Controlling drug delivery across the placenta

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.

Contribution of Reliable Chromatographic Data in QSAR for Modelling Bisphenol Transport across the Human Placenta Barrier

Regulatory measures and public concerns regarding bisphenol A (BPA) have led to its replacement by structural analogues, such as BPAF, BPAP, BPB, BPF, BPP, BPS, and BPZ. However, these alternatives are under surveillance for potential endocrine disruption, particularly during the critical period of fetal development. Despite their structural analogies, these BPs differ greatly in their placental transport efficiency. For predicting the fetal exposure of this important class of emerging contaminants, quantitative structure-activity relationship (QSAR) studies were developed to model and predict the placental clearance indices (CI). The most usual input parameters were molecular descriptors obtained by modelling, but for bisphenols (BPs) with structural similarities or heteroatoms such as sulfur, these descriptors do not contrast greatly. This study evaluated and compared the capacity of QSAR models based either on molecular or chromatographic descriptors or a combination of both to predict the placental passage of BPs. These chromatographic descriptors include both the retention mechanism and the peak shape on columns that reflect specific molecular interactions between solute and stationary and mobile phases and are characteristic of the molecular structure of BPs. The chromatographic peak shape such as the asymmetry and tailing factors had more influence on predicting the placental passage than the usual retention parameters. Furthermore, the QSAR model, having the best prediction capacity, was obtained with the chromatographic descriptors alone and met the criteria of internal and cross validation. These QSAR models are crucial for predicting the fetal exposure of this important class of emerging contaminants.

Placental ion channels: potential target of chemical exposure

The placenta is an important organ for the exchange of substances between the fetus and the mother, hormone secretion, and fetoplacental immunological defense. Placenta has an organ-specific distribution of ion channels and trophoblasts, and placental vessels express a large number of ion channels. Several placental housekeeping activities and pregnancy complications are at least partly controlled by ion channels, which are playing an important role in regulating hormone secretion, trophoblastic homeostasis, ion transport, and vasomotor activity. The function of several placental ion channels (Na, Ca, and Cl ion channels, cation channel, nicotinic acetylcholine receptors, and aquaporin-1) is known to be influenced by chemical exposure, i.e., their responses to different chemicals have been tested and confirmed in experimental models. Here, we review the possibility that placental ion channels are targets of toxicological concern in terms of placental function, fetal growth, and development.

Size-dependent placental retention effect of liposomes in ICR pregnant mice: Potential superiority in placenta-derived disease therapy

The great challenge in developing safe medications for placenta-derived diseases is to reduce or eliminate fetal drug exposure while still providing the necessary therapeutic effect. Rapid advances in nanotechnology have brought opportunities for the therapy of placenta-derived disease through accumulating the drug in the placenta while reducing its placental penetration. Among various nanocarriers, liposomes are regarded as an ideal type of carrier for placental drug delivery due to their biosafety and biodegradability. However, their placental retention effect with different particle sizes has not been studied. This research aimed to explore a suitable size of liposomes for placenta drug delivery. Cy 5 dye was chosen as a model molecule for tracing the distribution of three different-sized liposomes (∼80 nm, 200 nm, and 500 nm) in ICR pregnant mice. The stability, cytotoxicity, and cellular uptake study of Cy 5-loaded liposomes were performed. The in vivo fluorescence studies on ICR pregnant mice suggested that the particle size of liposomes was positively correlated with the degree of liposome aggregation in the placenta. The ratio of fluorescence in the placenta and fetus section (P/F value) was proposed to evaluate the placental retention effect of different-sized liposomes. The results showed that the liposomes with 500 nm had the highest P/F value and thus exhibited the strongest placental retention effect and the weakest placental penetration ability. Moreover, liquid chromatography-mass spectrometry analysis confirmed the reliability of the fluorescence section analysis in exploring the placental retention effect of nanovehicles. In general, this study introduced a simple and intuitive method to evaluate the placental retention effect of nanoplatforms and defined a suitable size of liposomes for placenta-derived disease drug delivery.

In Vitro Nephrotoxicity and Permeation of Vancomycin Hydrochloride Loaded Liposomes

Drugs can be toxic to the fetus depending on the amount that permeates across the maternal–fetal barrier. One way to limit the amount which penetrates this barrier is to increase the molecular size of the drug. In this study, we have achieved this by encapsulating our model antibiotic (vancomycin hydrochloride, a known nephrotoxic agent) in liposomes. PEGylated and non-PEGylated liposomes encapsulating vancomycin hydrochloride were prepared using two different methods: thin-film hydration followed by the freeze–thaw method and the reverse-phase evaporation method. These liposomes were characterized by their hydrodynamic size and zeta potential measurements, CryoTEM microscopy, loading and encapsulation efficiency studies, in vitro release measurements and in vitro cytotoxicity assays using NRK-52 E rat kidney cells. We also determined the in vitro permeability of these liposomes across the human placental cell and dog kidney cell barriers. Vancomycin hydrochloride-loaded PEGylated liposomes (VHCL-lipo) of a size less than 200 nm were prepared. The VHCL-lipo were found to have the faster release of vancomycin hydrochloride and resulted in greater viability of NRK-52E cells. In vitro, the VHCL-lipo permeated the human placental cell and dog kidney cell barriers to a lesser extent than the free vancomycin hydrochloride. The data suggest a reduction in nephrotoxicity and permeability of vancomycin hydrochloride after encapsulation in PEGylated liposomes.

Conjugation to PEG as a Strategy to Limit the Uptake of Drugs by the Placenta: Potential Applications for Drug Administration in Pregnancy

Here, we evaluated the feasibility of non-prodrug PEG-drug conjugates to decrease the accumulation of drugs within the placental tissues. The results showed that PEG was biocompatible with the human placenta with no alteration of the basal rate of proliferation or apoptosis in term placental explants. No significant changes in the released levels of lactate dehydrogenase and the human chorionic gonadotropin were observed after PEG treatment. The cellular uptake studies revealed that conjugating Cy5.5 and haloperidol to PEG significantly reduced (by up to ∼40-fold) their uptake by the placenta. These findings highlight the viability of novel non-prodrug polymer-drug conjugates to avoid the accumulation of drugs within the placenta.

Dynamic contrast enhanced magnetic resonance imaging: A review of its application in the assessment of placental function

It is important to develop a better understanding of placental insufficiency given its role in common maternofetal complications such as preeclampsia and fetal growth restriction. Functional magnetic resonance imaging offers unprecedented techniques for exploring the placenta under both normal and pathological physiological conditions. Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) is an established and very robust method to investigate the microcirculatory parameters of an organ and more specifically its perfusion. It is currently a gold standard in the physiological and circulatory evaluation of an organ. Its application to the human placenta could enable to access many microcirculatory parameters relevant to the placental function such as organ blood flow, fractional blood volume, and permeability surface area, by the acquisition of serial images, before, during, and after administration of an intravenous contrast agent. Widely used in animal models with gadolinium-based contrast agents, its application to the human placenta could be possible if the safety of contrast agents in pregnancy is established or they are confirmed to not cross the placenta.

Effect of Selected Antidepressants on Placental Homeostasis of Serotonin: Maternal and Fetal Perspectives

Depression is a prevalent condition affecting up to 20% of pregnant women. Hence, more than 10% are prescribed antidepressant drugs, mainly serotonin reuptake inhibitors (SSRIs) and selective serotonin and noradrenaline reuptake inhibitors (SNRIs). We hypothesize that antidepressants disturb serotonin homeostasis in the fetoplacental unit by inhibiting serotonin transporter (SERT) and organic cation transporter 3 (OCT3) in the maternal- and fetal-facing placental membranes, respectively. Paroxetine, citalopram, fluoxetine, fluvoxamine, sertraline, and venlafaxine were tested in situ (rat term placenta perfusion) and ex vivo (uptake studies in membrane vesicles isolated from healthy human term placenta). All tested antidepressants significantly inhibited SERT- and OCT3-mediated serotonin uptake in a dose-dependent manner. Calculated half-maximal inhibitory concentrations (IC₅₀) were in the range of therapeutic plasma concentrations. Using in vitro and in situ models, we further showed that the placental efflux transporters did not compromise mother-to-fetus transport of antidepressants. Collectively, we suggest that antidepressants have the potential to affect serotonin levels in the placenta or fetus when administered at therapeutic doses. Interestingly, the effect of antidepressants on serotonin homeostasis in rat placenta was sex dependent. As accurate fetal programming requires optimal serotonin levels in the fetoplacental unit throughout gestation, inhibition of SERT-/OCT3-mediated serotonin uptake may help explain the poor outcomes of antidepressant use in pregnancy.

Comparison of the materno-fetal transfer of fifteen structurally related bisphenol analogues using an ex vivo human placental perfusion model

Regulatory measures and public concerns regarding bisphenol A (BPA) have led to its replacement by a variety of alternatives in consumer products. Due to their structural similarity to BPA, these alternatives are under surveillance, however, for potential endocrine disruption. Understanding the materno-fetal transfer of these BPA-related alternatives across the placenta is therefore crucial to assess prenatal exposure risks. The objective of the study was to assess and compare the placental transfer of a set of 15 selected bisphenols (BPs) (BP 4-4, BPA, BPAF, BPAP, 3-3 BPA, BPB, BPBP, BPC, BPE, BPF, BPFL, BPM, BPP, BPS and BPZ) using the ex vivo human placental perfusion model. The UHPLC-MS/MS method for simultaneous quantification of these BPs in perfusion media, within a concentration range of 0.003-5 μM, was able to measure placenta transfer rates as low as 0.6%-4%. Despite their structural similarities, these BPs differed greatly in placental transport efficiency. The placental transfer rates of BP4-4, BPAP, BPE, BPF, 3-3BPA, BPB, BPA were similar to that of antipyrine, indicating that their main transport mechanism was passive diffusion. By contrast, the placental transfer rates of BPFL and BPS were very limited, and intermediate for BPBP, BPZ, BPC, BPM, BPP and BPAF, suggesting weak diffusional permeability and/or that their passage might involve efflux transport. These placental transfer data will be particularly useful for predicting the fetal exposure of this important class of emerging contaminants.

Hereditary Angioedema Attack in Utero and Treatment of the Mother and Fetus

Hereditary angioedema (HAE), an inherited deficiency of functional C1 esterase inhibitor (C1-INH), is characterized by unpredictable recurrent episodes of painful and often disabling swelling in subcutaneous and/or submucosal tissues. We report the case of a 23-year-old woman with type I HAE who had abdominal, facial, and peripheral attacks throughout her first pregnancy. A facial HAE attack occurred at week 38 of her pregnancy, and symptoms improved after self-administration of 50 U/kg of recombinant human C1-INH (total dose, 3500 U), but soon after she had an unusual abdominal sensation. Ultrasonography detected fetal lower lip swelling (∼3 times the normal size) and limb swelling. Physical examination of the mother found cervical dilatation, indicating the final stages of labor. Two hours after treatment of her HAE attack, she spontaneously delivered a healthy male infant. Photographs taken within 2 minutes of delivery revealed resolution of the infant’s facial edema, and the limb edema was resolved within 30 minutes. By 10 minutes postdelivery, the mother’s facial attack had almost completely resolved. Ten months after birth, genetic analysis confirmed that the infant had type I HAE. This is the first documented case of an HAE attack in utero. Treatment of the mother with recombinant human C1-INH was effective for the maternal and fetal attacks, with resolution within approximately 2 to 2.5 hours for both patients.

Design of nanomaterials for applications in maternal/fetal medicine

Pregnancy complications are commonplace and the challenges of treatment during pregnancy with few options available pose a risk to the health of both the mother and baby. Patients suffering from conditions such as preeclampsia, placenta accreta, and intrauterine growth restriction have few treatment options apart from emergency caesarean section. Fortunately, researchers are beginning to develop nanomedicine-based therapies that could be utilized to treat conditions affecting the mother, placenta, or fetus to improve the prognosis for mothers and their unborn children. This review summarizes the field's current understanding of nanoparticle biodistribution and therapeutic effect following systemic or vaginal administration and overviews the design parameters researchers should consider when developing nanomedicines for maternal/fetal health. It also describes safety considerations for nanomedicines to limit undesirable maternal or fetal side effects and discusses future work that should be performed to advance nanomedicine for maternal/fetal health. With additional development and implementation, the application of nanomedicine to treat pregnancy complications may mitigate the need for emergency caesarean sections and allow pregnancies to extend to term.

Megalin-targeting liposomes for placental drug delivery

Every year, complications during pregnancy affect more than 26 million women. Some of those diseases are associated with significant morbidity and mortality, as is the case of preeclampsia, the main cause of maternal deaths globally. The ability to improve the delivery of drugs to the placenta upon administration to the mother may offer new opportunities in the treatment of diseases of pregnancy. The objective of this study was to develop megalin-targeting liposome nanocarriers for placental drug delivery. Megalin is a transmembrane protein involved in clathrin-mediated endocytic processes, and is expressed in the syncytiotrophoblast (SynT), an epithelial layer at maternal-fetal interface. Targeting megalin thus offers an opportunity for the liposomes to hitchhike into the SynT, thus enriching the concentration of any associated therapeutic cargo in the placental tissue. PEGylated (2 KDa) lipids were modified with gentamicin (GM), a substrate to megalin receptors as we have shown in earlier studies, and used to prepare placental-targeting liposomes. The ability of the targeting liposomes to enhance accumulation of a fluorescence probe was assessed in an in vivo placental model - timed-pregnant Balb/c mice at gestational day (GD) 18.5. The targeting liposomes containing 10 mol% GM-modified lipids increased the accumulation of the conjugated fluorescence probe in the placenta with a total accumulation of 2.8% of the initial dose, which corresponds to a 94 fold increase in accumulation compared to the free probe (p < .0001), and 2-4 fold accumulation compared to the non-targeting control liposomes (p < .0001), as measured by both tissue extraction assay and ex vivo imaging. Furthermore, confocal images of placental SynT cross-sections show a 3-fold increase of the targeting liposomes compared with the non-targeting liposomes. The rate and extent of uptake of a fluorescent probe encapsulated within targeting liposomes was also probed in an in vitro model of the human placental barrier (polarized BeWo monolayers) using flow cytometry. Targeting liposomes containing 5 mol% GM-modified lipids enhanced the uptake of the probe by 1.5 fold compared to the non-targeting control. An increase to 10 mol% of the modified lipid resulted in further enhancement in uptake, which was 2 fold greater compared to control. In a competition assay, inhibition of the megalin receptors resulted in a significant reduction in uptake of the fluorescence probe encapsulated in GM-modified liposomes compared to the uptake without free inhibitor (p < .0001), implicating the involvement of megalin receptor in the internalization of the liposomes. Taken together, these results demonstrate that megalin-targeted liposomes may offer an opportunity to enhance the delivery of therapeutics to the placenta for the treatment of diseases of pregnancy.

The impact of intrauterine growth restriction on cytochrome P450 enzyme expression and activity

With the increased prevalence of non-communicable disease and availability of medications to treat these and other conditions, a pregnancy free from prescribed medication exposure is rare. Up to 99% of women take at least one medication during pregnancy. These medications can be divided into those used to improve maternal health and wellbeing (e.g., analgesics, antidepressants, antidiabetics, antiasthmatics), and those used to promote the baby's wellbeing in either fetal (e.g., anti-arrhythmics) or postnatal life (e.g., antenatal glucocorticoids). These medications are needed for pre-existing or coincidental illnesses in the mother, maternal conditions induced by the pregnancy itself through to conditions that arise in the fetus or that will be encountered by the newborn. Thus, medications administered to the mother may be used to treat the mother, the fetus or both. Metabolism of medications is regulated by a range of physiological processes that change during pregnancy. Other pathological processes such as placental insufficiency can in turn have both immediate and lifelong adverse health consequences for babies. Individuals born growth restricted are more likely to require medications but may also have an altered ability to metabolise these medications in fetal and postnatal life. This review aims to determine the effect of suboptimal fetal growth on the fetal expression of the drug metabolising enzymes (DMEs) that convert medications into active or inactive metabolites, and the transporters that remove both these medications and their metabolites from the fetal compartment.

The role of xenobiotic-metabolizing enzymes in the placenta: a growing research field

Introduction: The placenta is a temporary and unique organ that allows for the physical connection between a mother and fetus; this organ regulates the transport of gases and nutrients mediating the elimination of waste products contained in the fetal circulation. The placenta performs metabolic and excretion functions, on the basis of multiple enzymatic systems responsible for the oxidation, reduction, hydrolysis, and conjugation of xenobiotics. These mechanisms give the placenta a protective role that limits the fetal exposure to harmful compounds. During pregnancy, some diseases require uninterrupted treatment even if it is detrimental to the fetus. Drugs and other xenobiotics alter gene expression in the placenta with repercussions for the fetus and mother's well-being.Areas covered: This review provides a brief description of the human placental structure and function, the main drug and xenobiotic transporters and metabolizing enzymes, placenta-metabolized substrates, and alterations in gene expression that the exposure to xenobiotics may cause.Expert opinion: Research should be focused on the identification and validation of biological markers for the assessment of the harmful effects of some drugs in pregnancy, including the evaluation of polymorphisms and methylation patterns in chorionic villous samples and/or amniotic fluid.

Pregnant women, prescription, and fetal risk

Since the historical scandal of thalidomide in the 1960s, practitioners and future mothers are fearful of drugs during pregnancy. In-uterine exposure to drugs can induce major malformation of the fetus or even intrauterine fetal death. Prescribing drugs to a pregnant woman requires particular attention, and it is necessary to consider both the maternal needs and the proven and potential fetal risks. In this chapter, we review the mechanisms for medication transfer from mother to fetus, fetal risk according to pregnancy timeline, and the main dangerous drugs during pregnancy. We also focus on three prescription debates, which are relevant for neurodevelopmental disorder, because they each point to a paradigmatic situation-diethylstilbestrol, which shows transgenerational adversary effects; valproate, which impacts neurodevelopment as a whole; and antidepressants for which the adverse impact on neurodevelopment is still controversial given the impact of depression itself. Finally, we consider the implications for practice and toxicologic research to promote risk prevention.

Evaluation of Fetal and Maternal Vancomycin-Induced Kidney Injury during Pregnancy in a Rat Model

Previous literature suggests that maternal vancomycin crosses the placental barrier to the fetus. Further, early animal studies indicated that kidney injury was not observed in the progeny. These studies were conducted prior to the availability of sensitive biomarkers for kidney injury. Therefore, a previous finding of no renal damage to the infant may be misleading. Vancomycin was administered intravenously to pregnant rats at a dose of 250 mg/kg of body weight/day (N = 6 per trimester) on three consecutive gestational days (GD) during trimesters 1, 2, and 3 (T1, T2, and T3, respectively) in three independent cohorts. The dams carried to term and delivered vaginally on GD 21. Kidneys were harvested from dams and pups and homogenized. Samples were prepared by protein precipitation and injected in a liquid chromatography tandem mass spectrometer, and vancomycin was quantified. The kidney tissue homogenate from dams and pups were analyzed for kidney injury molecule-1 (KIM-1). As trimesters progressed, the quantity of vancomycin increased linearly in the kidneys of both rat dams and pups (P < 0.0001 for T1 and T3, P < 0.0001 for T2 and T3, and P < 0.0001 for T3 and T3 control for both rat dams and pups). KIM-1 concentrations in pup kidneys were significantly higher when dams were administered vancomycin in trimesters 1 (P = 0.0001) and 2 (P = 0.0024) than in controls in trimester 3. Data demonstrate persistence of vancomycin in maternal and rat pup kidneys in all three trimesters of pregnancy with associated damage to the kidney, as indicated by expression of KIM-1.

Surface-Functionalized Nanoparticles as Efficient Tools in Targeted Therapy of Pregnancy Complications

Minimizing exposure of the fetus to medication and reducing adverse off-target effects in the mother are the primary challenges in developing novel drugs to treat pregnancy complications. Nanomedicine has introduced opportunities for the development of novel platforms enabling targeted delivery of drugs in pregnancy. This review sets out to discuss the advances and potential of surface-functionalized nanoparticles in the targeted therapy of pregnancy complications. We first describe the human placental anatomy, which is fundamental for developing placenta-targeted therapy, and then we review current knowledge of nanoparticle transplacental transport mechanisms. Meanwhile, recent surface-functionalized nanoparticles for targeting the uterus and placenta are examined. Indeed, surface-functionalized nanoparticles could help prevent transplacental passage and promote placental-specific drug delivery, thereby enhancing efficacy and improving safety. We have achieved promising results in targeting the placenta via placental chondroitin sulfate A (plCSA), which is exclusively expressed in the placenta, using plCSA binding peptide (plCSA-BP)-decorated nanoparticles. Others have also focused on using placenta- and uterus-enriched molecules as targets to deliver therapeutics via surface-functionalized nanoparticles. Additionally, we propose that placenta-specific exosomes and surface-modified exosomes might be potential tools in the targeted therapy of pregnancy complications. Altogether, surface-functionalized nanoparticles have great potential value as clinical tools in the targeted therapy of pregnancy complications.

Trastuzumab in the Treatment of Pregnant Breast Cancer Patients - an Overview of the Literature

Breast cancer is one of the most common malignancies which appear during pregnancy. Since women are increasingly not giving birth until they are at a more advanced age, it can be assumed that the incidence of pregnancy-related breast cancers will continue to increase in the future. Because of pregnancy-induced changes and conservative diagnosis, these carcinomas are frequently not detected until they are at an advanced stage and thus generally require systemic adjuvant therapy. The available data on optimal chemotherapeutic management are limited. Particularly for the use of the target agent trastuzumab which could crucially contribute to improving the prognosis in the therapy of HER2-overexpressing breast cancer in non-pregnant women, there is a lack of definitive information regarding the profile of action and safety in pregnancy as well as with regard to any long-term effects on the child. Thirty-eight pregnancies on trastuzumab for the treatment of breast cancer were able to be analysed in the literature currently available. Information can be gained from this and conclusions can be drawn which can individualise and decisively improve therapeutic options in the future for the pregnant breast cancer patient.

Placenta-on-a-Chip: In Vitro Study of Caffeine Transport across Placental Barrier Using Liquid Chromatography Mass Spectrometry

Due to the particular structure and functionality of the placenta, most current human placenta drug testing methods are limited to animal models, conventional cell testing, and cohort/controlled testing. Previous studies have produced inconsistent results due to physiological differences between humans and animals and limited availability of human and/or animal models for controlled testing. To overcome these challenges, a placenta-on-a-chip system is developed for studying the exchange of substances to and from the placenta. Caffeine transport across the placental barrier is studied because caffeine is a xenobiotic widely consumed on a daily basis. Since a fetus does not carry the enzymes that inactivate caffeine, when it crosses a placental barrier, high caffeine intake may harm the fetus, so it is important to quantify the rate of caffeine transport across the placenta. In this study, a caffeine concentration of 0.25 mg mL-1 is introduced into the maternal channel, and the resulting changes are observed over a span of 7.5 h. A steady caffeine concentration of 0.1513 mg mL-1 is reached on the maternal side after 6.5 h, and a 0.0033 mg mL-1 concentration on the fetal side is achieved after 5 h.

Cytotoxicity, genotoxicity, transplacental transfer and tissue disposition in pregnant rats mediated by nanoparticles: the case of magnetic core mesoporous silica nanoparticles

Whether in the cosmetic or as therapeutic, the use of nanoparticles has been increasing and taking on global proportion. However, there are few studies about the physical potential of long-term use or use in special conditions such as chronic, AIDS, pregnant women and other special health circumstances. In this context, the study of the mutagenicity and the transplacental passage represents an important and reliable model for the primary evaluation of potential health risks, especially maternal and child health. In this study we performed mutagenicity, cytotoxic and transplacental evaluation of magnetic core mesoporous silica nanoparticles, radiolabeled with ^99mTc for determination of toxicogenic and embryonic/fetuses potential risk in animal model. Magnetic core mesoporous silica nanoparticles were produced and characterized by obtaining nanoparticles with a size of (58.9 ± 8.1 nm) in spherical shape and with intact magnetic core. The 99 m Tc radiolabeling process demonstrated high efficacy and stability in 98% yield over a period of 8 hours of stability. Mutagenicity assays were performed using Salmonella enteric serovar Typhimurium standard strains TA98, TA100 and TA102. Cytotoxicity assays were performed using WST-1. The transplacental evaluation assays were performed using the in vivo model with rats in two periods: embryonic and fetal stage. The results of both analyzes corroborate that the nanoparticles can i) generate DNA damage; ii) generate cytotoxic potential and iii) cross the transplantation barrier in both stages and bioaccumulates in both embryos and fetuses. The results suggest that complementary evaluations should be conducted in order to attest safety, efficacy and quality of nanoparticles before unrestricted approval of their use.

Guide for Drug Selection During Pregnancy and Lactation: What Pharmacists Need to Know for Current Practice

OBJECTIVE

To provide guidance for clinicians on risk assessment of medication use during pregnancy and lactation.

DATA SOURCES

Authors completed PubMed searches to identify articles focused on the use of medications in pregnancy, including fetal development, drug transfer across the placenta, trimester exposure, chronic conditions in pregnancy, medications in lactation, and lactation and chronic disease.

STUDY SELECTION AND DATA EXTRACTION

Articles were reviewed to provide overall guidance to medication selection during pregnancy. The following information was reviewed: medication use in pregnancy, including fetal development, drug transfer across the placenta, trimester exposure, chronic conditions in pregnancy, medications in lactation, and lactation and chronic disease.

DATA SYNTHESIS

This article will provide an overview of medication safety considerations during pregnancy and lactation. Information was interpreted to help clinicians predict the potential risk and benefit in each patient to make an evidence-based decision. The article concludes with guidance on risk assessment and how pharmacists may support fellow health care providers and their patients when considering medication use.

CONCLUSIONS

Information about the effects of medication use during reproductive periods is limited. With the removal of the Food and Drug Administration pregnancy categories, clinicians will be relying on pharmacists to aid in the appropriate selection of therapies for patients. It is critical that pharmacists keep abreast of resources available and be able to assess data to help prescribers and their patients.

Maternal-fetal transfer rates of PCBs, OCPs, PBDEs, and dioxin-like compounds predicted through quantitative structure-activity relationship modeling

The present study aims to predict the maternal-fetal transfer rates of the polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs), and dioxin-like compounds using a quantitative structure-activity relationship model. The relation between the maternal-fetal transfer rate and the contaminants' physicochemical properties was investigated by multiple linear regression (MLR), partial least square regression (PLS), and random forest regression (RF). The 10-fold cross-validation technique estimated low predictive performances for both MLR and PLS models (R ²_CV = 0.425 ± 0.0964 for MLR and R ²_CV = 0.492 ± 0.115 for PLS) and is in agreement with an external test (R ²_pred = 0.129 for MLR and R ²_pred = 0.123 for PLS). In contrast, the RF model exhibits good predictive performance, estimated through 10-fold cross-validation (R ²_CV = 0.566 ± 0.0885) and an external test set (R ²_pred = 0.519). Molecular weight and polarity were selected in all models as important parameters that may predict the ability of a molecule to cross the placenta to the fetus.

Co-culture of H295R Adrenocortical Carcinoma and BeWo Choriocarcinoma Cells to Study Feto-placental Interactions: Focus on Estrogen Biosynthesis

Estrogens are produced in large amounts during pregnancy, as a result of a tightly regulated cooperation between the maternal and fetal adrenal cortex, which produce androgen precursors, and the placental villous trophoblast, which transforms these precursors into estrogens. These estrogens play an important role in proper placental function, in adaptation of the mother to pregnancy, as well as in adequate fetal development. Disruption of estrogen production is associated with poor pregnancy outcomes and fetal malformation or altered fetal programming. Pregnant women may be exposed to endocrine disruptors from environmental sources or medications, and it is crucial to study the effects of such compounds on feto-placental steroidogenesis. The H295R/BeWo co-culture model offers the opportunity to study these interactions, by making it possible to evaluate the effects of chemical exposures on androgen and estrogen biosynthesis, as well as on various other aspects of feto-placental communication.

Transplacental Transfer of Monomethyl Phthalate and Mono(2-ethylhexyl) Phthalate in a Human Placenta Perfusion System

The transplacental passage of monomethylphtalate (mMP) and mono (2-ethylhexyl) phthalate (mEHP) was studied using an ex vivo placental perfusion model with simultaneous perfusion of fetal and maternal circulation in a single cotyledon. Umbilical cord blood and placental tissue collected both before and after perfusion were also analyzed. Placentas were obtained immediately after elective cesarean section and dually perfused in a recirculation system. mMP or mEHP was added to maternal perfusion medium to obtain concentrations at 10 and 25 μg/L, respectively. The placental transfer was followed analyzing samples from fetal and maternal perfusion media by liquid chromatography–mass spectrometry–mass spectrometry (LC-MS-MS). Four perfusions with mMP indicated a slow transplacental transfer, with a fetomaternal ratio (FM ratio) of 0.30 ± 0.03 after 150 min of perfusion. Four perfusions with mEHP indicated a very slow or nonexisting placental transfer. mEHP was only detected in fetal perfusion media from two perfusions, giving rise to FM ratios of 0.088 and 0.20 after 150 min of perfusion. Detectable levels of mMP, mEHP, monoethylphthalate (mEP), and monobutylphthalate were found in tissue. Higher tissue levels of mMP after perfusions with mMP compared to perfusions with mEHP suggest an accumulation of mMP during perfusion. No tendency for accumulation of mEHP was observed during perfusions with mEHP compared to perfusions with mMP. Detectable levels of mEHP and mEP were found in umbilical cord plasma samples. mMP and possibly other short-chained phthalate monoesters in maternal blood can cross the placenta by slow transfer, whereas the results indicate no placental transfer of mEHP. Further studies are recommended.

Placental control of drug delivery

The placenta serves as the interface between the maternal and fetal circulations and regulates the transfer of oxygen, nutrients, and waste products. When exogenous substances are present in the maternal bloodstream-whether from environmental contact, occupational exposure, medication, or drug abuse-the extent to which this exposure affects the fetus is determined by transport and biotransformation processes in the placental barrier. Advances in drug delivery strategies are expected to improve the treatment of maternal and fetal diseases encountered during pregnancy.

Use of local anesthetics for dental treatment during pregnancy; safety for parturient

Pregnancy induces significant anatomical and physiological changes in the mother. Many pregnant women need dental treatment due to poor oral hygiene related to pregnancy. However, most dentists are reluctant to provide, and most pregnant women are reluctant to receive, dental treatment during pregnancy. Theoretically, maternally administered drugs are transferred to the fetus. Depending on the types of drugs and the stage of pregnancy, the effects of drugs on the mother, as well as the fetus, may vary. Local anesthetics are the most widely used in dental treatment. It is, therefore, important to understand the potential effects of local anesthetics during pregnancy. In this review, we will focus on the maternal and fetal effects of local anesthetics widely used in dental treatment with consideration of the use of local anesthetics during pregnancy.

[Tyrosine kinase inhibitors and pregnancy: A risk to the fetus?]

The association of cancer and pregnancy is increasingly frequent. This is related, partially, to the increasingly belated age of pregnancy. The management of cancer in pregnancy is a complicated issue. The use of tyrosine kinase inhibitors (TKIs) during pregnancy remains rare and only few data are available concerning their transplacental passage. The aim of this work is to review the data described in the literature, in order to highlight the risks incurred by the fetus, associated with these TKIs' treatment. Up to 189 pregnancies of women treated with TKIs during part or throughout their pregnancy have been described. Clinical data are reassuring and would be in favor of taking the treatment in terms of the balance maternal profit versus fetal risk. These data must, nevertheless, be interpreted with caution.

Oxcarbazepine-loaded polymeric nanoparticles: development and permeability studies across in vitro models of the blood-brain barrier and human placental trophoblast

Encapsulation of antiepileptic drugs (AEDs) into nanoparticles may offer promise for treating pregnant women with epilepsy by improving brain delivery and limiting the transplacental permeability of AEDs to avoid fetal exposure and its consequent undesirable adverse effects. Oxcarbazepine-loaded nanoparticles were prepared by a modified solvent displacement method from biocompatible polymers (poly(lactic-co-glycolic acid) [PLGA] with or without surfactant and PEGylated PLGA [Resomer^® RGPd5055]). The physical properties of the developed nanoparticles were determined with subsequent evaluation of their permeability across in vitro models of the blood–brain barrier (hCMEC/D3 cells) and human placental trophoblast cells (BeWo b30 cells). Oxcarbazepine-loaded nanoparticles with encapsulation efficiency above 69% were prepared with sizes ranging from 140–170 nm, polydispersity indices below 0.3, and zeta potential values below -34 mV. Differential scanning calorimetry and X-ray diffraction studies confirmed the amorphous state of the nanoencapsulated drug. The apparent permeability (P_e) values of the free and nanoencapsulated oxcarbazepine were comparable across both cell types, likely due to rapid drug release kinetics. Transport studies using fluorescently-labeled nanoparticles (loaded with coumarin-6) demonstrated increased permeability of surfactant-coated nanoparticles. Future developments in enzyme-prodrug therapy and targeted delivery are expected to provide improved options for pregnant patients with epilepsy.

Ratio of cord to maternal serum PCB concentrations in relation to their congener-specific physicochemical properties

The aim was to characterize placental transfer of some congeners of polychlorinated biphenyls (PCBs) and to relate human in utero exposure to these pollutants to their physicochemical properties. We included into the study 1134 births during the period 2002-2003 from two highly PCB contaminated districts in eastern Slovakia. Concentrations of 15 PCB congeners (IUPAC No. 28, 52, 101, 123(+149), 118, 114, 153, 105, 138(+163), 167, 156(+171), 157, 180, 170, and 189) in umbilical cord (C) and maternal serum (M) were determined. The C/M ratios were significantly related, either positively or inversely depending on parameter, to the logarithm of partition coefficient octanol-water (KOW), to fusion enthalpy at the melting point, molecular weight, water solubility, total surface area of the molecule, solvent accessible surface area, melting point, molar volume, and molecular electronegativity distance vector. We found an inverse association between logKOW and lipid adjusted logC/M (const=1.078, b1=-0.179, p<0.001, R(2)=0.039). Parameters evaluated were interrelated except fusion enthalpy at the melting point and electron affinity vs. solubility. We discuss the possible role of cholesterol as a transplacental transporter of PCBs.

Bayesian importance parameter modeling of misaligned predictors: soil metal measures related to residential history and intellectual disability in children

In this paper, we propose a novel spatial importance parameter hierarchical logistic regression modeling approach that includes measurement error from misalignment. We apply this model to study the relationship between the estimated concentration of soil metals at the residence of mothers and the development of intellectual disability (ID) in their children. The data consist of monthly computerized claims data about the prenatal experience of pregnant women living in nine areas within South Carolina and insured by Medicaid during January 1, 1996 and December 31, 2001 and the outcome of ID in their children during early childhood. We excluded mother-child pairs if the mother moved to an unknown location during pregnancy. We identified an association of the ID outcome with arsenic (As) and mercury (Hg) concentration in soil during pregnancy, controlling for infant sex, maternal race, mother's age, and gestational weeks at delivery. There is some indication that Hg has a slightly higher importance in the third and fourth months of pregnancy, while As has a more uniform effect over all the months with a suggestion of a slight increase in risk in later months.

Tacrolimus placental transfer at delivery and neonatal exposure through breast milk

AIM(S)

The current investigation aims to provide new insights into fetal exposure to tacrolimus in utero by evaluating maternal and umbilical cord blood (venous and arterial), plasma and unbound concentrations at delivery. This study also presents a case report of tacrolimus excretion via breast milk.

METHODS

Maternal and umbilical cord (venous and arterial) samples were obtained at delivery from eight solid organ allograft recipients to measure tacrolimus and metabolite bound and unbound concentrations in blood and plasma. Tacrolimus pharmacokinetics in breast milk were assessed in one subject.

RESULTS

Mean (±SD) tacrolimus concentrations at the time of delivery in umbilical cord venous blood (6.6 ± 1.8 ng ml(-1)) were 71 ± 18% (range 45-99%) of maternal concentrations (9.0 ± 3.4 ng ml(-1)). The mean umbilical cord venous plasma (0.09 ± 0.04 ng ml(-1)) and unbound drug concentrations (0.003 ± 0.001 ng ml(-1)) were approximately one fifth of the respective maternal concentrations. Arterial umbilical cord blood concentrations of tacrolimus were 100 ± 12% of umbilical venous concentrations. In addition, infant exposure to tacrolimus through the breast milk was less than 0.3% of the mother's weight-adjusted dose.

CONCLUSIONS

Differences between maternal and umbilical cord tacrolimus concentrations may be explained in part by placental P-gp function, greater red blood cell partitioning and higher haematocrit levels in venous cord blood. The neonatal drug exposure to tacrolimus via breast milk is very low and likely does not represent a health risk to the breastfeeding infant.

[Placental transfer of drugs]

With more than 830,000 live births in France, a great number of pregnant women are concerned by a treatment during pregnancy and many questions revolve around appreciating medication-related risks during pregnancy. The human placenta is the interface between mother and fetus and remains difficult to study for ethical reasons. Placental transfer of drugs from mother to fetus is dependent on their physicochemical properties, maternal and fetal factors and placental factors. The human placental perfusion model is the only experimental model to study human placental transfer of drugs in organized placental tissue. In vitro models utilizing cell cultures are mostly limited to the investigation of cellular toxicity along pregnancy or specific transfer mechanisms, such as their interaction with transporters. Taking advantage of the complementarity of these models, it will be possible to develop a rational use of drugs during this period.

Prenatal antidepressant exposure: clinical and preclinical findings

Pharmacological treatment of any maternal illness during pregnancy warrants consideration of the consequences of the illness and/or medication for both the mother and unborn child. In the case of major depressive disorder, which affects up to 10-20% of pregnant women, the deleterious effects of untreated depression on the offspring can be profound and long lasting. Progress has been made in our understanding of the mechanism(s) of action of antidepressants, fetal exposure to these medications, and serotonin's role in development. New technologies and careful study designs have enabled the accurate sampling of maternal serum, breast milk, umbilical cord serum, and infant serum psychotropic medication concentrations to characterize the magnitude of placental transfer and exposure through human breast milk. Despite this progress, the extant clinical literature is largely composed of case series, population-based patient registry data that are reliant on nonobjective means and retrospective recall to determine both medication and maternal depression exposure, and limited inclusion of suitable control groups for maternal depression. Conclusions drawn from such studies often fail to incorporate embryology/neurotransmitter ontogeny, appropriate gestational windows, or a critical discussion of statistically versus clinically significant. Similarly, preclinical studies have predominantly relied on dosing models, leading to exposures that may not be clinically relevant. The elucidation of a defined teratological effect or mechanism, if any, has yet to be conclusively demonstrated. The extant literature indicates that, in many cases, the benefits of antidepressant use during pregnancy for a depressed pregnant woman may outweigh potential risks.

Early-life glucocorticoid exposure: the hypothalamic-pituitary-adrenal axis, placental function, and long-term disease risk

An adverse early-life environment is associated with long-term disease consequences. Adversity early in life is hypothesized to elicit developmental adaptations that serve to improve fetal and postnatal survival and prepare the organism for a particular range of postnatal environments. These processes, although adaptive in their nature, may later prove to be maladaptive or disadvantageous if the prenatal and postnatal environments are widely discrepant. The exposure of the fetus to elevated levels of either endogenous or synthetic glucocorticoids is one model of early-life adversity that contributes substantially to the propensity of developing disease. Moreover, early-life glucocorticoid exposure has direct clinical relevance because synthetic glucocorticoids are routinely used in the management of women at risk of early preterm birth. In this regard, reports of adverse events in human newborns have raised concerns about the safety of glucocorticoid treatment; synthetic glucocorticoids have detrimental effects on fetal growth and development, childhood cognition, and long-term behavioral outcomes. Experimental evidence supports a link between prenatal exposure to synthetic glucocorticoids and alterations in fetal development and changes in placental function, and many of these alterations appear to be permanent. Because the placenta is the conduit between the maternal and fetal environments, it is likely that placental function plays a key role in mediating effects of fetal glucocorticoid exposure on hypothalamic-pituitary-adrenal axis development and long-term disease risk. Here we review recent insights into how the placenta responds to changes in the intrauterine glucocorticoid environment and discuss possible mechanisms by which the placenta mediates fetal hypothalamic-pituitary-adrenal development, metabolism, cardiovascular function, and reproduction.

In vitro simulation of placental transport: part I. Biological model of the placental barrier

INTRODUCTION

The placental barrier (PB) is the thin biological membrane made of endothelial cells (EC), trophoblast cells (TC) and basal membrane that separates between maternal and fetal blood circulations within the placenta and facilitates feto-maternal transport characteristics, which are not completely understood.

METHODS

An in vitro biological model of the PB model was co-cultured of human TC (HTR8) and human umbilical vein EC (HUVEC) on both sides of a denuded amniotic membrane (AM) using custom designed wells.

RESULTS

Confocal and transmission electron microscopy (TEM) imaging confirmed the morphology expressions of human EC and TC. Further support on the integrity of the new PB model was obtained from the existence of tight junctions and permeability experiments with fluorescence markers of small and large molecules. The monolayer of EC demonstrated the limiting layer for the transport resistance across this complex barrier.

DISCUSSION AND CONCLUSION

This new in vitro viable model mimics the architecture of the human PB and can be used in in vitro simulations of transplacental transport studies.

Establishment of an in vitro model of the human placental barrier by placenta slice culture and ussing chamber

Our purpose was to establish an in vitro model of the human placental barrier based on placenta slice culture and Ussing chamber. The villous morphology, beta-human chorionic gonadotropin (β-hCG), mRNA and efflux function of P-glycoprotein (P-gp), and the permeability of the fluorescent marker were confirmed. The results showed that syncytiotrophoblast cells with abundant endoplasmic reticulum and mitochondria were covered with a dense microvillus in the placenta slice. The β-hCG secretion levels in the Ussing chamber were 274.13 ± 13.52 mIU/mL at 5 h, significantly higher than that in the incubator 95.2 ± 13.14 mIU/mL, and β-hCG continued to secrete for 48 h. P-gp mRNA was expressed in the placenta slice. The Rho123 apparent permeability coefficient (Papp) value from maternal side to the fetal side was 26.34 ± 1.87 nm/s, but it was significantly increased, to 289.55 ± 6.02 nm/s after adding verapamil. The Rho123 efflux value was >2. The fluorescein Papp value was (3.42 ± 0.24) × 10(-3) nm/s. In contrast, the fluorescein isothiocyanate-dextran (FD70) Papp value was (3.93 ± 0.08) × 10(-5) nm/s. This indicates that the placenta slice in the Ussing chamber had the activity of a placenta, and can act as a valuable in vitro model of placental barrier.

Maternal obesity alters feto-placental cytochrome P4501A1 activity

Cytochrome P4501A1 (CYP1A1), an important drug metabolizing enzyme, is expressed in human placenta throughout gestation as well as in fetal liver. Obesity, a chronic inflammatory condition, is known to alter CYP enzyme expression in non-placental tissues. In the present study, we test the hypothesis that maternal obesity alters the distribution of CYP1A1 activity in feto-placental unit. Placentas were collected from non-obese (BMI < 30) and obese (BMI > 30) women at term. Livers were collected from gestation day 130 fetuses of non-human primates fed either control diet or high-fat diet (HFD). Cytosol and microsomes were collected using differential centrifugation, and incubated with 7-ethoxyresorufin. The CYP1A1 specific activity (pmoles of resorufin formed/min/mg of protein) was measured at excitation/emission wavelength of 530/590 nm. Placentas of obese women had significantly reduced microsomal CYP1A1 activity compared to non-obese women (0.046 vs. 0.082; p < 0.05); however no such effect was observed on cytosolic activity. Similarly, fetal liver from HFD fed mothers had significantly reduced microsomal CYP1A1 activity (0.44 ± 0.04 vs. 0.20 ± 0.10; p < 0.05), with no significant difference in cytosolic CYP1A1 activity (control, 1.23 ± 0.20; HFD, 0.80 ± 0.40). Interestingly, multiple linear regression analyses of placental efficiency indicate cytosolic CYP1A1 activity is a main effect (5.67 ± 2.32 (β ± SEM); p = 0.022) along with BMI (-0.57 ± 0.26; p = 0.037), fetal gender (1.07 ± 0.26; p < 0.001), and maternal age (0.07 ± 0.03; p = 0.011). In summary, while maternal obesity affects microsomal CYP1A1 activity alone, cytosolic activity along with maternal BMI is an important determinant of placental efficiency. Together, these data suggest that maternal lifestyle could have a significant impact on CYP1A1 activity, and hints at a possible role for CYP1A1 in feto-placental growth and thereby well-being of fetus.

Pharmacotherapy in pregnancy; effect of ABC and SLC transporters on drug transport across the placenta and fetal drug exposure

Pharmacotherapy during pregnancy is often inevitable for medical treatment of the mother, the fetus or both. The knowledge of drug transport across placenta is, therefore, an important topic to bear in mind when deciding treatment in pregnant women. Several drug transporters of the ABC and SLC families have been discovered in the placenta, such as P-glycoprotein, breast cancer resistance protein, or organic anion/cation transporters. It is thus evident that the passage of drugs across the placenta can no longer be predicted simply on the basis of their physical-chemical properties. Functional expression of placental drug transporters in the trophoblast and the possibility of drug-drug interactions must be considered to optimize pharmacotherapy during pregnancy. In this review we summarize current knowledge on the expression and function of ABC and SLC transporters in the trophoblast. Furthermore, we put this data into context with medical conditions that require maternal and/or fetal treatment during pregnancy, such as gestational diabetes, HIV infection, fetal arrhythmias and epilepsy. Proper understanding of the role of placental transporters should be of great interest not only to clinicians but also to pharmaceutical industry for future drug design and development to control the degree of fetal exposure.

Current toxicological aspects on drug and chemical transport and metabolism across the human placental barrier

INTRODUCTION

Placenta plays an obligatory role in fetal growth and development by performing a multitude of functions, including embryo implantation, transport of nutrients and elimination of metabolic waste products and endocrine activity. Drugs and chemicals can transfer across the placental barrier from mother to fetus either by passive diffusion mechanisms and/or via a network of active transporters, which may lead to potential fetotoxicity effects. Placenta also expresses a wide variety of enzymes, being capable of metabolizing a large diversity of drugs and chemicals to metabolites of lower or even higher toxicity than parent compounds.

AREAS COVERED

The present review aims to summarize the current toxicological aspects in the emerging topic of drug transport and metabolism across the human placental barrier.

EXPERT OPINION

There is an emerging demand for accurate assessment of drug transport and metabolism across the human placental barrier, on the basis of a high throughput screening process in the early stages of drug design, to avoid drug candidates from potential fetotoxicity effects. In this aspect, combined studies, which take into account in vivo and in vitro investigations, as well as the ex vivo perfusion method and the recently developed computer-aided technologies, may significantly contribute to this direction.

Maternal undernutrition reduces P-glycoprotein in guinea pig placenta and developing brain in late gestation

Poor nutrition is a major cause of fetal growth restriction which increases neonatal morbidity and mortality, as well as the risk of adult onset diseases. The objective of the study was to determine the effect of maternal undernutrition on P-glycoprotein (P-gp) expression in the placenta and the brain of both the mother and the fetus. Maternal undernutrition in guinea pigs caused placental restriction, and thus decreased fetal weight. Pups in the maternal undernutrition (UN) group had fewer capillaries in the placenta and more capillaries in the brain of the fetus. Placental, maternal and fetal brain MDR1 mRNA expression was the same in the Control and UN groups. Maternal undernutrition resulted in a significant decrease in P-gp protein expression in the placenta and fetal brain, but not the maternal brain. These findings indicate that maternal undernutrition may impact on fetal exposure to drugs administered to the mother during pregnancy due to changes in placental transfer.

Monitoring maternal Beta carotene and retinol consumption may decrease the incidence of neurodevelopmental disorders in offspring

Retinoic acids (13-cis and 13-trans) are known teratogens, and their precursor is retinol, a form of vitamin A. In 1995, Rothman et al demonstrated an association between excessive vitamin A, >10,000 IU/day, during the first trimester of pregnancy and teratogenic effects, particularly in the central nervous system. However, vitamin A deficiency has long been known to be deleterious to the mother and fetus. Therefore, there may be a narrow therapeutic ratio for vitamin A during pregnancy that has not previously been fully appreciated. Neurodevelopmental disorders may not be apparent by macroscopic brain examination or imaging, and proving the existence of a behavioral teratogen is not straightforward. However, an excess of retinoic acid and some neurodevelopmental disorders are both associated with abnormalities in cerebellar morphology. Physical and chemical evidence strongly supports the notion that beta carotene crosses the placenta and is metabolized to retinol. Only very limited amounts of beta carotene are stored in fetal fat cells as evidenced by the fact that maternal fat is yellow from beta carotene, whereas non-brown neonatal fat is white. Furthermore, newborns of carotenemic mothers do not share the yellow complexion of their mothers. The excess 13-trans retinoic acid derived from metabolized beta carotene in the fetus increases the concentration of the more teratogenic 13-cis retinoic acid since the isomerization equilibrium is shifted to the left. Therefore, this paper proposes that consideration be given to monitoring all potential sources of fetal 13-cis and 13-trans retinoic acid, including nutritional supplements, dietary retinol, and beta carotene, particularly in the first trimester of pregnancy.

Transfer of PAMAM dendrimers across human placenta: prospects of its use as drug carrier during pregnancy

Dendrimers offer significant potential as nanocarriers for targeted delivery of drugs and imaging agents. The objectives of this study were to evaluate the transplacental transport, kinetics and biodistribution of PAMAM dendrimers ex-vivo across the human placenta in comparison with antipyrine, a freely diffusible molecule, using dually perfused re-circulating term human placental lobules. The purpose of this study is to determine if dendrimers as drug carriers can be used to design drug delivery systems directed at selectively treating either the mother or the fetus. The transplacental transfers of fluorescently (Alexa 488) tagged PAMAM dendrimer (16 kDa) and antipyrine (188 Da) from maternal to fetal circulation were measured using HPLC/dual UV and fluorescent detector (sensitivity of 10 ng/mL for dendrimer and 100 ng/mL for antipyrine respectively). C(max) for the dendrimer-Alexa (DA) in maternal perfusate (T(max)=15 min) was 18 times higher than in the fetal perfusate and never equilibrated with the maternal perfusate during 5.5 h of perfusion (n=4). DA exhibited a measurable but low transplacental transport of 2.26±0.12 μg/mL during 5.5h, where the mean transplacental transfer was 0.84±0.11% of the total maternal concentration and the feto-maternal ratio as percent was 0.073%±0.02. The biochemical and physiological analysis of the placentae perfused with DA demonstrated normal function throughout the perfusion. The immunofluorescence histochemistry confirmed that the biodistribution of DA in perfused placenta was sparsely dispersed, and when noted was principally seen in the inter-villous spaces and outer rim of the villous branches. In a few cases, DA was found internalized and localized in nuclei and cytoplasm of syncytiotrophoblast and inside the villous core; however, DA was mostly absent from the villous capillaries. In conclusion, the PAMAM dendrimers exhibited a low rate of transfer from maternal to the fetal side across the perfused human placenta, which is similar to other investigations of large macromolecules, e.g., IgG. These overall findings suggest that entry of drugs conjugated to polymers, i.e., dendrimers, would be limited in their transfer across the human placenta when compared to smaller drug molecules alone, suggesting novel methods for selectively delivering therapeutics to the pregnant woman without significant transfer to the fetus, especially since the half life of the dendrimer in blood is relatively short.