No description available.

No description available.

No description available.

Chorionic plate (CPA) and stem villous (SVA) arteries located at the fetal and maternal interface of the placenta respond to stimuli including hypoxia and acidic pH which can be the result of an intermittent blood supply. Unlike other vascular tissue the placenta lacks nervous control so any response to such stimuli will be autoregulated by ion channels. Members of the two pore domain potassium channel family (K2P) the Tandem of P domains in a weak inward rectifying (TWIK) related potassium channel (TREK-1) and the TWIK Related acid sensitive K+ channel (TASK-1/3) have been shown to respond to both intracellular and extracellular pH. The hypothesis that there is differential expression and modulation of these candidate ion channels in normal pregnancy was tested. Placentae (N) were collected with written informed consent from healthy patients undergoing elective Caesarean section at term (≥37 weeks). The functional responses of resistance sized arteries (≤500µm) (n) taken from the SVA and the CPA were characterised using wire myography. Vessels were pre-contracted with U46619 and the effect of extracellular pH was studied using 1M lactic acid to produce falls of 0.2 pH units over a range of pH 7.4-6.4. The effects of a variety of ion channel modulators along with tissue oxygenation (20%, 5% and 2% O2) were also investigated on the vascular response of CPA and SVA. Western blot analysis was performed on crude CPA and SVA tissue homogenates with separation by 12% SDS-PAGE to quantify expression of TASK-1/3 and TREK-1. The subcellular localisation of each ion channel was also examined with smooth muscle cells (SMC) cultured from the CPA and SVA by confocal immunofluorescence. CPA and SVA were equally positive for TASK 1/3 (N=31) and TREK 1 (N=40) at the protein level. SMC from CPA and SVA showed expression for TASK 1/3 (N=8) with an increased fluorescence stain around the peri nuclear region. TREK-1 (N=12) expression showed a linear organisation that closely overlapped with α actin IF stain. The acidic pH stimulation triggered a biphasic relaxation that was repeated with each subsequent pH insult. A change from pH 7.4-7.2 produced a 29 ± 3% (n=9) relaxation of CPA which increased to 61 ± 4% at the lowest pH of 6.4 in 20% pO2. Similarly, altering the pH of pre-constricted SVA caused a 21 ± 2% (n=6) fall at pH 7.2 with a maximum relaxation of 69 ± 2% at pH 6.4 (p<0.01). Lowering pO2 from 20% to 5% inhibited the relaxation response seen with CPA (45 ± 3%, n=8) and SVA (34 ± 3%, n=6) at pH 6.4. CPA were also treated with the TREK-1 blocker L-methionine (1mM) which increased the relaxation to 67 ± 7% (n=6 p<0.001) at pH 6.4. Similarly the TASK 1/3 blocker ZnCl2 (1mM) gave a maximum relaxation of 72 ± 5% (n=8 p<0.01) in 20% pO2. The TREK-1 opener riluzole demonstrated a potent relaxation with both CPA (75 ± 5%, n=6) and SVA (78 ± 5%, n=6) in 20% pO2. Our data has shown that tissue oxygenation and extracellular pH within the physiological range has an important role in controlling vasodilatation in the placenta. Protons are readily transported across the cell membrane and can activate a range of targets including the K2P channels. The relaxation by riluzole has not been previously reported and implicates a direct role for TREK-1 in controlling placental vessel function. However, when TREK-1 and TASK-3 channels were blocked, the response by CPA to lower pH was exaggerated, and reflects the complex pharmacology of pH on vascular function. This also suggests that K2P channel activity can be compensated for by other pH sensitive channels and work is currently underway to identify the role of other potential ion channels that may be involved in this pathway.

No description available.

Fetal growth restriction (FGR) signifies that the fetus has not achieved its growth potential and is associated with increased perinatal mortality and morbidity. The exact aetiology of FGR, in the absence of any identifiable fetal and maternal factors, remains unclear and is attributed to placental insufficiency. The FGR placenta has a characteristic phenotype including: increased resistance in the fetoplacental circulation, an alteration in trophoblast cell turnover and reduced activity of placental nutrient transport systems, the best characterised being the amino acid transporter, system A. The placenta strongly expresses the cortisol inactivating enzyme, 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). 11β-HSD2 activity was reduced in placentas from pregnancies complicated by FGR, suggesting increased exposure of the fetoplacental unit to maternal cortisol. In animal models, excessive exposure to glucocorticoids (GCs) is associated with a reduction in both fetal and placental weight. This reduction in placental weight was associated with abnormalities in placental function, consistent with those observed in the FGR placenta. This PhD investigated whether excess GC exposure during pregnancy is responsible placental insufficiency in human pregnancies and tested the hypotheses that excess GC exposure adversely affects placental vascular tone, trophoblast cell turnover and activity of the amino acid transporter, system A. Term placentas were collected from uncomplicated pregnancies and first trimester placental samples were obtained following elective surgical termination of pregnancy. Wire myography was used to explore the acute and chronic effects of GCs on term chorionic plate artery (CPA) function. The impact of GC treatment on trophoblast cell turnover in both first trimester and term placenta was investigated using the placental explant system. The effect of GCs on the activity of the system A transporter was also investigated in term explants and in isolated cytotrophoblasts where the expression of 11β-HSD2 was reduced using siRNA. Gene microarray studies on first trimester placental explants treated with GCs were utilised to identify genes regulated by GCs. Blunted constriction to thromboxane A2 was observed following acute GC treatment, whilst chronic exposure resulted in enhanced vasoconstriction, mimicking the altered reactivity of CPAs from pregnancies complicated by FGR. GC excess in first trimester placental explants increased apoptosis and decreased proliferation, thereby replicating the disordered turnover of the trophoblast observed in FGR placentas. No demonstrable effect was observed in cell turnover or system A activity in term placental explants treated with GCs, however, these experiments were hindered by the in-vitro regeneration of the syncytiotrophoblast in the model employed. The attenuation of 11β-HSD2 activity observed in FGR placentas was replicated in term primary cytotrophoblasts utilising siRNA to knock-down expression of 11β-HSD2. Preliminary results suggested an increase in system A activity in response to cortisol. Gene microarray studies identified a significant number of genes (~500) that were regulated by dexamethasone, confirming that GCs have an impact on many aspects of placental function. Potential mediators for the characteristic features of the FGR placenta replicated here in response to GC treatment were identified and validated at the mRNA level. The studies described in this thesis support the hypotheses that GC excess within the placenta contributes to the development of raised vascular resistance in the fetoplacental circulation and the disordered trophoblast turnover in placentas from pregnancies complicated by FGR. However, with the preliminary studies performed, the hypothesis that elevated levels of GCs contribute to the reduced placental amino acid transfer by the system A transporter in the FGR placenta can not be confidently disproven.

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Η ενδομήτρια καθυστέρηση ανάπτυξης ορίζεται ως παθολογική μείωση του ρυθμού εμβρυικής ανάπτυξης που καταλήγει σε ένα έμβρυο το οποίο δεν έχει την αναμενόμενη ανάπτυξη σύμφωνα με την ηλικία κύησης και το οποίο διατρέχει κίνδυνο αυξημένης περιγεννητικής νοσηρότητας και θνησιμότητας. Ενδομήτρια καθυστέρηση ανάπτυξης είναι η ανικανότητα του εμβρύου να διατηρήσει τον αναμενόμενο ρυθμό ανάπτυξης ανεξάρτητα αν το βάρος του είναι κάτω από τη 10η εκατοστιαία θέση. Όταν η ανάπτυξη του εμβρύου είναι κάτω από την 5η εκατοστιαία θέση τότε ίσως να μπορεί να θεωρηθεί πραγματική ενδομήτρια καθυστέρηση ανάπτυξης. Σύμφωνα με το αμερικανικό κολέγιο γυναικολόγων και μαιευτήρων American College of Obstetricians and Gynecologists (ACOG) η ενδομήτρια καθυστέρηση ανάπτυξης ορίζεται ως το έμβρυο που αποτυγχάνει να έχει τον αναμενόμενο ρυθμό ανάπτυξης. Πολλές φορές οι όροι ενδομήτρια καθυστέρηση ανάπτυξης (IUGR) και μικρό για την ηλικία κύησης (SGA) συγχέονται και για αυτό το λόγο διευκρινίζεται ότι ο όρος μικρό για την ηλικία κύησης (SGA) αναφέρεται σε έμβρυο του οποίου το εκτιμώμενο βάρος είναι κάτω από τη 10η εκατοστιαία θέση. Από το σύνολο των μικρών για την ηλικία κύησης (SGA) εμβρύων το 40% είναι υγιή, 20% είναι μικρά εξαιτίας χρωμοσωμικών και περιβαλλοντικών παραγόντων και 40% διατρέχουν ιδιαίτερα αυξημένο κίνδυνο ενδομήτριου θανάτου και σχετίζονται με ενδομήτρια καθυστέρηση ανάπτυξης. Η ενδομήτρια καθυστέρηση ανάπτυξης είναι μια πολυσυστηματική διαταραχή και διακρίνεται σε: Α) Συμμετρική. Όταν η ανάπτυξη της κεφαλής και της κοιλιάς επιβραδύνονται συμμετρικά. Είναι λιγότερο συχνή, 20%-30%. Β) Ασύμμετρη. Δυσανάλογη ελάττωση του μεγέθους της κοιλιάς σε σχέση με αυτό της κεφαλής. Είναι περισσότερο συχνή, 70%-80%, και οφείλεται συνήθως σε μητροπλακουντιακή ανεπάρκεια και συμβαίνει μετά την 28η εβδομάδα. Στη φάση αυτή γίνεται η μεγαλύτερη εναπόθεση λίπους. Η ενδομήτρια καθυστέρηση ανάπτυξης αποτελεί κύριο πρόβλημα στην περιγεννητική ιατρική, είναι η ΔΕΥΤΕΡΗ αιτία θανάτου μετά την προωρότητα. 52% των ανεξήγητων ξαφνικών θανάτων των εμβρύων συσχετίζονται με ανάπτυξη IUGR. 10% των περιπτώσεων περιγεννητικής θνησιμότητας στην Ευρώπη είναι αποτέλεσμα μη διαγνωσμένης IUGR. Η επίπτωση της ενδομήτριας καθυστέρησης ανάπτυξης είναι 8% στον γενικό πληθυσμό. / Intrauterine growth restriction (IUGR) is the failure of the fetus to achieve his/her intrinsic growth potential and is associated with significantly increased perinatal morbidity and mortality. IUGR affects 10% of pregnancies and perinatal mortality rates are 4-8 times higher for infants with this disorder. Intrauterine growth restriction is not a specific disease entity with a unique pathophysiology, but the result of suboptimal intrauterine growth conditions in conjunction with a variety of disorders from genetic to metabolic, vascular, coagulative, autoimmune, as well as infectious. Newborns with intrauterine growth restriction (IUGR) present reduced fat mass and undergo adaptational changes of endocrine/metabolic mechanisms as a result of intrauterine malnutrition. Recently, it was shown that fat-secreted adipokines such as visfatin, a novel adipokine improving glucose tolerance through insulin-mimetic effects, and vaspin , profoundly influence insulin sensitivity and energy metabolism.

Η ενδοθηλίνη-1 (ET-1) είναι ένα πεπτίδιο αποτελούμενο από 21 αμινοξέα. Είναι ισχυρός αγγειοσυσπαστικός παράγοντας και μιτογόνο των λείων μυϊκών κυττάρων. Στο πλάσμα ασθενών που πάσχουν από σοβαρού βαθμού υπέρταση ή προεκλαμψία έχουν ανιχνευθεί υψηλές συγκεντρώσεις ΕΤ-1. Ο ακριβής ρόλος της ΕΤ-1 σε σχέση με την ανθρώπινη αναπαραγωγή είναι ακόμη σε μεγάλο βαθμό ένα αίνιγμα. Μητρικές και εμβρυικές συγκεντρώσεις στο πλάσμα της ενδοθηλίνης έχουν μελετηθεί πρόσφατα σε σχέση με την εγκυμοσύνη. Αυτοί περιλαμβάνουν ενδομήτρια καθυστέρηση της ανάπτυξης (IUGR) και προεκλαμψία. Οι ακριβείς μηχανισμοί για αυτές τις παθολογικές διαδικασίες και η αύξηση των συγκεντρώσεων πλάσματος της ενδοθηλίνης είναι ακόμη σε μεγάλο βαθμό άγνωστοι, αν και υπάρχουν στοιχεία που να υποδηλώνουν ότι η ενδοθηλίνη συνδέεται με βλάβη του ενδοθηλίου των κυττάρων. Υπάρχουν τώρα κάποιες ενδείξεις ότι οι αμνιακές συγκεντρώσεις της ενδοθηλίνης είναι αυξημένες σε κυήσεις που σχετίζονται με προ-εκλαμψία. Ο σκοπός αυτής της προοπτικής μελέτης ήταν να καταγράψει την συγκέντρωση ενδοθηλίνης στο αμνιακό υγρό σε γυναίκες με φυσιολογικές κυήσεις συγκριτικά με τις γυναίκες που εμφανίζουν προεκλαμψία , IUGR και προώρη ρήξη εμβρυικων υμένων. Εξετάσθηκε το αμνιακό υγρό που προήλθε από αμνιοπαρακέντηση από 125 γυναίκες κατά το δεύτερο τρίμηνο της εγκυμοσύνης . Τα επίπεδα της ενδοθηλίνης μετρήθηκαν με μια ευαίσθητη και ειδική εξεταση ραδιοανοσοπροσδιορισμού. Η συγκέντρωση στο αμνιακό υγρό της ενδοθηλίνης είναι αυξημένη από το δεύτερο τρίμηνο σε γυναίκες που αργότερα αναπτύσσουν PPROM, PROM, IUGR και προεκλαμψία με στατιστικά σημαντική διαφορά. Έχει αποδειχθεί ότι τα επίπεδα ΕΤ1 συσχετίζονται με το βάρος γέννησης των νεογνών, για τη κυήση που περιπλέκονται με IUGR, με το βάρος γέννησης των νεογνών, και με την ηλικία κύησης για την ομάδα PPROM, κια με το βάρος γέννησης των νεογνών σε κυήσεις με προεκλαμψία. Η διερεύνηση επιπέδων ΕΤ-1 στο αμινιακό υγρό δευτέρου τριμήνου μπορεί να είναι ένας εξαιρετικά σημαντικός χώρος έρευνας στο μέλλον, καθώς θα μπορούσε να ρίξει περισσότερο φως για την πρώιμη ανέυρεση των παθοφυσιολογικων διαδικασιών της πλακουντιακής δυσλειτουργίας. / Endothelin-1 (ET-1) is a peptide consisting of 21 amino acids. It is a strong vasoconstrictor and mitogenic factor with significant activity on to the smooth muscle cells. High concentrations of ET-1 have been detected in plasma of patients with severe hypertension or preeclampsia. The exact role of ET-1 in relation to human reproduction is still largely an enigma. Maternal and fetal plasma concentrations of ET-1 have been studied recently in relation to pregnancy. These include intrauterine growth retardation (IUGR) and preeclampsia. The exact mechanisms of these pathological processes and increased plasma concentrations of ET-1 are still largely unknown, although there is evidence to suggest that ET-1 is associated with impaired endothelial cells. There is now some evidence that amniotic ET-1 concentrations are elevated in pregnancies associated with pre-eclampsia. The purpose of this prospective observational study was to record the ET-1 concentration in second trimester amniotic fluid and compare with the levels in women who develop preeclampsia, IUGR and premature rupture of membranes. The amniotic fluid samples were obtained from 125 women by amniocentesis during the second trimester of pregnancy. The levels of ET-1 were measured with a sensitive and specific radioimmunoassay examination (ELISA). The amniotic fluid concentrations of ET-1 are statistically significantly higher from the second trimester in women who later develop PPROM, PROM, IUGR with preeclampsia. This study showed that ET-1 levels correlated with the birth weight of newborns in the pregnancies complicated by IUGR, the birth weight of newborns and the gestational age for the group PPROM, and with the birth weight of newborns in pregnancies with preeclampsia . Investigating the levels of ET-1 in the second trimester amniotic fluid can be an extremely important research area in the future, and could shed more light on the early discovery of the pathophysiological process of placental dysfunction.