Evaluating a reconstructed human barrier culture system as an in vitro model for the human placenta
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Contributing OfficeNational Center for Toxicological Research
Abstract
The human placenta supports pregnancy by facilitating and regulating the exchange of substances between the fetus and the mother. The potential exists for exogenous substances, including toxins, crossing the placental barrier and possibly harming the developing fetus. For ethical reasons, in vivo toxicity testing isn’t possible in humans, so, currently, the testing of embryo-fetal toxicity of human pharmaceuticals and other exogenous toxicants relies on tests that use animal pregnancy models. A concern about this approach is species-specific differences in placental function and regulators of placental development that can pose challenges when extrapolating findings from embryo-fetal toxicity studies in nonclinical species to humans. Therefore, it is very important to have alternative methods that can add to the body of knowledge when evaluating drug-induced embryo-fetal toxicity(ies). In this project, we investigated an in vitro co-culture model for the human placental barrier that potentially can be employed in embryo-fetal toxicity studies. We used trophoblasts (BeWo b30) to model the syncytiotrophoblast and human primary placental villous endothelial cells (HPVEC) to model the fetal capillary endothelium in the human placental barrier. Preliminary tests were done on the co-culture system to validate its integrity and functionality. Transepithelial electrical resistance (TEER) measurements, the Na-F exclusion assay, and analysis of intercellular junctions with immunocytochemistry demonstrated the formation of tight barriers in the co-culture model. We will further characterize the structure and transport functionality of the BeWo-HPVEC co-culture system to evaluate its similarity to the human placental barrier using 1) PCR arrays to quantify and profile RNA expression for drug metabolizing enzymes (Phase I and Phase II metabolizing enzymes) and transporter proteins in the reconstructed human placental barrier culture system and compare to mRNA expression profiles exhibited by the human placenta barrier in vivo; and 2) evaluating the barrier function by comparing the transport of glucose and reference compounds widely used in ex vivo placenta perfusion experiments.