PLACENTA-ON-A-CHIP - The Future of Drug Discovery In Women’s Health

INTRODUCTION

Pregnancy presents many challenges when it comes to drug development. Biological changes that a woman experiences be­tween conception and delivery may alter the way medications are absorbed, transported, and metabolized, and certain drugs may cross the placental barrier, affecting fetal health.¹ Concerns for the health of the mother and fetus have limited clinical studies in pregnant populations, so investigations into the effects of thera­peutic agents during pregnancy have been virtually non-existent for decades. However, a lack of knowledge about antenatal care is also dangerous, as the vast majority of pregnant women today experience health concerns that require treatment, and often have to resort to taking unapproved medications during gestation. In addition, obstetric complications – many of which are preventable or treatable – still threaten the lives of many mothers and babies worldwide, due to a lack of research into the management of these conditions. Today, scientists are seeking innovative methods to model the physiology and pharmacology of human pregnancy. The following article will discuss the current challenges that face pregnancy therapeutics, new opportunities the field of microflu­idics offers for obstetric research, and how one Canadian re­search group – the Labouta Laboratory – is pioneering nanotechnology drug delivery models for the safe and effective treatment of antenatal conditions.

MATERNAL HEALTH & DISEASE

The physiological effects of pregnancy are extensive, affect­ing almost every bodily system over the course of 39 weeks. In addition to hormonal variations, an increase in blood volume and a developing fetus, more obvious changes to a woman’s body include the expansion of the uterus – the hollow, muscular organ that supports the fetus – and the formation of the placenta in the first trimester.²

The placenta is a temporary, dynamic, and highly specialized organ attached to the wall of the uterus that plays an important role in facilitating nutrient and oxygen exchange, protecting the fetus from harmful substances in the maternal circulation, and producing hormones to support fetal development.³ Additionally, the placenta is known to play an important role in health and dis­ease, providing immunity to the growing fetus by acting as a bar­rier to protect it from infections and other maternal disorders that can occur at any stage of pregnancy. Some of the most common of these health concerns are high blood pressure, gestational di­abetes, pre-eclampsia, preterm labor, and miscarriage and, al­though the placenta can – to some extent – protect the fetus from these effects, medical management of disease during pregnancy is still essential.

TREATING FOR TWO

More than half of pregnant women currently take prescrip­tion medications or over-the-counter drugs at some point during gestation to control pre-existing illnesses or acute conditions.⁴ In fact, the use of pharmaceuticals during pregnancy is on the rise, partly because of advancing maternal age, as well as the growing incidence of long-term health conditions that require ongoing therapy even before women conceive. The majority of these med­ications appear to have little to no effect on the fetus, indicating it is possible to have a long and healthy pregnancy while med­ically managing maternal health. However, ethical issues sur­rounding the inclusion of pregnant women in clinical trials, as well as regulatory concerns about drug development for maternal and fetal conditions, means many drugs have never been directly studied in the context of pregnancy.¹

BARRIERS TO RESEARCH

Many factors need to be taken into account to carry out effective pharmaco­logical studies while prioritizing fetal and maternal health. The abundance of phys­ical and physiological changes that occur during gestation can influence pharmaco­kinetics – the way in which a person’s body handles an administered drug, distributing and eliminating it from the body. This can affect how well the medicine works, and doses that are therapeutic in the non-preg­nant state may have to be modified to achieve the required therapeutic levels in pregnancy. An additional consideration when treating pregnant women is potential adverse effects of drugs on the developing fetus. Congenital malformations occur in between 2% and 3% of newborn babies worldwide, with approximately 1% to 2% of this total being due to teratogenicity – the presence of certain harmful substances in medicines that can breach the placental barrier and impact normal fetal develop­ment, alter the placenta itself, or modify a pregnant woman’s physiology, harming the fetus indirectly.^5,6

The potential risks of treating diseases during pregnancy, combined with ongoing controversies around the inclusion of preg­nant women in clinical research, necessi­tate a complete shift in the way that we study pregnancy therapeutics. Researchers are therefore focusing their efforts on de­signing a model that effectively recapitu­lates the human pregnancy, so that drug testing can be carried out in vitro, without risks to the mother or fetus.

REPLICATING THE PRENATAL ENVIRONMENT

Establishing an efficient replica of ob­stetric physiology and pharmacology is a difficult task. Human pregnancy is a unique phenomenon; women experience a longer gestation period – even when body size is adjusted for – as well as a drawn-out labor and delivery process compared to many other animals.⁷ In ad­dition, adverse pregnancy outcomes, like preterm birth and pre-eclampsia, are much more common in humans than other species. Although a number of ani­mal models have been proposed for use in pregnancy studies, including small pri­mates and mouse models, they typically have poor physiological relevance to human gestation, offering weak predictive power and typically requiring genetic modification in order to study human dis­eases.⁸ Another model, which has histori­cally been used to study placental function in response to therapies, uses end-of-term human placental tissue that is discarded after delivery. However, even ex vivo mod­els based directly on the human placenta are not truly representative of the fluctuat­ing nature of this complex organ, which changes significantly in terms of both structure and function between the first and third trimesters.

Motivated by the challenges of exist­ing models, scientists are now implement­ing new and advanced technologies to replicate human pregnancy and enhance empirical knowledge in this field. One re­search group, based in the Labouta Labo­ratory, has pioneered the use of microfluidics technologies – the manipula­tion of fluids in small volumes – to design a novel model of the human placenta. This lab-on-a-chip model relies on a microflu­idic cell culture device containing tiny mi­crochannels inhabited by living cells, which are arranged carefully to replicate tissue- and organ-level physiology.⁹ The technology has allowed researchers at the university to culture placental cells and matrices, creating a dynamic model that enables investigations into how therapeu­tics interact with the placental barrier. The team is using this model to develop and test safe and effective nanoparticle-based therapies to treat obstetric complications.

STUDYING PREGNANCY PHARMACOLOGY

Effective nanoparticle drug delivery has already been demonstrated for the treatment of widespread infectious dis­eases and cancers, in which nanoparticles – engineered particles on the nanometer scale – have been successfully exploited to load, carry, and deliver drugs to the re­quired tissues.¹⁰ Applying these treatment methodologies in the field of obstetrics opens up new avenues for treating preg­nancy-associated diseases with minimal off-target effects, because nanoparticles can be engineered to deliver drugs selec­tively to an organ with precise dosages, controlled release, and reduced side ef­fects. Using another custom microfluidics system from Dolomite Microfluidics, the Labouta Laboratory is applying nanotech­nology to deliver microRNAs to modelled placental tissue, enabling research into the effects of different formulations on both maternal and fetal tissues.

The placenta-on-a-chip model will allow researchers to develop a better un­derstanding of placental function, includ­ing how nanoparticles interact with the various cellular layers of this barrier under both physiological and pathological con­ditions. As research progresses, this will enable selective development of drugs that target the fetus, as well as medications that cannot cross the placental barrier, de­pending on the aim of the project. For ex­ample, when developing a medication to treat congenital conditions, it is important that therapeutic substances can travel through the mother’s bloodstream and cross the placenta to reach the fetus. On the other hand, it is crucial that nanopar­ticles targeted at placental tissues or neighboring cells – to treat maternal con­ditions such as pre-eclampsia – have ther­apeutic effects on maternal physiology without transferring through the placenta or adversely affecting fetal tissues.

DEVELOPING SAFER PREGNANCY THERAPEUTICS

The main focus of the laboratory’s current work is developing an effective treatment for congenital diaphragmatic hernia (CDH), a birth defect of the di­aphragm. Most congenital abnormalities are considered rare, but CDH is one of the most common of these conditions – occur­ring in as many as 1 in every 2,500 live births – with potentially serious outcomes, including death shortly after birth or life-long respiratory issues that require re­source-intensive surveillance and medical care.¹¹ Until now, there has been no avail­able cure for this serious prenatal abnor­mality, but the team in the Labouta Laboratory is using microfluidic technolo­gies from Dolomite to design novel therapeutic microRNA-loaded lipid nanoparticles to treat the developing fetus in the mother’s womb.

Although microfluidics is a fairly new approach to drug development, it is al­ready considered the gold standard tech­nique for RNA delivery, lending many ben­efits to the treatment of CDH. This technology enables the production of small, lipid-based vesicles to deliver ther­apeutic RNA directly to the impaired fetal respiratory tract. Encapsulating microRNAs within purposely formulated lipid nanoparticles offers the potential for more controlled and sustained release, while re­ducing toxicity and minimizing adverse side effects. In addition, downsizing parti­cles to the nanometric scale reduces the volume of reagents needed during drug delivery, making microfluidics a cost- and resource-efficient way for the laboratory to investigate novel treatments for conditions like CDH that, until now, have remained poorly understood.

A FORWARD-THINKING APPROACH

It is essential that adequate and con­sistent information is available to expec­tant mothers about pregnancy complications and new and existing med­ications, so that they can make informed decisions to optimize pregnancy out­comes. Given the potential risks of including pregnant women in in vivo human studies, and the limitations of existing pla­cental models, microfluidics offers a safer, more effective, and increasingly adaptive methodology for modelling pregnancy pharmacology. Researchers in the Labouta Laboratory continue to increase the com­plexity of their placenta-on-a-chip models and, as their research progresses, they are confident this technology will aid the de­velopment of novel therapies to treat a wide range of maternal and fetal condi­tions. The rapidly growing field of mi­crofluidics therefore has the potential to completely transform the prenatal drug development landscape and improve the availability of pregnancy-approved med­ications to women across the globe.

SUMMARY

The development of medicines to treat maternal and fetal conditions has historically been limited by a lack of knowledge of pregnancy physiology and pharmacokinetics, combined with ethical and regulatory concerns regarding the in­clusion of pregnant populations in clinical trials. Microfluidics technologies offer sig­nificant potential to the field of pregnancy therapeutics, because nanoparticles can be engineered to minimize fetal drug ex­posure when required, and deliver thera­pies safely to intended tissues. Similarly, placenta-on-a-chip technology offers high potential for testing the antenatal safety of therapeutics. Researchers in the Labouta Laboratory are developing increasingly complex microfluidics models of the pla­centa, and these studies have the potential to improve both maternal and fetal sur­vival rates – as well as quality of life after birth – providing novel and exciting oppor­tunities to an area of research that has long been overlooked.

REFERENCES

1. David, A.L. et al. 2022. Improving devel­opment of drug treatments for pregnant women and the fetus. Therapeutic Innova­tion & Regulatory Science, 56(6):976–990. doi: 10.1007/s43441-022-00433-w.
2. Pascual, Z.N. and Langaker, M.D. 2023. Physiology, Pregnancy. StatPearls Publish­ing. Available at: https://www.ncbi.nlm.nih.gov/books/NBK559304/.
3. Weinberg, D.H. 2022. Human placenta project, Eunice Kennedy Shriver National Institute of Child Health and Human Devel­opment. U.S. Department of Health and Human Services. Available at: https://www.nichd.nih.gov/research/sup­ported/human-placenta-project/default.
4. Gunatilake, R. and Patil, A.S. 2023. Drug use during pregnancy, MSD Manual Con­sumer Version. MSD Manuals. Available at: https://www.msdmanuals.com/home/women-s-health-issues/drug-use-during-preg­nancy/drug-use-during-pregnancy.
5. Leung, C. et al. 2022. Principles of drug use and management in pregnancy. Phar­maceutical Journal, 309(7963). doi: 10.1211/pj.2022.1.150391.
6. Tetro, N. et al. 2018. The placental barrier: The Gate and the fate in drug distribution. Pharmaceutical Research, 35(4). doi: 10.1007/s11095-017-2286-0.
7. Mika, K. et al. 2021. Evolutionary tran­scriptomics implicates new genes and pathways in human pregnancy and ad­verse pregnancy outcomes. eLife, 10. doi: 10.7554/elife.69584.
8. Carter, A.M. 2020. Animal models of human pregnancy and placentation: Alter­natives to the mouse. Reproduction, 160(6). doi: 10.1530/rep-20-0354.
9. Bhatia, S.N. and Ingber, D.E. 2014. Mi­crofluidic organs-on-chips. Nature Biotech­nology, 32(8):760–772. doi: 10.1038/nbt.2989.
10. Pritchard, N. et al. 2020. Nanoparticles in pregnancy: The next frontier in Repro­ductive Therapeutics. Human Reproduc­tion Update, 27(2):280–304. doi: 10.1093/humupd/dmaa049.
11. The Children’s Hospital of Philadelphia. 2014. Congenital diaphragmatic hernia (CDH). Available at: https://www.chop.edu/conditions-dis­eases/congenital-diaphragmatic-hernia-cdh.

Dr. Hagar Labouta is the Keenan Research Chair of Nanomedicine at Unity Health Toronto, and an Assistant Professor in the Leslie Dan Faculty of Pharmacy at the University of Toronto. Previously, her laboratory was affiliated with the College of Pharmacy at the University of Manitoba. She has extensive research experience in the areas of nanomedicine, drug delivery, and biomedical engineering, as well as a strong publication record, and is a co-inventor of an international patent for the development of carrier systems for intracellular drug targeting. She earned her PhD in Pharmaceutical Nanotechnology at Saarland University in Germany under the supervision of Professor Marc Schneider, followed by post-doctoral research under the supervision of Professor Claus-Michael Lehr in the Drug Delivery Department at the Helmholtz Institute for Pharmaceutical Research. After emigrating to Canada, she continued her post-doctoral studies at the University of Calgary, where she focused on other areas of nanomedicine in the Departments of Chemistry and Biomedical Engineering, under the supervision of Professors David Cramb and Kristina Rinker, respectively. The Labouta Laboratory is supported by several local, national, and international funds.