A Tubular 3D In Vitro Model of Placental Trophoblasts for Transport Studies

Successful pregnancy outcomes largely depend on the functional integrity of the placental barrier, which serves as a crucial interface between the maternal and fetal bloodstreams. Accurate modeling of the placental barrier is essential for understanding its physiological processes, developing therapeutics, and conducting transport studies for drug discovery and development that could have averted clinical disasters such as thalidomide-induced teratogenesis. Current models often fail to mimic the placental barrier's complex multilayer structure and consistently form nonleaky barriers due to traditional cell-seeding techniques and the inability to replicate the intricate architecture of the placental barrier. To our knowledge, a true 3D model that recapitulates the multilayer structure, mimics the syncytiotrophoblast layer with high confluency, facilitates cell-extracellular matrix interactions, and supports transport studies under dynamic conditions has not been previously reported. Here, we utilize the self-assembly process of BeWo placental trophoblastic cells and collagen I, a major component of the placental extracellular matrix, to create 3D tubular constructs. These constructs represent a significant advancement in the fabrication of physiologically relevant placental barrier models, enabling the modeling of the syncytiotrophoblast layer with underlying supportive cytotrophoblast layers and allowing for transport studies under dynamic conditions. Fluorescence imaging confirmed syncytial fusion and the formation of a continuous barrier. Permeability tests demonstrated that our model closely mirrors the in vivo transport properties of the placental barrier, highlighting the dominant role of the syncytiotrophoblast layer in governing the placental barrier transport. These models can be utilized for further transport studies, drug development and delivery, and placental barrier tissue engineering.