Publications (13) View all
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Article: Effects of oxygen on cell turnover and expression of regulators of apoptosis in human placental trophoblast.
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ABSTRACT: Pre-eclampsia (PE) and intrauterine growth restriction (IUGR) are associated with aberrant cell turnover, including increased apoptosis, in placental villous trophoblast. The increased apoptosis is associated with exaggerated expression of p53, which promotes cell cycle arrest or apoptosis via downstream proteins such as p21 or Bax. These changes in apoptosis and p53 expression are purported to result from exposure to altered oxygen tension. Using a model of villous trophoblast turnover, we examined the effect of 20%, 6% and 1% ambient oxygen (O(2)) on apoptosis, necrosis, proliferation and expression of p53 and related regulators of cell turnover, compared to both fresh tissue. Altered O(2) tension exerted an effect on cell turnover in cultured term villous tissue: cytotrophoblast proliferation was increased by culture in 20% O(2) and reduced in 1% O(2) (median proliferative index: fresh tissue=0.32%, 20% O(2)=0.9%, 6% O(2)=0.28%, 1% O(2)=0.07%). Apoptosis was increased in all culture environments, but was significantly enhanced by culture in 1% O(2) (median apoptotic index: fresh tissue=0.64%, 20% O(2)=2.96%, 6% O(2)=3.81%, 1% O(2)=9.2%). Necrotic cell death was also increased by culture in 1% O(2) compared to 6% and 20% O(2). The expression of p53, p21 and Mdm2 in both cytotrophoblast and stromal cells was increased following culture in 1% O(2). There was no alteration in the expression of Bax or Bcl-2. This study provides evidence that p53 is elevated in trophoblast following exposure to hypoxia. The potential role of the p53-pathway in the control of cell turnover in villous trophoblast and the regulation of p53 by altered O(2) tension merits further investigation.Placenta 03/2008; 29(2):175-86. · 3.69 Impact Factor -
Article: SNAT4 isoform of system A amino acid transporter is expressed in human placenta.
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ABSTRACT: The system A amino acid transporter is encoded by three members of the Slc38 gene family, giving rise to three subtypes: Na+-coupled neutral amino acid transporter (SNAT)1, SNAT2, and SNAT4. SNAT2 is expressed ubiquitously in mammalian tissues; SNAT1 is predominantly expressed in heart, brain, and placenta; and SNAT4 is reported to be expressed solely by the liver. In the placenta, system A has an essential role in the supply of neutral amino acids needed for fetal growth. In the present study, we examined expression and localization of SNAT1, SNAT2, and SNAT4 in human placenta during gestation. Real-time quantitative PCR was used to examine steady-state levels of system A subtype mRNA in early (6-10 wk) and late (10-13 wk) first-trimester and full-term (38-40 wk) placentas. We detected mRNA for all three isoforms from early gestation onward. There were no differences in SNAT1 and SNAT2 mRNA expression with gestation. However, SNAT4 mRNA expression was significantly higher early in the first trimester compared with the full-term placenta (P < 0.01). We next investigated SNAT4 protein expression in human placenta. In contrast to the observation for gene expression, Western blot analysis revealed that SNAT4 protein expression was significantly higher at term compared with the first trimester (P < 0.05). Immunohistochemistry and Western blot analysis showed that SNAT4 is localized to the microvillous and basal plasma membranes of the syncytiotrophoblast, suggesting a role for this isoform of system A in amino acid transport across the placenta. This study therefore provides the first evidence of SNAT4 mRNA and protein expression in the human placenta, both at the first trimester and at full term.AJP Cell Physiology 02/2006; 290(1):C305-12. · 3.54 Impact Factor -
Article: E-cadherin in the assessment of aberrant placental cytotrophoblast turnover in pregnancies complicated by pre-eclampsia.
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ABSTRACT: E-cadherin is a cell-cell adhesion protein expressed in cytotrophoblasts, which is lost as they differentiate and syncytialise. We have exploited E-cadherin as a marker of cytotrophoblasts to investigate villous tissue composition in first and third trimester placentae, both in normal pregnancy and pregnancies complicated by pre-eclampsia. We have achieved this by measuring expression levels of E-cadherin at the mRNA level, using Q-PCR, and at the protein level using semi-quantitative Western blotting. We have also combined E-cadherin immunohistochemistry with morphometric analysis of area measurements to define cytotrophoblast and syncytiotrophoblast compartments. This novel use of E-cadherin has revealed a decrease in the proportion of cytotrophoblasts in villous tissue as pregnancy progresses, in the absence of changes in syncytiotrophoblast cover. Moreover, in pre-eclampsia, placental E-cadherin was raised compared to syncytiotrophoblast, suggesting either exaggerated cytotrophoblast proliferation or impaired cytotrophoblast differentiation, both alterations of potential pathogenic importance.Histochemie 01/2006; 124(6):499-506. · 2.59 Impact Factor -
Article: Gestational profile of Na+/H+ exchanger and Cl-/HCO3- anion exchanger mRNA expression in placenta using real-time QPCR.
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ABSTRACT: The onset of maternal blood flow (10-12 weeks gestation) results in increased oxygenation of the placenta. We investigated whether the expressions of Na+/H+ exchanger (NHE) and Cl-/HCO3- anion exchanger (AE), thought to have an important role in maintaining intracellular pH of the syncytiotrophoblast and fetal pH homeostasis, are altered at the same time as this increase in blood flow. Real-time quantitative PCR was used to examine steady state levels of NHE (NHE1, 2, 3) and AE (AE1, 2) mRNA expression in early (6-9 weeks) and late (10-13 weeks) first trimester and full-term (38-40 weeks) placentas. beta-Actin, IF2B and GAPDH mRNA was also measured. None of the genes showed a significant difference in expression between the early and late first trimester groups. However, NHE2 (p < 0.001) and GAPDH (p < 0.05) mRNA expression significantly increased 18- and 3.7-fold between early first trimester and term. In conclusion, this study provides additional evidence that GAPDH is an unsuitable housekeeping gene for normalization of transcript levels in placenta. The expression of NHE and AE in the villous placenta is not altered concomitant with the onset of maternal blood flow. However, NHE2 transcripts appear to be gestationally regulated, which may contribute to changes in NHE activity.Placenta 02/2005; 26(1):93-8. · 3.69 Impact Factor -
Article: TASK channel expression in human placenta and cytotrophoblast cells.
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ABSTRACT: The multinucleate syncytiotrophoblast is the transporting epithelium of the human placental villus, formed throughout pregnancy by fusion and differentiation of underlying mononucleate cytotrophoblast cells. Similar to other epithelia, K+ channels will impact on syncytiotrophoblast transport properties during its development and differentiation. Therefore we investigated expression and activity of the two-pore domain K+ channels TASK1 and 2 in relation to gestation and differentiation, using villous tissue from first and third trimester and cultured cytotrophoblast cells at mononucleate and multinucleate stages of culture. Quantitative real-time polymerase chain reaction (PCR), immunofluorescence, and 86Rb+ (K) efflux were used to investigate TASK channel expression and function. TASK2 mRNA expression was higher in first trimester than term (10 to 13 vs 38 to 40 weeks, P < .05). Other K+ alpha-subunit mRNAs, including TASK1, remained unaltered but the regulatory BKCa beta-subunit, like TASK2, was higher in first trimester than term (P < .001). Immunofluorescence showed that TASK2 had an intracellular localization within the trophoblast of first trimester villi but was less abundant and restricted to stem villi at term. TASK2 also showed intracellular localization in mononucleate cytotrophoblast cells in culture and expression was lost with multinucleation. By contrast, TASK1 was localised, independently of cell nucleation, to cytotrophoblast cell plasma membranes. 86Rb+ (K) efflux was measured from multinucleated cytotrophoblast cells. Both basal and pH 8.0-stimulated efflux was inhibited by the TASK1 antagonist anandamide (n = 5 for both conditions; P < .01 and P < .001, respectively). TASK1 and 2 are expressed in placental trophoblast cells and TASK1 activity may have a role in regulating syncytiotrophoblast homeostasis and/or solute transport functions.Journal of the Society for Gynecologic Investigation 02/2006; 13(1):30-9. · 2.26 Impact Factor
