(L-462) A Microengineered Biomimetic Model of The Placental Barrier to Study Environmental Exposures During Pregnancy

Introduction:: Introduction: Exposure to toxic heavy metals contributes to the development of pregnancy complications that can adversely affect fetal development. Despite increasing evidence suggesting the negative health impact of heavy metals, investigating their adverse effects in the context of human pregnancy remains a major challenge due to the difficulty of human subject research and the limited capacity of animal models to properly represent the anatomy and function of the human reproductive system. Motivated by a problem, here we describe an advanced microengineered in vitro model designed to reverse engineer the maternal-fetal interface in the human placenta. This biomimetic system enables advanced capabilities to grow primary human trophoblast cells and 3D fetal microvascular endothelial cells in a physiological spatial arrangement and dynamic culture conditions to engineer the placental barrier in vitro that can emulate regulated material transport between maternal and fetal circulations. Using cadmium (CdCl₂) as a representative example of heavy metals, we investigate whether and how this environmental chemical affects the human placental barrier and its physiological function as a gatekeeper. Our study also examines the role of membrane transporters including the breast cancer resistance protein (BCRP) in the maternal-to-fetal transfer of cadmium to provide insights into efflux transporter-medicated protection against environmental exposures during pregnancy.


Materials and Methods:: Methods: We used soft lithography to construct a compartmentalized elastomeric device consisting of two overlapping chambers separated by a thin semipermeable membrane. Following device fabrication and sterilization, the device consisted of two chambers, in sequential contact as follows: a basal 3D vascular chamber, and was seeded with 10mg/ml fibrinogen hydrogel containing primary human microvillus endothelial cells (Amnion Foundation) at 3.5×10⁶ cell/ml and primary human placental fibroblasts (Amnion Foundation) at 5×10⁶ cell/ml. After 7 days, an apical chamber that represented the maternal compartment was seeded with primary human trophoblasts (Amnion Foundation) in CTBPRO2GRO Media. The vascularized placenta-on-a-chip tissue was cultured under perfusion conditions by using syringe pumps connected to each chamber. To mimic the physiological process of placental development, we treated the trophoblast cell layer in the maternal chamber with forskolin (50 µM) to induce syncytialization. The syncytialized maternal tissue was then exposed to the flow of medium containing cadmium (0.5-50 µM), and trophoblast responses were analyzed using various techniques including microfluorimetry, ELISA, and RT-PCR.


Results, Conclusions, and Discussions:: Results: Our microengineered placenta on a chip model is composed of two microfabricated 3D chambers separated by a semipermeable membrane. The design of this microdevice makes it possible to mimic tissue compartmentalization in the native human placental barrier by permitting long-term co-culture of primary human trophoblasts, primary human microvillus endothelial cells, and human placental fibroblasts in a physiological 3D microenvironment to engineer fully syncytialized maternal tissue supported by vascularized, perfusable 3D stromal tissues. Our microengineered model of the human placental barrier formed a tight barrier (evaluated by expression of E-cadherin and VE-cadherin, TEER, and permeability measurement), secreted the pregnancy hormone human chorionic gonadotropin beta (hCGβ), and supported physiological maternal-to-fetal transport of glucose. Following CdCl₂ treatment, we observed concentration-dependent deleterious responses in the maternal and fetal tissues, as demonstrated by reduced cell viability and placental hormone secretion, compromised barrier function, and increased secretion of proinflammatory cytokines. The results also indicated upregulated expression of metallothioneins IA and IIA (MT-IA/IIA) metal binding proteins. Finally, being able to acquire all the cells from one donor, we also introduced placental villous macrophages of fetal origin, Hofbauer cells, to our perfusable microvessels and assessed the deleterious potential of heavy metals in placenta tissue in the presence of immune cells.



Conclusions: The placenta-on-a-chip is an innovative and translational in vitro platform for the study of environmental chemical toxicity in the human placenta. In our advanced model, by using donor specific cells, we are confident that this technology may advance our ability to model, interrogate, and predict the potential of xenobiotics to disrupt placentation and maintenance of human pregnancy.


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