinated cellular activities during development and differentiation processes, and its dysfunction or mutation of connexin genes have been irnplicated in pathologies. In the human placenta, two distinct differentiation pathways of cytotrophoblastic cell coexist leading to a double model: fusion phenotype (villous trophoblast) and proliferative/invasive phenotype (extravillous trophoblast). This review focuses on current knowledge on the connexin expression and the irnplication of GJIC in trophoblastic differentiation. Experimental evidence obtained in hurnan placenta demonstrates the involvement of connexin 43-gap junctions in the trophoblastic fusion process and of a connexin switch during the spatially and ternporally controlled proliferation/invasion process
Human endogenous retrovirus K (HERV-K) is expressed in villous and extravillous cytotrophoblast cells of the human placenta
Human endogenous retroviruses (HERVs) have been shown to be important in physiological and pathophysiological processes in humans. Several HERVs have been found to be expressed in the placenta—a tissue with special immunomodulatory functions that is responsible for nutrition of the embryo and the ability of the semiallogenic trophoblast to invade. The envelope proteins of HERV-W (also known as syncytin 1) and HERV-FRD (syncytin 2) were shown to be involved in cell fusion leading to the generation of the syncytiotrophoblast. Syncytin 2 was further shown to have immunosuppressive properties. Herein we analyse the expression of another HERV, HERV-K, which is characterised by open reading frames for all viral genes. Using immunohistochemistry and Western blot analysis, expression of the transmembrane envelope (TM) protein of HERV-K was studied in normal placental and decidual tissues obtained at different gestational ages. The TM protein was expressed exclusively in villous (VT) and extravillous cytotrophoblast (EVT) cells, but not in the syncytiotrophoblast or other cells. The expression of the TM protein of HERV-K in EVT cells was confirmed by Western blot analysis of isolated c-erbB2-expressing cytotrophoblast cells. Thus, this is the first report showing expression of the TM protein of HERV-K in normal human placental tissue with an exclusive expression in cytotrophoblast cells, suggesting a potential involvement of HERV-K in placentogenesis and pregnancy. Since retroviral TM proteins including the TM protein of HERV-K have immunosuppressive properties, expression of the TM protein of HERV-K may contribute to immune protection of the fetus
Human Trophoblast in Trisomy 21: A Model for Cell–Cell Fusion Dynamic Investigation
International audienceTrophoblastic cell fusion is one essential step of the human trophoblast differentiation leading to formation of the syncytiotrophoblast, site of the numerous placental functions. This process is multifactorial and finely regulated. Using the physiological model of primary culture of trophoblastic cells isolated from human placenta, we have identified different membrane proteins directly involved in trophoblastic cell fusion: connexin 43, ZO-1 and recently syncytins. These fusogenic membrane retroviral envelop glycoproteins: syncytin-1 (encoded by the HERV-W gene) and syncytin-2 (encoded by the FRD gene) and their receptors are major factors involved in human placental development. Disturbances of syncytiotrophoblast formation are observed in trisomy 21-affected placentas. Overexpression of the copper/zinc superoxide dismutase (SOD-1), encoded by chromosome 21 as well as an abnormal hCG signaling are implicated in the defect of syncytiotrophoblast formation. This abnormal trophoblast fusion and differentiation in trisomy 21-affected placenta is reversible in vitro by different ways
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