Trophoblast organoids with physiological polarity model placental structure and function

Human trophoblast organoids (TOs) are a three-dimensional ex vivo culture model that can be used to study various aspects of placental development, physiology and pathology. However, standard culturing of TOs does not recapitulate the cellular orientation of chorionic villi in vivo given that the multi-nucleated syncytiotrophoblast (STB) develops largely within the inner facing surfaces of these organoids (STB(in)). Here, we developed a method to culture TOs under conditions that recapitulate the cellular orientation of chorionic villi in vivo. We show that culturing STB(in) TOs in suspension with gentle agitation leads to the development of TOs containing the STB on the outer surface (STB(out)). Using membrane capacitance measurements, we determined that the outermost surface of STB(out) organoids contain large syncytia comprising >50 nuclei, whereas STB(in) organoids contain small syncytia (<10 nuclei) and mononuclear cells. The growth of TOs under conditions that mimic the cellular orientation of chorionic villi in vivo thus allows for the study of a variety of aspects of placental biology under physiological conditions.