The placenta is the interface between mother and fetus, and as such controls the exchange of nutrients, waste products, and therapeutic agents. The potential toxicity, teratogenicity, and therapeutic effects of drugs on the fetus are controlled by their metabolism and clearance by maternal organs (particularly the liver and kidney), their transport across the placenta, and their metabolism by the placenta. Given functional differences in these properties between species, testing in animal models does not always predict adverse drug effects in human pregnancy. Here, we propose to extend our parent project by adapting our model to investigate the role of the placenta in drug transport, specifically, transport of nucleoside analogs such as remdesivir, which was recently found to have efficacy against COVID-19. The syncytiotrophoblast layer of the placenta is largely responsible for drug transport and metabolism. In our model, human trophoblast stem cells (hTSCs) are seeded on the maternal side of the construct and allowed to syncytialize. For this supplement project, we will introduce drugs that are known or suspected to be actively transported across the placenta into the upper chamber, which represents the maternal blood space, and examine the products that accumulate in the trophoblast cells or are transferred to the lower chamber, which represents the placental villous capillaries on the fetal side. We propose to use this model to evaluate the functional differences between wild type hTSCs and mutant hTSCs deficient in transporters that actively move drugs in and out of trophoblast cells. With the recent publication reporting clinical benefit from remdesivir for COVID-19, there is intense interest in the safety of this medication in pregnancy. Remdesivir is a nucleoside analog that blocks SARS-CoV-2 replication, likely by inhibiting RNA-dependent RNA synthesis, as it does for the related MERS coronavirus. The effects of remdesivir in pregnancy are unknown. In this project, we aim to use CRISPR-Cas9 to knock out ENT1, CNT1, OCTN1, and MRP1 in hTSCs and evaluate the effects of these mutations on transport of remdesivir and emtricitabine from the maternal to fetal compartment in our 3D placenta model and accumulation of these drugs in the trophoblast cells. The proposed research will therefore accelerate the understanding of transplacental permeability of antiviral drugs across the maternal-fetal barrier and elucidate the involvement of transporters towards the development of therapeutics for use in pregnancy that are safe and effective for both the mother and fetus, consistent with the objectives of the parent grant.
This supplement project seeks to use a physiologically relevant 3D human placenta-on-a-chip to accelerate the understanding of transplacental permeability of antiviral drugs (e.g. remdesivir) across the maternal-fetal barrier and elucidate the involvement of transporters towards the development of therapeutics for use in pregnancy that are safe and effective for both the mother and fetus.
