Microphysiological systems of the placental barrier

Human trophoblast organoids for improved prediction of placental ABC transporter-mediated drug transport

ATP-binding cassette (ABC) transporters, the important transmembrane efflux transporters, play an irreplaceable role in the placenta barrier. The disposition and drug-drug interaction of clinical drugs are also closely related to the functions of ABC transporters. The trophoblast is a unique feature of the placenta, which is crucial for normal placentation and maintenance during pregnancy. ABC transporters are abundantly expressed in placental syncytiotrophoblast, especially P-gp, BCRP, and MRPs. However, due to the lack of appropriate modeling systems, the molecular mechanisms of regulation between ABC transporters and trophoblast remains unclear. In this report, trophoblast organoids were cultured from human placental villi and developed into three-dimension structures with cavities. Trophoblast organoids exhibited transporter expression and localization comparable to that in villous tissue, indicating their physiological relevance for modeling drug transport. Moreover, fluorescent substrates can accumulate in organoids and be selectively inhibited by inhibitors, indicating the efflux function of ABC transporters (P-gp, BCRP, MRP1, and MRP2) in organoids. Two commonly used hypertension drugs and three antipsychotics were chosen to further validate this drug transport model and demonstrate varying degrees of inhibitory effects on ABC transporters. Overall, a new drug transport model mediated by ABC transporter has been successfully established based on human trophoblast organoids, which can be used to study drug transport in the placenta.

Assessment of nanotoxicity in a human placenta-on-a-chip from trophoblast stem cells

Maternal exposure to nanoparticles during gestation poses potential risks to fetal development. The placenta, serving as a vital interface for maternal-fetal interaction, plays a pivotal role in shielding the fetus from direct nanoparticle exposure. However, the impact of nanoparticles on placental function is still poorly understood, primarily due to the absence of proper human placental models. In this study, we established a placenta-on-a-chip model capable of recapitulating nanoparticle exposure to assess potential nanotoxicity. The model was assembled by coculturing human trophoblast stem cells (hTSCs) and endothelial cells within a dynamic microsystem. hTSCs exhibited progressive differentiation into syncytiotrophoblasts under continuous fluid flow, forming a bilayered trophoblastic epithelium that mimicking both structural and functional aspects of human placental villi. Copper oxide nanoparticles (CuO NPs) were introduced into the trophoblastic side to simulate maternal blood exposure. Our findings revealed that CuO NPs hindered hTSCs differentiation, leading to diminished hormone secretion and impaired glucose transport. Subsequent analysis indicated that CuO NPs disrupted the autophagic flux in trophoblasts and induced apoptosis. Furthermore, the placenta-on-a-chip model exhibited inflammatory responses to CuO NP exposure, including maternal macrophage activation, inflammatory cytokine secretion, and endothelial barrier disruption. Dysfunction of the placental barrier and the ensuing inflammatory cascades may contribute to aberrant fetal development. Overall, our placenta-on-a-chip model offers a promising platform for assessing nanoparticle exposure-related risks and conducting toxicology studies.

Modeling the human placenta: in vitro applications in developmental and reproductive toxicology

During its temporary tenure, the placenta has extensive and specialized functions that are critical for pre- and post-natal development. The consequences of chemical exposure in utero can have profound effects on the structure and function of pregnancy-associated tissues and the life-long health of the birthing person and their offspring. However, the toxicological importance and critical functions of the placenta to embryonic and fetal development and maturation have been understudied. This narrative will review early placental development in humans and highlight some in vitro models currently in use that are or can be applied to better understand placental processes underlying developmental toxicity due to in utero environmental exposures.

Organ-on-a-chip: future of female reproductive pathophysiological models

The female reproductive system comprises the internal and external genitalia, which communicate through intricate endocrine pathways. Besides secreting hormones that maintain the female secondary sexual characteristics, it also produces follicles and offspring. However, the in vitro systems have been very limited in recapitulating the specific anatomy and pathophysiology of women. Organ-on-a-chip technology, based on microfluidics, can better simulate the cellular microenvironment in vivo, opening a new field for the basic and clinical research of female reproductive system diseases. This technology can not only reconstruct the organ structure but also emulate the organ function as much as possible. The precisely controlled fluidic microenvironment provided by microfluidics vividly mimics the complex endocrine hormone crosstalk among various organs of the female reproductive system, making it a powerful preclinical tool and the future of pathophysiological models of the female reproductive system. Here, we review the research on the application of organ-on-a-chip platforms in the female reproductive systems, focusing on the latest progress in developing models that reproduce the physiological functions or disease features of female reproductive organs and tissues, and highlighting the challenges and future directions in this field.

Association between the Maternal Gut Microbiome and Macrosomia

Fetal macrosomia is defined as a birthweight ≥4000 g and causes harm to pregnant women and fetuses. Studies reported that the maternal intestinal microbiome plays a key role in the establishment, growth, and development of the fetal intestinal microbiome. However, whether there is a relationship between maternal gut microbiota and macrosomia remains unclear. Our study aimed to identify gut microbiota that may be related to the occurrence of macrosomia, explore the possible mechanisms by which it causes macrosomia, and establish a prediction model to determine the feasibility of predicting macrosomia by early maternal gut microbiota. We conducted a nested case-control study based on an early pregnancy cohort (ChiCTR1900020652) in the Maternity and Child Health Hospital of Hunan Province on fecal samples of 93 women (31 delivered macrosomia as the case group and 62 delivered normal birth weight newborns as the control group) collected and included in this study. We performed metagenomic analysis to compare the composition and function of the gut microbiome between cases and controls. Correlation analysis was used to explore the association of differential species and differential functional pathways. A random forest model was used to construct an early pregnancy prediction model for macrosomia. At the species level, there were more Bacteroides salyersiae, Bacteroides plebeius, Ruminococcus lactaris, and Bacteroides ovatus in the intestinal microbiome of macrosomias' mothers compared with mothers bearing fetuses that had normal birth weight. Functional pathways of the gut microbiome including gondoate biosynthesis, L-histidine degradation III, cis-vaccenate biosynthesis, L-arginine biosynthesis III, tRNA processing, and mannitol cycle, which were more abundant in the macrosomia group. Significant correlations were found between species and functional pathways. Bacteroides plebeius was significantly associated with the pathway of cis-vaccenate biosynthesis (r = 0.28, p = 0.005) and gondoate biosynthesis (r = 0.28, p < 0.001) and Bacteroides ovatus was positively associated with the pathway of cis-vaccenate biosynthesis (r = 0.29, p = 0.005) and gondoate biosynthesis (r = 0.32, p = 0.002). Bacteroides salyersiae was significantly associated with the pathway of cis-vaccenate biosynthesis (r = 0.24, p = 0.018), gondoate biosynthesis (r = 0.31, p = 0.003), and L-histidine degradation III (r = 0.22, p = 0.291). Finally, four differential species and four clinical indicators were included in the random forest model for predicting macrosomia. The areas under the working characteristic curves of the training and validation sets were 0.935 (95% CI: 0.851~0.979) and 0.909 (95% CI: 0.679~0.992), respectively. Maternal gut microbiota in early pregnancy may play an important role in the development of macrosomia and can be used as potential predictors to prevent macrosomia.

New approach methods on the bench side to accelerate clinical trials during pregnancy

INTRODUCTION

Pregnant women are therapeutic orphans as they are excluded from clinical drug development and therapeutic trials. We identify limitations in conducting clinical trials and propose two 'New Approach Methods'(NAMs) to overcome them.

AREAS COVERED

NAMs have proven invaluable tools in basic and clinical research to understand human health and disease better, elucidate mechanisms, and study the efficacy and toxicity of therapeutics that have not been possible through animal-based methodologies. The lack of humanized experimental models of FMi and drugs that can safely and effectively cross FMi to reduce the risk of adverse pregnancy has hindered progress in the field of reproductive pharmacology. This report discusses two technological advancements in perinatal research and medicine to accelerate clinical trials during pregnancy. (1) We have developed a humanized microphysiologic system, an Organ-on-a-chip (OOC) platform, to study FMi and their utility in pharmacological studies, and (2) use of extracellular vesicles (EVs) as drug delivery vehicles that are immunologically inert and can cross the fetomaternal barriers.

EXPERT OPINION

We provide an overview of NAMs that can accelerate preclinical trials and develop drugs to cross the feto-maternal barriers to reduce the risk of adverse pregnancy outcomes like preterm birth.

Bridging barriers: advances and challenges in modeling biological barriers and measuring barrier integrity in organ-on-chip systems

Biological barriers such as the blood-brain barrier, skin, and intestinal mucosal barrier play key roles in homeostasis, disease physiology, and drug delivery - as such, it is important to create representative in vitro models to improve understanding of barrier biology and serve as tools for therapeutic development. Microfluidic cell culture and organ-on-a-chip (OOC) systems enable barrier modelling with greater physiological fidelity than conventional platforms by mimicking key environmental aspects such as fluid shear, accurate microscale dimensions, mechanical cues, extracellular matrix, and geometrically defined co-culture. As the prevalence of barrier-on-chip models increases, so does the importance of tools that can accurately assess barrier integrity and function without disturbing the carefully engineered microenvironment. In this review, we first provide a background on biological barriers and the physiological features that are emulated through in vitro barrier models. Then, we outline molecular permeability and electrical sensing barrier integrity assessment methods, and the related challenges specific to barrier-on-chip implementation. Finally, we discuss future directions in the field, as well important priorities to consider such as fabrication costs, standardization, and bridging gaps between disciplines and stakeholders.

Fetus Exposure to Drugs and Chemicals: A Holistic Overview on the Assessment of Their Transport and Metabolism across the Human Placental Barrier

BACKGROUND

The placenta exerts a crucial role in fetus growth and development during gestation, protecting the fetus from maternal drugs and chemical exposure. However, diverse drugs and chemicals (xenobiotics) can penetrate the maternal placental barrier, leading to deleterious, adverse effects concerning fetus health. Moreover, placental enzymes can metabolize drugs and chemicals into more toxic compounds for the fetus. Thus, evaluating the molecular mechanisms through which drugs and chemicals transfer and undergo metabolism across the placental barrier is of vital importance. In this aspect, this comprehensive literature review aims to provide a holistic approach by critically summarizing and scrutinizing the potential molecular processes and mechanisms governing drugs and chemical transfer and metabolism across the placental barrier, which may lead to fetotoxicity effects, as well as analyzing the currently available experimental methodologies used to assess xenobiotics placental transfer and metabolism.

METHODS

A comprehensive and in-depth literature review was conducted in the most accurate scientific databases such as PubMed, Scopus, and Web of Science by using relevant and effective keywords related to xenobiotic placental transfer and metabolism, retrieving 8830 published articles until 5 February 2024. After applying several strict exclusion and inclusion criteria, a final number of 148 relevant published articles were included.

RESULTS

During pregnancy, several drugs and chemicals can be transferred from the mother to the fetus across the placental barrier by either passive diffusion or through placental transporters, resulting in fetus exposure and potential fetotoxicity effects. Some drugs and chemicals also appear to be metabolized across the placental barrier, leading to more toxic products for both the mother and the fetus. At present, there is increasing research development of diverse experimental methodologies to determine the potential molecular processes and mechanisms of drug and chemical placental transfer and metabolism. All the currently available methodologies have specific strengths and limitations, highlighting the strong demand to utilize an efficient combination of them to obtain reliable evidence concerning drug and chemical transfer and metabolism across the placental barrier. To derive the most consistent and safe evidence, in vitro studies, ex vivo perfusion methods, and in vivo animal and human studies can be applied together with the final aim to minimize potential fetotoxicity effects.

CONCLUSIONS

Research is being increasingly carried out to obtain an accurate and safe evaluation of drug and chemical transport and metabolism across the placental barrier, applying a combination of advanced techniques to avoid potential fetotoxic effects. The improvement of the currently available techniques and the development of novel experimental protocols and methodologies are of major importance to protect both the mother and the fetus from xenobiotic exposure, as well as to minimize potential fetotoxicity effects.

A self-assembly and cellular migration based fabrication of high-density 3D tubular constructs of barrier forming membranes

Three-dimensional (3D) in vitro models, superior in simulating physiological conditions compared to 2D models, offer intricate cell-cell and cell-ECM interactions with diverse signaling cues like fluid shear stress and growth factor gradients. Yet, developing 3D tissue barrier models, specifically perfusable luminal structures with dense, multicellular constructs maintained for extended durations with oxygen and nutrients, remains a technical challenge. Here, we describe a molding-based approach for the fabrication of free-standing, perfusable, high cellular density tissue constructs using a self-assembly and migration process to form functional barriers. This technique utilizes a polytetrafluoroethylene (PTFE)-coated stainless-steel wire, held by stainless steel needles, as a template for a perfusable channel within an elongated PDMS well. Upon adding a bio-ink mix of cells and collagen, it self-assembles into a high cell density layer conformally around the wire. Removing the wire reveals a hollow construct, connectable to an inlet and outlet for perfusion. This scalable method allows creating varied dimensions and multicellular configurations. Notably, post-assembly, cells such as human umbilical vein endothelial cells (HUVECs) migrate to the surface and form functional barriers with adherens junctions. Permeability tests and fluorescence imaging confirm that these constructs closely mimic in vivo endothelial barrier permeability, exhibiting the lowest permeability among all in vitro models in the literature. Unlike traditional methods involving uneven post-seeding of endothelial cells leading to subpar barriers, our approach is a straightforward alternative for fabricating complex perfusable 3D tissue constructs and effective tissue barriers for use in various applications, including tissue engineering, drug screening, and disease modeling.

Micro Trojan horses: Engineering extracellular vesicles crossing biological barriers for drug delivery

The biological barriers of the body, such as the blood-brain, placental, intestinal, skin, and air-blood, protect against invading viruses and bacteria while providing necessary physical support. However, these barriers also hinder the delivery of drugs to target tissues, reducing their therapeutic efficacy. Extracellular vesicles (EVs), nanostructures with a diameter ranging from 30 nm to 10 μm secreted by cells, offer a potential solution to this challenge. These natural vesicles can effectively pass through various biological barriers, facilitating intercellular communication. As a result, artificially engineered EVs that mimic or are superior to the natural ones have emerged as a promising drug delivery vehicle, capable of delivering drugs to almost any body part to treat various diseases. This review first provides an overview of the formation and cross-species uptake of natural EVs from different organisms, including animals, plants, and bacteria. Later, it explores the current clinical applications, perspectives, and challenges associated with using engineered EVs as a drug delivery platform. Finally, it aims to inspire further research to help bioengineered EVs effectively cross biological barriers to treat diseases.

Engineered plant extracellular vesicles for natural delivery across physiological barriers

Extracellular vesicles (EVs) are nanoscale luminal vesicles that participate in the information transfer of proteins, nucleic acids, and lipids between cells, thereby playing a role in the treatment of diseases and the delivery of nutrients. In recent years, plant-derived EVs (PDEVs) containing bioactive compounds have attracted increasing interest due to their better biocompatibility and lower cytotoxicity in healthy tissues. In the biomedical field, PDEVs have been used as cargo carriers to achieve various functions through engineering modification techniques. This review focuses on the biogenesis, isolation, and identification of PDEVs. We discuss the surface functionalization of PDEVs to enhance therapeutic efficacy, thereby improving their efficiency as a next-generation drug delivery vehicle and their feasibility to treat diseases across the physiological barriers, while critically analyzing the current challenges and opportunities.

Screening the optimal housekeeping genes (HKGs) of placenta tissues by RNA-sequence and qRT-PCR throughout gestation in goat (Capra Hircus)

Selection of stable housekeeping genes (HKGs) is very important for accurate calculation of relative expression levels of target genes by quantitative real-time polymerase chain reaction (qRT-PCR). At present, the appropriate HKGs have not been identified in placental tissues throughout the pregnancy of the goat. In our study, 20 HKGs were tentatively selected from RNA-seq data and previous reports. The cycle threshold (Ct) of HKGs was determined by qRT-PCR in trophoblast membrane and cotyledon villus collected from 38 Dazu Black goats on gestation days of 20, 25, 30, 45, 60, 90, 120, and 150 (birth). The expression stability of the HKGs was analyzed by geNorm, Normfinder, Bestkeeper and Delta Ct algorithms, and comprehensively evaluated by ReFinder and ComprFinder. In addition, the optimal HKGs were further verified by placenta-specific genes (SPP1, VEGFA and PAG6). The 16 candidate HKGs (except POP4, TBP, RNF10, UBC) showed a qualified Ct value, less than 28. Among them, YWHAZ, EIF3K and PPIB showed the most stable expression in placental tissues during early, mid-late pregnancy and postpartum, but the least stable expression was B2M at early and mid-late stage, and PPIB at postpartum. After comprehensive analysis, RPLP0, EIF3K and YWHAZ were found to be the most stable placental HKGs throughout pregnancy. The classical HKGs, ACTB, GAPDH and 18S RNA have unstable expressions and even ranked at the bottom of the list from comprehensive index, suggesting an inappropriate for target gene normalization. Taken together, our study confirmed that YWHAZ, EIF3K, HMBS and RPLP0 may be the optimal HKGs in goat placenta at different stage of pregnancy, which provided a valuable reference of HKGs on functional gene expression detection for further research on placenta development and growth in ruminants.

Retinoic Acid-PPARα Mediates β-Carotene Resistance to Placental Dysfunction Induced by Deoxynivalenol

Deoxynivalenol (DON), one of the most polluted mycotoxins in the environment and food, has been proven to have strong embryonic and reproductive toxicities. However, the effects of DON on placental impairment and effective interventions are still unclear. This study investigated the effect of β-carotene on placental functional impairment and its underlying molecular mechanism under DON exposure. Adverse pregnancy outcomes were caused by intraperitoneal injection of DON from 13.5 to 15.5 days of gestation in mice, resulting in higher enrichment of DON in placenta than in other tissue samples. Interestingly, 0.1% β-carotene dietary supplementation could significantly alleviate DON-induced pregnancy outcomes. Additionally, in vivo and in vitro placental barrier models demonstrated the association of DON-induced placental function impairment with placental permeability barrier disruption, angiogenesis impairment, and oxidative stress induction. Moreover, β-carotene regulated DON-induced placental toxicity by activating the expressions of claudin 1, zonula occludens-1, and vascular endothelial growth factor-A through retinoic acid-peroxisome proliferator-activated receptor α signaling.

Advance in placenta drug delivery: concern for placenta-originated disease therapy

In the therapy of placenta-originated diseases during pregnancy, the main challenges are fetal exposure to drugs, which can pass through the placenta and cause safety concerns for fetal development. The design of placenta-resident drug delivery system is an advantageous method to minimize fetal exposure as well as reduce adverse maternal off-target effects. By utilizing the placenta as a biological barrier, the placenta-resident nanodrugs could be trapped in the local placenta to concentrate on the treatment of this abnormal originated tissue. Therefore, the success of such systems largely depends on the placental retention capacity. This paper expounds on the transport mechanism of nanodrugs in the placenta, analyzes the factors that affect the placental retention of nanodrugs, and summarizes the advantages and concerns of current nanoplatforms in the treatment of placenta-originated diseases. In general, this review aims to provide a theoretical basis for the construction of placenta-resident drug delivery systems, which will potentially enable safe and efficient clinical treatment for placenta-originated diseases in the future.

Research progress on the mechanism of Treponema pallidum breaking through placental barrier

Congenital syphilis, a significant cause of fetal mortality worldwide, is a congenital infectious disease instigated by the vertical transmission of Treponema pallidum during pregnancy. Clinical manifestations include preterm delivery, stillbirth, neonatal skin lesions, skeletal abnormalities, and central nervous system aberrations. The ongoing increase in the incidence of congenital syphilis, coupled with complexities in diagnosis, necessitates a detailed understanding of its pathogenesis for the development of improved diagnostic approaches, and to interrupt the route of vertical transmission. Drawing from the broader body of research associated with vertical transmission pathogens, we aim to clarify the potential mechanisms by which Treponema pallidum breaches the placental barrier to infect the fetus.

Developmental transcriptomic patterns can be altered by transgenic overexpression of Uty

The genetic material encoded on X and Y chromosomes provides the foundation by which biological sex differences are established. Epigenetic regulators expressed on these sex chromosomes, including Kdm6a (Utx), Kdm5c, and Ddx3x have far-reaching impacts on transcriptional control of phenotypic sex differences. Although the functionality of UTY (Kdm6c, the Y-linked homologue of UTX), has been supported by more recent studies, its role in developmental sex differences is not understood. Here we test the hypothesis that UTY is an important transcriptional regulator during development that could contribute to sex-specific phenotypes and disease risks across the lifespan. We generated a random insertion Uty transgenic mouse (Uty-Tg) to overexpress Uty. By comparing transcriptomic profiles in developmental tissues, placenta and hypothalamus, we assessed potential UTY functional activity, comparing Uty-expressing female mice (XX + Uty) with wild-type male (XY) and female (XX) mice. To determine if Uty expression altered physiological or behavioral outcomes, adult mice were phenotypically examined. Uty expression masculinized female gene expression patterns in both the placenta and hypothalamus. Gene ontology (GO) and gene set enrichment analysis (GSEA) consistently identified pathways including immune and synaptic signaling as biological processes associated with UTY. Interestingly, adult females expressing Uty gained less weight and had a greater glucose tolerance compared to wild-type male and female mice when provided a high-fat diet. Utilizing a Uty-overexpressing transgenic mouse, our results provide novel evidence as to a functional transcriptional role for UTY in developing tissues, and a foundation to build on its prospective capacity to influence sex-specific developmental and health outcomes.

Sources, Degradation, Ingestion and Effects of Microplastics on Humans: A Review

Celluloid, the predecessor to plastic, was synthesized in 1869, and due to technological advancements, plastic products appear to be ubiquitous in daily life. The massive production, rampant usage, and inadequate disposal of plastic products have led to severe environmental pollution. Consequently, reducing the employment of plastic has emerged as a pressing concern for governments globally. This review explores microplastics, including their origins, absorption, and harmful effects on the environment and humans. Several methods exist for breaking down plastics, including thermal, mechanical, light, catalytic, and biological processes. Despite these methods, microplastics (MPs, between 1 and 5 mm in size) continue to be produced during degradation. Acknowledging the significant threat that MPs pose to the environment and human health is imperative. This form of pollution is pervasive in the air and food and infiltrates our bodies through ingestion, inhalation, or skin contact. It is essential to assess the potential hazards that MPs can introduce. There is evidence suggesting that MPs may have negative impacts on different areas of human health. These include the respiratory, gastrointestinal, immune, nervous, and reproductive systems, the liver and organs, the skin, and even the placenta and placental barrier. It is encouraging to see that most of the countries have taken steps to regulate plastic particles. These measures aim to reduce plastic usage, which is essential today. At the same time, this review summarizes the degradation mechanism of plastics, their impact on human health, and plastic reduction policies worldwide. It provides valuable information for future research on MPs and regulatory development.

Microfluidic technology and simulation models in studying pharmacokinetics during pregnancy

Introduction: Preterm birth rates and maternal and neonatal mortality remain concerning global health issues, necessitating improved strategies for testing therapeutic compounds during pregnancy. Current 2D or 3D cell models and animal models often fail to provide data that can effectively translate into clinical trials, leading to pregnant women being excluded from drug development considerations and clinical studies. To address this limitation, we explored the utility of in silico simulation modeling and microfluidic-based organ-on-a-chip platforms to assess potential interventional agents. Methods: We developed a multi-organ feto-maternal interface on-chip (FMi-PLA-OOC) utilizing microfluidic channels to maintain intercellular interactions among seven different cell types (fetal membrane-decidua-placenta). This platform enabled the investigation of drug pharmacokinetics in vitro. Pravastatin, a model drug known for its efficacy in reducing oxidative stress and inflammation during pregnancy and currently in clinical trials, was used to test its transfer rate across both feto-maternal interfaces. The data obtained from FMi-PLA-OOC were compared with existing data from in vivo animal models and ex vivo placenta perfusion models. Additionally, we employed mechanistically based simulation software (Gastroplus®) to predict pravastatin pharmacokinetics in pregnant subjects based on validated nonpregnant drug data. Results: Pravastatin transfer across the FMi-PLA-OOC and predicted pharmacokinetics in the in silico models were found to be similar, approximately 18%. In contrast, animal models showed supraphysiologic drug accumulation in the amniotic fluid, reaching approximately 33%. Discussion: The results from this study suggest that the FMi-PLA-OOC and in silico models can serve as alternative methods for studying drug pharmacokinetics during pregnancy, providing valuable insights into drug transport and metabolism across the placenta and fetal membranes. These advanced platforms offer promising opportunities for safe, reliable, and faster testing of therapeutic compounds, potentially reducing the number of pregnant women referred to as "therapeutic orphans" due to the lack of consideration in drug development and clinical trials. By bridging the gap between preclinical studies and clinical trials, these approaches hold great promise in improving maternal and neonatal health outcomes.

Cysteamine and N-Acetyl-cysteine Alleviate Placental Oxidative Stress and Barrier Function Damage Induced by Deoxynivalenol

Sows are highly sensitive to deoxynivalenol (DON) and susceptible to reproductive toxicity caused by oxidative stress, but the potential mechanisms and effective interventions remain unclear. Here, we investigated the role of two antioxidants (cysteamine and N-acetyl-cysteine) in regulating the reproductive performance, redox status, and placental barrier function of sows and their potential mechanisms under DON exposure. Maternal dietary supply of antioxidants from day 85 of gestation to parturition reduced the incidence of stillbirths and low-birth-weight piglets under DON exposure. Moreover, the alleviation of DON-induced reproductive toxicity by dietary antioxidants was associated with the alleviation of placental oxidative stress, the enhancement of the placental barrier, and the vascular function of sows. Furthermore, in vivo and in vitro vascularized placental barrier modeling further demonstrated that antioxidants could reverse both DON transport across the placenta and DON-induced increase of placental barrier permeability. The molecular mechanism of antioxidant resistance to DON toxicity may be related to the signal transducer and activator of the transcription-3-occludin/zonula occludens-1 signaling pathway. Collectively, these results demonstrate the potential of antioxidants to protect the mother from DON-induced reproductive toxicity by alleviating placental oxidative stress and enhancing the placental barrier.

Healthy and diseased placental barrier on-a-chip models suitable for standardized studies

Pathologies associated with uteroplacental hypoxia, such as preeclampsia are among the leading causes of maternal and perinatal morbidity in the world. Its fundamental mechanisms are yet poorly understood due to a lack of good experimental models. Here we report an in vitro model of the placental barrier, based on co-culture of trophoblasts and endothelial cells against a collagen extracellular matrix in a microfluidic platform. The model yields a functional syncytium with barrier properties, polarization, secretion of relevant extracellular membrane components, thinning of the materno-fetal space, hormone secretion, and transporter function. The model is exposed to low oxygen conditions and perfusion flow is modulated to induce a pathological environment. This results in reduced barrier function, hormone secretion, and microvilli as well as an increased nuclei count, characteristics of preeclamptic placentas. The model is implemented in a titer plate-based microfluidic platform fully amenable to high-throughput screening. We thus believe this model could aid mechanistic understanding of preeclampsia and other placental pathologies associated with hypoxia/ischemia, as well as support future development of effective therapies through target and compound screening campaigns. STATEMENT OF SIGNIFICANCE: : The human placenta is a unique organ sustaining fetus growth but is also the source of severe pathologies, such as Preeclampsia. Though leading cause of perinatal mortality in the world, preeclampsia remains untreatable due to a lack of relevant in vitro placenta models. To better understand the pathology, we have developed 3D placental barrier models in a microfluidic device. The platform allows parallel culture of 40 perfused physiological miniaturized placental barriers, comprising a differentiated syncytium and endothelium that have been validated for transporter functions. Exposure to a hypoxic and ischemic environment enabled the mimicking of preeclamptic characteristics in high-throughput, which we believe could lead to a better understanding of the pathology as well as support future effective therapies development.

Extracellular vesicles are dynamic regulators of maternal glucose homeostasis during pregnancy

Homeostatic regulation of the maternal milieu during pregnancy is critical for maternal and fetal health. The placenta facilitates critical communication between maternal and fetal compartments, in part, through the production of extracellular vesicles (EVs). EVs enable tissue synchrony via cell-cell and long-distance communication and are at their highest circulating concentration during pregnancy. While much work has been done investigating how physiological challenges in pregnancy affect the fetus, the role of placental communication in maternal health has not been well examined. We previously identified placental O-glycosyl transferase (OGT), a glucose-sensing enzyme, as a target of maternal stress where OGT levels and activity affected the O-glycosylation of proteins critical for EV cargo loading and secretion. Here, we hypothesized that placental OGT plays an essential role in maternal homeostatic regulation during pregnancy via its regulation of maternal circulating EV concentrations. Our studies found that changes to key metabolic factors over the circadian cycle, including glucocorticoids, insulin, and glucose, were significantly associated with changes in circulating EV concentration. Targeting placental OGT in mice, we found a novel significant positive relationship between placental OGT and maternal circulating EV concentration that was associated with improving maternal glucose tolerance during pregnancy. Finally, an intravenous elevation in EVs, matching the concentration of EVs during pregnancy, shifted non-pregnant female glucose sensitivity, blunted glucose variance, and improved synchrony of glucose uptake. These data suggest an important and novel role for circulating EVs as homeostatic regulators important in maternal health during pregnancy.

Penetration and translocation of functional inorganic nanomaterials into biological barriers

With excellent physicochemical properties, inorganic nanomaterials (INMs) have exhibited a series of attractive applications in biomedical fields. Biological barriers prevent successful delivery of nanomedicine in living systems that limits the development of nanomedicine especially for sufficient delivery of drugs and effective therapy. Numerous researches have focused on overcoming these biological barriers and homogeneity of organisms to enhance therapeutic efficacy, however, most of these strategies fail to resolve these challenges. In this review, we present the latest progress about how INMs interact with biological barriers and penetrate these barriers. We also summarize that both native structure and components of biological barriers and physicochemical properties of INMs contributed to the penetration capacity. Knowledge about the relationship between INMs structure and penetration capacity will guide the design and application of functional and efficient nanomedicine in the future.

Testing of drugs using human feto-maternal interface organ-on-chips provide insights into pharmacokinetics and efficacy

Objectives: To improve preclinical drug testing during pregnancy, we developed multiple microfluidic organ-on-chip (OOC) devices that represent the structure, functions, and responses of the two feto-maternal interfaces (FMis) in humans (fetal membrane [FMi-OOC] and placenta [PLA-OOC]). This study utilized feto-maternal interface OOCs to test the kinetics and efficacy of drugs during pregnancy. Study design: The FMi-OOC contained amnion epithelial, mesenchymal, chorion trophoblast, and decidual cells. The PLA-OOC contained cytotrophoblasts (BeWo), syncytiotrophoblasts (BeWo + forskolin), and human umbilical vein endothelial cell lines. Therapeutic concentrations of either pravastatin or rosuvastatin (200 ng mL^-1), a model drug for these experiments, were applied to either decidua (in FMi-OOC) and syncytiotrophoblasts (in PLA-OOC) chambers under normal and oxidative stress conditions (induced by cigarette smoke extract [CSE 1 : 25]) to evaluate maternal drug exposure during normal pregnancy or oxidative stress (OS) associated pathologies, respectively. We determined statin pharmacokinetics and metabolism (LC-MS/MS), drug-induced cytotoxicity (LDH assay), and efficacy to reduce OS-induced inflammation (multiplex cytokine assay). Results: Both OOCs mimicked two distinct human feto-maternal interfaces. The drugs tested permeated the maternal-fetal cell layers of the FMi-OOC and PLA-OOC within 4 hours and generated cell and time-specific statin metabolites from various cell types without causing any cytotoxicity. OS-induced pro-inflammatory cytokines were effectively reduced by statins by increasing anti-inflammatory cytokine response across the FMi-OOC and PLA-OOC. Conclusion: Two distinct feto-maternal interface OOCs were developed, tested, and validated for their utility to conduct preclinical trials during pregnancy. We demonstrated that the placenta and fetal membranes-decidual interface both are able to transport and metabolize drugs and that the safety and efficacy of a drug can be determined using the anatomical structures recreated on OOCs.

Biomaterials science and engineering to address unmet needs in women's health

Medical conditions that primarily or disproportionately affect women have historically been poorly studied. In contrast to the musculoskeletal and cardiovascular systems, there is no lengthy record of biomaterials research addressing women's health needs. In this article, the historical reasons for this discrepancy are examined. The anatomy of both the nonpregnant and pregnant reproductive tissues is reviewed, including the ovaries, uterus, and (fetal) placenta. Examples of biomaterials-related women's health research are described, including tissue engineering, organoids, and microphysiological systems. The future of the field is considered with dual focuses. First, there is a significant need for novel approaches to advance women's health through materials and biomaterials, particularly in complex biomimetic hydrogels. Second, there is an exciting opportunity to enlarge the community of biomaterials scientists and engineers working in women's health to encourage more contributions to its rapidly emerging product development pipeline.

Graphical abstract

A review on microplastics and nanoplastics in the environment: Their occurrence, exposure routes, toxic studies, and potential effects on human health

Microplastics (MPs) and nanoplastics (NPs) are emerging environmental pollutants, having a major ecotoxicological concern to humans and many other biotas, especially aquatic animals. The physical and chemical compositions of MPs majorly determine their ecotoxicological risks. However, comprehensive knowledge about the exposure routes and toxic effects of MPs/NPs on animals and human health is not fully known. Here this review focuses on the potential exposure routes, human health impacts, and toxicity response of MPs/NPs on human health, through reviewing the literature on studies conducted in different in vitro and in vivo experiments on organisms, human cells, and the human experimental exposure models. The current literature review has highlighted ingestion, inhalation, and dermal contacts as major exposure routes of MPs/NPs. Further, oxidative stress, cytotoxicity, DNA damage, inflammation, immune response, neurotoxicity, metabolic disruption, and ultimately affecting digestive systems, immunology, respiratory systems, reproductive systems, and nervous systems, as serious health consequences.

Engineered models for placental toxicology: Emerging approaches based on tissue decellularization

Recent increases in prescriptions and illegal drug use as well as exposure to environmental contaminants during pregnancy have highlighted the critical importance of placental toxicology in understanding and identifying risks to both mother and fetus. Although advantageous for basic science, current in vitro models often fail to capture the complexity of placental response, likely due to their inability to recreate and monitor aspects of the microenvironment including physical properties, mechanical forces and stiffness, protein composition, cell-cell interactions, soluble and physicochemical factors, and other exogenous cues. Tissue engineering holds great promise in addressing these challenges and provides an avenue to better understand basic biology, effects of toxic compounds and potential therapeutics. The key to success lies in effectively recreating the microenvironment. One strategy to do this would be to recreate individual components and then combine them. However, this becomes challenging due to variables present according to conditions such as tissue location, age, health status and lifestyle. The extracellular matrix (ECM) is known to influence cellular fate by working as a storage of factors. Decellularized ECM (dECM) is a recent tool that allows usage of the original ECM in a refurbished form, providing a relatively reliable representation of the microenvironment. This review focuses on using dECM in modified forms such as whole organs, scaffold sheets, electrospun nanofibers, hydrogels, 3D printing, and combinations as building blocks to recreate aspects of the microenvironment to address general tissue engineering and toxicology challenges, thus illustrating their potential as tools for future placental toxicology studies.

Differences and Interactions in Placental Manganese and Iron Transfer across an In Vitro Model of Human Villous Trophoblasts

Manganese (Mn) as well as iron (Fe) are essential trace elements (TE) important for the maintenance of physiological functions including fetal development. However, in the case of Mn, evidence suggests that excess levels of intrauterine Mn are associated with adverse pregnancy outcomes. Although Mn is known to cross the placenta, the fundamentals of Mn transfer kinetics and mechanisms are largely unknown. Moreover, exposure to combinations of TEs should be considered in mechanistic transfer studies, in particular for TEs expected to share similar transfer pathways. Here, we performed a mechanistic in vitro study on the placental transfer of Mn across a BeWo b30 trophoblast layer. Our data revealed distinct differences in the placental transfer of Mn and Fe. While placental permeability to Fe showed a clear inverse dose-dependency, Mn transfer was largely independent of the applied doses. Concurrent exposure of Mn and Fe revealed transfer interactions of Fe and Mn, indicating that they share common transfer mechanisms. In general, mRNA and protein expression of discussed transporters like DMT1, TfR, or FPN were only marginally altered in BeWo cells despite the different exposure scenarios highlighting that Mn transfer across the trophoblast layer likely involves a combination of active and passive transport processes.

Exposure to two-dimensional ultrathin Ti3C2 (MXene) nanosheets during early pregnancy impairs neurodevelopment of offspring in mice

Background

Two-dimensional ultrathin Ti₃C₂ (MXene) nanosheets have been extensively explored for various biomedical applications. However, safety issues and the effects of Ti₃C₂ on human health remain poorly understood.

Results

To explore the influence on foetal or offspring after exposure to Ti₃C₂ nanosheets, we established a mouse model exposed to different doses of Ti₃C₂ nanosheets during early pregnancy in this study. We found that Ti₃C₂ nanosheets had negligible effect on the reproductive ability of maternal mice, including average pregnancy days, number of new-borns, and neonatal weight, etc. Unexpectedly, abnormal neurobehavior and pathological changes in the cerebral hippocampus and cortex in adult offspring were observed following Ti₃C₂ nanosheet treatment. In further studies, it was found that Ti₃C₂ exposure led to developmental and functional defects in the placenta, including reduced area of labyrinth, disordered secretion of placental hormones, and metabolic function derailment. The long-chain unsaturated fatty acids were significantly higher in the placenta after Ti₃C₂ exposure, especially docosahexaenoic acid (DHA) and linoleic acid. The metabolic pathway analysis showed that biosynthesis of unsaturated fatty acids was upregulated while linoleic acid metabolism was downregulated.

Conclusions

These developmental and functional defects, particularly metabolic function derailment in placenta may be the cause for the neuropathology in the offspring. This is the first report about the effects of Ti₃C₂ nanosheet exposure on pregnancy and offspring. The data provides a better understanding of Ti₃C₂ nanosheets safety. It is suggested that future studies should pay more attention to the long-term effects of nanomaterials exposure, including the health of offspring in adulthood, rather than only focus on short-term effects, such as pregnancy outcomes. Metabolomics could provide clues for finding the prevention targets of the biological negative effect of Ti₃C₂ nanosheets.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01313-z.

Joan Hunt Senior award lecture: New tools to shed light on the 'black box' of pregnancy

Correct establishment of the placenta is critical to the success of a pregnancy, but many of the key events take place during or shortly after implantation and are inaccessible for study. This inaccessibility, coupled with the lack of a suitable preclinical animal model, means that knowledge of human early placental development and function is extremely limited. Hence, the first trimester is often referred to as the 'black box' of pregnancy. However, recent advances in the derivation of trophoblast stem cells and organoid cultures of the trophoblast and endometrium are opening new opportunities for basic and translational research, providing for the first time cells that faithfully replicate their tissue of origin and proliferate and differentiate in culture in a stable and reproducible manner. These cells are valuable new tools for investigating cell-lineage differentiation and maternal-fetal interactions, but become even more powerful when combined with advances in bioengineering, microfabrication and microfluidic technologies. Assembloids of the endometrium comprising various cell types as model systems to investigate events at implantation, and placentas-on-a-chip for the study of nutrient transfer or drug screening are just two examples. This is a rapidly advancing field that may usher in more personalised approaches to infertility and pregnancy complications. Many of the developments are still at the proof-of-principle phase, but with continued refinement they are likely to shed important light on events that are fundamental to our reproduction as individuals and as a species, yet for ethical reasons are hidden from view.

Significance of the placental barrier in antenatal viral infections

The placenta provides a significant physical and physiological barrier to prevent fetal infection during pregnancy. Nevertheless, it is at times breached by pathogens and leads to vertical transmission of infection from mother to fetus. This review will focus specifically on the Zika flavivirus, the HIV retrovirus and the emerging SARS-CoV2 coronavirus, which have affected pregnant women and their offspring in recent epidemics. In particular, we will address how viral infections affect the immune response at the maternal-fetal interface and how the placental barrier is physically breached and discuss the consequences of infection on various aspects of placental function to support fetal growth and development. Improved understanding of how the placenta responds to viral infections will lay the foundation for developing therapeutics to these and emergent viruses, to minimise the harms of infection to the offspring.

Syncytialization alters the extracellular matrix and barrier function of placental trophoblasts

The human placenta is of vital importance for proper nutrient and waste exchange, immune regulation, and overall fetal health and growth. Specifically, the extracellular matrix (ECM) of placental syncytiotrophoblasts, which extends outward from the placental chorionic villi into maternal blood, acts on a molecular level to regulate and maintain this barrier. Importantly, placental barrier dysfunction has been linked to diseases of pregnancy such as preeclampsia and intrauterine growth restriction. To help facilitate our understanding of the interface and develop therapeutics to repair or prevent dysfunction of the placental barrier, in vitro models of the placental ECM would be of great value. In this study, we aimed to characterize the ECM of an in vitro model of the placental barrier using syncytialized BeWo choriocarcinoma cells. Syncytialization caused a marked change in syndecans, integral proteoglycans of the ECM, which matched observations of in vivo placental ECM. Syndecan-1 expression increased greatly and predominated the other variants. Barrier function of the ECM, as measured by electric cell-substrate impedance sensing (ECIS), increased significantly during and after syncytialization, whereas the ability of THP-1 monocytes to adhere to syncytialized BeWos was greatly reduced compared with nonsyncytialized controls. Furthermore, ECIS measurements indicated that ECM degradation with matrix metalloproteinase-9 (MMP-9), but not heparanase, decreased barrier function. This decrease in ECIS-measured barrier function was not associated with any changes in THP-1 adherence to syncytialized BeWos treated with heparanase or MMP-9. Thus, syncytialization of BeWos provides a physiologically accurate placental ECM with a barrier function matching that seen in vivo.

Successful Prediction of Human Fetal Exposure to P-Glycoprotein Substrate Drugs Using the Proteomics-Informed Relative Expression Factor Approach and PBPK Modeling and Simulation

Many women take drugs during their pregnancy to treat a variety of clinical conditions. To optimize drug efficacy and reduce fetal toxicity, it is important to determine or predict fetal drug exposure throughout pregnancy. Previously, we developed and verified a maternal-fetal physiologically based pharmacokinetic (m-f PBPK) model to predict fetal K_p,uu (unbound fetal plasma AUC/unbound maternal plasma AUC) of drugs that passively cross the placenta. Here, we used in vitro transport studies in Transwell, in combination with our m-f PBPK model, to predict fetal K_p,uu of drugs that are effluxed by placental P-glycoprotein (P-gp)-namely, dexamethasone, betamethasone, darunavir, and lopinavir. Using Transwell, we determined the efflux ratio of these drugs in hMDR1-MDCK^cP-gpKO cells, in which human P-gp was overexpressed and the endogenous P-gp was knocked out. Then, using the proteomics-informed efflux ratio-relative expressive factor approach, we predicted the fetal K_p,uu of these drugs at term. Finally, to verify our predictions, we compared them with the observed in vivo fetal K_p,uu at term. The latter was estimated using our m-f PBPK model and published fetal [umbilical vein (UV)]/maternal plasma drug concentrations obtained at term (UV/maternal plasma). Fetal K_p,uu predictions for dexamethasone (0.63), betamethasone (0.59), darunavir (0.17), and lopinavir (0.08) were successful, as they fell within the 90% confidence interval of the corresponding in vivo fetal K_p,uu (0.30-0.66, 0.29-0.71, 0.11-0.22, 0.04-0.19, respectively). This is the first demonstration of successful prediction of fetal K_p,uu of P-gp drug substrates from in vitro studies. SIGNIFICANCE STATEMENT: For the first time, using in vitro studies in cells, this study successfully predicted human fetal K_p,uu of P-gp substrate drugs. This success confirms that the m-f PBPK model, combined with the ER-REF approach, can successfully predict fetal drug exposure to P-gp substrates. This success provides increased confidence in the use of the ER-REF approach, combined with the m-f PBPK model, to predict fetal K_p,uu of drugs (transported by P-gp or other transporters), both at term and at earlier gestational ages.

Next generation strategies for preventing preterm birth

Preterm birth (PTB) is defined as delivery before 37 weeks of gestation. Globally, 15 million infants are born prematurely, putting these children at an increased risk of mortality and lifelong health challenges. Currently in the U.S., there is only one FDA approved therapy for the prevention of preterm birth. Makena is an intramuscular progestin injection given to women who have experienced a premature delivery in the past. Recently, however, Makena failed a confirmatory trial, resulting the Center for Drug Evaluation and Research's (CDER) recommendation for the FDA to withdrawal Makena's approval. This recommendation would leave clinicians with no therapeutic options for preventing PTB. Here, we outline recent interdisciplinary efforts involving physicians, pharmacologists, biologists, chemists, and engineers to understand risk factors associated with PTB, to define mechanisms that contribute to PTB, and to develop next generation therapies for preventing PTB. These advances have the potential to better identify women at risk for PTB, prevent the onset of premature labor, and, ultimately, save infant lives.

Organ-on-a-chip technology for the study of the female reproductive system

Over the past decade, organs-on-a-chip and microphysiological systems have emerged as a disruptive in vitro technology for biopharmaceutical applications. By enabling new capabilities to engineer physiological living tissues and organ units in the precisely controlled environment of microfabricated devices, these systems offer great promise to advance the frontiers of basic and translational research in biomedical sciences. Here, we review an emerging body of interdisciplinary work directed towards harnessing the power of organ-on-a-chip technology for reproductive biology and medicine. The focus of this topical review is to provide an overview of recent progress in the development of microengineered female reproductive organ models with relevance to drug delivery and discovery. We introduce the engineering design of these advanced in vitro systems and examine their applications in the study of pregnancy, infertility, and reproductive diseases. We also present two case studies that use organ-on-a-chip design principles to model placental drug transport and hormonally regulated crosstalk between multiple female reproductive organs. Finally, we discuss challenges and opportunities for the advancement of reproductive organ-on-a-chip technology.

Bioengineered Microphysiological Placental Models: Towards Improving Understanding of Pregnancy Health and Disease

Driven by a lack of appropriate human placenta models, recent years have seen the introduction of bioengineered in vitro models to better understand placental health and disease. Thus far, the focus has been on the maternal-foetal barrier. However, there are many other physiologically and pathologically significant aspects of the placenta that would benefit from state-of-the-art bioengineered models, in particular, integrating advanced culture systems with contemporary biological concepts such as organoids. This critical review defines and discusses the key parameters required for the development of physiologically relevant in vitro models of the placenta. Specifically, it highlights the importance of cell type, mechanical forces, and culture microenvironment towards the use of physiologically relevant models to improve the understanding of human placental function and dysfunction.

Diseases and conditions that impact maternal and fetal health and the potential for nanomedicine therapies

Maternal mortality rates in the United States have steadily increased since 1987 to the current rate of over 16 deaths per 100,000 live births. Whereas most of these deaths are related to an underlying condition, such as cardiovascular disease, many pregnant women die from diseases that emerge as a consequence of pregnancy. Both pre-existing and emergent diseases and conditions are difficult to treat in pregnant women because of the potential harmful effects of the treatment on the developing fetus. Often the health of the woman and the health of the baby are at odds and must be weighed against each other when medical treatment is needed, frequently leading to iatrogenic preterm birth. However, the use of engineered nanomedicines has the potential to fill the treatment gap for pregnant women. This review describes several conditions that may afflict pregnant women and fetuses and introduces how engineered nanomedicines may be used to treat these illnesses. Although the field of maternal-fetal nanomedicine is in its infancy, with additional research and development, engineered nanotherapeutics may greatly improve outcomes for pregnant women and their offspring in the future.

Bioengineering Approaches for Placental Research

Research into the human placenta's complex functioning is complicated by a lack of suitable physiological in vivo models. Two complementary approaches have emerged recently to address these gaps in understanding, computational in silico techniques, including multi-scale modeling of placental blood flow and oxygen transport, and cellular in vitro approaches, including organoids, tissue engineering, and organ-on-a-chip models. Following a brief introduction to the placenta's structure and function and its influence on the substantial clinical problem of preterm birth, these different bioengineering approaches are reviewed. The cellular techniques allow for investigation of early first-trimester implantation and placental development, including critical biological processes such as trophoblast invasion and trophoblast fusion, that are otherwise very difficult to study. Similarly, computational models of the placenta and the pregnant pelvis at later-term gestation allow for investigations relevant to complications that occur when the placenta has fully developed. To fully understand clinical conditions associated with the placenta, including those with roots in early processes but that only manifest clinically at full-term, a holistic approach to the study of this fascinating, temporary but critical organ is required.

Research on nanoparticles in human perfused placenta: State of the art and perspectives

Increasing human exposure to nanoparticles (NPs) from various sources raises concerns for public health, especially for vulnerable risk groups like pregnant women and their developing fetuses. However, nanomedicine and the prospect of creating safe and effective NP-based formulations of drugs hold great promise to revolutionize treatment during pregnancy. With maternal and fetal health at stake, risks and opportunities of NPs in pregnancy need to be carefully investigated. Importantly, a comprehensive understanding of NP transport and effects at the placenta is urgently needed considering the central position of the placenta at the maternal-fetal interface and its many essential functions to enable successful pregnancy. The perfusion of human placental tissue provides a great opportunity to achieve predictive human relevant insights, circumventing uncertainties due to considerable differences in placental structure and function across species. Here, we have reviewed the current literature on the ex vivo human placenta perfusion of NPs. From 16 available studies, it was evident that placental uptake and transfer of NPs are highly dependent on their characteristics like size and surface modifications, which is in line with previous observations from in vitro and animal transport studies. These studies further revealed that special considerations apply for the perfusion of NPs and we identified relevant controls that should be implemented in future perfusion studies. While current studies mostly focused on placental transfer of NPs to conclude on potential fetal exposure, the ex vivo placental perfusion model has considerable potential to reveal novel insights on NP effects on placental tissue functionality and signaling that could indirectly affect maternal-fetal health.