Placenta

Title Page/Editorial Board

2012-07-01

A rhythmic placenta? Circadian variation, clock genes and placental function

B.J. Waddell, M.D. Wharfe, R.C. Crew, P.J. Mark — 2012-04-23

Abstract: Physiological rhythms entrained by the circadian clock are present in virtually all organs including those of the reproductive system. In mammals, circadian timing is driven by a ‘master clock’ in the suprachiasmatic nucleus that influences peripheral tissue clocks via endocrine, autonomic and behavioral cues. The molecular clock machinery comprises a network of ‘clock’ genes, namely Clock, Bmal1, Per1, Per2, Per3, Cry1 and Cry2. These clock genes generate endogenous oscillations that drive rhythmic expression of downstream genes and thus physiological and behavioral processes. Importantly, disturbances in clock gene expression are implicated in a range of pathologies including cancer and obesity. The recent recognition that clock genes are expressed in the placenta, together with observations linking circadian disruption with compromised placental function, suggests that circadian variation may be an important component of the normal placental phenotype. In this review we consider this possibility in the context of maternal circadian physiology in pregnancy. While there is good evidence for rhythmic expression of several genes in the rodent placenta, the conventional transcriptional-translational feedback loops of the clock machinery appear less robust and coordinated. Further study is needed to elucidate the function of the placental clock genes across gestation and among different species, particularly those in which greater circadian development occurs in utero. Such studies will likely provide important insights into placental physiology and pathology.

Multiple injections of anti-mouse β2glycoprotein 1 antibody induce FcRγ-dependent fetal growth restriction (FGR) in mice

R. Kawaguchi, S. Nunomura, N. Umehara, T. Nikaido, B. Huppertz, T. Tanaka, C. Ra — 2012-04-27

Abstract: Objectives: The antiphospholipid syndrome (APS) is characterized by the presence of circulating antiphospholipid antibodies (aPLs), is a leading cause for thromboembolic events, repeated miscarriage, fetal loss and is a major risk factor for fetal growth restriction (FGR) and preeclampsia. In human, anti-β2 glycoprotein I (aβ2GPI) antibody is one of the aPLs and considered to be a specific and important marker for APS. However, pathophysiological changes induced by aβ2GPI antibodies in FGR are largely unknown.Methods: In the present study, we developed a murine FGR model induced by multiple injections of WBCAL-1, a well-characterized mouse aβ2GPI monoclonal antibody.Results: Administration of WBCAL-1, but not the isotype control antibody and saline, into pregnant mice specifically decreased the size of fetuses and placentas without affecting the number of delivered pups. Also, a significant increase in urinary albumin and electron microscopic changes, such as splitting layers of basal membranes in the placental labyrinth and rearrangement of pores in glomerular endothelial cells, were observed in WBCAL-1 treated mice. WBCAL-1 injection did not induce any changes in blood pressure and typical parameters of blood thromboembolic symptoms. Furthermore, FcRγ deficiency protected the fetuses from aβ2GPI antibody-induced injuries.Conclusions: Our present findings suggest that proteinuria is a symptom associated with APS-related FGR with placental and renal tissue injuries, and that FcRγ might be a molecular target for prevention of aβ2GPI antibody-mediated obstetrical pathologies.

Phagocytosis of apoptotic trophoblastic debris protects endothelial cells against activation

Q. Chen, F. Guo, H.Y. Jin, S. Lau, P. Stone, L. Chamley — 2012-04-16

Abstract: During normal pregnancy trophoblastic debris is shed from the placenta into the maternal blood and endothelial cells may contribute to the phagocytosis of this material. Many researchers believe the majority of this trophoblastic material is apoptotic in normal pregnancy. Previously we demonstrated that phagocytosis of necrotic, but not apoptotic trophoblastic debris induced endothelial cell activation. In macrophages, phagocytosis of necrotic cell bodies leads to inflammation but phagocytosis of apoptotic bodies actively induces tolerogenic immune responses. We undertook this study to determine whether phagocytosis of apoptotic trophoblastic debris had a “tolerogenic” effect on endothelial cells analogous to their effect in macrophages. Apoptotic or necrotic trophoblastic debris was obtained from placental explants and endothelial cell activation was examined by quantifying, cell surface ICAM-1 expression using ELISAs, or monocyte adhesion. The response of endothelial cells to the activating stimuli of necrotic trophoblastic debris, interleukin-6 (IL-6), Lipopolysaccharide (LPS) or phorbol mysterate acetate (PMA) was reduced in endothelial cells that had phagocytosed apoptotic trophoblastic debris. This protective effect was short-lived being not apparent 24 h after removal of the trophoblastic debris. This work demonstrates that the ability of the endothelial cells to respond to a variety of activating stimuli is reduced by prior phagocytosis of apoptotic trophoblast debris. This might explain why endothelial cells are not activated by the small numbers of necrotic trophoblastic debris that may be found in normal pregnancy. This phenomenon may also contribute to the maternal vascular adaptation that occurs in normal pregnancy.

Tissue-wide overexpression of alpha-T-catenin results in aberrant trophoblast invasion but does not cause embryonic mortality in mice

K. Tyberghein, S. Goossens, J.J. Haigh, F. van Roy, J. van Hengel — 2012-04-25

Abstract: Transcriptional activation of CTNNA3, encoding αT-catenin, by the Y153H mutated form of the human STOX1 transcription factor was proposed to be responsible for altered fetal trophoblast invasion into the maternal endometrium during placentation in pre-eclampsia. Here we have generated a mouse model to investigate the in vivo effects of ectopic αT-catenin expression on trophoblast invasion. Histological analysis was used to determine the invasive capacities of trophoblasts from transgenic embryos, as well as proliferation rates of spongiotrophoblasts in the junctional zone. Augmented expression of αT-catenin reduced the number of invading trophoblasts but did not cause embryonic mortality. The, αT-catenin positive cells could still invade into the decidual layer and migrated as deeply as wild-type trophoblasts. Furthermore, the junctional zone is enlarged in placentas of mice overexpressing αT-catenin due to hyperproliferation of the residing spongiotrophoblasts, suggesting a pivotal role of αT-catenin levels in the control of the proliferative versus invasive state of trophoblasts during placentation. Our study provides, for the first time, in vivo data on the effects of increased levels of αT-catenin in the placenta.

NUR77 inhibits the expression of TIMP2 and increases the migration and invasion of HTR-8/SVneo cells induced by CYR61

X. Zhang, G. Yan, Z. Diao, H. Sun, Y. Hu — 2012-05-01

Abstract: Objective: To investigate the function and mechanism of CYR61 on the migration and invasion of the trophoblast cell line, HTR-8/SVneo cells.Study design: The mRNA and protein levels of NUR77 in the placentas of normal and preeclampsia (PE) women were evaluated using real-time PCR and Western blot, respectively. Paraffin-embedded tissues were processed for localization of NUR77 protein in placental villus by immunohistochemistry. HTR-8/SVneo cells were cultured in the presence of CYR61, Ad-NUR77 or a small interfering RNA for NUR77 (Ad-sinur77). The expression of NUR77 in the HTR-8/SVneo cells was detected and the effects of CYR61 on the migration and invasion of HTR-8/SVneo cells were assessed in wound-healing and transwell experiments, respectively. Gelatin zymography was used to measure the MMP2 release in HTR-8/SVneo cells.Results: NUR77 is significantly decreased in the placenta of women with PE compared with the levels during a normal pregnancy. CYR61 can significantly increase the expression of NUR77 in HTR-8/SVneo cells. CYR61, as well as NUR77, can promote HTR-8/SVneo cells migration and invasion, which can be blocked by Ad-sinur77. Both CYR61 and Ad-nur77 reduced the mRNA expression of TIMP2 in HTR-8/SVneo cells.Conclusions: CYR61 may promote HTR-8/SVneo cells migration and invasion through the upregulation of NUR77, leading to the increase of MMP2 release and the downregulation of TIMP2 expression.

Sex-specific basis of severe placental dysfunction leading to extreme preterm delivery

M.G. Walker, B. Fitzgerald, S. Keating, J.G. Ray, R. Windrim, J.C.P. Kingdom — 2012-04-19

Abstract: Objectives: Since pregnancies with a male fetus have higher perinatal complications attributed to placental dysfunction, including severe pre-eclampsia and intrauterine growth restriction, the objective of our study was to formally evaluate placental pathology for a placental origin of these sex-specific differences.Design: Retrospective study at Mount Sinai Hospital in Toronto, Canada. Identification of 262 singleton pregnancies affected by severe pre-eclampsia and/or intrauterine growth restriction who delivered between 22 and 32 weeks' gestation from 2000 to 2010. Detailed placental pathology was reviewed, and data from 140 pregnancies with male fetuses were compared with 122 pregnancies with female fetuses. A comparison group of 40 unaffected pregnancies who delivered in the same gestational range was used to determine baseline rates of placental pathology.Main outcome measured: Detailed placental pathology, including placental development/differentiation, velamentous umbilical cord insertion, maternal-fetal interface pathology, villous infarction, hemorrhagic lesions, villous development, and fetal vascular under-perfusion.Results: Impaired placental development and differentiation was equally common amongst males (73/140, 52.1%) and females (69/122, 56.6%). Male placentas exhibited significantly higher rates of chronic deciduitis (17.9% vs. 9.0%; relative risk [RR] 1.98, 95% confidence interval [CI] 1.02–3.86) and velamentous umbilical cord insertion (9.5% vs. 1.7%; RR 5.66, 95% CI 1.30–24.6), and a significantly lower frequency of villous infarction (55.4% vs. 73.7%; RR 0.75, 95% CI 0.62–0.90) than female placentas. No significant differences were noted for other lesions.Conclusions: Fetal sex exerts a differential effect on the placental pathology that mediates severe pre-eclampsia and/or IUGR. Placental pathology at birth may provide insight into the mechanisms linking adverse in utero events with long-term adult disease since, for example, a male tendency to an inflammatory pathology at the maternal-fetal interface may be linked to the excess risk of coronary artery disease.

Raised uterine artery impedance is associated with increased maternal arterial stiffness in the late second trimester

T.R. Everett, A.A. Mahendru, C.M. McEniery, I.B. Wilkinson, C.C. Lees — 2012-04-26

Abstract: Objective: To assess the relationship between uterine artery Doppler pulsatility index (PI) and maternal global arterial stiffness and aortic stiffness in women at high a priori risk of preeclampsia in the late second trimester of pregnancy.Methods: A prospective cohort study was performed. 99 women were recruited from the high-risk obstetric ultrasound clinic in the second trimester; median (±IQR) age and gestation were 33 (29–37) years and 23+6 (23+3–24+4) weeks respectively. Transabdominal uterine artery Doppler was performed and mean values recorded. Women returned at a later date, median gestation (±IQR) 26+5 (25+6–28+0) weeks, for measurement of blood pressure, augmentation index (AIx) and aortic pulse wave velocity (aPWV).Results: Uterine artery PI is positively associated with both AIx (r = 0.4, P <0.0001, 95% CI: 0.22–0.55) and aPWV (r = 0.22, P = 0.03, 95% CI: 0.02–0.40). No relationship was found between uterine artery PI and mean arterial pressure or pulse pressure. AIx was significantly higher in women with uterine artery PI > 1.45 (P = 0.003, 95% CI: 3.1–14.9) but not aPWV (P = 0.45). AIx, but not aPWV, was significantly higher in women who developed preeclampsia (14% vs 9%, 95% CI: 2.0–8.6, P = 0.0018) or IUGR (11% vs 9%, 95% CI: 0.3–4.2, P = 0.027). AIx showed a negative correlation with birth weight z-score (r = −0.25, 95% CI: −0.43 to −0.06, P = 0.013).Conclusion: Increasing uterine artery Doppler PI reflects impaired placentation and increasing risk of preeclampsia. We show a positive association between uterine artery Doppler PI and both global arterial and aortic stiffness. We also show that increased maternal arterial stiffness is associated with a lower birth weight. These findings may represent evidence of an early effect of impaired placentation on the maternal vasculature. Alternatively, given the association between preeclampsia and later cardiovascular disease, ineffective placentation may result from impaired arterial function.

An unusual feature of yolk sac placentation in Necromys lasiurus (Rodentia, Cricetidae, Sigmodontinae)

P.O. Favaron, A.M. Carter, A.M. Mess, M.F. de Oliveira, M.A. Miglino — 2012-04-30

Abstract: We studied the development of the inverted yolk sac in a New World rodent, Necromys lasiurus during early placentation. Ten implantation sites were investigated by means of histology, immunohistochemistry and electron microscopy. The yolk sac was villous near its attachment to the placenta. Elsewhere it was non-villous and closely attached to the uterus. The uterine glands were shallow and wide mouthed. They were associated with vessels and filled with secretion, suggesting the release of histotroph. This feature was absent at later stages. The intimate association of the yolk sac with specialized glandular regions of the uterus may represent a derived character condition of Necromys and/or sigmodont rodents.

Dicer-dependent miRNAs provide an endogenous restraint on cytotrophoblast proliferation

K. Forbes, F. Farrokhnia, J.D. Aplin, M. Westwood — 2012-04-20

Abstract: Mature microRNAs (miRNAs) are processed from non-functional (pre)-miRNAs by the enzyme Dicer. In this study, manipulation of Dicer level was used to explore the influence of miRNAs on cytotrophoblast proliferation in human placenta. Immunohistochemistry (IHC) showed Dicer in cytotrophoblast, but not in terminally differentiated syncytiotrophoblast. siRNA-mediated knockdown of Dicer was used to effect a global reduction in miRNA in first trimester placental explants, as a result of which cytotrophoblast proliferation was significantly enhanced. QPCR and IHC analysis following Dicer knockdown revealed that the expression of two nodal pro-mitogenic signalling molecules expressed within cytotrophoblast, ERK and SHP-2, was significantly enhanced. Studies are now required to identify individual miRNAs involved in regulating trophoblast proliferation.

Use of Matrigel in culture affects cell phenotype and gene expression in the first trimester trophoblast cell line HTR8/SVneo

A.R. Highet, V.J. Zhang, G.K. Heinemann, C.T. Roberts — 2012-04-27

Abstract: There is inconsistent use of Matrigel for experiments with the HTR8/SVneo first trimester trophoblast and other cell lines. We quantified the effects of Matrigel on the expression of genes considered to be markers of extravillous cytotrophoblast (EVT) differentiation and invasive potential. Culture on Matrigel promoted formation of “endothelial-like” tubes and reduced mRNA expression of matrix metalloproteinase 2 (MMP2), cytokeratin 7 (KRT7) and integrin alpha 1 (ITGA1), while increasing VE-cadherin (CDH5) expression consistent with a vascular phenotype. This process may constitute part of the endothelial cell mimicry exhibited by endovascular EVTs invading the maternal spiral arteries. HTR8/SVneo appears to be phenotypically polymorphic and adopt endovascular morphology on Matrigel.

Fetoplacental angiogenesis in diabetes mellitus

T.M. Mayhew — 2012-04-30

I write in response to the recent article by Jirkovská et al. . By combining immunohistochemistry with 3D reconstruction based on stacks of optical sections obtained by confocal microscopy, the authors indicate that the degree of branching angiogenesis in fetoplacental capillaries is greater in placentas associated with maternal diabetes mellitus type 1 (DM1) and is accompanied by increases in capillary length, diameter and surface area. In their Introduction (p344), the authors draw attention to an earlier finding : that placentas from pregnancies complicated by gestational diabetes mellitus also display enhanced capillary branching. Further, they reported that this finding is “in contrast to the previously accepted opinion that the placental capillary growth in the second half of pregnancy is exclusively longitudinal” . This is a misinterpretation of the results presented by Mayhew .

Fetoplacental angiogenesis

M. Jirkovská — 2012-05-01

In his respectable bibliography, Terry Mayhew paid his attention also to placentas from pregnancies complicated by maternal diabetes mellitus, and we cited his findings repeatedly in our papers regarding this subject. Unfortunately, in our article we misinterpreted his conclusion presented in . The origin of our misinterpretation was a misunderstanding of the term “longitudinal growth of capillaries”, and a confusion of it with the “capillary growth by elongation”.

IFPA Pages

2012-07-01