Oxygen Sensitivity of Placental Trophoblast Connexins 43 and 46: A Role in Preeclampsia?

Effects of valproic acid on syncytialization in human placental trophoblast cell lines

The placenta is a critical organ for fetal development and a healthy pregnancy, and has multifaceted functions (e.g., substance exchange and hormone secretion). Syncytialization of trophoblasts is important for maintaining placental functions. Epilepsy is one of the most common neurological conditions worldwide. Therefore, this study aimed to reveal the influence of antiepileptic drugs, including valproic acid (VPA), carbamazepine, lamotrigine, gabapentin, levetiracetam, topiramate, lacosamide, and clobazam, at clinically relevant concentrations on syncytialization using in vitro models of trophoblasts. To induce differentiation into syncytiotrophoblast-like cells, BeWo cells were treated with forskolin. Exposure to VPA was found to dose-dependently influence syncytialization-associated genes (ERVW-1, ERVFRD-1, GJA1, CGB, CSH, SLC1A5, and ABCC4) in differentiated BeWo cells. Herein, the biomarkers between differentiated BeWo cells and the human trophoblast stem model (TSCT) were compared. In particular, MFSD2A levels were low in BeWo cells but abundant in TSCT cells. VPA exposure affected the expression of ERVW-1, ERVFRD-1, GJA1, CSH, MFSD2A, and ABCC4 in differentiated cells (ST-TSCT). Furthermore, VPA exposure attenuated BeWo and TSCT cell fusion. Finally, the relationships between neonatal/placental parameters and the expression of syncytialization markers in human term placentas were analyzed. MFSD2A expression was positively correlated with neonatal body weight, head circumference, chest circumference, and placental weight. Our findings have important implications for better understanding the mechanisms of toxicity of antiepileptic drugs and predicting the risks to placental and fetal development.

Establishment of an in vitro placental barrier model cultured under physiologically relevant oxygen levels

The human placental barrier facilitates many key functions during pregnancy, most notably the exchange of all substances between the mother and fetus. However, preclinical models of the placental barrier often lacked the multiple cell layers, syncytialization of the trophoblast cells and the low oxygen levels that are present within the body. Therefore, we aimed to design and develop an in vitro model of the placental barrier that would reinstate these factors and enable improved investigations of barrier function. BeWo placental trophoblastic cells and human umbilical vein endothelial cells were co-cultured on contralateral sides of an extracellular matrix-coated transwell insert to establish a multilayered barrier. Epidermal growth factor and forskolin led to significantly increased multi-nucleation of the BeWo cell layer and increased biochemical markers of syncytial fusion, for example syncytin-1 and hCGβ. Our in vitro placental barrier possessed size-specific permeability, with 4000-Da molecules experiencing greater transport and a lower apparent permeability coefficient than 70 000-Da molecules. We further demonstrated that the BeWo layer had greater resistance to smaller molecules compared to the endothelial layer. Chronic, physiologically low oxygen exposure (3-8%) increased the expression of hypoxia-inducible factor 1α and syncytin-1, further increased multi-nucleation of the BeWo cell layer and decreased barrier permeability only against smaller molecules (457 Da/4000 Da). In conclusion, we built a novel in vitro co-culture model of the placental barrier that possessed size-specific permeability and could function under physiologically low oxygen levels. Importantly, this will enable future researchers to better study the maternal-fetal transport of nutrients and drugs during pregnancy.

A modified parachute assay for assessment of gap junction intercellular communication in placental trophoblast cells

Gap junction intercellular communication (GJIC) is a necessary process for placental development. GJIC can be assessed with a parachute assay, where fluorescent dye-loaded donor cells are 'parachuted' onto acceptor cells and dye diffuses to adjacent cells with active GJIC. During co-culture, donor cells can attach, but the assay does not allow their distinction from acceptor cells, which presents as a major limitation. We have developed a modified parachute assay that permits distinction between donor and acceptor cells, using the extravillous trophoblast cell line HTR-8/SVneo and a lentiviral transduction technique. Using PKA activator CW008 as a positive control and 12-o-tetradecanoylphorbol-13-acetate as a negative control, this modified parachute assay reliably detects both enhanced and attenuated GJIC. Importantly, the ease and accuracy of quantification over currently available methods makes this modified assay optimal for automation and represents a useful tool for in vitro placental toxicological testing.

Hypoxia‑induced internalization of connexin 26 and connexin 43 in pulmonary epithelial cells is involved in the occurrence of non‑small cell lung cancer via the P53/MDM2 signaling pathway

Reports have highlighted an association between connexins (CXs) or gap junction proteins and non-small cell lung cancer (NSCLC). In the present study, it was aimed to elucidate the regulatory mechanism of CX26 and CX43 under hypoxic conditions in NSCLC. Clinical samples were collected for analysis of CX26 and CX43 expression and clinical cancerization followed by quantification of CX26 and CX43 expression. Following the establishment of an in vitro hypoxia model, P53/murine double minute-2 (MDM2) signaling pathway-, proliferation- and epithelial-mesenchymal transition (EMT)-related genes were quantified to evaluate the influence of CX26 and CX43 on the biological functions of pulmonary epithelial cells in NSCLC. In addition, the proliferation and tumorigenicity of cancer cells were assessed by EdU staining and xenograft tumors, respectively. Decreased expression of CX26 and CX43 was found in cancer tissues compared with surrounding normal tissue. Hypoxia was shown to activate the P53/MDM2 axis and stimulate the downregulation, ubiquitination and degradation of CX26 and CX43, which were translocated from the membrane to the cytoplasm. Low levels of CX26 and CX43 were demonstrated to further promote EMT and the induction of the proliferation and tumorigenicity of cancer cells. These results were reflected by decreased E-cadherin expression and increased N-cadherin expression, along with increased cell migration, promoted cell proliferation ability and elevated relative protein expression of Oct4 and Nanog, and accelerated tumor growth, accompanied by a higher number of metastatic nodes. Taken together, the key observations of the present study demonstrate that the internalization of CX26 and CX43 promoted proliferation, EMT and migration and thus induced NSCLC via aberrant activation of the P53/MDM2 signaling pathway under hypoxic conditions.

Endometrial thickness influences neonatal birth weight in pregnancies with obstetric complications achieved after fresh IVF-ICSI cycles

PURPOSE

Pregnancy-associated complications, duration of gestation and parity are well-known predictors of neonatal birth weight. Assisted reproductive technology (ART) affects neonatal birth weight as well. Endometrial thickness as measured on the day of HCG triggering may therefore impact on the neonatal birth weight.

METHODS

The data of 764 singleton deliveries achieved after fresh transfer between November 1997 and 2014 were collected retrospectively with the intention to analyze the relationship of maternal and neonatal characteristics with endometrial thickness and the possible predictive value of endometrial thickness on neonatal birth weight.

RESULTS

Higher maternal age (p < 0.001), diminished ovarian reserve (p < 0.001), endometriosis (p = 0.008) and hypogonadotropic hypogonadism (p < 0.001) predicted thin endometrium. Neonatal birth weight (p = 0.004), longer duration of pregnancy (p = 0.008), parity (p = 0.026) and higher maternal BMI (p = 0.003) were correlated significantly with the degree of endometrial proliferation. Endometrial thickness strongly predicted neonatal birth weight (p = 0.004). After adjusting regression analysis for maternal age and BMI, parity, neonatal gender and pregnancy duration, endometrial thickness remained predictive for neonatal birth weight in pregnancies with obstetric complications (p = 0.017). In uneventful pregnancies duration and parity are determinants of neonatal birth weight.

CONCLUSIONS

Our findings suggest that endometrial thickness is an additional ART-related factor influencing neonatal birth weight. This finding should be confirmed in large cohort studies.

Scrutinising the regulators of syncytialization and their expression in pregnancy-related conditions

The placenta is important for the success of gestation and foetal development. In fact, this specialized pregnancy organ is essential for foetal nourishment, support, and protection. In the placenta, there are different cell populations, including four subtypes of trophoblasts. Cytotrophoblasts fuse and differentiate into the multinucleated syncytiotrophoblast (syncytialization). Syncytialization is a hallmark of placentation and is highly regulated by numerous molecules with distinct roles. Placentas from pregnancies complicated by preeclampsia, intrauterine growth restriction or trisomy 21 have been associated with a defective syncytialization and an altered expression of its modulators. This work proposes to review the molecules that promote or inhibit both fusion and biochemical differentiation of cytotrophoblasts. Moreover, it will also analyse the syncytialization modulators abnormally expressed in pathological placentas, highlighting the molecules that may contribute to the aetiology of these diseases.