Iron transfer across a functional syncytialized trophoblast monolayer

Studying iron transfer across trophoblast monolayers is crucial given the significance of iron in maintaining a healthy pregnancy and supporting fetal growth and development. To get insights into the complex mechanism of transplacental iron transfer, we developed a standardized Transwell®-based monolayer model using BeWo (clone b30) cells. Our proposed method is divided into two parts: 1. the monitoring of monolayer formation and 2. the subsequent performance of an iron transfer assay. Monolayer formation on the Transwell® system is monitored by continuous measurement of transepithelial resistance (TEER) using a volt-ohm meter. In parallel, the leakage is monitored by assessing the paracellular permeability (apparent permeability coefficient, Papp) of the fluorescent dye Lucifer yellow. The subsequent iron transfer assay examines apical Transferrin-mediated iron uptake, intracellular storage, and transfer of iron to the basal compartment of the Transwell®. The treatment of BeWo cells with and without forskolin (20 μM) allows to investigate the effect of syncytium formation on iron transfer kinetics. Our results revealed that monolayer formation in BeWo cells takes approximately 5-6 days. Forskolin-treated BeWo cells transport significantly more iron to the fetal compartment indicating that syncytialization promotes iron transfer across the placental barrier. This method enables the fundamental exploration of materno-fetal iron transfer mechanisms and their regulatory processes, which directly impact fetal well-being and development during pregnancy.