The placenta as an experimental model

Spatial transcriptomics of fetal membrane-Decidual interface reveals unique contributions by cell types in term and preterm births

During pregnancy, two fetomaternal interfaces, the placenta-decidua basalis and the fetal membrane-decidua parietals, allow for fetal growth and maturation and fetal-maternal crosstalk, and protect the fetus from infectious and inflammatory signaling that could lead to adverse pregnancy outcomes. While the placenta has been studied extensively, the fetal membranes have been understudied, even though they play critical roles in pregnancy maintenance and the initiation of term or preterm parturition. Fetal membrane dysfunction has been associated with spontaneous preterm birth (PTB, < 37 weeks gestation) and preterm prelabor rupture of the membranes (PPROM), which is a disease of the fetal membranes. However, it is unknown how the individual layers of the fetal membrane decidual interface (the amnion epithelium [AEC], the amnion mesenchyme [AMC], the chorion [CTC], and the decidua [DEC]) contribute to these pregnancy outcomes. In this study, we used a single-cell transcriptomics approach to unravel the transcriptomics network at spatial levels to discern the contributions of each layer of the fetal membranes and the adjoining maternal decidua during the following conditions: scheduled caesarian section (term not in labor [TNIL]; n = 4), vaginal term in labor (TIL; n = 3), preterm labor with and without rupture of membranes (PPROM; n = 3; and PTB; n = 3). The data included 18,815 genes from 13 patients (including TIL, PTB, PPROM, and TNIL) expressed across the four layers. After quality control, there were 11,921 genes and 44 samples. The data were processed by two pipelines: one by hierarchical clustering the combined cases and the other to evaluate heterogeneity within the cases. Our visual analytical approach revealed spatially recognized differentially expressed genes that aligned with four gene clusters. Cluster 1 genes were present predominantly in DECs and Cluster 3 centered around CTC genes in all labor phenotypes. Cluster 2 genes were predominantly found in AECs in PPROM and PTB, while Cluster 4 contained AMC and CTC genes identified in term labor cases. We identified the top 10 differentially expressed genes and their connected pathways (kinase activation, NF-κB, inflammation, cytoskeletal remodeling, and hormone regulation) per cluster in each tissue layer. An in-depth understanding of the involvement of each system and cell layer may help provide targeted and tailored interventions to reduce the risk of PTB.

Isolation and characterization human chorion membrane trophoblast and mesenchymal cells

INTRODUCTION

To develop protocols for isolation and culture of human chorionic mesenchymal and trophoblast cells and test their differential responsiveness to oxidative stress.

METHODS

Chorion trophoblast cells (CTC) and chorion mesenchymal cells (CMC) were isolated from term fetal membranes by modifying current protocols. Their purity and characteristics were tested using bright field microscopy and after staining for cytokeratin (CK)-7 and vimentin. Cigarette smoke extract (CSE) was used to stimulate cells, and we determined reactive oxygen species (ROS) production using 2'7'-dichlorodihydro-fluorescein assay, stress signaler p38MAPK activation (Western blot) and senescence by flow cytometry. Co-treatment with antioxidant N-acetyl cystine (NAC) either alone or in combination with SB203580 (p38MAPK inhibitor) was used to test oxidative stress (OS)- and p38MAPK-mediated effects.

RESULTS

The isolation and cell culture protocol used in this study yielded 92% pure CTC and 100% pure CMC. CSE treatment significantly induced ROS production, P-p38MAPK activation, and senescence in both cell types compared to controls. Cotreatment with NAC reduced ROS production and p38MAPK activation, and co-treatment with both NAC and SB203580 reduced senescence. ROS response in CMC was higher than CTC; however, senescence of CTC was 10-fold higher than CMC.

CONCLUSIONS

We introduce approaches for proper isolation and culture of CTC and CMC without any influence or overgrowth of one specific type cell that can confound results. Using this approach, we determined differential effects of CTC and CMC to OS condition seen at term labor. Both CTC and CMC undergo p38MAPK-mediated senescence; however, the rate of senescence is higher in CTC.

Fetal membrane architecture, aging and inflammation in pregnancy and parturition

Preterm birth is the single major cause of infant mortality. Short and long term outcomes for infants are often worse in cases of preterm premature rupture of the fetal membranes (pPROM). Thus, increased knowledge of the structure characteristics of fetal membranes as well as the mechanisms of membrane rupture are essential if we are to develop effective treatment strategies to prevent pPROM. In this review, we focus on the role of inflammation and senescence in fetal membrane biology.

Novel concepts on pregnancy clocks and alarms: redundancy and synergy in human parturition

The signals and mechanisms that synchronize the timing of human parturition remain a mystery and a better understanding of these processes is essential to avert adverse pregnancy outcomes. Although our insights into human labor initiation have been informed by studies in animal models, the timing of parturition relative to fetal maturation varies among viviparous species, indicative of phylogenetically different clocks and alarms; but what is clear is that important common pathways must converge to control the birth process. For example, in all species, parturition involves the transition of the myometrium from a relaxed to a highly excitable state, where the muscle rhythmically and forcefully contracts, softening the cervical extracellular matrix to allow distensibility and dilatation and thus a shearing of the fetal membranes to facilitate their rupture. We review a number of theories promulgated to explain how a variety of different timing mechanisms, including fetal membrane cell senescence, circadian endocrine clocks, and inflammatory and mechanical factors, are coordinated as initiators and effectors of parturition. Many of these factors have been independently described with a focus on specific tissue compartments.In this review, we put forth the core hypothesis that fetal membrane (amnion and chorion) senescence is the initiator of a coordinated, redundant signal cascade leading to parturition. Whether modified by oxidative stress or other factors, this process constitutes a counting device, i.e. a clock, that measures maturation of the fetal organ systems and the production of hormones and other soluble mediators (including alarmins) and that promotes inflammation and orchestrates an immune cascade to propagate signals across different uterine compartments. This mechanism in turn sensitizes decidual responsiveness and eventually promotes functional progesterone withdrawal in the myometrium, leading to increased myometrial cell contraction and the triggering of parturition. Linkage of these processes allows convergence and integration of the gestational clocks and alarms, prompting a timely and safe birth. In summary, we provide a comprehensive synthesis of the mediators that contribute to the timing of human labor. Integrating these concepts will provide a better understanding of human parturition and ultimately improve pregnancy outcomes.

Amnion-Epithelial-Cell-Derived Exosomes Demonstrate Physiologic State of Cell under Oxidative Stress

At term, the signals of fetal maturity and feto-placental tissue aging prompt uterine readiness for delivery by transitioning quiescent myometrium to an active stage. It is still unclear how the signals reach the distant myometrium. Exosomes are a specific type of extracellular vesicle (EVs) that transport molecular signals between cells, and are released from a wide range of cells, including the maternal and fetal cells. In this study, we hypothesize that i) exosomes act as carriers of signals in utero-placental compartments and ii) exosomes reflect the physiologic status of the origin cells. The primary aims of this study were to determine exosomal contents in exosomes derived from primary amnion epithelial cells (AEC). We also determined the effect of oxidative stress on AEC derived exosomal cargo contents. AEC were isolated from amniotic membrane obtained from normal, term, not in labor placentae at delivery, and culture under standard conditions. Oxidative stress was induced using cigarette smoke extract for 48 hours. AEC-conditioned media were collected and exosomes isolated by differential centrifugations. Both growth conditions (normal and oxidative stress induced) produced cup shaped exosomes of around 50 nm, expressed exosomes enriched markers, such as CD9, CD63, CD81 and HSC70, embryonic stem cell marker Nanog, and contained similar amounts of cell free AEC DNA. Using confocal microscopy, the colocalization of histone (H) 3, heat shock protein (HSP) 70 and activated form of pro-senescence and term parturition associated marker p38 mitogen activated protein kinase (MAPK) (P-p38 MAPK) co-localized with exosome enrich marker CD9. HSP70 and P-p38 MAPK were significantly higher in exosomes from AEC grown under oxidative stress conditions than standard conditions (p<0.05). Finally, mass spectrometry and bioinformatics analysis identified 221 different proteins involved in immunomodulatory response and cell-to-cell communication. This study determined AEC exosome characteristics and their cargo reflected the physiologic status of the cell of origin and suggests that AEC-derived exosomal p38 MAPK plays a major role in determining the fate of pregnancy. Understanding the propagation of fetal signals and their mechanisms in normal term pregnancies can provide insights into pathologic activation of such signals associated with spontaneous preterm parturitions.

Transfer of cocaine and benzoylecgonine across the perfused human placental cotyledon

OBJECTIVE

Our aim was to measure the transfer of cocaine and its major metabolite benzoylecgonine across the human term placenta.

STUDY DESIGN

By means of in vitro perfusion of the human term placental cotyledon the transfer of these compounds was measured.

RESULTS

The steady-state maternal-to-fetal transfer of cocaine (0.18 +/- 0.05 microgram/ml/min) was significantly greater than benzoylecgonine transfer (0.02 +/- 0.01 microgram/ml/min) (p < 0.05). When the perfused tissue was analyzed 32% +/- 7% of the maternal cocaine dose was retained by the placental tissue, whereas only 12% +/- 12% of the maternal benzoylecgonine dose was retained by the placental compartment.

CONCLUSIONS

These results suggest (1) the placenta may serve as a depot for large amounts of cocaine, thus offering some degree of fetal protection after bolus administration; (2) fetal exposure may be prolonged by placental retention and subsequent release of cocaine and benzoylecgonine; and (3) benzoylecgonine does not cross the placenta as readily as does cocaine. Variability in placental handling of cocaine and benzoylecgonine may therefore determine fetal exposure to these agents.

Villitis in normal term human placentae: frequency of the lesion determined by monoclonal antibody to HLA-DR antigen

Chronic villitis is a placental lesion of unestablished etiology. It is characterized by destruction of chorionic villi with a mononuclear infiltrate and focal areas of fibrinoid necrosis. The lesion frequently is seen in normal placentae, yet more lesions have been reported in placentae from abnormal pregnancies. We measured the extent of villitis in 25 normal term placentae by using both light microscopy and immunocytology for class II (HLA-DR) antigens of the major histocompatibility complex. HLA-DR antigens were found to be characteristic of villitis areas. Normal placentae showed striking variations in the incidence of villitis, but these variations did not correlate with clinical outcome.

Association of lipid peroxidation during luteal regression in the rat and natural aging in the rotifer

Lipid peroxides (LP) were measured in whole homogenates and membrane fractions from luteinized rat ovaries and in homogenates of aging rotifers. There was a significant increase in the accumulation of LP as plasma progesterone levels declined during luteal regression. Lipid peroxide levels also increased with age in rotifers. This study indicates that lipid peroxide accumulation is associated with cellular breakdown and suggests that the rat corpus luteum may be used as a mammalian aging model.

The human placenta does not contain lipofuscin pigment

Autofluorescent granules are present in the villous syncytiotrophoblast of the human placenta, most prominently during the first trimester. These granules differ in both size and hue from classical lipofuscin granules, have different staining characteristics, and are shown by electron microscopy to be syncytial lipid droplets. It is concluded that previous reports of the presence of lipofuscin pigment in the placenta are unfounded.

The ontogeny of epidermal growth factor receptors during mouse development

In an attempt to understand the role(s) of epidermal growth factor (EGF) in vivo during murine development, we have examined the 125I-EGF binding characteristics of EGF-receptors in membrane preparations of tissues from the 12th day of gestation to parturition. Using autoradiography, the earliest time that we could detect EGF-receptors was on trophoblast cells cultured for 3 days as blastocyst outgrowths. Trophoblast eventually forms a large portion of the placenta, where EGF-receptors have long been recognized. We measured the number and affinity of EGF-receptors on tissues dissected from conceptuses from the 12th day of gestation in order to identify a stage when tissues may be most sensitive to EGF. Whereas the number of EGF receptors increases during gestation for all tissues examined, the affinity of the receptors declines for carcass and placenta and remains relatively unchanged for brain and liver. This suggests that EGF may function differently throughout development. Our hypothesis is that EGF (or its embryonic equivalent) initially stimulates proliferation in embryonic cells and then stimulates differentiation as the tissues mature. In the adult, its main role could be to stimulate tissue repair after damage.