Transplacental migration of maternal natural killer and T cells assessed by ex vivo human placenta perfusion

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.

Ex vivo human placental transfer study on recombinant Von Willebrand factor (rVWF)

Deficiency or mutation of von Willebrand factor (VWF) leads to a coagulation disorder (von Willebrand disease; VWD) which requires a lifelong therapy. For avoiding maternal complications treatment may be necessary also in pregnancy, but placental transfer to the fetus might impact its coagulation system and evoke undesired side effects. As VWF is a very large molecule it may be assumed that it does not pass the placental barrier. To prove this hypothesis the materno-fetal transfer of recombinant VWF (rVWF) has been analyzed ex vivo in a total of 21 valid dual side placenta perfusions. Three groups of five placentas each have been perfused with physiological and up to ten-fold increased concentrations of rVWF for 2 h. Six placentas have been used for control perfusions. A series of different control parameters has been assessed for documentation of intactness and functionality of the placenta and the perfusion system. In not a single analysis, independent of time and concentration, rVWF was detected in the fetal circuit. In the maternal circuit VWF concentration decreased slightly during perfusion. These results demonstrate that recombinant VWF does not pass the human placenta.

Cytogenomics of six human trophoblastic cell lines

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.

N-cadherin knockdown leads to disruption of trophoblastic and endothelial cell interaction in a 3D cell culture model - New insights in trophoblast invasion failure

INTRODUCTION

Trophoblast homing to maternal spiral arteries is mandatory for successful placentation. Cell-cell adhesion molecules regulate this process and adhesion molecule expression is altered in impaired placentation. We hypothesize that, similar to immune cell recruitment, trophoblast cell adherence and rolling are primarily mediated by adhesion molecules like, cadherins, immunoglobulins, selectins and their partnering ligands. Here, the interdependence of adhesion molecule expression in trophoblastic cell lines of diverse origin was investigated in relation to their interaction with endothelial cell networks on Matrigel® co-cultures and the effect of specific adhesion molecule knockdown analyzed.

METHODS

Trophoblastic cells were labeled in red and co-cultured with green HUVEC networks on Matrigel®. Association was quantified after collection of fluorescence microscopy pictures using Wimasis® internet platform and software. Expression of adhesion molecules was analyzed by PCR and Western blot, immuno-fluorescence and flow cytometry. The impact of adhesion molecules on trophoblast-endothelial-cell interaction was investigated using siRNA technique.

RESULTS

N-cadherin and CD162 were specifically expressed in the trophoblast cell line HTR-8/SVneo, which closely adhere to and actively migrate toward HUVEC networks on Matrigel®. Suppression of N-cadherin led to a significant alteration in trophoblast-endothelial cell interaction. Expression of VE-cadherin in closely interacting trophoblast cells was not confirmed in vitro.

DISCUSSION

We identified N-cadherin to mediate specific interaction between HUVEC and the migrating trophoblast cells HTR-8/SVneo in a Matrigel® co-culture model. VE-cadherin contribution could not be confirmed in vitro. Our results support the hypothesis that impaired N-cadherin but not VE-cadherin expression is involved in trophoblast recruitment to the maternal endothelium.

Immune-modulatory effects of syncytiotrophoblast extracellular vesicles in pregnancy and preeclampsia

Unique immunologic adaptations exist to successfully establish and maintain pregnancy and to avoid an immune attack against the semi allogenic fetus. These adaptations occur both locally at the maternofetal interface and in the peripheral circulation and affect the innate as well as the adaptive immune system. Pregnancy is characterized by a general inflammatory state with activation of monocytes and granulocytes, but also with suppressive lymphocytes (regulatory T cells), and skewing towards T helper 2 immunity. The pregnancy complication preeclampsia is associated with an exaggerated inflammatory state and predominance of T helper 1 and 17 immunity. The syncytiotrophoblast has been found to secrete extracellular vesicles as communication factors into the maternal circulation. Syncytiotrophoblast extracellular vesicles from normal pregnancy have been shown to interact with monocytes, granulocytes, T cells and natural killer cells and influence the function of these cells. In doing so, they may support the inflammatory state of normal pregnancy as well as the suppressive lymphocyte phenotype. During preeclampsia, syncytiotrophoblast extracellular vesicles are not only increased in numbers but also showed an altered molecular load. Based on data from in vitro studies, it can be suggested that syncytiotrophoblast extracellular vesicles from preeclamptic pregnancies may support the exaggerated inflammatory state during preeclampsia. In this review, we discuss the immunological functions of syncytiotrophoblast extracellular vesicles and their involvement in adapting the maternal peripheral immunological adaptations to pregnancy.

Unique trophoblast stem cell- and pluripotency marker staining patterns depending on gestational age and placenta-associated pregnancy complications

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.

IFPA meeting 2015 workshop report III: nanomedicine applications and exosome biology, xenobiotics and endocrine disruptors and pregnancy, and lipid

Workshops are an important part of the IFPA annual meeting, as they allow for discussion of specialized topics. At the IFPA meeting 2015 there were twelve themed workshops, three of which are summarized in this report. These workshops were related to various aspects of placental biology but collectively covered areas of pregnancy pathologies and placental metabolism: 1) nanomedicine applications and exosome biology; 2) xenobiotics and endocrine disruptors and pregnancy; 3) lipid mediators and placental function.

PP009. Hypoxia alters syncytiotrophoblastic microparticles (STBM)-related coagulation capacities

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.

The placenta in toxicology. Part IV: Battery of toxicological test systems based on human placenta

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.

The placenta in toxicology. Part III: Pathologic assessment of the placenta

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.

PP055. Preliminary results of the more prepared study (microparticle orientated risk evaluation in the prediction of preeclampsia among risk gravidas): A multicenter prospective prognostic marker study

INTRODUCTION

Preeclampsia (PE) is a potentially dangerous pregnancy pathology contributing to a higher worldwide mortality and morbidity. The negative influence of syncytiotrophoblastic microparticles (STBMs) on the placenta and maternal endothelia is thought to play a key role in generating the inflammatory effects that lead to PE symptoms. Doppler sonography of the uterine arteries assists in identifying a risk population, however, the positive predictive value for this method is low.

OBJECTIVES

Aim of this study is to evaluate whether STBMs can serve as an accessory marker to conventional Doppler sonography to better identify pregnant women who will actually develop PE.

METHODS

Pregnant women between 19-21 gestational weeks (GW) with abnormal uterine perfusion were enrolled into this prospective study. Plasma samples were taken at inclusion (baseline) and at two further visits at 8 week intervals to follow STBM concentration alterations during pregnancy. The primary endpoint assessed is PE and/or hemolysis, elevated liver, low platelets (HELLP) syndrome. Other PE-associated pathologies (intrauterine growth retardation [IUGR], intrauterine fetal demise [IUFD], placental abruption, premature delivery) constitute the secondary endpoints. Maternal STBM concentrations were measured using a home made Enzyme Linked Sorbent Assay (ELSA) which specifically measures STBMs. The receiver operating characteristics (ROC) for baseline measures are graphically displayed and area under curve (AUC) is estimated including 95% confidence levels.

RESULTS

Of the 73 women included in the study, 16 developed PE (cases) and 56 did not (control). After analyses of mid-gestational probes, the ROC curve was in close proximity to the line of no-discrimination.

CONCLUSION

Our preliminary results indicate that the maternal STBM concentration at mid-gestation does not predict the development of PE or associated pregnancy pathologies. Further analysis is underway to assess whether STBM measurements at later gestational time points can predict PE shortly before onset of disease.