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Introduction: The transplacental passage of cells between a mother and her fetus, known as microchimerism, is a less studied process during pregnancy. The frequency of maternal microchimeric cells in fetal tissues in physiological pregnancies and mechanisms responsible for transplacental cell trafficking are poorly understood. This study aimed to evaluate the placental trafficking of maternal peripheral blood mononuclear cells (PBMC) using human ex vivo placenta perfusion., Methods: Ten placentas and maternal PBMC were obtained after healthy pregnancies. Flow cytometry was used to characterize PBMC subtypes. They showed a higher percentage of CD3 + T cells compared to CD56 + NK cells. The isolated PBMC were stained with a fluorescent dye and perfused through the maternal circuit of the placenta in an ex vivo perfusion system. Subsequent immunofluorescence staining for CD3 + T cells and CD56 + NK cells was performed on placental tissue sections, and the number of detectable PBMC in different tissue areas was counted using fluorescence microscopy., Results: The applied method allowed discrimination of perfused autologous maternal cells from cells resident in the placenta before perfusion. Further, it allows additional immunohistochemical labelling and distinction of immune cell subsets. Perfused PBMC were detected in all analyzed placentas, mostly in contact to the syncytiotrophoblast. CD3 + T cells were identified more frequently than CD56 + NK cells and some CD3 + T cells were found inside fetoplacental tissues and vasculature. The results indicate that also other PBMCs than T or NK cells adhere to or enter villous tissue, but they have not been specified in this analysis., Discussion: Previous studies have detected maternal cells in the fetal circulation which we could mimick in our ex vivo placenta perfusion experiments with fluorescence labelled autologous maternal PBMC. The applied experimental settings did not allow comparison of transmigration abilities of PBMC subsets, but slight modifications of the model will permit further studies of cell transfer processes and microchimerism in pregnancy., Competing Interests: Declaration of competing interest Herewith, I declare that no conflict of interest exists with any of the authors., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Trophoblastic cell lines are established models used to examine human placenta physiology and disease. We performed concurrent cytogenetic analyses of six established and well-studied trophoblastic cell lines including JAR, BeWo, JEG-3, AC-1M59, HTR8/SVneo, and ACH-3P. All cell lines showed near triploid or tetraploid karyotypes with unique inter- and intra-clonal aberrations, which result possibly from long-term culture or defects in the placenta or its malignant choriocarcinoma origin. Variable aneuploidy in 'standard' cell lines is under-appreciated and may not reflect the in vivo situation. It has the potential to negatively impact our understanding of normal cell function and cause disagreement between studies., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The current Zika virus (ZIKV) outbreak is associated with neurological malformations and disorders in neonates. Areas of increased incidence of malformations may overlap with dengue-hyperendemic areas. ZIKV infection is enhanced by antibodies against dengue virus (DENV) in cell culture and inbred mice. Sufficiently powered clinical studies or primate studies addressing the enhancement of fetal ZIKV infection after previous dengue infection are not available. The human placenta is susceptible to ZIKV in vitro, but it is unknown whether antibody-dependent enhancement of ZIKV infection occurs at the placental barrier. Here we studied ZIKV infection in placental tissue in the presence of DENV-immune sera. Explants from the amniochorionic membrane, the chorionic villi, and the maternal decidua were infected with ZIKV in the presence of DENV type 1-, 2-, or 4-immune sera, or controls. Presence of DENV antibodies of any type enhanced the percentage of successful infections of organ explants between 1.42- and 2.67-fold, and led to a faster replication as well as significantly increased virus production. No enhancement was seen with yellow fever or chikungunya virus control sera. Pre-existing DENV antibodies may pose an increased risk of trans-placental ZIKV transmission.

Preeclampsia (PE) and intrauterine growth retardation (IUGR) are rare but severe pregnancy complications that are associated with placental insufficiency often resulting in premature birth. The clinical pathologies are related to gross placental pathologies and trophoblastic deficiencies that might derive from inflammatory processes and oxidative stress injury. The mesenchymal core of placental villi has been identified as a possible niche for trophoblast progenitor cells that are called upon to replenish the injured syncytiotrophoblast layer. These progenitor cells are known to express trophoblast stem cell (CDX2) and pluripotency (SOX2, NANOG and OCT4A) markers, however only little data is available characterizing the expression of these transcription factors beyond the blastocyst stage. We aimed to describe the expression of these factors in healthy 1st and 3rd trimester placentae as well as PE, IUGR and combined PE+IUGR placentae. We analyzed 8 respective samples derived from 1st trimester (elective abortions), and 3rd trimester (healthy controls, PE, IUGR and combined PE+IUGR). We accomplished immunoperoxidase staining to detect the stem cell markers: CDX2 (trophectoderm), SOX2, NANOG and OCT4A (embryonal). Immunoreative scoring was used for objective analyses of staining patterns. All markers display clearly elevated signals in 1st trimester villous samples as compared to healthy 3rd trimester counterparts. Especially CDX2 and NANOG were specific to the cytotrophoblast layer and the mesenchymal core. Specific and differential expression patterns were visible in the villous/extravillous compartment of each placenta-associated pregnancy complication (PE: pan elevated expression; IUGR elevated SOX2 in basal plate; combined PE+IUGR pan loss of expression). Reduction of stem cell transcription factor expression in term placentae indicates temporal regulation, and probably a specific function which is yet to be elucidated. The differential expression patterns within placentae complicated with placenta-associated pregnancy complications indicate that PE, IUGR and combined PE+IUGR are separate entities. It is unclear whether the alterations are the cause or the effect of the clinical pathology.

Problem: The pregnancy-associated disease preeclampsia is related to the release of syncytiotrophoblast extracellular vesicles (STBEV) by the placenta. To improve functional research on STBEV, reliable and specific methods are needed to quantify them. However, only a few quantification methods are available and accepted, though imperfect. For this purpose, we aimed to provide an enzyme-linked sorbent assay (ELSA) to quantify STBEV in fluid samples based on their microvesicle characteristics and placental origin., Method of Study: Ex vivo placenta perfusion provided standards and samples for the STBEV quantification. STBEV were captured by binding of extracellular phosphatidylserine to immobilized annexin V. The membranous human placental alkaline phosphatase on the STBEV surface catalyzed a colorimetric detection reaction., Results and Conclusion: The described ELSA is a rapid and simple method to quantify STBEV in diverse liquid samples, such as blood or perfusion suspension. The reliability of the ELSA was proven by comparison with nanoparticle tracking analysis., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

This short review is derived from the peer-reviewed literature and the experience and case materials of the authors. Brief illustrated summaries are presented on the gross and histologic normal anatomy of rodent and macaque placentas, including typical organ weights, with comments on differences from the human placenta. Common incidental findings, background lesions, and induced toxic lesions are addressed, and a recommended strategy for pathologic evaluation of placentas is provided.

This review summarizes the potential and also some limitations of using human placentas, or placental cells and structures for toxicology testing. The placenta contains a wide spectrum of cell types and tissues, such as trophoblast cells, immune cells, fibroblasts, stem cells, endothelial cells, vessels, glands, membranes, and many others. It may be expected that in many cases the relevance of results obtained from human placenta will be higher than those from animal models due to species specificity of metabolism and placental structure. For practical and economical reasons, we propose to apply a battery of sequential experiments for analysis of potential toxicants. This should start with using cell lines, followed by testing placenta tissue explants and isolated placenta cells, and finally by application of single and dual side ex vivo placenta perfusion. With each of these steps, the relative workload increases while the number of feasible repeats decreases. Simultaneously, the predictive power enhances by increasing similarity with in vivo human conditions. Toxic effects may be detected by performing proliferation, vitality and cell death assays, analysis of protein and hormone expression, immunohistochemistry or testing functionality of signaling pathways, gene expression, transport mechanisms, and so on. When toxic effects appear at any step, the subsequent assays may be cancelled. Such a system may be useful to reduce costs and increase specificity in testing questionable toxicants. Nonetheless, it requires further standardization and end point definitions for better comparability of results from different toxicants and to estimate the respective in vivo translatability and predictive value.

Introduction: Endothelial dysfunction is thought to be the cause of preeclampsia (PE) symptoms. Severe forms of PE are correlated to the release of syncytiotrophoblastic microparticles (STBM), which triggers inflammatory processes on the endothelium. The thrombogenic potential of STBMs is not well characterized. We investigated the pro-coagulant activity of STBMs., Methods: STBMs were derived from placentae perfused under norm- and hypoxic conditions and quantified with our house-"ELISA". Surface phospholipid-dependent thrombin formation of microparticles was determined with a commercial ELISA. Rate and absolute platelet aggregation in platelet-rich plasma (PRP), while fibrin production in platelet free plasma, was measured in absence and presence of STBMs using a PAP-4 aggregometer., Results: STBM concentration and STBM-induced thrombin formation is stable under normoxic and elevated under hypoxic conditions. STBMs derived from hypoxic placentae increase the rate of fibrinogenesis. Maximum platelet aggregation is stable under normoxic, while highly variable under hypoxic conditions. STBMs of hypoxic placentae cannot alter the rate of platelet aggregation, while normoxic STBMs adjust the rate according to need., Conclusion: Hypoxia negatively affects fibrinogenesis and the platelet aggregation-modulating effects of STBMs, which might be due to a phenotype alteration. All observed results may contribute to the impaired microcirculation seen in PE., (Copyright © 2013. Published by Elsevier B.V.)